US20100108521A1 - Methods and apparatus for electrodeionization - Google Patents

Abstract

The present invention relates generally to the deionization of liquids through the use of electrodeionization methods and apparatuses. The apparatuses may be configured to minimize the fouling of the electrode chambers and to provide continuous regeneration of the ion exchange materials. The apparatuses may be configured according to the desired levels of deionization for anions, cations, or both. Finally, methods are presented for various uses of the apparatuses.

Description

FIELD OF THE INVENTION
• This invention relates generally to the field of deionization of liquids, in particular to water purification through deionization. More specifically, the present invention pertains to electrodeionization (EDI) apparatuses and various methods of using the same, directing liquid through the apparatuses in different ways to achieve different deionization characteristics.
BACKGROUND OF THE INVENTION
• Electrodeionization (EDI) is known in the art as a process which removes ionized species from liquids, such as water, using electrically active media and an electric potential to influence ion transport. Examples of electrically active media comprise ion exchange materials and ion exchange membranes. In general “ion exchange materials” denotes solid (perhaps highly porous) materials that, when brought into contact with a liquid, cause ions in the liquid to be interchanged with ions in the exchange material. “Ion exchange membrane” or “ion selective membrane” generally denotes a membrane porous to some ions, perhaps containing ion exchange sites, and useful for controlling the flow of ions across the membrane, typically permitting the passage of some types of ions while blocking others. In general, ion exchange membranes selectively permit the transport of some types of ions and not others, and also block the passage of the bulk liquid carrying the ions. A combination of ion selective membranes and ion exchange materials are sandwiched between two electrodes (anode (+) and cathode (−)) under a direct current (DC) electric field to remove ions from the liquid. The electric field may be applied in a continuous manner or may be applied in an intermittent manner. Cationic exchange materials (or cation materials for short) can be used to remove positively charged ions, such as calcium, magnesium, sodium, among others, replacing them with hydronium (H₃O⁺ or H⁺) ions. Anionic exchange materials (or anion materials for short) can be used to remove negatively charged ions, such as chloride, nitrate, silica, among others, replacing them with hydroxide ions. The hydronium and hydroxide ions may subsequently be united to form water molecules. Eventually, the ion exchange materials become saturated with contaminant ions and become less effective at treating the liquid. Once these materials are significantly contaminated, high-purity liquid flowing past them may acquire trace amounts of contaminant ions by “displacement effects.” In conventional deionization, the saturated (or exhausted) ion exchange media must be chemically recharged or regenerated periodically with a strong acid (for cation materials) or a strong base (for anion materials). The process of regenerating the ion exchange media with concentrated solutions of strong acids or strong bases presents considerable cost, time, safety, and waste disposal issues.
• Continuous electrodeionization (CEDI), a subset of EDI, uses a combination of ion exchange materials and ion exchange membranes, and direct current in a manner so as to continuously deionize liquids and also to eliminate the need to chemically regenerate the ion exchange media. The “continuous” label of CEDI applies to the condition wherein the electric field may be applied to the apparatus in a continuous manner while product liquid is being produced. CEDI includes processes such as continuous deionization, filled cell electrodialysis, or electrodiaresis. The ionic transport properties of electrically active media are an important separation parameter.
• In the EDI apparatus illustratedFIG. 1, contaminant ions migrate through theion depletion chambers103,107 and into theelectrode chambers101,109. The ion exchange materials in the compositebed depletion chamber105,anion depletion chamber103 andcation depletion chamber107 are regenerated by water splitting in the compositebed depletion chamber105. Hydronium produced from water splitting migrates towards the cathode passing though thecation exchange membrane106 of the compositebed depletion chamber105, into thecation depletion chamber107 and ultimately into thecathode chamber109. Similarly, hydroxide produced from water splitting migrates towards the anode passing though theanion exchange membrane104 of the compositebed depletion chamber105, into theanion depletion chamber103 and ultimately into theanode chamber101. Electrochemically produced hydronium, which results from oxidation of water at the anode, maintains electroneutrality as hydroxide and contaminant anions migrate into the anode chamber. Similarly, electrochemically produced hydroxide, which results from the reduction of water at the cathode, maintains electroneutrality as hydronium and contaminant cations migrate into the cathode chamber. In the apparatus illustrated inFIG. 1, the feed water hardness must be less than about 1-2 parts-per-million (ppm) (as CaCO₃), otherwise precipitation of calcium as calcium carbonate or magnesium as magnesium hydroxide may occur in the cathode chamber causing an increase in device resistance or an increase in the backpressure, decreased flow, and potential plugging in the apparatus. By flowing the electrode rinse first through the anode chamber and then through the cathode chamber, the hardness problem may be reduced since the anode electrode rinse is slightly acidic and thus will help minimize precipitation of calcium carbonate and magnesium hydroxide. Still, feed water with hardness above several ppm (as CaCO₃) can cause problems in the apparatus. Another potential problem with this apparatus can occur in the anode chamber. Common anions such as chloride and nitrate can be oxidized in the anode chamber to form electrochemically active species (ClO₂and NO₂, respectively). These electrochemically active species can damage the ion exchange material in the anode chamber resulting in decreased lifetime of the EDI apparatus.
• Thus, there is a need for an EDI apparatus which reduces or overcomes problems arising from electrode fouling by precipitation or damage to the ion exchange materials of the electrode compartment by electrochemically active compounds (such as oxidizers) while maintaining some or all of the advantages of homogeneous-material ion depletion chambers.
• FIG. 1 illustrates an EDI apparatus that may be used for “general purpose” liquid deionization. The apparatus comprises three ion depletion chambers,103,105,107, and two electrode chambers,101,109, separated by four ion exchange membranes,102,104,106, and108. This configuration offers improved deionization capability but may add additional complexity or cost for applications where the deionization requirement is selective. For some applications, the required water purity may require the exhaustive removal of anions or cations, but not both. This is the case in many forms of chemical analysis where a specific element or ion or a group of elements or ions are of interest. For example, in ion chromatography, either anions or cations are typically analyzed using different chemistries. For anion analysis by ion chromatography, the water used to prepare eluent or dilute samples or standards should be free of all anions as any anion in the water will likely manifest itself and either affect calibration (non-zero intercept) or compromise detection by increasing background conductivity. Other examples requiring feed water sources free from specific ions are silicate analyzers, sodium analyzers or phosphate analyzers as typically used to monitor high purity water. In these applications, the primary requirement is that the feed water has concentrations of the analyte(s) at or near the lowest possible levels, typically sub-ppb (part-per-billion) or ppt (part-per-trillion). Since many of these analyzers are used on-line (continuous analysis), it is desirable to have a continuous, highly purified feed water source for the analyzer. Currently, there are no commercially available water purifiers which can easily interface with analytical instruments and supply feed water with extremely low contaminant levels of the analyte ions. Therefore, there is a need for a simple, cost-effective EDI apparatus that may be devoted to a specific purpose.
SUMMARY OF THE INVENTION
• Accordingly and advantageously the present invention discloses methods and apparatuses that may address one or more of the issues discussed above. In some embodiments of the present invention, a composite bed concentrate chamber is used to collect and remove the contaminant ions from the liquid. The contaminant ions are hindered from entering the electrode chambers, thus reducing the electrode fouling associated with conventional EDI apparatuses.
• In other embodiments of the present invention, the ion exchange efficiency of chambers including homogeneous ion exchange materials may be combined with the benefits of chambers or layers including composite anion-cation ion exchange materials to produce liquids with very low concentrations of contaminant ions. In some embodiments of the present invention, the interface between adjacent layers may be transverse to the applied electric field. In some embodiments of the present invention, the interface between adjacent layers may be parallel to the applied electric field.
• These and other advantages are achieved in accordance with the present invention as described in detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
• To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The drawings are not to scale and the relative dimensions of various elements in the drawings are depicted schematically and not to scale.
• In the configurations disclosed below, liquid streams flow through the electrode chambers and “concentrate” chambers. In the following configurations, the electrode chambers may act as concentrate chambers or as a source of hydronium and hydroxide ions for regeneration of the ion exchange materials. As concentrate chambers, contaminant ions may eventually migrate into the electrode chambers (under the force of the applied electric field) and may be removed from the electrode chamber by a liquid flow stream. The electrode chamber flow streams may typically be directed to waste. For simplicity of the drawings, the electrode chamber and concentrate chamber rinse streams are not shown.
• The techniques of the present invention may be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:
• FIG. 1 is a schematic representation of an EDI configuration.
• FIG. 2A-2D are schematic representations of EDI configurations of embodiments of the present invention.
• FIG. 3A-3C are schematic representations of EDI configurations of embodiments of the present invention.
• FIG. 4A-4C are schematic representations of EDI configurations of embodiments of the present invention.
• FIG. 5 is a schematic representation of an EDI configuration of one embodiment of the present invention.
• FIG. 6 is a schematic representation of an EDI configuration of one embodiment of the present invention.
• FIG. 7 is a schematic representation of an EDI configuration of one embodiment of the present invention.
• FIG. 8 is a schematic representation of an EDI configuration of one embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTIONAbbreviations and Definitions
• The following abbreviations and definitions are used herein:
• The abbreviation “EDI”=electrodeionization;
• The abbreviation “CEDI”=continuous electrodeionization;
• The abbreviation “IC”=ion chromatography;
• The abbreviation “AM”=anion exchange membrane;
• The abbreviation “CM”=cation exchange membrane;
• The term “applied electric field” is understood to be the electric field arising from a voltage applied between the anode and the cathode within the EDI apparatus.
• InFIGS. 1-8, the anode chamber has been labeled as “anode” for brevity.
• InFIGS. 1-8, the cathode chamber has been labeled as “cathode” for brevity.
• The term “depletion chamber” is defined as a chamber through which the product liquid stream flows during one of the steps of the process. A depletion chamber may be filled with one of a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material, or may be comprised of “layers” of various ion exchange materials.
• The abbreviation “LDC”=layered depletion chamber which is a specific type of “depletion chamber” and is defined as a chamber that comprises “layers” of various ion exchange materials wherein the liquid to be processed flows through the layers in a sequential manner.
• The term “concentrate chamber” is defined as a chamber wherein the product liquid stream does not flow. Typical examples of a concentrate chamber include an electrode chamber (either anode or cathode), an anodic concentrate chamber (a chamber located adjacent to the anode chamber and separated therefrom by an ion exchange membrane), or a cathodic concentrate chamber (a chamber located adjacent to the cathode chamber and separated therefrom by an ion exchange membrane), or a central concentrate chamber (wherein the concentrate chamber is not adjacent to an electrode chamber), among others. Typically, in some embodiments of the present invention, the electrode chambers (either anode or cathode), are not filled with ion exchange material. A concentrate chamber may be filled with a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material.
• The term “mixed ion exchange material” is defined as a mixture of anion and cation exchange materials wherein the anion exchange material is responsible for about 50% of the total ion exchange capacity and the cation exchange material is responsible for about 50% of the total ion exchange capacity. The term “mixed ion exchange material” also refers to a chamber that contains a mixture of anion and cation exchange materials wherein the anion exchange material is responsible for a range of about 40% to about 60% of the total ion exchange capacity and the cation exchange material is responsible for the balance of the total ion exchange capacity. This definition is meant to be consistent with the conventional understanding of a “mixed bed” as containing a 50/50 mixture of anion/cation ion exchange materials as well as a small range, typically from ˜40% to ˜60% on either side of the 50/50 mixture.
• The abbreviation “ACC”=anodic concentrate chamber which is defined as a concentrate chamber adjacent to the anode and separated from the anode by an ion exchange membrane. The ACC may contain a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. This is a chamber wherein the product liquid stream does not flow.
• The abbreviation “CCC”=cathodic concentrate chamber which is defined as a concentrate chamber adjacent to the cathode and separated from the cathode by an ion exchange membrane. The CCC may contain a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. This is a chamber wherein the product liquid stream does not flow.
• The abbreviation “ADC”=anion depletion chamber is defined as a chamber that includes therein a homogeneous volume of anion exchange material. These chambers have been labeled as “anion bed” in the legend ofFIGS. 1-8 for brevity.
• The abbreviation “CDC”=cation depletion chamber is defined as a chamber that includes therein a homogeneous volume of cation exchange material. These chambers have been labeled as “cation bed” in the legend ofFIGS. 1-8 for brevity.
• The abbreviation “CBCC”=composite bed concentrate chamber. A composite bed concentrate chamber may be filled with a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material.
• The abbreviation “ACBCC”=anodic composite bed concentrate chamber is defined as the composite bed concentrate chamber adjacent to the anode and separated from the anode by an ion exchange membrane. The ion exchange membrane may be an AM or a CM. The ACBCC chamber may be filled with a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material.
• The abbreviation “CCBCC”=cathodic composite bed concentrate chamber is defined as the composite bed concentrate chamber adjacent to the cathode and separated from the cathode by an ion exchange membrane. The ion exchange membrane may be an AM or a CM. The CCBCC chamber may be filled with a mixed ion exchange material, a doped anion exchange material, or a doped cation exchange material.
• The abbreviation “ACBDC”=anodic composite bed depletion chamber is defined as the composite bed depletion chamber adjacent to the anode and separated from the anode by an ion exchange membrane. The ion exchange membrane may be an AM or a CM. The ACBDC chamber may be filled with a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material.
• The abbreviation “CCBDC”=cathodic composite bed depletion chamber is defined as the composite bed depletion chamber adjacent to the cathode and separated from the cathode by an ion exchange membrane. The ion exchange membrane may be an AM or a CM. The CCBDC chamber may be filled with a mixed ion exchange material, a doped anion exchange material, or a doped cation exchange material.
• The abbreviation “CBDC”=composite bed depletion chamber is defined as the composite bed depletion chamber that is not adjacent to either the cathode chamber or the anode chamber. The CBDC chamber may be filled with a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material.
• The terms “dopant” and “doping agent” refer to a material that is added to another material. In EDI, a dopant may include materials such as an inert material, an electrically active non-ion exchange material (for example, a metal material), ion exchange materials, or mixtures thereof. Typically, ion exchange material, such as anion exchange materials or cation exchange materials is added to a volume of the opposite ion exchange materials to adjust the electrical conductivity. In some instances, doping of ion exchange materials facilitate the transport of contaminant ions or may provide for water splitting which can produce regenerant ions (hydronium and hydroxide).
• The term “doped cation exchange material” is defined as a composite of anion and cation exchange materials wherein the cation exchange material is responsible for at least about 60% of the total ion exchange capacity and the remainder of the total ion exchange capacity is contributed by anion exchange material. That is, the mixture is primarily a cation exchange material. This definition is meant to distinguish a “doped cation exchange material” from the conventional understanding of a “mixed ion exchange bed” (or material)”. That is, “mixed ion exchange material (or bed)” is used herein to denote a bed having approximately equal cation and anion ion exchange capacities (typically equal to within about ±10%) while “doped cation exchange material” denotes an ion exchange material in which cation exchange clearly predominates and the anion exchange material is a “dopant” or minority contributor. The doped cation exchange materials may be advantageous in that they can be used to alter the conductivity through the EDI apparatus and improve the performance of the EDI apparatus.
• The term “doped anion exchange material” is defined in a complimentary manner to “doped cation exchange material” described above. That is, “doped anion exchange material” is a composite of anion and cation exchange materials wherein the anion exchange material is responsible for at least about 60% of the total ion exchange capacity and the remainder of the total ion exchange capacity is contributed by the cation exchange material. That is, the mixture is primarily an anion exchange material. This definition is meant to distinguish a “doped anion exchange material” from the conventional understanding of a “mixed ion exchange bed”. The doped anion exchange materials may be advantageous in that they can be used to alter the conductivity through the EDI apparatus and improve the performance of the EDI apparatus.
• The terms “hard” and “hardness” when used in reference to water, indicates water that contains concentrations (typically expressed in parts-per-million, (ppm)) of various minerals, such as calcium and magnesium carbonates, bicarbonates, sulfates, or chlorides. The presence of such dissolved minerals typically arises from prolonged contact with rocky substrates and soils. Such hardness in water tends to discolor, scale, and corrode materials.
• The term “scale” refers to a solid deposit on a surface in contact with a liquid in which the deposit includes mineral compounds present in the liquid, e.g., calcium carbonate.
• The term “water splitting” refers to the hydrolysis of water to hydronium and hydroxide ions, which occurs at the interface of anion exchange materials and cation exchange materials in the presence of an electric potential. This is not a true electrochemical process, and differs from the electrolysis of water at an electrode in that water splitting does not produce hydrogen or oxygen gas whereas conventional electrolysis of water produces both gases.
• The terms “eluant” and “eluent” refer to a substance used to effect the separation of ions from a separation column in an elution process. Examples of eluents include, but are not limited to, an acid or a base.
• The term “elution” refers to the process of using an eluent to extract ions from a separation column.
• The term “eluate” refers to the product or substance that is separated from a column in an elution process.
• After considering the following description, those skilled in the art will clearly realize that the teachings of the invention can be readily utilized in liquid purification, specifically deionization, through the use of various EDI apparatuses and methods in various ways.
• Two earlier patent applications are assigned to the Assignee of the present invention and describe five chambered EDI apparatuses. One is entitled “Method of Ion Chromatography wherein a Specialized Electrodeionization Apparatus is Used” (application Ser. No. 11/403,737) and published as US 2006/0231404. The other is entitled “Chambered Electrodeionization Apparatus with Uniform Current Density, and Method of Use” (application Ser. No. 11/403,734 and published as US 2006/0231403). The entire contents of both applications are hereby incorporated herein by reference in their entirety.
• A related patent application filed concurrently herewith and entitled “Methods and Apparatus for Electrodeionization Utilizing Layered Chambers” is assigned to the Assignee of the present invention. The entire contents of this application are hereby incorporated herein by reference in its entirety.
• The types of ion exchange materials that are typically of the most interest for the deionizations described herein are strong acid cation exchange materials and strong base anion exchange materials. The strong acid cation exchange material advantageously has a sulfonate-type ion exchange site (or functional group) while the anion exchange material typically has a quaternary amine ion exchange site (or functional group). There are different types of cation and anion exchange materials which are not inherently excluded from use in connection with the deionizations described herein, but one type of cation exchange material and one type of anion exchange material as described are typically found to provide adequate performance in practice and are generally used.
• If the anion exchange material and cation exchange material are mixed in the desired ratio of substantially equal cation and anion exchange capacities, this is referred to as a “mixed” bed. This comports with the conventional understanding of a “mixed bed ion exchange material” as an ion exchange material that has approximately equal anion and cation exchange capacity with one type of anion exchange material and one type of cation exchange material. This is typically achieved by mixing a cation exchange material (typically a cation exchange resin) with an anion exchange material (typically an anion exchange resin) in a ratio such that the cation and anion exchange capacities of the final mixture are roughly equal. In practice, it is usually not feasible to achieve precise equality but commonly the range of anion capacity in the mixed bed can be about 40%-60% with the remaining capacity as cation capacity.
• The “composite bed” concept as used herein relates to a composite as a mixture of a cation exchange material and an anion exchange material without reference to the proportions of each. That is, in a composite bed the ion exchange capacity ratio could range from about 1% to about 99% of either material, and the balance comprising the opposite material type. Generally, three types of composite beds are considered:
• • 1. A “mixed bed” where the ratio of anion to cation ion exchange capacity is approximately 1:1 with a range of about 10% (that is, 40%-60% of either cation or anion capacity).
  • 2. A “doped” anion bed where the anion capacity is at least about 60% and the remaining ion exchange capacity is cation.
  • 3. A “doped” cation bed where the cation capacity is at least about 60% and the remaining ion exchange capacity is anion.
• Simply put, as the proportion of cation exchange material P_cin a “composite bed” is increased from about 1% to about 99% we encounter first the particular type of composite bed called a “doped anion bed” for P_cless than about 40%. A “mixed bed” is produced for P_cgreater than about 40% and less than about 60%, and a “doped cation bed” for P_Cgreater than about 60%.
• The EDI apparatus shown inFIG. 1 is an example of an EDI apparatus, which comprises five discreet membrane bound chambers in electrical communication (although other embodiments can have more than five chambers). The apparatus illustrated inFIG. 1 comprises ananode chamber101 separated from anADC103 by afirst AM102. Theanode chamber101 includes therein an anode that is typically in electrical contact with thefirst AM102. TheADC103 typically includes therein a homogeneous volume of anion exchange material. A composite bed depletion chamber (or simply CBDC)105 may be placed on the cathode-side of theADC103. TheADC103 and theCBDC105 may be separated by asecond AM104. TheCBDC105 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The doped anion exchange material, or doped cation exchange material versions may be advantageous in that they can be used to alter the conductivity through the EDI apparatus and improve the performance of the EDI apparatus. ACDC107 may be placed on the cathode-side of theCBDC105. TheCBDC105 and theCDC107 may be separated by afirst CM106. TheCDC107 typically includes therein a homogeneous volume of cation exchange material. TheCDC107 may be separated from thecathode chamber109 by asecond CM108. Thecathode chamber109 includes therein a cathode that is typically in electrical contact with thesecond CM108. When additional (more than five) membrane bound chambers are present, they may be typically present in pairs of additional homogeneous anion and cation depletion chambers, which may be added next to existing like chambers, which are present between an electrode and theCBDC105. An electrical current runs through the EDI apparatus transverse to the membranes, conventionally from left to right for the apparatus depicted inFIG. 1 as the direction of flow of positive charges.
• Each CDC may be bounded by two cation exchange membranes and typically includes a volume of homogeneous cation exchange material. The cation exchange material may comprise cation exchange resins, cation exchange particles, cation exchange fibers, cation exchange screens, cation exchange monoliths, and combinations thereof. Typically, the cation exchange material may be a volume of homogeneous cation exchange resin.
• The CBDC may be bounded by a cation exchange membrane from a CDC and an anion exchange membrane from an ADC, and the chamber may contain a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The ion exchange material may comprise ion exchange resins, ion exchange particles, ion exchange fibers, ion exchange screens, ion exchange monoliths, and combinations thereof.
• Each ADC may be bounded by two anion exchange membranes and typically includes a volume of homogeneous anion exchange material. The anion exchange material may comprise anion exchange resins, anion exchange particles, anion exchange fibers, anion exchange screens, anion exchange monoliths, and combinations thereof. Typically, the anion exchange material may be a volume of homogeneous anion exchange resin.
• The ion exchange membranes used in the CEDI apparatuses to practice some embodiments of the present invention work by passive transfer and not reactive chemistry. They may contain functional sites, which allow for the exchange of ions. The transfer of ions through the ion exchange membrane is based upon the charge of the ion. The ion exchange membranes may readily admit small ions but resist the passage of bulk liquid for example. Ion exchange membranes may be anion exchange membranes (AM) or cation exchange membranes (CM), wherein they are selective to anions or cations respectively. An AM may transport anions through the membrane, but the membrane prevents the bulk flow of liquid from one side of the membrane to the other. A CM may transport cations through the membrane, but the membrane prevents the bulk flow of liquid from one side of the membrane to the other. A property common to both types of membranes is that they must be conductive so that ions may migrate through the ion exchange membrane towards their respective electrodes.
• An example of an anion exchange membrane is a microporous copolymer of styrene and divinylbenzene that has been chloromethylated and then the pendant —CH₂Cl groups that were introduced to the aromatic rings were then quaternized with a tertiary amine R₁R₂R₃N where R₁, R₂, and R₃represent organic groups and may represent different organic groups or may represent the same organic group. This results in a membrane which may be a strong base anion exchanger. In some cases, the anion exchange membrane may also contain a binder polymer or an inert fabric. An example of an anion exchange membrane that may be used in connection with some embodiments of the present invention is the AMI-7001S membrane (a product of Membranes International, Glen Rock, N.J.). Other anion exchange membranes which provide a strong base anion exchanger may also be used.
• An example of a cation exchange membrane is a microporous copolymer of styrene and divinylbenzene that has undergone sulfonation, resulting in the monosubstitution of —SO₃H groups on the aromatic rings of the copolymer. This results in a membrane which may be a strong acid cation exchanger. In some cases, the cation exchange membrane may also contain a binder polymer or an inert fabric. An example of a cation exchange membrane that may be used in connection with some embodiments of the present invention is the CMI-7000S membrane (a product of Membranes International, Glen Rock, N.J.). Other cation exchange membranes which provide a strong acid cation exchanger may also be used.
• The ion exchange materials used in the EDI apparatuses of the kind used to practice some embodiments of the present invention may contain functional sites, which allow for the exchange of ions. The interaction between ions and the ion exchange materials is based upon the charge of the ion. The ion exchange materials may readily admit small ions and molecules but resist the intrusion of species of even a few hundred atomic mass units. Ion exchange materials may be anion exchange materials or cation exchange materials, wherein they are selective to anions or cations respectively.
• An example of an anion exchange resin is a microporous copolymer of styrene and divinylbenzene that has been chloromethylated and then the pendant —CH₂Cl groups that were introduced to the aromatic rings were then quaternized with a tertiary amine R₁R₂R₃N where R₁, R₂, and R₃represent organic groups and may represent different organic groups or may represent the same organic group. This results in a resin which may be a strong base anion exchanger. There are several commercially available resins of this type. One example of an anion exchange resin that may be used is the Dowex 1×4 (200 mesh) resin (a product of Dow Chemical Company, Midland, Mich.), which contains 4% divinylbenzene and is in the ionic form Cl⁻. Other anion exchange resins which provide a strong base anion exchanger may also be used.
• An example of a cation exchange resin is a microporous copolymer of styrene and divinylbenzene that has undergone sulfonation, resulting in the monosubstitution of —SO₃H groups on the aromatic rings of the copolymer. This results in a resin which may be a strong acid cation exchanger. There are several commercially available resins of this type. One example of a cation exchange resin that may be used is the Dowex 50W×4 (200 mesh) resin (a product of Dow Chemical Company, Midland, Mich.), which contains 4% divinylbenzene and is in the ionic form H⁺. Other cation exchange resins which provide a strong acid cation exchanger may also be used.
• The CBDC may serve two functions, among others. First, when an electric field is applied, water splitting occurs wherever anion and cation exchange materials are in direct contact with one another. Water splitting occurs where a cation and anion exchange material contact one another, or where a cation exchange material contacts an anion exchange membrane, or where an anion exchange material contacts a cation exchange membrane. Water splitting results in the production of hydroxide and hydronium, which serve to maintain the anion exchange material in the hydroxide form and the cation exchange material in the hydronium form, respectively. As well as keeping the ion exchange materials of the CBDC fully regenerated, the hydroxide and hydronium formed at the ion exchange material/ion exchange membrane interfaces of the CBDC serve to provide hydroxide for the at least one ADC(s) and hydronium for the at least one CDC(s).
• A second function of the CBDC may be to remove from the feed water, the few remaining (if any) anions not removed by the ADC and the few remaining (if any) cations not removed by the CDC. Ion transport in a composite bed ion exchange material relies on both water splitting as well as electrophoretic migration of the ion through the material. Water splitting may displace contaminant ions from the ion exchange material. These contaminant ions may be driven through the composite ion exchange material bed of the CBDC towards their respective electrode chambers. Thus, contaminant cations may be driven through the CBDC, through a CM, through the CDC(s), and through a CM, to the cathode chamber. Likewise, contaminant anions may be driven through the CBDC, through an AM, through the ADC(s), and through an AM, to the anode chamber.
• Water splitting generates hydronium and hydroxide ions which may be used to regenerate ion exchange materials. Under the force of an applied electric field, water splitting can occur at the junction of anion and cation exchange materials. These junctions occur in the CBDC, since this chamber contains both anion and cation exchange materials and membranes. Hydronium from the CBDC may travel through the CM to the CDC, thus regenerating the cation exchange materials found within. Likewise, hydroxide from the CBDC may travel through the AM to the ADC, thus regenerating the anion exchange materials found within.
• The following discussion will describe the movement of ions through the CBDC. For this discussion, it will be assumed that the CBDC is filled with ion exchange particles. An example of such ion exchange particles includes ion exchange resins. For a contaminant ion to be removed from the CBDC, the contaminant ion must either come in contact with the respective membrane or be retained by an ion exchange material particle in contact with a like ion exchange membrane (cation material-cation membrane or anion material-anion membrane). An ion that is in an ion exchange material particle and electrophoretically migrating through the ion exchange material can only move to the next like particle (anion or cation exchange) if the two particles are in contact with one another, or if the contaminant ion leaves the ion exchange material particle as a result of water splitting. Since the CBDC contains a mixture of anion and cation exchange materials, it is statistically unlikely, for the typical densities of materials used in practice, that there will be a continuous path of like material particles of any significant distance, thus, electrophoretic migration in the central chamber is advantageously accompanied by displacement and retention (caused by water splitting) for efficient ion removal. This is in contrast to the mechanism of ion removal in the ADC and CDC where no water splitting occurs (since these chambers contain only one type of ion exchange material). In the ADC and CDC, contaminant ions may be removed by electrophoretic migration through the material bed to and through the ion exchange membrane and ultimately to the electrode chamber.
• For example, chloride retained by the anion exchange material of the CBDC may be displaced by water splitting. The hydroxide ions formed from water splitting may displace the contaminant anions (for example Cl⁻) from the anion exchange material and the chloride goes into solution where it is “paired” with hydronium ions from the water splitting reaction. The contaminant Cl⁻ (as hydrochloric acid, HCl) may now move through the composite material bed where it may be retained again by anion exchange, where the displacement-retention mechanisms continue to occur. Eventually, the contaminant Cl⁻ may come in contact with an anion exchange material particle that is in contact with the anion exchange membrane, and the contaminant Cl⁻ ion may be passed through the AM into the ADC.
• The analogous situation occurs for a cation contaminant. For example, sodium retained by the cation exchange material of the CBDC may be displaced by water splitting. The hydronium ions formed from water splitting may displace the contaminant cations (for example Na⁺) from the cation exchange material and the cation goes into solution where it is “paired” with hydroxide ions from the water splitting reaction. The contaminant Na⁺ (as sodium hydroxide, NaOH) may now move through the composite material bed where it may be retained again by cation exchange, where the displacement-retention mechanisms continue to occur. Eventually, the contaminant Na⁺ may come in contact with a cation exchange material particle that is in contact with the cation exchange membrane, and thus the contaminant Na⁺ ion may be passed through the cation membrane into the CDC.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 1 comprises first causing the liquid to be deionized to flow through theCDC107. TheCDC107 may be capable of removing cations. TheCDC107 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM108 and into thecathode chamber109. The contaminant cations may be removed from the system in thecathode chamber109. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in thecathode chamber109 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber109. The anions are attracted toward the anode under the influence of the applied electric field but will not be allowed to pass through afirst CM106 into theadjacent CBDC105. Therefore, the anions will be retained in the liquid. The liquid exiting theCDC107 has a reduced level of cations relative to the in-coming liquid stream.
• Following passage through107, the liquid is then flowed through theADC103. TheADC103 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM102 and into theanode chamber101. The contaminant anions may be removed from the system in theanode chamber101. The cations are not allowed to pass through asecond AM104 that defines the cathode-side of theADC103. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions are effectively contained in theanode chamber101 until they are flushed from the system by the waste liquid stream that removes ions from theanode chamber101. Any remaining cations are largely unaffected while passing through theADC103. The liquid exiting theADC103 may be largely free of anionic contamination.
• Following passage through103, the liquid is then flowed through theCBDC105. TheCBDC105 may be capable of effectively removing any remaining cations or anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM104 and into theADC103. The contaminant anions may be removed from the system in theanode chamber101. One benefit of this configuration is that this prevents fouling and scaling of theanode chamber101 since the anions cannot react with cations to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC103 or contained in theanode chamber101 until they are flushed from the system by the waste liquid stream that removes ions from theanode chamber101. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM106 and into theCDC107. The contaminant cations may be removed from the system in thecathode chamber109. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively removed in theCDC107 or contained in thecathode chamber109 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber109.
• Water splitting occurs in theCBDC105 since it may include therein a composite of anion and cation exchange materials. The water splitting in theCBDC105 serves to regenerate thesecond AM104 that separates theCBDC105 from theADC103 as well as thefirst CM106 that separates theCBDC105 from theadjacent CDC107. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC107 where they may be effective in regenerating the cation exchange material contained therein. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC103 where they may be effective in regenerating the anion exchange material contained therein.
Example 1
• An EDI device as shown inFIG. 1 was constructed using machined high density polyethylene hardware to retain the electrodes, membranes and material. In this example, the device was substantially cylindrical in shape with a substantially circular cross-section. Other shapes and cross-sections are feasible, but circular was convenient for this example. The internal flow dimensions of theADC103 were 1.27 cm in diameter and 3.81 cm in length. The internal flow dimensions of theCBDC105 were 1.27 cm in diameter and 1.27 cm in length. The internal flow dimensions of theCDC107 were 1.27 cm in diameter and 3.81 cm in length.
• Theanode chamber101, for this example, contained platinum gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). In contact with the anode and separating the anode chamber from the ADC was an anion exchange membrane102 (AMI-7001S, a product of Membranes International, Glen Rock, N.J.). The ADC was filled with an anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.). Ananion membrane104 separated the ADC from theCBDC105. The CBDC contained a doped anion material bed. The doped anion material bed consisted of a composite of an anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) and a cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) with an ion exchange capacity ratio of 3:1 anion to cation. The cation and anion exchange resins were in the hydronium and hydroxide forms, respectively. Separating theCDC107 from the CBDC was a cation exchange membrane106 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). The CDC was filled with a cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.). The CDC was separated from thecathode chamber109 by a cation membrane108 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). The cathode compartment contained platinum gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). The cathode was in direct contact with thecation membrane108 separating the CDC and cathode chamber. A pump (GP40, a product of Dionex, Sunnyvale, Calif.) was used to deliver reverse osmosis (RO) quality water (specific conductance 15.1 μS/cm, S=Siemens) at a flow rate of 2.0 mL/min to the EDI device shown inFIG. 1. A conductivity detector (CD20, a product of Dionex, Sunnyvale, Calif.) with a flow cell was used for the conductivity measurements. From the pump, the RO water flow was directed to theCDC107, then to theADC103, then to theCBDC105 and then to the flow-through conductivity cell. A peristaltic pump (MASTERFLEX LS, a product of the Cole-Parmer company, Vernon Hills, IL) was used to deliver deionized water at a flow rate of 2.0 mL/min to the anode chamber and then to the cathode chamber and then to waste.
• Initially, the conductance of the water exiting the EDI device was 8.3 μS/cm. Using a laboratory power supply, (E3612A, a product of Agilent, Santa Clara, Calif.) a constant current of 40 mA was applied and the initial voltage was 42V. Gas evolution was observed immediately from the anode and cathode chambers. The initial background conductivity of the product water increased to 85 μS/cm and over a 1 hour period the conductivity decreased to 1.2 μS/cm. The EDI device was allowed to operate continuously for 7 days. The data in Table 1 shows results for the device ofFIG. 1.

• TABLE 1
  Conductance Measurements vs. Time

  		Conductivity
  Hours	Voltage	(μS/cm)

  0.0	0.0	8.3
  1	37	1.2
  2	33	0.91
  10	40	0.10
  24	32	0.088
  48	26	0.065
  72	24	0.061
  96	25	0.059
  120	25	0.058
  144	27	0.057
  168	29	0.060

• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 1 comprises first causing the liquid to be deionized to flow through theADC103. TheADC103 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM102 and into theanode chamber101. The contaminant anions may be removed from the system in theanode chamber101. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions are effectively contained in theanode chamber101 until they are flushed from the system by the waste liquid stream that removes ions from theanode chamber101. Any cations are largely unaffected while passing through theADC103. The liquid exiting theADC103 may be largely free of anionic contamination.
• Following passage through103, the liquid is then flowed through theCDC107. TheCDC107 may be capable of removing cations. TheCDC107 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM108 and into thecathode chamber109. The contaminant cations may be removed from the system in thecathode chamber109. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in thecathode chamber109 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber109. The anions are attracted toward the anode under the influence of the applied electric field but will not be allowed to pass through afirst CM106 into theadjacent CBDC105. Therefore, the anions will be retained in the liquid. The liquid exiting theCDC107 has a reduced level of cations relative to the in-coming liquid stream.
• Following passage through107, the liquid is then flowed through theCBDC105. TheCBDC105 may be capable of effectively removing any remaining cations or anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM104 and into theADC103. The contaminant anions may be removed from the system in theanode chamber101. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC103 or contained in theanode chamber101 until they are flushed from the system by the waste liquid stream that removes ions from theanode chamber101. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM106 and into theCDC107. The contaminant cations may be removed from the system in thecathode chamber109. One benefit of this configuration is that this prevents fouling and scaling of thecathode chamber109 since the cations cannot react with anions to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively removed in theCDC107 or contained in thecathode chamber109 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber109.
• Water splitting occurs in theCBDC105 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC105 serves to regenerate thesecond AM104 that separates theCBDC105 from theADC103 as well as thefirst CM106 that separates theCBDC105 from theadjacent CDC107. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC107 where they may be effective in regenerating the cation exchange material contained therein. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC103 where they may be effective in regenerating the anion exchange material contained therein.
• An alternative EDI apparatus is illustrated inFIGS. 2A and 2B. In this apparatus, composite bed depletion chambers may be placed adjacent to the anode and cathode chambers and separated from the electrode chambers by an AM and a CM, respectively. The composite bed depletion chamber adjacent to the anode will be defined as the anodic composite bed depletion chamber (ACBDC). The composite bed depletion chamber adjacent to the cathode will be defined as the cathodic composite bed depletion chamber (CCBDC). In each case, these composite bed depletion chambers may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material.
• The ACBDC and CCBDC depletion chambers may be capable of removing both anions and cations and may be used as a final “polishing” bed. In this configuration, the apparatus comprises two composite bed polishing chambers and most contaminant ions are received into the composite bed concentrate chamber (CBCC). Typically in this configuration, the CBCC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. Depending on the application, the flow order through the depletion chambers may be varied. Water splitting occurs in the ACBDC and CCBDC which may contribute to the regeneration of these chambers as well as to the regeneration of the anion and cation depletion chambers.
• The apparatus illustrated inFIG. 2A andFIG. 2B comprises ananode chamber201 including an anode therein. AnACBDC203 may be placed on the cathode-side of the anode chamber. The anode chamber and the ACBDC may be separated by afirst AM202. The ACBDC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC205 may be placed on the cathode-side of the ACBDC. The ACBDC and the CDC may be separated by afirst CM204. The CDC typically includes therein a homogeneous volume of cation exchange material. ACBCC207 may be placed on the cathode-side of the CDC. The CDC and the CBCC may be separated by asecond CM206. The CBCC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC209 may be placed on the cathode-side of the CBCC. The CBCC and the ADC may be separated by asecond AM208. The ADC typically includes therein a homogeneous volume of anion exchange material. ACCBDC211 may be placed on the cathode-side of the ADC. The ADC and the CCBDC may be separated by athird AM210. The CCBDC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The CCBDC may be separated from acathode chamber213 by athird CM212. The cathode chamber includes a cathode therein. The apparatus as illustrated inFIG. 2A andFIG. 2B may be operated in continuous mode or in intermittent mode.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIGS. 2A and 2B, makes use of the flow path depicted inFIG. 2A, and comprises first causing the liquid to be deionized to flow through theACBDC203. TheACBDC203 may be capable of removing both anions and cations. The anions are attracted to theadjacent anode chamber201 under the influence of the applied electric field and may be allowed to pass through afirst AM202 and may be removed from the liquid. The cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM204 into theadjacent CDC205. TheCDC205 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theACBDC203 has a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theACBDC203 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theACBDC203 serves to regenerate thefirst AM202 that separates theACBDC203 from theanode chamber201 as well as thefirst CM204 that separates theACBDC203 from theadjacent CDC205. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC205 where they may be effective in regenerating the cation exchange material contained therein.
• Following passage through203, the liquid is then flowed through theCDC205. TheCDC205 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations are effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Anions are largely unaffected while passing through theCDC205. The liquid exiting theCDC205 may be largely free of cationic contamination.
• Following passage through205, the liquid is then flowed through theADC209. TheADC209 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207 and into theCDC205. One benefit of this configuration is that this prevents fouling and scaling of thecathode chamber213 since the anions cannot react with cations to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Cations are largely unaffected while passing through theADC209. The liquid exiting theADC209 may be largely free of anionic contamination.
• Following passage through209, the liquid is then flowed through theCCBDC211. TheCCBDC211 may be capable of removing both anions and cations. The cations are attracted to theadjacent cathode chamber213 under the influence of the applied electric field and may be allowed to pass through athird CM212 and may be removed from the liquid. The anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through athird AM210 into theadjacent ADC209. TheADC209 typically includes therein anion exchange materials and may be effective at removing the contaminant anions. The anions may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theCCBDC211 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCCBDC211 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCCBDC211 serves to regenerate thethird CM212 that separates theCCBDC211 from thecathode chamber213 as well as thethird AM210 that separates theCCBDC211 from theadjacent ADC209. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC209 where they may be effective in regenerating the anion exchange material contained therein.
• The apparatus and method of use illustrated inFIG. 2A address the cathode fouling and ion exchange degradation problems common in convention EDI apparatuses since the cathode chamber may not receive the contaminant ions and water splitting in the composite bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, cation membranes, anion exchange materials, and the cation exchange materials.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIGS. 2A and 2B comprises reversing the flow depicted inFIG. 2A and first causing the liquid to be deionized to flow through theCCBDC211. TheCCBDC211 may be capable of removing both anions and cations. The cations are attracted to theadjacent cathode chamber213 under the influence of the applied electric field and may be allowed to pass through athird CM211 and may be removed from the liquid. The anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through athird AM210 into theadjacent ADC209. TheADC209 typically includes therein anion exchange materials and may be effective at removing the contaminant anions. The anions may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theCCBDC211 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCCBDC211 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCCBDC211 serves to regenerate thethird CM212 that separates theCCBDC211 from thecathode chamber213 as well as thethird AM210 that separates theCCBDC211 from theadjacent ADC209. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC209 where they may be effective in regenerating the anion exchange material contained therein.
• Following passage through211, the liquid is then flowed through theADC209. TheADC209 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207 and into theCDC205. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Cations are largely unaffected while passing through theADC209. The liquid exiting theADC209 may be largely free of anionic contamination.
• Following passage through209, the liquid is then flowed through theCDC205. TheCDC205 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations are effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Anions are largely unaffected while passing through theCDC205. The liquid exiting theCDC205 may be largely free of cationic contamination.
• Following passage through205, the liquid is then flowed through theACBDC203. TheACBDC203 may be capable of removing both anions and cations. The anions are attracted to theadjacent anode chamber201 under the influence of the applied electric field and may be allowed to pass through afirst AM202 and may be removed from the liquid. The cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM204 into theadjacent CDC205. TheCDC205 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theACBDC203 has a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theACBDC203 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theACBDC203 serves to regenerate thefirst AM202 that separates theACBDC203 from theanode chamber201 as well as thefirst CM204 that separates theACBDC203 from theadjacent CDC205. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC205 where they may be effective in regenerating the cation exchange material contained therein.
• The apparatus and methods of use illustrated inFIG. 2A address the anode fouling and ion exchange degradation problems common in convention EDI apparatuses since the anode chamber may not receive the contaminant ions and water splitting in the composite bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, cation membranes, anion exchange materials, and the cation exchange materials.
• Another method for performing electrodeionization utilizing the apparatus as illustrated inFIGS. 2A and 2B, makes use of the flow path depicted inFIG. 2B, and comprises first causing the liquid to be deionized to flow through theCDC205. TheCDC205 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Anions are largely unaffected while passing through theCDC205. The liquid exiting theCDC205 may be largely free of cationic contamination.
• Following the passage through205, the liquid is then flowed through theADC209. TheADC209 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207 and into theCDC205. One benefit of this configuration is that the majority of anions may be removed into theCBCC207 thus preventing the formation of oxidants such as ClO₂in the anode chamber (from contaminant chloride) which may damage the ion exchange membranes. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Cations are largely unaffected while passing through theADC209. The liquid exiting theADC209 may be largely free of anionic contamination.
• Following the passage through209, the liquid is then flowed through theCCBDC211. TheCCBDC211 may be capable of removing both anions and cations. The cations are attracted to theadjacent cathode chamber213 under the influence of the applied electric field and may be allowed to pass through athird CM212 and may be removed from the liquid. The anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through athird AM210 into theadjacent ADC209. TheADC209 typically includes therein anion exchange materials and may be effective at removing the contaminant anions. The anions may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theCCBDC211 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCCBDC211 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCCBDC211 serves to regenerate thethird CM212 that separates theCCBDC211 from thecathode chamber213 as well as thethird AM210 that separates theCCBDC211 from theadjacent ADC209. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC209 where they may be effective in regenerating the anion exchange material contained therein.
• Following the passage through211, the liquid is then flowed through theACBDC203. TheACBDC203 may be capable of removing both anions and cations.
• The anions are attracted to theadjacent anode chamber201 under the influence of the applied electric field and may be allowed to pass through afirst AM202 and may be removed from the liquid. The cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM204 into theadjacent CDC205. TheCDC205 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theACBDC203 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theACBDC203 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theACBDC203 serves to regenerate thefirst AM202 that separates theACBDC203 from theanode chamber201 as well as thefirst CM204 that separates theACBDC203 from theadjacent CDC205. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC205 where they may be effective in regenerating the cation exchange material contained therein.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 2B comprises first causing the liquid to be deionized to flow through theADC209. TheADC209 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207 and into theCDC205. One benefit of this configuration is that the majority of anions may be removed into theCBCC207 thus preventing the formation of oxidants such as ClO₂in the anode chamber (from contaminant chloride) which may damage the ion exchange membranes. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Cations are largely unaffected while passing through theADC209. The liquid exiting theADC209 may be largely free of anionic contamination.
• Following the passage through209, the liquid is then flowed through theCDC205. TheCDC205 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. Anions are largely unaffected while passing through theCDC205. The liquid exiting theCDC205 may be largely free of cationic contamination.
• Following the passage through205, the liquid is then flowed through theACBDC203. TheACBDC203 may be capable of removing both anions and cations. The anions are attracted to theadjacent anode chamber201 under the influence of the applied electric field and may be allowed to pass through afirst AM202 and may be removed from the liquid. The cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM204 into theadjacent CDC205. TheCDC205 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM206 and into theCBCC207. The contaminant cations may be removed from the system in theCBCC207. The cations are not allowed to pass through asecond AM208 that defines the cathode-side of theCBCC207. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theACBDC203 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theACBDC203 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theACBDC203 serves to regenerate thefirst AM202 that separates theACBDC203 from theanode chamber201 as well as thefirst CM204 that separates theACBDC203 from theadjacent CDC205. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC205 where they may be effective in regenerating the cation exchange material contained therein.
• Following the passage through203, the liquid is then flowed through theCCBDC211. TheCCBDC211 may be capable of removing both anions and cations. The cations are attracted to theadjacent cathode chamber213 under the influence of the applied electric field and may be allowed to pass through athird CM212 and may be removed from the liquid. The anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through athird AM210 into theadjacent ADC209. TheADC209 typically includes therein anion exchange materials and may be effective at removing the contaminant anions. The anions may be allowed to pass through asecond AM208 and into theCBCC207. The contaminant anions may be removed from the system in theCBCC207. The anions are not allowed to pass through asecond CM206 that defines the anode-side of theCBCC207. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC209 or contained in theCBCC207 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC207. The liquid exiting theCCBDC211 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCCBDC211 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCCBDC211 serves to regenerate thethird CM212 that separates theCCBDC211 from thecathode chamber213 as well as thethird AM210 that separates theCCBDC211 from theadjacent ADC209. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC209 where they may be effective in regenerating the anion exchange material contained therein.
Example 2
• An EDI device as shown inFIG. 2B was constructed using machined high density polyethylene hardware to retain the electrodes, membranes and resin. The internal flow dimensions of theACBDC203 were 1.27 cm in diameter and 1.27 cm in length. TheADC205 was 1.27 cm in diameter and 3.81 cm in length. The internal flow dimensions of theCBCC207 were 1.27 cm in diameter and 1.27 cm in length. The internal flow dimensions of theCDC209 were 1.27 cm in diameter and 3.81 cm in length. The internal flow dimensions of theCCBDC211 were 1.27 cm in diameter and 1.27 cm in length.
• Theanode chamber201, for this example, contained platinum gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). In contact with the anode and separating theanode chamber201 from theACBDC203 was an anion exchange membrane202 (AMI-7001S, a product of Membranes International, Glen Rock, N.J.). The ACBDC contained a homogenous mixture of cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) and anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) in the hydronium and hydroxide forms, respectively. The ion exchange capacity ratio of anion to cation was 1:1 (a mixed bed). Separating theACBDC203 from theCDC205 was a cation exchange membrane204 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). The CDC was filled with a cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.). Separating theCDC205 from theCBCC207 was a cation exchange membrane206 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). The CBCC chamber contained a homogenous mixture of cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) and anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) in the hydronium and hydroxide forms, respectively. The ion exchange capacity ratio of anion to cation was 1:1 (a mixed bed). TheCBCC207 was separated from theADC209 by an anion membrane208 (AMI-7001, a product of Membranes International, Glen Rock, N.J.). The ADC was filled with an anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.). TheADC209 was separated from theCCBDC211 by an anion exchange membrane210 (AMI-7001, a product of Membranes International, Glen Rock, N.J.). The CCBDC was filled with a homogenous mixture cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) and anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) in the hydronium and hydroxide forms, respectively. The ion exchange capacity ratio of anion to cation was 1:1 (a mixed bed). Separating theCCBDC211 from thecathode chamber213 was a cation exchange membrane212 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). A pump (GP40, a product of Dionex, Sunnyvale, Calif.) was used to deliver RO quality water (specific conductance 14.3 μs/cm) at a flow rate of 3.0 mL/min to the EDI device shown inFIG. 2B. A conductivity detector (CD20, a product of Dionex, Sunnyvale, Calif.) with a flow cell was used for the conductivity measurements. From the pump, the RO water flow was directed to theCDC205, then to theADC209, then theCCBDC211, next to theACBDC203 and then to the flow through the conductivity cell. From the conductivity cell, the flow was directed to theanode chamber201 and then thecathode chamber213 and finally to waste.
• Initially, the conductance of the water exiting the EDI device was 4.8 μS/cm. Using a laboratory power supply (E3612A, a product of Agilent, Santa Clara, Calif.) a constant current of 20 mA was applied and the initial voltage was 55V. Gas evolution was observed immediately from the anode and cathode chambers. The initial background conductivity of the product water increased to about 60 μS/cm and over a 1 hour period the conductivity decreased to 0.72 μS/cm. The EDI device was allowed to operate continuously for 9 days. The data in Table 2 shows results for the device ofFIG. 28.

• TABLE 2
  Conductance Measurements vs. Time

  		Conductivity
  Hours	voltage	(μS/cm)

  0.0	0.0	4.8
  1	51	0.72
  2	49	0.21
  10	40	0.081
  24	32	0.069
  48	26	0.071
  72	24	0.061
  96	25	0.058
  120	25	0.058
  144	27	0.056
  168	29	0.057
  192	29	0.057
  216	28	0.058

• The apparatus and methods of use illustrated inFIG. 2B address the electrode fouling and ion exchange degradation problems since the electrode chambers may not receive the contaminant ions and water splitting in the composite bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, cation membranes, anion exchange materials, and the cation exchange materials.
• One benefit of the apparatuses and methods illustrated inFIG. 2A andFIG. 2B is that it may be possible to use “harder” (i.e., higher levels of mineral compounds) liquids (i.e., water) in the input stream without damaging the apparatus or degrading the efficiency of the apparatus. Input liquids which may contain significant concentrations of calcium, magnesium, and carbonate are problematic for conventional EDI apparatuses if these cations are removed directly to the cathode chamber. In the configurations as illustrated inFIG. 2A andFIG. 2B, the cations may be removed to the CBCC at the center of the apparatus and thereby reduces the scaling within the cathode chamber.
• FIG. 2C illustrates an EDI apparatus that may be equivalent toFIG. 2A with the polarity of the electric field reversed (i.e. the anode and cathodes are switched). That is, the path from anode to cathode inFIG. 2C traverses the same EDI components in the same order as the path from cathode to anode inFIG. 2A. The apparatus illustrated inFIG. 2C comprises ananode chamber220 including an anode therein. AnACBCC222 may be placed on the cathode-side of the anode chamber. The anode chamber and the ACBCC may be separated by afirst CM221. The ACBCC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC224 may be placed on the cathode-side of the ACBCC. The ACBCC and the ADC may be separated by afirst AM223. The ADC typically includes therein a homogeneous volume of anion exchange material. ACBDC226 may be placed on the cathode-side of the ADC. The ADC and the CBDC may be separated by asecond AM225. The CBDC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC228 may be placed on the cathode-side of the CBDC. The CBDC and the CDC may be separated by asecond CM227. The CDC typically includes therein a homogeneous volume of cation exchange material. ACCBCC230 may be placed on the cathode-side of the CDC. The CDC and the CCBCC may be separated by athird CM229. The CCBCC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The CCBCC may be separated from acathode chamber232 by athird AM231. The cathode chamber includes a cathode therein. The apparatus as illustrated inFIG. 2C may be operated in continuous mode or in intermittent mode.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 2C comprises first causing the liquid to be deionized to flow through theCDC228. TheCDC228 may be capable of removing cations. TheCDC228 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through athird CM229 and into theCCBCC230. The contaminant cations may be removed from the system in theCCBCC230. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCBCC230 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC230. The anions are attracted toward the anode under the influence of the applied electric field but will not be allowed to pass through asecond CM227 into theadjacent CBDC226. Therefore, the anions will be retained in the liquid. The liquid exiting theCDC228 has a reduced level of both cations relative to the in-coming liquid stream.
• Following the passage through228, the liquid is then flowed through theADC224. TheADC224 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM223 and into theACBCC222. The contaminant anions may be removed from the system in theACBCC222. The anions are not allowed to pass through afirst CM221 that defines the anode-side of theACBCC222. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions are effectively contained in theACBCC222 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC222. Any remaining cations are largely unaffected while passing through theADC224. The liquid exiting theADC224 may be largely free of anionic contamination.
• Following the passage through224, the liquid is then flowed through theCBDC226. TheCBDC226 may be capable of effectively removing any remaining cations or anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM225 and into theADC224. The contaminant anions may be removed from the system in theACBCC222. The anions are not allowed to pass through afirst CM221 that defines the anode-side of theACBCC222 and into theanode chamber220. One benefit of this configuration is that this prevents fouling and scaling of theanode chamber220 since the anions cannot pass throughCM221 and into theanode chamber220. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC224 or contained in theACBCC222 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC222. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM227 and into theCDC228. The contaminant cations may be removed from the system in theCCBCC230. The cations are not allowed to pass through athird AM231 that defines the cathode-side of theCCBCC230 and into thecathode chamber232. One benefit of this configuration is that this prevents fouling and scaling of thecathode chamber232 since the cations cannot react with anions to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively removed in theCDC228 or contained in theCCBCC230 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC230. This design also reduces degradation in the anode chamber since anions do not enteranode chamber220.
• Water splitting occurs in theCBDC226 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC226 serves to regenerate thesecond AM225 that separates theCBDC226 from theADC224 as well as thesecond CM227 that separates theCBDC226 from theadjacent CDC228. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC228 where they may be effective in regenerating the cation exchange material contained therein andCM229. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC224 where they may be effective in regenerating the anion exchange material contained therein andAM223.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 2C comprises first causing the liquid to be deionized to flow through the ADC. TheADC224 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM223 and into theACBCC222. The contaminant anions may be removed from the system in theACBCC222. The anions are not allowed to pass through afirst CM221 that defines the anode-side of theACBCC222. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions are effectively contained in theACBCC222 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC222. Any remaining cations are largely unaffected while passing through theADC224. The liquid exiting theADC224 may be largely free of anionic contamination.
• Following the passage through224, the liquid is then flowed through theCDC228. TheCDC228 may be capable of removing cations. TheCDC228 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through athird CM229 and into theCCBCC230. The contaminant cations may be removed from the system in theCCBCC230. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCBCC230 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC230. The anions are attracted toward the anode under the influence of the applied electric field but will not be allowed to pass through asecond CM227 into theadjacent CBDC226. Therefore, the anions will be retained in the liquid. The liquid exiting theCDC228 has a reduced level of both cations and anions relative to the in-coming liquid stream.
• Following the passage through228, the liquid is then flowed through theCBDC226. TheCBDC226 may be capable of effectively removing any remaining cations or anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM225 and into theADC224 and continue throughAM223 into theACBCC222. The contaminant anions may be removed from the system in theACBCC222. The anions are not allowed to pass through afirst CM221 that defines the anode-side of theACBCC222 and into theanode chamber220. One benefit of this configuration is that this prevents fouling and scaling of theanode chamber220 since the anions cannot pass throughCM221 and enter theanode chamber220. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC224 or contained in theACBCC222 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC222. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM227 and into theCDC228 and continue throughCM229 into theCCBCC230. The contaminant cations may be removed from the system in theCCBCC230. The cations are not allowed to pass through athird AM231 that defines the cathode-side of theCCBCC230 and into thecathode chamber232. One benefit of this configuration is that this prevents fouling and scaling of thecathode chamber232 since the cations cannot react with anions to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively removed in theCDC228 or contained in theCCBCC230 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC230.
• Water splitting occurs in theCBDC226 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC226 serves to regenerate thesecond AM225 that separates theCBDC226 from theADC224 as well as thesecond CM227 that separates theCBDC226 from theadjacent CDC228. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC228 where they may be effective in regenerating the cation exchange material contained therein andCM229. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC224 where they may be effective in, regenerating the anion exchange material contained therein andAM223.
• FIG. 2D illustrates an EDI apparatus that is similar toFIG. 2C except that the ACBCC chamber has been replaced with an ACC and the CCBCC has been replaced with a CCC. The apparatus illustrated inFIG. 2D comprises ananode chamber240 including an anode therein. AnACC242 may be placed on the cathode-side of the anode chamber. The anode chamber and the ACC may be separated by afirst CM241. The ACC typically includes therein a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC244 may be placed on the cathode-side of the ACC. The ACC and the ADC may be separated by afirst AM243. The ADC may include therein a homogeneous volume of anion exchange material. ACBDC246 may be placed on the cathode-side of the ADC. The ADC and the CBDC may be separated by asecond AM245. The CBDC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC248 may be placed on the cathode-side of the CBDC. The CBDC and the CDC may be separated by asecond CM247. The CDC typically includes therein a homogeneous volume of cation exchange material. ACCC250 may be placed on the cathode-side of the CDC. The CDC and the CCC may be separated by athird CM249. The CCC may include therein a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The CCC may be separated from acathode chamber252 by athird AM251. The cathode chamber includes a cathode therein. The apparatus as illustrated inFIG. 2D may be operated in continuous mode or in intermittent mode.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 2D comprises first causing the liquid to be deionized to flow through theCDC248. TheCDC248 may be capable of removing cations. TheCDC248 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through athird CM249 and into theCCC250. The contaminant cations may be removed from the system in theCCC250. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCC250 until they are flushed from the system by the waste liquid stream that removes ions from theCCC250. The anions are attracted toward the anode under the influence of the applied electric field but will not be allowed to pass through asecond CM247 into theadjacent CBDC246. Therefore, the anions will be retained in the liquid. The liquid exiting theCDC248 has a reduced level of cations relative to the in-coming liquid stream.
• Following the passage through248, the liquid is then flowed through theADC244. TheADC244 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM243 and into theACC242. The contaminant anions may be removed from the system in theACC242. The anions are not allowed to pass through afirst CM241 that defines the anode-side of theACC242. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions are effectively contained in theACC242 until they are flushed from the system by the waste liquid stream that removes ions from theACC242. Any remaining cations are largely unaffected while passing through theADC244. The liquid exiting theADC244 may be largely free of anionic contamination.
• Following the passage through244, the liquid is then flowed through theCBDC246. TheCBDC246 may be capable of effectively removing any remaining cations or anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM245 and into theADC244. The contaminant anions may be removed from the system in theACC242. The anions are not allowed to pass through afirst CM241 that defines the anode-side of theACC242 and into theanode chamber240. One benefit of this configuration is that this prevents fouling and scaling of theanode chamber240 since the anions cannot react with cations to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC244 or contained in theACC242 until they are flushed from the system by the waste liquid stream that removes ions from theACC242. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM247 and into theCDC248. The contaminant cations may be removed from the system in theCCC250. The cations are not allowed to pass through athird AM251 that defines the cathode-side of theCCC250 and into thecathode chamber252. One benefit of this configuration is that this prevents fouling and scaling of thecathode chamber252 since the cations cannot react with anions to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively removed in theCDC248 or contained in theCCC250 until they are flushed from the system by the waste liquid stream that removes ions from theCCC250.
• Water splitting occurs in theCBDC246 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC246 serves to regenerate thesecond AM245 that separates theCBDC246 from theADC244 as well as thesecond CM247 that separates theCBDC246 from theadjacent CDC248. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC248 where they may be effective in regenerating the cation exchange material contained therein. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC244 where they may be effective in regenerating the anion exchange material contained therein.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 2D comprises first causing the liquid to be deionized to flow through the ADC. TheADC244 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM243 and into theACC242. The contaminant anions may be removed from the system in theACC242. The anions are not allowed to pass through afirst CM241 that defines the anode-side of theACC242. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions are effectively contained in theACC242 until they are flushed from the system by the waste liquid stream that removes ions from theACC242. Any remaining cations are largely unaffected while passing through theADC244. The liquid exiting theADC244 may be largely free of anionic contamination.
• Following the passage through244, the liquid is then flowed through theCDC248. TheCDC248 may be capable of removing cations. TheCDC248 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through athird CM249 and into theCCC250. The contaminant cations may be removed from the system in theCCC250. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCC250 until they are flushed from the system by the waste liquid stream that removes ions from theCCC250. The anions are attracted toward the anode under the influence of the applied electric field but will not be allowed to pass through asecond CM247 into theadjacent CBDC246. Therefore, the anions will be retained in the liquid. The liquid exiting theCDC248 has a reduced level of both cations relative to the in-coming liquid stream.
• Following the passage through248, the liquid is then flowed through theCBDC246. TheCBDC246 may be capable of effectively removing any remaining cations or anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM245 and into theADC244. The contaminant anions may be removed from the system in theACC242. The anions are not allowed to pass through afirst CM241 that defines the anode-side of theACC242 and into theanode chamber240. One benefit of this configuration is that this prevents fouling and scaling of theanode chamber240 since the anions cannot react with cations to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC244 or contained in theACC242 until they are flushed from the system by the waste liquid stream that removes ions from theACC242. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM247 and into theCDC248. The contaminant cations may be removed from the system in theCCC250. The cations are not allowed to pass through athird AM251 that defines the cathode-side of theCCC250 and into thecathode chamber252. One benefit of this configuration is that this prevents fouling and scaling of thecathode chamber252 since the cations cannot react with anions to form insoluble scaling materials (i.e., CaCO₃, Mg(OH)₂, etc.). The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively removed in theCDC248 or contained in theCCC250 until they are flushed from the system by the waste liquid stream that removes ions from theCCC250.
• Water splitting occurs in theCBDC246 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC246 serves to regenerate thesecond AM245 that separates theCBDC246 from theADC244 as well as thesecond CM247 that separates theCBDC246 from theadjacent CDC248. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and enter theadjacent CDC248 where they may be effective in regenerating the cation exchange material contained therein. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC244 where they may be effective in regenerating the anion exchange material contained therein.
• The apparatus and method of use illustrated inFIGS. 2A-D address the cathode fouling and ion exchange degradation problems common in conventional EDI apparatuses since the cathode and anode chambers may not receive the contaminant ions and water splitting in the composite or doped bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, cation membranes, anion exchange materials, and the cation exchange materials.
• By removing the CCBDC and the CM adjacent to the cathode from the apparatus ofFIG. 2A andFIG. 2B, an apparatus, with the advantages of minimal electrode fouling or electrode degradation is illustrated schematically inFIG. 3A. AnACBDC303 may be placed on the cathode-side of theanode chamber301. Theanode chamber301 and theACBDC303 may be separated by afirst AM302. The ACBDC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC305 may be placed on the cathode-side of theACBDC303. TheACBDC303 and theCDC305 may be separated by afirst CM304. The CDC typically includes therein a homogeneous volume of cation exchange material. ACBCC307 may be placed on the cathode-side of theCDC305. TheCDC305 and theCBCC307 may be separated by asecond CM306. The CBCC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC309 may be placed on the cathode-side of theCBCC307. TheCBCC307 and theADC309 may be separated by asecond AM308. The ADC typically includes therein a homogeneous volume of anion exchange material. TheADC309 may be separated from acathode chamber311 by athird AM310. The cathode chamber includes a cathode therein.
• InFIG. 3A, the majority of the contaminant ions may be drawn into theCBCC307. TheACBDC303 may serve as the final ion depletion chamber. As the product liquid passes through theACBDC303, residual contaminant anions may be removed into theanode chamber301. Since the majority of contaminant anions may be removed by theADC309, the trace amounts of residual anions removed by theACBDC303 and into theanode chamber301 will not cause significant electrode degradation. The apparatus as illustrated inFIG. 3A may be operated in continuous mode or in intermittent mode.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 3A comprises first causing the liquid to be deionized to flow through theCDC305. The CDC may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through a secondcation exchange membrane306 and into theCBCC307. The contaminant cations may be removed from the system in theCBCC307. The cations are not allowed to pass through asecond AM308 that defines the cathode-side of theCBCC307. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC307 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC307. The liquid exiting theCDC305 may be largely free of cationic contamination.
• Following the passage through305, the liquid is then flowed through theADC309. TheADC309 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through a secondanion exchange membrane308 and into theCBCC307. The contaminant anions may be removed from the system in theCBCC307. The anions are not allowed to pass through asecond CM306 that defines the anode-side of theCBCC307 and into theCDC305. One benefit of this configuration is that this prevents degradation of theanode chamber301 since anions cannot enter the anode chamber. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC309 or contained in theCBCC307 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC307. The liquid exiting theADC309 may be largely free of anionic contamination.
• Following the passage through309, the liquid is then flowed through theACBDC303. TheACBDC303 may be capable of removing both anions and cations. The remaining anions are attracted to theadjacent anode chamber301 under the influence of the applied electric field and may be allowed to pass through afirst AM302 and may be removed from the liquid. The remaining cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM304 into theadjacent CDC305. TheCDC305 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through a secondcation exchange membrane306 and into theCBCC307. The contaminant cations may be removed from the system in theCBCC307. The cations are not allowed to pass through asecond AM308 that defines the cathode-side of theCBCC307. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC307 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC307. The liquid exiting theACBDC303 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theACBDC303 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theACBDC303 may serve to regenerate thefirst AM302 that separates theACBDC303 from theanode chamber301 as well as thefirst CM304 that separates theACBDC303 from theadjacent CDC305. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC305 where they may be effective in regenerating the cation exchange material contained therein.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 3A comprises first causing the liquid to be deionized to flow through theADC309. TheADC309 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM308 and into theCBCC307. The contaminant anions may be removed from the system in theCBCC307. The anions are not allowed to pass through asecond CM306 that defines the anode-side of theCBCC307 and into theCDC305. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC309 or contained in theCBCC307 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC307. The liquid exiting theADC309 may be largely free of anionic contamination.
• Following the passage through309, the liquid is then flowed through theCDC305. TheCDC305 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM306 and into theCBCC307. The contaminant cations may be removed from the system in theCBCC307. The cations are not allowed to pass through asecond AM308 that defines the cathode-side of theCBCC307. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC307 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC307. The liquid exiting theCDC305 may be largely free of cationic contamination.
• Following the passage through305, the liquid is then flowed through theACBDC303. TheACBDC303 may be capable of removing both anions and cations. The remaining anions are attracted to theadjacent anode chamber301 under the influence of the applied electric field and may be allowed to pass through afirst AM302 and may be removed from the liquid. The remaining cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM304 into theadjacent CDC305. TheCDC305 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM306 and into theCBCC307. The contaminant cations may be removed from the system in theCBCC307. The cations are not allowed to pass through asecond AM308 that defines the cathode-side of theCBCC307. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC307 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC307. The liquid exiting theACBDC303 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theACBDC303 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theACBDC303 may serve to regenerate theAM302 that separates theACBDC303 from theanode chamber301 as well as thefirst CM304 that separates theACBDC303 from theadjacent CDC305. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC305 where they may be effective in regenerating the cation exchange material contained therein.
• FIG. 3B illustrates an EDI apparatus that may be equivalent toFIG. 3A with the polarity of the electric field reversed (i.e. the anode and cathodes are switched). That is, the path from anode to cathode inFIG. 3B traverses the same EDI components in the same order as the path from cathode to anode inFIG. 3A. The apparatus illustrated inFIG. 3B comprises ananode chamber320. The anode chamber includes an anode therein. AnADC322 may be placed on the cathode-side of theanode chamber320. Theanode chamber320 and theADC322 may be separated by afirst AM321. The ADC typically includes therein a homogeneous volume of anion exchange material. ACBDC324 may be placed on the cathode-side of theADC322. TheADC322 and theCBDC324 may be separated by asecond AM323. The CBDC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC326 may be placed on the cathode-side of theCBDC324. TheCBDC324 and theCDC326 may be separated by afirst CM325. The CDC typically includes therein a homogeneous volume of cation exchange material. ACCBCC328 may be placed on the cathode-side of theCDC326. TheCDC326 may be separated from theCCBCC328 by asecond CM327. TheCCBCC328 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. TheCCBCC328 may be separated from thecathode chamber330 by athird AM329. The cathode chamber includes a cathode therein.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 3B comprises first causing the liquid to be deionized to flow through theCDC326. The CDC may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through a secondcation exchange membrane327 and into theCCBCC328. The contaminant cations may be removed from the system in theCCBCC328. The cations are not allowed to pass through athird AM329 that defines the cathode-side of theCCBCC328. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCBCC328 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC328. The liquid exiting theCDC326 may be largely free of cationic contamination.
• Following the passage through326, the liquid is then flowed through theADC322. TheADC322 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM321 and into theanode chamber320. The contaminant anions may be removed from the system in theanode chamber320. The cations are not allowed to pass through asecond AM323 that defines the cathode-side of theADC322 and into theCBDC324. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC322. The liquid exiting theADC322 may be largely free of anionic contamination.
• Following the passage through322, the liquid is then flowed through theCBDC324. TheCBDC324 may be capable of removing both anions and cations. The remaining anions are attracted to theadjacent ADC322 under the influence of the applied electric field and may be allowed to pass through asecond AM323 and may be removed from the liquid. The remaining cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM325 into theadjacent CDC326. TheCDC326 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through a secondcation exchange membrane327 and into theCCBCC328. The contaminant cations may be removed from the system in theCCBCC328. The cations are not allowed to pass through athird AM329 that defines the cathode-side of theCCBCC328. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCBCC328 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC328. The liquid exiting theCBDC324 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC324 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC324 may serve to regenerate thesecond AM323 that separates theADC322 from theCBDC324 as well as thefirst CM325 that separates theCBDC324 from theadjacent CDC326. Hydroxide ions generated by the water splitting are attracted to the anode and may enter theadjacent ADC322 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC326 where they may be effective in regenerating the cation exchange material contained therein.
• InFIG. 3B, cations may be drawn into theCCBCC328 and are removed from the system by the waste liquid stream. TheCBDC324 may serve as the final ion depletion chamber. The apparatus as illustrated inFIG. 3B may be operated in continuous mode or in intermittent mode.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 3B comprises first causing the liquid to be deionized to flow through theADC322. TheADC322 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM321 and into theanode chamber320. The contaminant anions may be removed from the system in theanode chamber320. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC322 or contained in theanode chamber320 until they are flushed from the system by the waste liquid stream that removes ions from theanode chamber320. The liquid exiting theADC322 may be largely free of anionic contamination.
• Following the passage through322, the liquid is then flowed through theCDC326. TheCDC326 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM327 and into theCCBCC328. The contaminant cations may be removed from the system in theCCBCC328. The cations are not allowed to pass through athird AM329 that defines the cathode-side of theCCBCC328. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCBCC328 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC328. The liquid exiting theCDC326 may be largely free of cationic contamination.
• Following the passage through326, the liquid is then flowed through theCBDC324. TheCBDC324 may be capable of removing both anions and cations. The remaining anions are attracted to theadjacent ADC322 under the influence of the applied electric field and may be allowed to pass through asecond AM321 and may be removed from the liquid. The remaining anions may then pass throughAM321 and intoanode chamber320. The remaining cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM325 into theadjacent CDC326. TheCDC326 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM327 and into theCCBCC328. The contaminant cations may be removed from the system in theCCBCC328. The cations are not allowed to pass through athird AM329 that defines the cathode-side of theCCBCC328. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCBCC328 until they are flushed from the system by the waste liquid stream that removes ions from theCCBCC328. The liquid exiting theCBDC324 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC324 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC324 may serve to regenerate thesecond AM323 that separates theCBDC324 from theADC322 andAM321 as well as thefirst CM325 that separates theCBDC324 from theadjacent CDC326 andCM327. Hydroxide ions generated by the water splitting are attracted to the anode and may enter theadjacent ADC322 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC326 where they may be effective in regenerating the cation exchange material contained therein.
• The apparatus illustrated inFIG. 3C comprises ananode chamber340. The anode chamber includes an anode therein. AnADC342 may be placed on the cathode-side of theanode chamber340. Theanode chamber340 and theADC342 may be separated by afirst AM341. The ADC typically includes therein a homogeneous volume of anion exchange material. ACBDC344 may be placed on the cathode-side of theADC342. TheADC342 and theCBDC344 may be separated by asecond AM343. The CBDC may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC346 may be placed on the cathode-side of theCBDC344. TheCBDC344 and theCDC346 may be separated by afirst CM345. The CDC typically includes therein a homogeneous volume of cation exchange material. ACCC348 may be placed on the cathode-side of theCDC346. TheCDC346 may be separated from theCCC348 by asecond CM347. TheCCC348 may include therein a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. TheCCC348 may be separated from thecathode chamber350 by athird AM349. The cathode chamber includes a cathode therein.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 3C comprises first causing the liquid to be deionized to flow through theCDC346. The CDC may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through a secondcation exchange membrane347 and into theCCC348. The contaminant cations may be removed from the system in theCCC348. The cations are not allowed to pass through athird AM349 that defines the cathode-side of theCCC348. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCC348 until they are flushed from the system by the waste liquid stream that removes ions from theCCC348. The liquid exiting theCDC346 may be largely free of cationic contamination.
• Following the passage through346, the liquid is then flowed through theADC342. TheADC342 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM341 and into theanode chamber340. The contaminant anions may be removed from the system in theanode chamber340. The cations are not allowed to pass through asecond AM343 that defines the cathode-side of theADC342 and into theCBDC344. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC342. The liquid exiting theADC342 may be largely free of anionic contamination.
• Following the passage through342, the liquid is then flowed through theCBDC344. TheCBDC344 may be capable of removing both anions and cations. The remaining anions are attracted to theadjacent ADC342 under the influence of the applied electric field and may be allowed to pass through asecond AM343 intoADC342 and may pass throughAM341 intoanode chamber340 and may be removed from the liquid. The remaining cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM345 into theadjacent CDC346. TheCDC346 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM347 and into theCCC348. The contaminant cations may be removed from the system in theCCC348. The cations are not allowed to pass through athird AM349 that defines the cathode-side of theCCC348. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCC348 until they are flushed from the system by the waste liquid stream that removes ions from theCCC348. The liquid exiting theCBDC344 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC344 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC344 may serve to regenerate thesecond AM343 that separates thefirst ADC342 from theCBDC344 as well as thefirst CM345 that separates theCBDC344 from theadjacent CDC346. Hydroxide ions generated by the water splitting are attracted to the anode and may enter the adjacent ADC first342 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC346 where they may be effective in regenerating the cation exchange material contained therein.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 3C comprises first causing the liquid to be deionized to flow through theADC342. TheADC342 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM341 and into theanode chamber340. The contaminant anions may be removed from the system in theanode chamber340. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC342 or contained in theanode chamber340 until they are flushed from the system by the waste liquid stream that removes ions from theanode chamber340. The liquid exiting theADC342 may be largely free of anionic contamination.
• Following the passage through342, the liquid is then flowed through theCDC346. TheCDC346 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM347 and into theCCC348. The contaminant cations may be removed from the system in theCCC348. The cations are not allowed to pass through athird AM349 that defines the cathode-side of theCCC348. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCC348 until they are flushed from the system by the waste liquid stream that removes ions from theCCC348. The liquid exiting theCDC346 may be largely free of cationic contamination.
• Following the passage through346, the liquid is then flowed through theCBDC344. TheCBDC344 may be capable of removing both anions and cations. The remaining anions are attracted to theadjacent ADC342 under the influence of the applied electric field and may be allowed to pass through asecond AM343 and may be removed from the liquid. The remaining cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through afirst CM345 into theadjacent CDC346. TheCDC346 typically includes therein cation exchange materials and may be effective at removing the contaminant cations. The cations may be allowed to pass through asecond CM347 and into theCCC348. The contaminant cations may be removed from the system in theCCC348. The cations are not allowed to pass through athird AM349 that defines the cathode-side of theCCC348. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCCC348 until they are flushed from the system by the waste liquid stream that removes ions from theCCC348. The liquid exiting theCBDC344 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC344 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC344 may serve to regenerate thesecond AM343 that separates theCBDC344 from theADC342 as well as thefirst CM345 that separates theCBDC344 from theadjacent CDC346. Hydroxide ions generated by the water splitting are attracted to the anode and may enter theadjacent ADC342 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC346 where they may be effective in regenerating the cation exchange material contained therein.
• The apparatus and methods of use illustrated inFIG. 3A-C address the electrode fouling and ion exchange degradation problems since the electrode chambers receive a reduced quantity of the contaminant ions and water splitting in the composite bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, cation membranes, and the cation exchange materials. As was discussed for the apparatus illustrated inFIG. 2A andFIG. 2B, theCBCC207 may be used to remove the cations and thus minimizes scaling in the cathode chamber.
• Similar apparatuses toFIG. 3A-C are illustrated inFIGS. 4A-C. In the apparatus illustrated inFIG. 4A, the ACBDC and the AM adjacent to the anode from the apparatus ofFIG. 2A andFIG. 2B have been removed.
• The apparatus illustrated inFIG. 4A comprises ananode chamber401. ACDC403 may be placed on the cathode-side of theanode chamber401. Theanode chamber401 and theCDC403 may be separated by afirst CM402. TheCDC403 typically includes therein a homogeneous volume of cation exchange material. ACBCC405 may be placed on the cathode-side of theCDC403. TheCDC403 and theCBCC405 may be separated by asecond CM404. TheCBCC405 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC407 may be placed on the cathode-side of theCBCC405. TheCBCC405 and theADC407 may be separated by afirst AM406. TheADC407 typically includes therein a homogeneous volume of anion exchange material. ACCBDC409 may be placed on the cathode-side of theADC407. TheADC407 and theCCBDC409 may be separated by asecond AM408. TheCCBDC409 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. TheCCBDC409 may be separated from acathode chamber411 by athird CM410. The cathode chamber includes a cathode therein.
• This results in an apparatus with the advantages of minimal electrode fouling or electrode degradation. TheCCBDC409 may act as the final ion depletion chamber for the product liquid. Most contaminant ions may be removed into theCBCC405. Any cations present in the product liquid after theADC407 may be removed by theCCBDC409 and exit into the cathode chamber. Since the quantity of cations being removed into the cathode chamber may be very small, scaling in the cathode chamber may be insignificant.
• The apparatus illustrated inFIG. 4A is also advantageous when deionizing liquids with high concentrations of chloride ions. In conventional EDI apparatuses where the anions may be removed through the anode chamber, oxidation may occur wherein chloride may be oxidized to chlorine, chlorite, and hypochlorite among others. This may cause degradation of the EDI apparatus. The configuration as illustrated inFIG. 4A may remove the majority of the anions through the CBCC chamber, thus resolving the issues present in most conventional EDI apparatuses. The apparatus as illustrated inFIG. 4A may be operated in continuous mode or in intermittent mode.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 4A comprises first causing the liquid to be deionized to flow through theCDC403. TheCDC403 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM404 and into theCBCC405. The contaminant cations may be removed from the system in theCBCC405. The cations are not allowed to pass through afirst AM406 that defines the cathode-side of theCBCC405. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC405 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC405. The liquid exiting theCDC403 may be largely free of cationic contamination.
• Following the passage through403, the liquid is then flowed through theADC407. TheADC407 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM406 and into theCBCC405. The contaminant anions may be removed from the system in theCBCC405. The anions are not allowed to pass through asecond CM404 that defines the anode-side of theCBCC405 and into theCDC403. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC407 or contained in theCBCC405 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC405. The liquid exiting theADC407 may be largely free of anionic contamination.
• Following the passage through407, the liquid is then flowed through theCCBDC409. TheCCBDC409 may be capable of removing both anions and cations. The remaining cations are attracted to theadjacent cathode chamber411 under the influence of the applied electric field and may be allowed to pass through athird CM410 and may be removed from the liquid. The remaining anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through asecond AM408 into theadjacent ADC407. TheADC407 typically includes therein anion exchange materials and may be effective at retaining the contaminant anions. The anions may be allowed to pass through afirst AM406 and into theCBCC405. The contaminant anions may be removed from the system in theCBCC405. The anions are not allowed to pass through asecond CM404 that defines the anode-side of theCBCC405. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC407 or contained in theCBCC405 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC405. The liquid exiting theCCBDC409 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCCBDC409 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCCBDC409 may serve to regenerate thethird CM410 that separates theCCBDC409 from thecathode chamber411 as well as thesecond AM408 that separates theCCBDC409 from theadjacent ADC407. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC407 where they may be effective in regenerating the anion exchange material contained therein.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 4A comprises first causing the liquid to be deionized to flow through theADC407. TheADC407 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM406 and into theCBCC405. The contaminant anions may be removed from the system in theCBCC405. The anions are not allowed to pass through asecond CM404 that defines the anode-side of theCBCC405 and into theCDC403. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC407 or contained in theCBCC405 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC405. The liquid exiting theADC407 may be largely free of anionic contamination.
• Following the passage through407, the liquid is then flowed through theCDC403. TheCDC403 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM404 and into theCBCC405. The contaminant cations may be removed from the system in theCBCC405. The cations are not allowed to pass through afirst AM406 that defines the cathode-side of theCBCC405. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC405 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC405. The liquid exiting theCDC403 may be largely free of cationic contamination.
• Following the passage through403, the liquid is then flowed through theCCBDC409. TheCCBDC409 may be capable of removing both anions and cations. The remaining cations are attracted to theadjacent cathode chamber411 under the influence of the applied electric field and may be allowed to pass through athird CM410 and may be removed from the liquid. The remaining anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through asecond AM408 into theadjacent ADC407. TheADC407 typically includes therein anion exchange materials and may be effective at retaining the contaminant anions. The anions may be allowed to pass through afirst AM406 and into theCBCC405. The contaminant anions may be removed from the system in theCBCC405. The anions are not allowed to pass through asecond CM404 that defines the anode-side of theCBCC405. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC407 or contained in theCBCC405 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC405. The liquid exiting theCCBDC409 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCCBDC409 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCCBDC409 may serve to regenerate thethird CM410 that separates theCCBDC409 from the cathode chamber as well as thesecond AM408 that separates theCCBDC409 from theadjacent ADC407. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC407 where they may be effective in regenerating the anion exchange material contained therein.
Example 3
• An EDI device as shown inFIG. 4A was constructed using machined high density polyethylene hardware to retain the electrodes, membranes and resin. The internal flow dimensions of theADC407 were 1.27 cm in diameter and 3.81 cm in length. The internal flow dimensions of theCBCC405 were 1.27 cm in diameter and 1.27 cm in length. The internal flow dimensions of theCDC403 were 1.27 cm in diameter and 3.81 cm in length. The internal flow dimensions of theCCBDC409 were 1.27 cm (diameter) and 1.27 cm (length). All cation materials were in the hydronium form and all anion materials were in the hydroxide form.
• Theanode chamber401, for this example, contained platinum gauze electrodes (Unique Wire Weaving Inc, Hillside, N.J.). In contact with the anode and separating theanode chamber401 from theADC403 was a cation exchange membrane402 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). TheCDC403 was filled with a cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.). Separating theCDC403 from theCBCC405 was a cation exchange membrane404 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). TheCBCC405 chamber contained a mixture of cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) and anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.). The ion exchange capacity ratio of anion to cation was 1:1 (a mixed bed). The cation resin and anion resin were in the in the hydronium and hydroxide forms, respectively. TheCBCC405 was separated from theADC407 by an anion membrane406 (AMI-7001, a product of Membranes International, Glen Rock, N.J.). TheADC407 was filled with an anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.). TheADC407 was separated from theCCBDC409 by an anion exchange membrane408 (AMI-7001, a product of Membranes International, Glen Rock, N.J.). TheCCBDC409 was filled contains a mixture of cation exchange resin (DOWEX™ 50W×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) and anion exchange resin (DOWEX™ 1×4 (200 mesh), a product of The Dow Chemical Company, Midland, Mich.) in the hydronium and hydroxide forms, respectively. The ion exchange capacity ratio of anion to cation was 1:2 (a doped cation bed). Separating theCCBDC409 from thecathode chamber411 was a cation exchange membrane410 (CMI-7000, a product of Membranes International, Glen Rock, N.J.). A pump (GP40, a product of Dionex, Sunnyvale, Calif.) was use to deliver RO quality water (specific conductance 10.7 μs/cm) at a flow rate of 2.0 mL/min to the EDI device shown inFIG. 4. A conductivity detector (CD20, a product of Dionex, Sunnyvale, Calif.) with a flow cell was used for the conductivity measurements. From the pump, the RO water flow was directed to theCDC403, then to theADC407, next to theCCBDC409 and then to the flow through conductivity cell. From the conductivity cell, the flow was directed to theanode chamber401 and then thecathode chamber411 and finally to waste.
• Initially, the conductance of the water exiting the EDI device was 2.2 μS/cm. Using a laboratory power supply (E3612A, a product of Agilent, Santa Clara, Calif.) a constant current of 40 mA was applied and the initial voltage was 48V. Gas evolution was observed immediately from the anode and cathode chambers. The initial background conductivity of the product water increased to 48 μS/cm and over a 1 hour period the conductivity decreased to 0.67 μS/cm. The EDI device was allowed to operate continuously for 9 days. The data in Table 3 shows results for the device ofFIG. 4.

• TABLE 3
  Conductance Measurements vs. Time

  		Conductivity
  Hours	Voltage	(μS/cm)

  0.0	0.0	2.2
  1	41	0.67
  2	37	0.23
  10	32	0.079
  24	20	0.062
  48	22	0.071
  72	24	0.059
  96	24	0.055
  120	26	0.055
  144	27	0.056
  168	26	0.055
  192	27	0.055
  216	28	0.057

• FIG. 4B illustrates an EDI apparatus that may be equivalent toFIG. 4A with the polarity of the electric field reversed (i.e. the anode and cathodes are switched). That is, the path from anode to cathode inFIG. 4B traverses the same EDI components in the same order as the path from cathode to anode inFIG. 4A. The apparatus illustrated inFIG. 4B comprises ananode chamber420. The anode chamber includes an anode therein. AnACBCC422 may be placed on the cathode-side of theanode chamber420. Theanode chamber420 and theACBCC422 may be separated by afirst CM421. TheACBCC422 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC424 may be placed on the cathode-side of theACBCC422. TheACBCC422 and theADC424 may be separated by afirst AM423. TheADC424 typically includes therein a homogeneous volume of anion exchange material. ACBDC426 may be placed on the cathode-side of theADC424. TheADC424 and theCBDC426 may be separated by asecond AM425. TheCBDC426 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC428 may be placed on the cathode-side of theCBDC426. TheCBDC426 and theCDC428 may be separated by asecond CM427. TheCDC428 typically includes therein a homogeneous volume of cation exchange material. TheCDC428 may be separated from acathode chamber430 by athird CM429. The cathode chamber includes a cathode therein.
• This results in an apparatus with the advantages of minimal anode fouling or anode degradation. TheCBDC426 may act as the final ion depletion chamber for the product liquid. Most contaminant anions may be removed into theACBCC422. Any cations present in the product liquid after theCDC428 may be removed by theCBDC426.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 4B comprises first causing the liquid to be deionized to flow through theCDC428. TheCDC428 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through athird CM429 and into thecathode chamber430. The contaminant cations may be removed from the system in thecathode chamber430. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in thecathode chamber430 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber430. The liquid exiting theCDC428 may be largely free of cationic contamination.
• Following the passage through428, the liquid is then flowed through theADC424. TheADC424 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM423 and into theACBCC422. The contaminant anions may be removed from the system in theACBCC422. The anions are not allowed to pass through afirst CM421 that defines the anode-side of theACBCC422 and into theanode chamber420. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC424 or contained in theACBCC422 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC422. The liquid exiting theADC424 may be largely free of anionic contamination.
• Following the passage through424, the liquid is then flowed through theCBDC426. TheCBDC426 may be capable of removing both anions and cations. The remaining cations are attracted to thecathode chamber430 under the influence of the applied electric field and may be allowed to pass through asecond CM427 and into theCDC428. The remaining anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through asecond AM425 into theadjacent ADC424. TheADC424 typically includes therein anion exchange materials and may be effective at retaining the contaminant anions. The anions may be allowed to pass through afirst AM423 and into theACBCC422. The contaminant anions may be removed from the system in theACBCC422. The anions are not allowed to pass through afirst CM421 that defines the anode-side of theACBCC422. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC424 or contained in theACBCC422 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC422. The liquid exiting theCBDC426 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC426 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC426 may serve to regenerate thesecond CM427 that separates theCBDC426 from theCDC428 as well as thesecond AM425 that separates theCBDC426 from theadjacent ADC424. Hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC424 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC428 where they may be effective in regenerating the cation exchange material contained therein.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 4B comprises first causing the liquid to be deionized to flow through theADC424. TheADC424 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM423 and into theACBCC422. The contaminant anions may be removed from the system in theACBCC422. The anions are not allowed to pass through afirst CM421 that defines the anode-side of theACBCC422 and into theanode chamber420. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC424 or contained in theACBCC422 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC422. The liquid exiting theADC424 may be largely free of anionic contamination.
• Following the passage through424, the liquid is then flowed through theCDC428. TheCDC428 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through athird CM429 and into thecathode chamber430. The contaminant cations may be removed from the system in thecathode chamber430. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in thecathode chamber430 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber430. The liquid exiting theCDC428 may be largely free of cationic contamination.
• Following the passage through428, the liquid is then flowed through theCBDC426. TheCBDC426 may be capable of removing both anions and cations. The remaining cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM427 and into theadjacent CDC428. The remaining anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through asecond AM425 into theadjacent ADC424. TheADC424 typically includes therein anion exchange materials and may be effective at retaining the contaminant anions. The anions may be allowed to pass through afirst AM423 and into theACBCC422. The contaminant anions may be removed from the system in theACBCC422. The anions are not allowed to pass through afirst CM421 that defines the anode-side of theACBCC422. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC424 or contained in theACBCC422 until they are flushed from the system by the waste liquid stream that removes ions from theACBCC422. The liquid exiting theCBDC426 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC426 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC426 may serve to regenerate thesecond CM427 that separates theCBDC426 from theCDC428 as well as thesecond AM425 that separates theCBDC426 from theadjacent ADC424. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC424 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC428 where they may be effective in regenerating the cation exchange material contained therein.
• The apparatus illustrated inFIG. 4C comprises ananode chamber440. The anode chamber includes an anode therein. AnACC442 may be placed on the cathode-side of theanode chamber440. Theanode chamber440 and theACC442 may be separated by afirst CM441. TheACC442 may include therein a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC444 may be placed on the cathode-side of theACC442. TheACC442 and theADC444 may be separated by afirst AM443. TheADC444 typically includes therein a homogeneous volume of anion exchange material. ACBDC446 may be placed on the cathode-side of theADC444. TheADC444 and theCBDC446 may be separated by asecond AM445. TheCBDC446 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC448 may be placed on the cathode-side of theCBDC446. TheCBDC446 and theCDC448 may be separated by asecond CM447. TheCDC448 typically includes therein a homogeneous volume of cation exchange material. TheCDC448 may be separated from acathode chamber450 by athird CM449. The cathode chamber includes a cathode therein.
• This results in an apparatus with the advantages of minimal anode fouling or anode degradation. TheCBDC446 may act as the final ion depletion chamber for the product liquid. Most contaminant anions may be removed into theACC442. Any cations present in the product liquid after theCDC448 may be removed by theCBDC446.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 4C comprises first causing the liquid to be deionized to flow through theCDC448. TheCDC448 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through athird CM449 and into thecathode chamber450. The contaminant cations may be removed from the system in thecathode chamber450. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in thecathode chamber450 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber450. The liquid exiting theCDC448 may be largely free of cationic contamination.
• Following the passage through448, the liquid is then flowed through theADC444. TheADC444 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM443 and into theACC442. The contaminant anions may be removed from the system in theACC442. The anions are not allowed to pass through afirst CM441 that defines the anode-side of theACC442 and into theanode chamber440. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC444 or contained in theACC442 until they are flushed from the system by the waste liquid stream that removes ions from theACC442. The liquid exiting theADC444 may be largely free of anionic contamination.
• Following the passage through444, the liquid is then flowed through theCBDC446. TheCBDC446 may be capable of removing both anions and cations. The remaining cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM447 and into theCDC448. The remaining anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through asecond AM445 into theadjacent ADC444. TheADC444 typically includes therein anion exchange materials and may be effective at retaining the contaminant anions. The anions may be allowed to pass through afirst AM443 and into theACC442. The contaminant anions may be removed from the system in theACC442. The anions are not allowed to pass through afirst CM441 that defines the anode-side of theACC442. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC444 or contained in theACC442 until they are flushed from the system by the waste liquid stream that removes ions from theACC442. The liquid exiting theCBDC446 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC446 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC446 may serve to regenerate thesecond CM447 that separates theCBDC446 from theCDC448 as well as thesecond AM445 that separates theCBDC446 from theadjacent ADC444. Hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC444 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC448 where they may be effective in regenerating the cation exchange material contained therein.
• Another method (not shown) for performing electrodeionization utilizing the apparatus as illustrated inFIG. 4C comprises first causing the liquid to be deionized to flow through theADC444. TheADC444 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through afirst AM443 and into theACC442. The contaminant anions may be removed from the system in theACC442. The anions are not allowed to pass through afirst CM441 that defines the anode-side of theACC442 and into theanode chamber440. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC444 or contained in theACC442 until they are flushed from the system by the waste liquid stream that removes ions from theACC442. The liquid exiting theADC444 may be largely free of anionic contamination.
• Following the passage through444, the liquid is then flowed through theCDC448. TheCDC448 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through athird CM449 and into thecathode chamber450. The contaminant cations may be removed from the system in thecathode chamber450. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in thecathode chamber450 until they are flushed from the system by the waste liquid stream that removes ions from thecathode chamber450. The liquid exiting theCDC448 may be largely free of cationic contamination.
• Following the passage through448, the liquid is then flowed through theCBDC446. TheCBDC446 may be capable of removing both anions and cations. The remaining cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM447 and into theadjacent CDC448. The remaining anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through asecond AM445 into theadjacent ADC444. TheADC444 typically includes therein anion exchange materials and may be effective at retaining the contaminant anions. The anions may be allowed to pass through afirst AM443 and into theACC442. The contaminant anions may be removed from the system in theACC442. The anions are not allowed to pass through afirst CM441 that defines the anode-side of theACC442. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theADC444 or contained in theACC442 until they are flushed from the system by the waste liquid stream that removes ions from theACC442. The liquid exiting theCBDC446 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCBDC446 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCBDC446 may serve to regenerate thesecond CM447 that separates theCBDC446 from theCDC448 as well as thesecond AM445 that separates theCBDC446 from theadjacent ADC444. Additionally, hydroxide ions generated by the water splitting are attracted to the anode and enter theadjacent ADC444 where they may be effective in regenerating the anion exchange material contained therein. Additionally, hydronium ions generated by the water splitting are attracted to the cathode and may enter theadjacent CDC448 where they may be effective in regenerating the cation exchange material contained therein.
• The apparatus and methods of use illustrated inFIGS. 4A-C address the electrode fouling and ion exchange degradation problems since the electrode chambers may receive a reduced quantity of the contaminant ions and water splitting in the composite bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, cation membranes, anion exchange materials, and the cation exchange materials.
• In summary, the EDI apparatuses shown inFIGS. 2,3, and4 offer the advantages of homogeneous ion depletion chambers for enhanced ion removal, at least one composite bed depletion chamber for the final removal (“polishing”) of trace ionic contaminants, at least one concentrate chamber for removal of ions, reduced electrode fouling or chemical degradation of ion exchange materials in the vicinity of the electrodes, and a simple design requiring only a single pair of electrodes.
• In some applications, it may be desirable to remove a selective group of ions such as anion or cations, but the complete removal of both types of ions is not required. In this case, a simplified apparatus may be employed. The following discussion describes dual depletion chamber electrodeionization apparatuses which may be particularly configured for selective ion removal and may be interfaced directly to chemical analyzers or other analytical instrumentation.
• Previously, multi depletion chamber apparatuses for the production of ultra pure liquid were discussed. These apparatuses comprised three or more discreet ion depletion chambers. In these configurations, these apparatuses combined the advantages of homogeneous ion exchange beds for enhanced ion removal, composite ion exchange bed(s) for the final removal of trace ionic contaminants, concentrate chamber(s) for removal of ions, and a simple design requiring only a single pair of electrodes. The apparatuses in the previous discussion contained at least one cation, at least one anion, at least one composite depletion, and at least one concentrate chambers.
• Another embodiment of the present invention is illustrated inFIG. 5. The apparatus illustrated inFIG. 5 comprises ananode chamber501 including an anode therein. AnADC503 may be placed on the cathode-side of theanode chamber501. Theanode chamber501 and theADC503 may be separated by afirst AM502. TheADC503 typically includes therein a homogeneous volume of anion exchange material. ACCBDC505 may be placed on the cathode-side of theADC503. TheCCBDC505 and theADC503 may be separated by asecond AM504. TheCCBDC505 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. TheCCBDC505 may be separated from acathode chamber507 by aCM506. Thecathode chamber507 typically includes a cathode therein. The apparatus as illustrated inFIG. 5 may be operated in continuous mode or in intermittent mode.
• A method for performing electrodeionization utilizing the apparatus is illustrated inFIG. 5. The liquid may be initially directed through theADC503. TheADC503 typically includes therein an inlet and an outlet port. The inlet and outlet ports may be configured so that the liquid may travel through substantially all of the length of theADC503. The inlet port is positioned closest to thefirst AM502 to minimize the distance the anions must travel under the force of the electric field into theanode chamber501. This typically maximizes the interaction between the liquid and the anion exchange material. TheADC503 may remove most of the anions from the liquid. The anions will be attracted toward the anode by the applied electric field. The anions may be allowed to pass through thefirst AM502 and into theanode chamber501 where they may be removed by the waste stream used to flush theanode chamber501. Cations will be retained within the liquid. Although the cations will be attracted toward the cathode by the applied electric field, they will not be allowed to pass through thesecond AM504 of the cathode-side of theADC503.
• Following the passage through503, the liquid then passes through theCCBDC505 where both anions and cations may be removed from the liquid. The cations will be attracted toward the cathode by the applied electric field. The cations may pass through theCM506 and into thecathode chamber507 where they may be removed from the system. The anions will be attracted toward the anode by the applied electric field. The anions may pass through thesecond AM504, through theADC503, through thefirst AM502 and into theanode chamber501 where they may be removed from the system. The apparatus ofFIG. 5 may produce liquid with significantly reduced levels of anions and reduced levels of cations.
• TheCM506,ADC503,first AM502, andsecond AM504 illustrated inFIG. 5 may be regenerated by water splitting that occurs within theCCBDC505. Hydroxide ions will be attracted toward the anode by the applied electric field and may regenerate theADC503,first AM502, andsecond AM504 as they travel toward the anode. TheCM506 may be regenerated by water splitting that occurs within theCCBDC505. Hydronium ions will be attracted toward the cathode by the applied electric field and may regenerate theCM506 as they travel toward the cathode.
• The apparatus as illustrated inFIG. 5 is thus capable of being used in a manner that renders it suitable for deionization, especially anion removal, for low ionic strength liquids. Examples of low ionic strength liquids include water that has received reverse osmosis, distillation, or prior deionization treatment. The apparatus as illustrated inFIG. 5 is thus capable of producing a liquid with very low concentrations of anions and thus may be suitable for purifying liquids for use in analytical techniques such as ion chromatography, inductively coupled plasma mass spectrometry, and atomic absorption spectroscopy, among others.
• Another embodiment of the present invention is illustrated inFIG. 6. The apparatus illustrated inFIG. 6 comprises ananode chamber601 including an anode therein. AnACBDC603 may be placed on the cathode-side of theanode chamber601. Theanode chamber601 and theACBDC603 may be separated by anAM602. TheACBDC603 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACDC605 may be placed on the cathode-side of theACBDC603. TheCDC605 and theACBDC603 may be separated by afirst CM604. TheCDC605 typically includes therein a homogeneous volume of cation exchange material. TheCDC605 may be separated from acathode chamber607 by asecond CM606. Thecathode chamber607 typically includes a cathode therein. The apparatus as illustrated inFIG. 6 may be operated in continuous mode or in intermittent mode.
• A method for performing electrodeionization utilizing the apparatus is illustrated inFIG. 6. The liquid may be initially directed through theCDC605. TheCDC605 typically includes therein an inlet and an outlet port. The inlet and outlet ports are configured so that the liquid may travel through substantially all of the length of theCDC605. The inlet port is positioned closest to thesecond CM606 to minimize the distance the cations must travel under the force of the electric field into thecathode chamber607. This typically maximizes the interaction between the liquid and the cation exchange material. TheCDC605 may remove most of the cations from the liquid. The cations will be attracted toward the cathode by the applied electric field. The cations may be allowed to pass through thesecond CM606 and into thecathode chamber607 where they may be removed by the waste stream used to flush thecathode chamber607. Anions will be retained within the liquid. Although the anions will be attracted toward the anode by the applied electric field, they will not be allowed to pass through thefirst CM604 on the anode-side of theCDC605.
• Following the passage through605, the liquid then passes through theACBDC603 where both anions and cations may be removed from the liquid. The cations will be attracted toward the cathode by the applied electric field. The cations may pass through thefirst CM604, through theCDC605, through thesecond CM606 and into thecathode chamber607 where they may be removed from the system. The anions will be attracted toward the anode by the applied electric field. The anions may pass through theAM602 and into theanode chamber601 where they may be removed from the system. The apparatus ofFIG. 6 may produce liquid with significantly reduced levels of cations and reduced levels of anions.
• TheAM602,CDC605,first CM604, andsecond CM606 illustrated inFIG. 6 may be regenerated by water splitting that occurs within theACBDC603. Hydronium ions will be attracted toward the cathode by the applied electric field and may regenerate thefirst CM604,CDC605, andsecond CM606 as they travel toward the cathode. TheAM602 may be regenerated by water splitting that occurs within theACBDC603. Hydroxide ions will be attracted toward the anode by the applied electric field and may regenerate theAM602 as they travel toward the anode.
• The apparatus as illustrated inFIG. 6 is thus capable of being used in a manner that renders it suitable for deionization, especially cation removal, for low ionic strength liquids. Examples of low ionic strength liquids include water that has received reverse osmosis, distillation, or prior deionization treatment. The apparatus as illustrated inFIG. 6 is thus capable of producing a liquid with very low concentrations of cations and thus may be suitable for purifying liquids for use in analytical techniques such as ion chromatography, inductively coupled plasma mass spectrometry, and atomic absorption spectroscopy, among others.
• FIG. 7 illustrates an EDI apparatus comprising two ion depletion chambers, a concentrate chamber, an anode chamber, and a cathode chamber. The two electrode chambers and the concentrate chamber have a flow of waste stream liquid used to flush the contaminant ions from the chambers. The apparatus illustrated inFIG. 7 comprises ananode chamber701 including an anode therein. ACDC703 may be placed on the cathode-side of theanode chamber701. Theanode chamber701 and theCDC703 may be separated by afirst CM702. TheCDC703 typically includes therein a homogeneous volume of cation exchange material. ACBCC705 may be placed on the cathode-side of theCDC703. TheCDC703 and theCBCC705 may be separated by asecond CM704. TheCBCC705 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACCBDC707 may be placed on the cathode-side of theCBCC705. TheCBCC705 and theCCBDC707 may be separated by anAM706. TheCCBDC707 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. TheCCBDC707 may be separated from acathode chamber709 by athird CM708. Thecathode chamber709 typically includes a cathode therein. The apparatus as illustrated inFIG. 7 may be operated in continuous mode or in intermittent mode.
• This results in an apparatus with the advantages of minimal electrode fouling or electrode degradation. TheCCBDC707 may act as the final ion depletion chamber for the product liquid. Most contaminant ions may be removed into theCBCC705. Any cations present in the product liquid after the CDC may be removed by theCCBDC707 and exit into the cathode chamber. Since the quantity of cations being removed into the cathode chamber may be very small, scaling in the cathode chamber may be insignificant.
• The apparatus illustrated inFIG. 7 is also advantageous when deionizing liquids with high concentrations of chloride ions. In conventional EDI apparatuses where the anions may be removed through the anode chamber, oxidation may occur wherein chloride may be oxidized to chlorine, chlorite, and hypochlorite among others. This may cause degradation of the EDI apparatus. The configuration as illustrated inFIG. 7 may remove the majority of the anions through the CBCC chamber, thus resolving the issues present in most conventional EDI apparatuses.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 7 comprises first causing the liquid to be deionized to flow through theCDC703. The interaction between the liquid and theCDC703 may be maximized by placing the inlet to theCDC703 near thesecond CM704 and the outlet of theCDC703 near thefirst CM702. Alternatively, the inlet port may be positioned closest to thesecond CM704 to minimize the distance the cations must travel under the force of the electric field into the CBCC. This causes the liquid to traverse the length of theCDC703 as it flows from the inlet to the outlet. TheCDC703 may be capable of effectively removing contaminant cations from the liquid stream. The cations are attracted to the cathode under the influence of the applied electric field and may be allowed to pass through asecond CM704 and into theCBCC705. The contaminant cations may be removed from the system in theCBCC705. The cations are not allowed to pass through anAM706 that defines the cathode-side of theCBCC705. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively contained in theCBCC705 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC705. The liquid exiting theCDC703 may be largely free of cationic contamination.
• Following the passage through703, the liquid is then flowed through theCCBDC707. The interaction between the liquid and theCCBDC707 may be maximized by placing the inlet to theCCBDC707 near theAM706 and the outlet of theCCBDC707 near thethird CM708. This causes the liquid to traverse the length of theCCBDC707 as it flows from the inlet to the outlet. The inlet port is positioned closest to theAM706 to minimize the distance the anions must travel under the force of the electric field into theCBCC chamber705. TheCCBDC707 may be capable of removing both anions and cations. The remaining cations are attracted to theadjacent cathode chamber709 under the influence of the applied electric field and may be allowed to pass through athird CM708 and may be removed from the liquid. The anions are attracted toward the anode under the influence of the applied electric field and may be allowed to pass through anAM706 into theadjacent CBCC705. The contaminant anions may be removed from the system in theCBCC705. The anions are not allowed to pass through asecond CM704 that defines the anode-side of theCBCC705. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively removed in theCBCC705 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC705. The liquid exiting theCCBDC707 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theCCBDC707 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theCCBDC707 may serve to regenerate thethird CM708 that separates theCCBDC707 from thecathode chamber709 as well as theAM706 that separates theCCBDC707 from theadjacent CBCC705.
• The apparatus and method of use illustrated inFIG. 7 address the electrode fouling and ion exchange degradation problems since the electrode chambers may receive a reduced quantity of the contaminant ions and water splitting in the composite bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, and cation membranes.
• FIG. 8 illustrates an EDI apparatus comprising two ion depletion chambers, a concentrate chamber, an anode chamber, and a cathode chamber. The two electrode chambers and the concentrate chamber have a flow of waste stream liquid used to flush the contaminant ions from the chambers. The apparatus illustrated inFIG. 8 comprises ananode chamber801 including an anode therein. AnACBDC803 may be placed on the cathode-side of theanode chamber801. Theanode chamber801 and theACBDC803 may be separated by afirst AM802. TheACBDC803 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. ACBCC805 may be placed on the cathode-side of theACBDC803. TheACBDC803 and theCBCC805 may be separated by aCM804. TheCBCC805 may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. AnADC807 may be placed on the cathode-side of theCBCC805. TheCBCC805 and theADC807 may be separated by asecond AM806. TheADC807 typically includes therein a homogeneous volume of anion exchange material. TheADC807 may be separated from acathode chamber809 by athird AM808. Thecathode chamber809 typically includes a cathode therein. The apparatus as illustrated inFIG. 8 may be operated in continuous mode or in intermittent mode.
• InFIG. 8, the majority of the contaminant ions may be drawn into theCBCC805. TheACBDC803 may serve as the final ion depletion chamber. As the product liquid passes through theACBDC803, residual contaminant anions may be removed into theanode chamber801. Since the majority of contaminant anions may be removed by theADC807, the trace amounts of residual anions removed by theACBDC803 and into theanode chamber801 will not cause significant electrode degradation.
• A method for performing electrodeionization utilizing the apparatus as illustrated inFIG. 8 comprises first causing the liquid to be deionized to flow through theADC807. The interaction between the liquid and theADC807 may be maximized by placing the inlet to theADC807 near thesecond AM806 and the outlet of theADC807 near thethird AM808. This causes the liquid to traverse the length of theADC807 as it flows from the inlet to the outlet. TheADC807 may be capable of effectively removing contaminant anions from the liquid stream. The anions are attracted to the anode under the influence of the applied electric field and may be allowed to pass through asecond AM806 and into theCBCC805. The contaminant anions may be removed from the system in theCBCC805. The anions are not allowed to pass through aCM804 that defines the anode-side of theCBCC805. The anions cannot travel toward the cathode because of the influence of the applied electric field. Therefore, the anions may be effectively contained in theCBCC805 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC805. The liquid exiting theADC807 may be largely free of anionic contamination.
• Following the passage through807, the liquid is then flowed through theACBDC803. The interaction between the liquid and theACBDC803 may be maximized by placing the inlet to theACBDC803 near theCM804 and the outlet of theACBDC803 near thefirst AM802. This causes the liquid to traverse the length of theACBDC803 as it flows from the inlet to the outlet. TheACBDC803 may be capable of removing both anions and cations. The remaining anions are attracted to theadjacent anode chamber801 under the influence of the applied electric field and may be allowed to pass through afirst AM802 and may be removed from the liquid. The cations are attracted toward the cathode under the influence of the applied electric field and may be allowed to pass through aCM804 into theadjacent CBCC805. The contaminant cations may be removed from the system in theCBCC805. The cations are not allowed to pass through asecond AM806 that defines the cathode-side of theCBCC805. The cations cannot travel toward the anode because of the influence of the applied electric field. Therefore, the cations may be effectively removed in theCBCC805 until they are flushed from the system by the waste liquid stream that removes ions from theCBCC805. The liquid exiting theACBDC803 may have a reduced level of both anions and cations relative to the in-coming liquid stream.
• Water splitting occurs in theACBDC803 since it may include therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material. The water splitting in theACBDC803 may serve to regenerate thefirst AM802 that separates theACBDC803 from theanode chamber801 as well as theCM804 that separates theACBDC803 from theadjacent CBCC805.
• The apparatus and method of use illustrated inFIG. 8 address the electrode fouling and ion exchange degradation problems since the electrode chambers may receive a reduced quantity of the contaminant ions and water splitting in the composite bed depletion chambers generates hydronium and hydroxide ions for the regeneration of the anion membranes, and cation membranes.
• The foregoing descriptions of exemplary embodiments of the present invention have been presented for the purpose of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications, embodiments, and variations are possible in light of the above teaching.

Claims (14)

1. An electrodeionization apparatus comprising:

a. an anode chamber101 including an anode therein;

b. a first anion membrane102 contiguous with the anode chamber101;

c. an anion depletion chamber103 contiguous with the first anion membrane102, the anion depletion chamber including therein anion exchange materials;

d. a second anion membrane104 contiguous with the anion depletion chamber103;

e. a composite bed depletion chamber105 contiguous with the second anion membrane104, the composite bed concentrate chamber including therein one of a doped anion exchange material, or a doped cation exchange material;

f. a first cation membrane106 contiguous with the composite bed concentrate chamber105;

g. a cation depletion chamber107 contiguous with the first cation membrane106, the cation depletion chamber including therein cation exchange materials;

h. a second cation membrane108 contiguous with the cation depletion chamber107; and

i. a cathode chamber109 contiguous with the second cation membrane108 including a cathode therein.

2. An electrodeionization apparatus comprising:

a. an anode chamber201, including an anode therein;

b. a first anion membrane202 contiguous with the anode chamber201;

c. an anodic composite bed depletion chamber203 contiguous with the first anion membrane202, the anodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a first cation membrane204 contiguous with the anodic composite bed depletion chamber203;

e. a cation depletion chamber205 contiguous with the first cation membrane204, the cation depletion chamber including therein cation exchange materials;

f. a second cation membrane206 contiguous with the cation depletion chamber205;

g. a composite bed concentrate chamber207 contiguous with the second cation membrane206, the composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

h. a second anion membrane208 contiguous with the composite bed concentrate chamber207;

i. an anion depletion chamber209 contiguous with the second anion membrane208, the anion depletion chamber including therein anion exchange materials;

j. a third anion membrane210 contiguous with the anion depletion chamber209;

k. a cathodic composite bed depletion chamber211 contiguous with the third anion membrane210, the cathodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

l. a third cation membrane212 contiguous with the cathodic composite bed depletion chamber211; and

m. a cathode chamber213 contiguous with the third cation membrane212, the cathode chamber including therein a cathode.

3. An electrodeionization apparatus comprising:

a. an anode chamber220 including an anode chamber therein;

b. a first cation membrane221 contiguous with the anode chamber220;

c. an anodic composite bed concentrate chamber222 contiguous with the first cation membrane221, the anodic composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a first anion membrane223 contiguous with the anodic composite bed concentrate chamber222;

e. an anion depletion chamber224 contiguous with the first anion membrane223, the anion depletion chamber including therein anion exchange materials;

f. a second anion membrane225 contiguous with the anion depletion chamber224;

g. a composite bed depletion chamber226 contiguous with the second anion membrane225, the composite bed concentrate including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

h. a second cation membrane227 contiguous with the composite bed depletion chamber226;

i. a cation depletion chamber228 contiguous with the second cation membrane227, the cation depletion chamber including therein cation exchange materials;

j. a third cation membrane229 contiguous with the cation depletion chamber228;

k. a cathodic composite bed concentrate chamber230 contiguous with the third cation membrane229, the cathodic composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

l. a third anion membrane231 contiguous with the cathodic composite bed concentrate chamber230; and

m. a cathode chamber232 contiguous with the third anion membrane231 including a cathode therein.

4. An electrodeionization apparatus comprising:

a. an anode chamber240 including an anode therein;

b. a first cation membrane241 contiguous with the anode chamber240;

c. a anodic concentrate chamber242 contiguous with the first cation membrane241, the anodic concentrate chamber including therein one of a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a first anion membrane243 contiguous with the anodic concentrate chamber242;

e. an anion depletion chamber244 contiguous with the first anion membrane243, the anion depletion chamber including therein anion exchange materials;

f. a second anion membrane245 contiguous with the anion depletion chamber244;

g. a composite bed depletion chamber246 contiguous with the second anion membrane245, the composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

h. a second cation membrane247 contiguous with the composite bed depletion chamber246;

i. a cation depletion chamber248 contiguous with the second cation membrane247, the cation depletion chamber including therein cation exchange materials;

j. a third cation membrane249 contiguous with the cation depletion chamber248;

k. an cathodic concentrate chamber250 contiguous with the third cation membrane249, the cathodic concentrate chamber including therein one of a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

l. a third anion membrane251 contiguous with the cathodic concentrate chamber250; and

m. a cathode chamber252 contiguous with the third anion membrane251 including a cathode therein.

5. An electrodeionization apparatus comprising:

a. an anode chamber301 including an anode therein;

b. a first anion membrane302 contiguous with the anode chamber301;

c. an anodic composite bed depletion chamber303 contiguous with the first anion membrane302, the anodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a first cation membrane304 contiguous with the anodic composite bed depletion chamber303;

e. a cation depletion chamber305 contiguous with the first cation membrane304, the cation depletion chamber including therein cation exchange materials;

f. a second cation membrane306 contiguous with the cation depletion chamber305;

g. a composite bed concentrate chamber307 contiguous with the second cation membrane306, the composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

h. a second anion membrane308 contiguous with the composite bed concentrate chamber307;

i. an anion depletion chamber309 contiguous with the second anion membrane308, the anion depletion chamber including therein anion exchange materials;

j. a third anion membrane310 contiguous with the anion depletion chamber309; and

k. a cathode chamber311 contiguous with the third cation membrane310 including a cathode therein.

6. An electrodeionization apparatus comprising:

a. an anode chamber320 including an anode therein;

b. a first anion membrane321 contiguous with the anode chamber320;

c. an anion depletion chamber322 contiguous with the first anion membrane321, the anion depletion chamber including therein anion exchange materials;

d. a second anion membrane323 contiguous with the anion depletion chamber322;

e. a composite bed depletion chamber324 contiguous with the second anion membrane323, the composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

f. a first cation membrane325 contiguous with the composite bed depletion chamber324;

g. a cation depletion chamber326 contiguous with the first cation membrane325, the cation depletion chamber including therein cation exchange materials;

h. a second cation membrane327 contiguous with the cation depletion chamber326;

i. a cathodic composite bed concentrate chamber328 contiguous with the second cation membrane327, the cathodic composite bed concentrate chamber including therein a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

j. a third anion membrane329 contiguous with the cathodic composite bed concentrate chamber328; and

k. a cathode chamber330 contiguous with the third anion membrane329 including a cathode therein.

7. An electrodeionization apparatus comprising:

a. an anode chamber340 including an anode therein;

b. a first anion membrane341 contiguous with the anode chamber340;

c. an anion depletion chamber342 contiguous with the first anion membrane341, the anion depletion chamber including therein anion exchange materials;

d. a second anion membrane343 contiguous with the anion depletion chamber342;

e. a composite bed depletion chamber344 contiguous with the second anion membrane343, the composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

f. a first cation membrane345 contiguous with the composite bed depletion chamber344;

g. a cation depletion chamber346 contiguous with the first cation membrane345, the cation depletion chamber including therein cation exchange materials;

h. a second cation membrane347 contiguous with the cation depletion chamber346;

i. an cathodic concentrate chamber348 contiguous with the second cation membrane347, the cathodic concentrate chamber including therein one of a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

j. a third anion membrane349 contiguous with the cathodic concentrate chamber348; and

k. a cathode chamber350 contiguous with the third anion membrane349 including a cathode therein.

8. An electrodeionization apparatus comprising:

a. an anode chamber401 including an anode therein;

b. a first cation membrane402 contiguous with the anode chamber401;

c. a cation depletion chamber403 contiguous with the first cation membrane402, the cation depletion chamber including therein cation exchange materials;

d. a second cation membrane404 contiguous with the cation depletion chamber403;

e. a composite bed concentrate chamber405 contiguous with the second cation membrane404, the composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

f. a first anion membrane406 contiguous with the composite bed concentrate chamber405;

g. an anion depletion chamber407 contiguous with the first anion membrane406, the anion depletion chamber including therein anion exchange materials;

h. a second anion membrane408 contiguous with the anion depletion chamber407;

i. a cathodic composite bed depletion chamber409 contiguous with the second anion membrane408, the cathodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

j. a third cation membrane410 contiguous with the cathodic composite bed depletion chamber409; and

k. a cathode chamber411 contiguous with the third cation membrane410 including a cathode therein.

9. An electrodeionization apparatus comprising:

a. an anode chamber420 including an anode;

b. a first cation membrane421 contiguous with the anode chamber420;

c. an anodic composite bed concentrate chamber422 contiguous with the first cation membrane421, the anodic composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a first anion membrane423 contiguous with the anodic composite bed concentrate chamber422;

e. an anion depletion chamber424 contiguous with the first anion membrane423, the anion depletion chamber including therein anion exchange materials;

f. a second anion membrane425 contiguous with the anion depletion chamber424;

g. a composite bed depletion chamber426 contiguous with the second anon membrane425, the composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

h. a second cation membrane427 contiguous with the composite bed depletion chamber426;

i. an cation depletion chamber428 contiguous with the second cation membrane427, the cation depletion chamber including therein cation exchange materials;

j. a third cation membrane429 contiguous with the cation depletion chamber428; and

k. a cathode chamber430 contiguous with the third cation membrane429 including a cathode.

10. An electrodeionization apparatus comprising:

a. an anode chamber440 including an anode therein;

b. a first cation membrane441 contiguous with the anode chamber440;

c. an anodic concentrate chamber442 contiguous with the first cation membrane441, the anodic concentrate chamber including therein one of a homogeneous volume of anion exchange material, or a homogeneous volume of cation exchange material, or a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a first anion membrane443 contiguous with the anodic concentrate chamber442;

e. an anion depletion chamber444 contiguous with the first anion membrane443, the anion depletion chamber including therein anion exchange materials;

f. a second anion membrane445 contiguous with the anion depletion chamber444;

g. a composite bed depletion chamber446 contiguous with the second anion membrane445, the composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

h. a second cation membrane447 contiguous with the composite bed depletion chamber446;

i. an cation depletion chamber448 contiguous with the second cation membrane447, the cation depletion chamber including therein cation exchange materials;

j. a third cation membrane449 contiguous with the cation depletion chamber448; and

k. a cathode chamber450 contiguous with the third cation membrane449 including a cathode therein.

11. An electrodeionization apparatus comprising:

a. an anode chamber501 including an anode therein;

b. a first anion membrane502 contiguous with the anode chamber501;

c. an anion depletion chamber503 contiguous with the first anion membrane502, the anion depletion chamber including therein anion exchange materials;

d. a second anion membrane504 contiguous with the anion depletion chamber503;

e. a cathodic composite bed depletion chamber505 contiguous with the second anion membrane504, the cathodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

f. a cation membrane506 contiguous with the composite bed depletion chamber505; and

g. a cathode chamber507 contiguous with the cation membrane506 including a cathode therein.

12. An electrodeionization apparatus comprising:

a. an anode chamber601 including an anode;

b. a first anion membrane602 contiguous with the anode chamber601;

c. an anodic composite bed depletion chamber603 contiguous with the first anion membrane602, the anodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a first cation membrane604 contiguous with the anodic composite bed depletion chamber603;

e. a cation depletion chamber605 contiguous with the first cation membrane604, the cation depletion chamber including therein cation exchange materials;

f. a second cation membrane606 contiguous with the cation depletion chamber605; and

g. a cathode chamber607 contiguous with the second cation membrane606 including a cathode therein.

13. An electrodeionization apparatus comprising:

a. an anode chamber701 including an anode therein;

b. a first cation membrane702 contiguous with the anode chamber;

c. a cation depletion chamber703 contiguous with the first cation membrane702, the cation depletion chamber including therein cation exchange materials;

d. a second cation membrane704 contiguous with the cathodic composite bed depletion chamber703;

e. a composite bed concentrate chamber705 contiguous with the second cation membrane704, the composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

f. an anion membrane706 contiguous with the composite bed concentrate chamber705;

g. a cathodic composite bed depletion chamber707 contiguous with the anion membrane706, the cathodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

h. a third cation membrane708 contiguous with the cation composite bed depletion chamber707; and

i. a cathode chamber709 contiguous with the third cation membrane708 including a cathode therein.

14. An electrodeionization apparatus comprising:

a. an anode chamber801 including an anode therein;

b. a first anion membrane802 contiguous with the anode chamber801;

c. an anodic composite bed depletion chamber803 contiguous with the first anion membrane802, the anodic composite bed depletion chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

d. a cation membrane804 contiguous with the anodic composite bed depletion chamber803;

e. a composite bed concentrate chamber805 contiguous with the cation membrane804, the composite bed concentrate chamber including therein one of a mixed ion exchange material, or a doped anion exchange material, or a doped cation exchange material;

f. a second anion membrane806 contiguous with the composite bed concentrate chamber805;

g. an anion depletion chamber807 contiguous with the second anion membrane806, the anion depletion chamber including therein anion exchange materials;

h. a third anion membrane808 contiguous with the anion depletion chamber807; and

a cathode chamber809 contiguous with the third cation membrane808 including a cathode therein.

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