Fenton treatment process without external medicament and sludge generationTechnical Field
The invention relates to an electric Fenton treatment process without an external medicament and sludge generation, and belongs to the technical field of wastewater treatment.
Background
Advanced oxidation technology based on hydroxyl radical (.OH) is widely applied to advanced treatment of biochemical tail water and pretreatment of industrial wastewater. This is mainly due to the extremely strong oxidizing power (+2.8v vs. SHE) of the. OH, which is able to efficiently decompose most of the hardly degradable organic contaminants. However, the Fe2+/Fe3+ in the Fenton technology is blocked in circulation, so that the problems of high medicament consumption, high iron sludge yield and the like in the process of generating OH by the Fenton technology are caused. According to Fenton oxidation wastewater treatment engineering technical Specification (HJ 1095-2020), the dosage of H2O2 reaches 2 times of the theoretical value, and the dosage of FeSO4 reaches 5 times of the theoretical value. This is mainly due to the fact that the reaction rate of Fe2+ oxidation (76M-1s-1) during the Fenton reaction is much greater than that of Fe3+ reduction (0.01M-1s-1), resulting in accumulation of Fe3+. Although the accumulation problem of Fe3+ in the Fenton reaction process can be relieved by means of light, electricity, chelating agent addition and the like, the continuous addition of medicaments such as H2O2, feSO4 and the like is still needed in the reaction process, and the problems of high medicament consumption and high iron mud yield in the Fenton process can not be fundamentally solved.
Disclosure of Invention
The invention aims to: the invention aims to provide a Fenton treatment process which can not only maintain an excellent organic pollutant removal effect, but also solve the problems of high medicament consumption and high iron sludge production of the existing Fenton process.
The technical scheme is as follows: the Fenton treatment process is carried out based on a system which consists of a bioelectricity synthesis H2O2 solid-state reactor and a UV activation H2O2 reactor; the bioelectricity synthesis H2O2 solid-state reactor comprises a microorganism anode chamber, a solid electrolyte layer and an air diffusion cathode; the microbial anode chamber and the solid electrolyte layer of the bioelectricity synthesis H2O2 solid-state reactor are separated by a cation exchange membrane, the air diffusion cathode and the solid electrolyte layer are separated by an anion exchange membrane, and the air diffusion cathode is used for supplying oxygen by an aeration device; the UV activated H2O2 reactor comprises an ultraviolet lamp and a sleeve; anode chamber effluent and a solid electrolyte layer formed H2O2 solution in a bioelectrical synthesis H2O2 solid state reactor flowed into a UV activated H2O2 reactor.
The working process of the system of the invention is as follows: waste water is pumped into a microbial anode chamber of the bioelectricity synthesis H2O2 solid-state reactor, air is pumped into an air diffusion cathode of the bioelectricity synthesis H2O2 solid-state reactor, and H2O2 solution is formed in a solid-state electrolyte layer under the external voltage; then, H2O2 solution formed by anode chamber effluent and a solid electrolyte layer in the bioelectricity synthesis H2O2 solid-state reactor flows into a UV activated H2O2 reactor, H2O2 generates OH under the activation of ultraviolet lamps, and the OH oxidizes organic pollutants which are difficult to biochemically degrade in the anode chamber effluent, so that the organic pollutants which are difficult to biochemically degrade and degrade in the wastewater are removed together.
The microbial anode is a carbon felt or carbon brush loaded with activated sludge and multi-wall carbon nanotube complex. The addition of multi-walled carbon nanotubes to the bioanode can significantly enhance microbial anode performance. The high conductivity of the multiwall carbon nanotubes constructs a high-efficiency electron transport network, which not only accelerates the electron transfer speed of microorganisms to the anode, but also increases the effective surface area of the anode; the three-dimensional network structure formed by the multi-wall carbon nano-tubes not only provides more microorganism attachment points, but also constructs a stable electron transfer network, which is important for improving the long-term stability and efficiency of the microbial anode. In this way, electrons generated by microorganisms which cannot be directly contacted with the surface of the anode can be captured and utilized, so that the utilization rate of the microorganisms and the overall performance of the bioelectricity synthesis H2O2 solid-state reactor are improved.
The carbon felt of the activated sludge and multi-wall carbon nano tube composite or the carbon brush of the activated sludge and multi-wall carbon nano tube composite is prepared by adopting the following method, and the specific steps are as follows:
(1) Adding the multiwall carbon nanotube into N-methyl pyrrolidone, and performing ultrasonic treatment to form uniform multiwall carbon nanotube dispersion; wherein the concentration of the multiwall carbon nanotube dispersion liquid is 0.5-1.0 g/L; the ultrasonic treatment time is 4.0-6.0 h;
(2) Adding glass beads into the activated sludge from the microbial fuel cell reactor, and performing vibration scattering treatment to form uniform activated sludge dispersion; wherein the MLSS of the activated sludge is 1.0-100 g/L; the average diameter of the glass beads is 10-1000 mu m;
(3) Adding the activated sludge dispersion liquid dropwise into the stirred multiwall carbon nanotube dispersion liquid, uniformly mixing and centrifuging to form an activated sludge and multiwall carbon nanotube complex; wherein the volume ratio of the multiwall carbon nanotube dispersion liquid to the activated sludge dispersion liquid is 1:0.5-1:100; the dropping speed of the activated sludge dispersion liquid is 0.1-100 mL/min; the centrifugal speed after uniform mixing is 3000-10000 rpm;
(4) Uniformly mixing the activated sludge and multi-wall carbon nano tube complex with a culture solution, and then adding the mixture into a bioelectricity synthesis H2O2 solid reactor for 7 days of domestication and film formation growth to form a carbon felt carrying the activated sludge and multi-wall carbon nano tube complex or a carbon brush carrying the activated sludge and multi-wall carbon nano tube complex; the formula of the culture solution is as follows: 1.0 g/L sodium acetate, 50 mM Phosphate Buffered Saline (PBS), 5.0 mL/L vitamin solution, and 12.5 mL/L trace mineral solution; the domestication voltage is 0.4-1.0V.
Wherein the solid electrolyte layer is formed by closely stacking polymer microspheres containing quaternary ammonium groups (including but not limited to DOWEX 1X 2, DOWEX 1X 4, DOWEX 1X 8, amberlite IRA-400, diaion SA10A, 201X 7 and other gel-type anion exchange resins). The solid electrolyte layer can transfer anions due to the quaternary ammonium group, and HO2- and OH- generated by the air cathode migrate to the anode under the action of an electric field and combine with H+ penetrating through the cation exchange membrane to form H2O2 solution.
Wherein the air diffusion cathode is a carbon fiber film loaded with carbon black or a carbon cloth loaded with carbon black. The air diffusion cathode can react without introducing pure oxygen and only by introducing air, and HO2- and OH- are generated.
The carbon fiber film loaded with carbon black or the carbon cloth loaded with carbon black is prepared by the following method, and the method specifically comprises the following steps: spraying the carbon black dispersion liquid on a hydrophobic carbon fiber film or carbon cloth; wherein the loading of the carbon black on the carrier is 0.46-5.0 mg/cm2.
The carbon black dispersion liquid is prepared by the following method, and specifically comprises the following steps: adding carbon black and Nafion 117 solution (mass fraction is 5%) into absolute ethyl alcohol to obtain mixed solution; and (3) carrying out ultrasonic treatment on the mixed solution to obtain the catalyst dispersion liquid without wall hanging, wherein the ultrasonic treatment is not less than 4.0 h. And adding the catalyst dispersion liquid into a spray gun, spraying on a hydrophobic carbon fiber film or carbon cloth, and placing the spray gun into a vacuum oven at 60 ℃ for drying after spraying to obtain the carbon black-loaded air diffusion cathode.
The operating voltage of the bioelectricity synthesis H2O2 solid-state reactor is 0.2-1.0V.
Wherein, the volume ratio of the anode chamber water to the H2O2 solution generated by the solid electrolyte layer in the bioelectricity synthesis H2O2 solid-state reactor is 50-200: 1 into a UV activated H2O2 reactor.
The operation voltage of the bioelectricity synthesis H2O2 solid-state reactor is 0.2-1.0V.
The hydraulic retention time of the wastewater in the bioelectricity synthesis H2O2 solid-state reactor is 5-20H; the hydraulic retention time of the wastewater in the UV activated H2O2 reactor is 10-60 min.
The working principle of the bioelectricity synthesis H2O2 solid-state reactor (MBES) in the system of the invention is as follows:
the biochemical degradation organic pollutants in the wastewater are decomposed in the bioanode to release electrons, H+ and CO2, and the electrons are transmitted to an external loop through an anode interface; then, the electrons reach the air diffusion cathode and the carbon black catalyst reduces the exposed oxygen to HO2- and OH-; finally, H+ spans the cation exchange membrane under electric field drive, whereas HO2- and OH- span the anion exchange membrane and combine in the solid electrolyte layer to form a H2O2 solution. The electromotive force of MBES is greater than 0 as seen by the standard electrode potentials of the two half reactions, indicating that MBES can spontaneously react. Therefore, MBES can realize in-situ synthesis of H2O2 solution in the wastewater treatment process:
anode half reaction:
Cathode half reaction:
The working principle of the UV activated H2O2 reactor (UV/H2O2) in the system of the invention is as follows: h2O2 solution formed by anode chamber effluent and a solid electrolyte layer in the bioelectricity synthesis H2O2 solid-state reactor is mixed and flows into a UV activation H2O2 reactor, H2O2 generates OH under the activation of ultraviolet lamps, and the OH oxidizes organic pollutants which are difficult to biochemically degrade in the anode chamber effluent, so that the biochemical degradation and the removal of the organic pollutants which are difficult to biochemically degrade in wastewater are realized. Therefore, the Fenton treatment process can realize the activation of H2O2 without Fe2+/Fe3+ circulation, so that the whole system does not need an external medicament and no sludge is generated.
The beneficial effects are that: compared with the prior art, the invention has the following remarkable advantages: according to the Fenton treatment process, H2O2 is synthesized through bioelectricity, and then H2O2 is activated in series to produce OH, so that the removal rate of ciprofloxacin in hospital wastewater is 95%; under the low voltage of 0.3V, the invention realizes the in-situ bioelectricity synthesis of 20mg/L H2O2 solution in the sewage treatment process through the waste water and the air, thereby avoiding the consumption of chemical reagents in the traditional Fenton technology; meanwhile, under UV activation, H2O2 activation and production of OH are realized through a non-Fe2+/Fe3+ circulation mode, and the generation of iron mud in the traditional Fenton technology is avoided, so that the problems of high medicament consumption and high iron mud yield in the traditional Fenton technology are solved.
Drawings
FIG. 1 is a schematic reaction diagram of the treatment process of the present invention;
FIG. 2 is a schematic diagram of the treatment process of the present invention;
FIG. 3 is a graph showing the performance of the solid state reactor for biosynthesis of H2O2 in accordance with the present invention; wherein A is Faraday efficiency and the variation trend of voltage between grooves along with current density; b is the yield of H2O2 at different current densities:
FIG. 4 is a graph showing the performance of the UV activated H2O2 reactor of the present invention; wherein, A is the CIP removal rate in simulated hospital wastewater under different H2O2 adding concentrations; b is the CIP removal rate of the simulated hospital wastewater at the same treatment time for CIP with the same initial concentration under different H2O2 addition concentrations.
Detailed Description
As shown in fig. 1-2, the Fenton treatment process provided by the invention comprises a bioelectricity synthesis H2O2 solid-state reactor 1 and a UV activation H2O2 reactor 2; the bioelectricity synthesis H2O2 solid-state reactor 1 comprises a microbial anode 3, a solid electrolyte layer 6 and an air diffusion cathode 4, wherein an anode chamber and the solid electrolyte layer 6 of the bioelectricity synthesis H2O2 solid-state reactor 1 are separated by a cation exchange membrane 5, the cathode chamber and the solid electrolyte layer 6 are separated by an anion exchange membrane 7, and the cathode chamber is also connected with an aeration device 11; the microbial anode 3 and the air diffusion cathode 4 are electrically connected with an external power supply; the UV activation H2O2 reactor 2 comprises an ultraviolet lamp 8 and a sleeve, wherein the ultraviolet lamp 8 is electrically connected with an external power supply; the anode chamber effluent in the bioelectrical synthesis H2O2 solid state reactor 1 and the H2O2 solution formed by the solid state electrolyte layer 6 flow into the UV activated H2O2 reactor 2.
The bioelectricity synthesis H2O2 solid-state reactor 1 is used for degrading part of biochemically degradable organic pollutants and simultaneously synthesizing H2O2 solution. Firstly, introducing wastewater into an anode chamber of a bioelectricity synthesis H2O2 solid-state reactor 1, removing part of biochemically degradable organic pollutants, simultaneously generating H+ and e-.H+, and allowing the H+ and e-.H+ to enter a solid-state electrolyte layer 6 through a cation exchange membrane 5; e- is transmitted to the air diffusion cathode 4 through an external circuit, and O2 in air is obtained at the air diffusion cathode 4 to obtain e-, and HO2- and OH- are generated. Finally, HO2- and OH- are driven by electric field force through the anion exchange membrane 7 into the solid electrolyte layer 6, and combine with H+ that permeates the cation exchange membrane 5 to produce a solution of H2O2.
The water discharged from the anode chamber in the bioelectricity synthesis H2O2 solid-state reactor 1 and the H2O2 solution formed by the solid-state electrolyte layer 6 flow into the UV activated H2O2 reactor 2, and H2O2 generates OH under the activation of ultraviolet lamps, and the OH oxidizes organic pollutants which are difficult to biochemically degrade in the water discharged from the anode chamber, so that the biochemical degradation and the removal of the organic pollutants which are difficult to biochemically degrade in the wastewater are realized.
The bioelectricity synthesis H2O2 solid reactor 1 is made of organic glass, and the sizes are 16 multiplied by 8 multiplied by cm (length multiplied by width multiplied by height).
The bioelectricity synthesis H2O2 solid-state reactor 1 is divided into three functional areas, the first part is an anode compartment, size of 8×8×8 cm (length x width x height); the microbial anode material is a carbon brush of a composite body of the supported activated sludge and the multiwall carbon nanotube, and the size of the carbon brush is 5 multiplied by 6 cm (diameter multiplied by length); the second part is a solid electrolyte layer 6 with the size of 8 multiplied by 1 cm (width multiplied by height multiplied by thickness), polymer microspheres containing quaternary ammonium groups (polymer microspheres with quaternary ammonium cationic groups on the surface) are filled in the solid electrolyte layer 6 to serve as solid electrolytes, and the anode chamber is separated from the solid electrolyte layer 6 by a cation exchange membrane 5; the third part is a gas diffusion cathode 4 with the size of 8×8×0.01 cm; the air diffusion cathode 4 is carbon cloth loaded with carbon black (the loading amount of the catalyst carbon black on the carbon cloth is 3.0 mg/cm2), and the air diffusion cathode 4 is separated from the solid electrolyte layer 6 by an anion exchange membrane 7.
The UV activated H2O2 reactor consisted essentially of an ultraviolet lamp 8 and a sleeve having a diameter of 5.0 cm and a length of 22 cm. Wherein the ultraviolet lamp 8 has a diameter of 2.0 cm and a length of 22 cm.
In this embodiment, the carbon brush loaded with the composite of activated sludge and multiwall carbon nanotubes is prepared by the following method, which specifically comprises the following steps:
(1) Adding 30 mg multi-wall carbon nano-tubes into 30 mL N-methyl pyrrolidone, and performing ultrasonic treatment on the mixture to obtain a uniform multi-wall carbon nano-tube dispersion liquid with the concentration of 1.0 g/L by using ultrasonic treatment 4.0 h;
(2) Taking 30mL activated sludge from a microbial fuel cell reactor, adding glass beads with average diameter of 200 mu m into the activated sludge, and carrying out vibration scattering treatment to form uniform activated sludge dispersion, wherein the MLSS of the activated sludge is 10 g/L;
(3) Adding the activated sludge dispersion liquid dropwise into the stirred multiwall carbon nanotube dispersion liquid at the speed of 1.0 mL/min, uniformly mixing and centrifuging to form an activated sludge and multiwall carbon nanotube complex; wherein, the volume ratio of the multiwall carbon nanotube dispersion liquid to the activated sludge dispersion liquid is 1:1, the centrifugal speed after uniform mixing is 6000 rpm;
(4) Preparing 500 mL culture solution, wherein the culture solution comprises 1.0 g/L sodium acetate, 50mM Phosphate Buffer Solution (PBS), 5.0 mL/L vitamin solution and 12.5 mL/L trace mineral solution (beneficial to microorganism growth); adding the activated sludge and multi-wall carbon nano tube complex obtained in the step (3) into a 500 mL culture solution, uniformly mixing, and then adding into a bioelectricity synthesis H2O2 solid-state reactor taking a carbon brush as a microbial anode to perform 7-day domestication and film-forming growth, so as to form the carbon brush carrying the activated sludge and multi-wall carbon nano tube complex.
The air diffusion cathode is prepared by the following method, and specifically comprises the following steps:
(1) Adding 32. 32 mg carbon black and 80 mu L of Nafion 117 solution (mass fraction is 5%) into 8.0 mL absolute ethyl alcohol to obtain a mixed solution;
(2) Ultrasonic treating the mixed solution for 4.0 h to form a uniform wall-hanging-free carbon black dispersion;
(3) And adding the carbon black dispersion liquid into a spray gun, spraying on carbon cloth, and putting the carbon black dispersion liquid into a vacuum oven at 60 ℃ for drying after spraying to obtain the carbon black-loaded air diffusion cathode.
The hospital wastewater has complex water quality and mainly contains various residual antibiotics including quinolones (ciprofloxacin, ofloxacin and norfloxacin) and sulfonamides (sulfamethoxazole, trimethoprim and sulfamethoxazole). First, simulated hospital wastewater (in which the initial CIP concentration is 10 mg/L) is pumped into the microbial anode chamber of the biosynthesis H2O2 solid-state reactor to remove biochemically degradable organic contaminants. Then, air was exposed to the air diffusion cathode of the bioelectrical H2O2 solid state reactor, forming H2O2 solution in the solid state electrolyte layer at different current densities (0.5, 1.0, 1.5 and 2.0 mA cm-2).
The faraday efficiency and H2O2 concentration of the bioelectrically synthesized H2O2 solid state reactor were calculated by measuring the yield of H2O2 at different current densities. As a result, as shown in fig. 3, the faraday efficiency decreases with increasing current density, and the cell-to-cell voltage increases with increasing current density. At the current density of 0.5 mA cm-2, the Faraday efficiency of the air diffusion cathode reaches more than 80%, and the concentration of H2O2 generated by the solid electrolyte layer is 18-mg/L; at a current density of 2.0 mA cm-2, the Faraday efficiency of the air diffusion cathode is 75-75%, and the concentration of H2O2 generated by the solid electrolyte layer reaches 65-mg/L.
Next, the anode chamber effluent and the H2O2 solution formed by the solid electrolyte layer in the bioelectricity synthesis H2O2 solid state reactor flow into a UV activated H2O2 reactor, wherein the water conservancy residence time of the anode chamber effluent in the UV activated H2O2 reactor is 60 min; finally, H2O2 generates OH under the activation of ultraviolet lamp, and the OH oxidizes organic pollutants which are difficult to be biochemically degraded in the water discharged from the anode chamber, so as to jointly remove the organic pollutants which can be biochemically degraded and are difficult to be biochemically degraded in the hospital wastewater.
The method is characterized in that the concentration of Ciprofloxacin (CIP) remained in hospital wastewater is simulated by measuring the concentration of different H2O2 (namely, H2O2 solution formed by anode chamber water and a solid electrolyte layer in a bioelectricity synthesis H2O2 solid state reactor is mixed according to different volume ratios and is sent into a UV activated H2O2 reactor), and the removal rate of the organic pollutant CIP difficult to biochemically degrade is calculated. As shown in FIG. 4, the CIP removal rate in simulated hospital wastewater is as high as 95% at the addition concentration of 10 mg/L H2O2; the CIP removal rate in simulated hospital wastewater is up to 96% under the addition concentration of 60 mg/L H2O2. Therefore, the Fenton treatment process can be applied to treatment of hospital wastewater, can realize efficient removal of antibiotics such as ciprofloxacin and the like without an external medicament, and simultaneously avoids generation of sludge in the traditional Fenton treatment process.