CN110975837A - Modified oyster shell, preparation method and application thereof - Google Patents

Abstract

The invention discloses a modified oyster shell, a preparation method and application thereof, wherein the modified oyster shell comprises oyster shell particles and an iron ion solution, and is prepared by reducing ferric iron dispersed on the surface of micropores of the oyster shell into nano zero-valent iron by using tea polyphenol extracted from dry green tea as a reducing agent under the protection of nitrogen. The preparation method comprises subjecting the oyster shell particles after soaking, ultrasonic treatment, cleaning, drying and sieving to low concentration acidification and high temperature calcination treatment to increase the pore diameter; mixing the oyster shell granules with the iron ion solution, and reducing the iron ions dispersed on the surface of the oyster shell into nano zero-valent iron by using tea polyphenol extracted from the dried green tea as a reducing agent to prepare the modified oyster shell. The modified oyster shell is used for removing typical anionic surfactant in rural grey water. The invention has the advantages that: the method is used for efficiently removing the typical anionic surfactant in the rural grey water, and can stably run for a long time; realizes the purpose of changing waste into valuable, has wide raw material source, simple operation, no toxicity and no pollution.

Description

Modified oyster shell, preparation method and application thereof

Technical Field

The invention belongs to the technical field of environmental protection, and particularly relates to modified oyster shells, a preparation method and application thereof, which are suitable for rural grey water treatment with small water volume or intermittent discharge.

Background

In domestic sewage, rural grey water is preferentially selected as raw water for wastewater reuse due to the advantages of easy shunting and collection, light pollution degree, small treatment difficulty and the like, drinking water can be saved by 25.6-30.4% by using the grey water, and the method has good reuse value, and is particularly suitable for water-deficient rural areas. The concentration of pollutants such as nitrogen and phosphorus in the grey water is lower, and the concentration of the anionic surfactant (LAS) is higher than that of the mixed domestic sewage. The anionic surfactant is a surfactant (mainly sodium alkyl benzene sulfonate) which is frequently used at present, the sodium dodecyl benzene sulfonate is the most typical sodium alkyl benzene sulfonate, and the sodium dodecyl benzene sulfonate can generate foam when the concentration is as low as 1 ppm, so that the environment attractiveness is seriously influenced; a large amount of foam which is not easy to disappear can also reduce the dissolved oxygen amount of water, so that the water body smells; meanwhile, the adsorption effect of the soil on organic poisons can be reduced, the composition of microorganisms in the soil is changed, and further pollution is caused. Therefore, both miscellaneous water standards and field irrigation standards set the corresponding standard limits for anionic surfactants.

According to the standard of the reclaimed water quality, aiming at the characteristics of small water quantity and intermittent discharge of the rural grey water, the traditional treatment technology cannot adapt to the rural grey water treatment due to factors such as complex procedure, poor treatment effect and high power consumption, and the filtration and adsorption technology can remove finer impurities and can also remove organic matters, inorganic matters and even salts in a dissolved state, so that the filtration and adsorption technology is suitable for treating the rural grey water.

At present, most of oyster shells are discarded or buried, which brings a lot of adverse effects to the environment. How to fully utilize oyster shell, change oyster shell into valuables belongs to the technical problem that technical personnel in the field are difficult to solve. Oyster shell divide into 3 layers according to the difference of formation mode and organizational structure: the outermost layer is the cuticle which has stronger resistance to corrosion from external chemical articles; the middle is a prismatic layer containing a large number of holes with the diameter of 2-10 mu m; the inner layer is a nacreous layer and mainly consists of calcite. The oyster shell has special physical structure and contains various organic and inorganic components, so that the oyster shell can generate a plurality of hole structures with different functions after being modified, has stronger adsorption, biological loading and catalytic decomposition performance, and can better remove various environmental pollutants.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a modified oyster shell which can effectively remove anionic surfactant in rural grey water, can stably run for a long time, and improves the living environment by utilizing the waste oyster shell. The invention also provides a preparation method of the modified oyster shell and application of the modified oyster shell.

In order to solve the technical problems

The invention provides a modified oyster shell, which comprises oyster shell particles, wherein the oyster shell particles are mixed in an iron ion solution, and the ferric iron dispersed on the surfaces of micropores of the oyster shell is reduced into nano zero-valent iron by using tea polyphenol extracted from dry green tea as a reducing agent under the protection of nitrogen.

The invention also provides a preparation method of the modified oyster shell, which comprises the following steps:

step 1, oyster shell pretreatment: pulverizing natural Concha Ostreae into Concha Ostreae particles, soaking in ultrapure water, ultrasonic treating, oven drying, and further pulverizing and sieving dried Concha Ostreae;

step 2, increasing the aperture of the oyster shell: placing the mixture into a drying oven for later use after acidification and calcination;

step 3, extracting tea polyphenol: dissolving dried green tea in ethanol solution, heating and stirring in water bath for extraction;

step 4, in-situ synthesis of the novel filter material: uniformly stirring the oyster shell granules prepared in thestep 2 and an iron ion solution in a three-neck flask, then dripping the tea polyphenol solution extracted in thestep 3 into the oyster shell granules at a constant speed by using a constant-pressure dropping funnel under the condition of nitrogen protection, and continuously stirring for 10-20 min after dripping;

step 5, separation and cleaning: separating solid modified oyster shells generated at the bottom of the three-neck flask from the solution, and washing with ultrapure water and absolute ethyl alcohol for multiple times;

andstep 6, drying treatment: and (5) putting the oyster shells cleaned in the step (5) into a vacuum constant-temperature drying box to obtain the oyster shells modified by the nano zero-valent iron.

Preferably, the modified oyster shells prepared in thestep 6 are stored in a brown reagent bottle and put into a vacuum constant-temperature drying oven for standby.

The modified oyster shell is used for removing anionic surfactant in rural grey water.

The modified oyster shell is used as a filter material for water treatment according to the filtration and adsorption principle; the method uses tea polyphenol extracted from dry green tea to disperse Fe pre-dispersed on the surface of oyster shell³⁺Reducing into Fe, and further preparing the modified oyster shell with nano zero-valent iron, wherein the obtained product is green and environment-friendly; the modified oyster shell prepared by the method not only improves the oxidation resistance and the dispersibility of the nano zero-valent iron, but also can be used as a new filter material for efficiently removing anionic surfactant in rural grey water, and can stably run for a long time; in addition, the method also has the advantages of changing waste into valuable, wide raw material source, low cost, simple operation, no toxicity, no pollution and the like. And the treated grey water can be used for irrigation or toilet flushing, so that the rural water environment protection level is improved, and the contradiction of water resource shortage in rural areas is relieved.

The invention has the advantages that:

1. the modified oyster shell of the invention is used as a novel filter material, and has good effect of removing anionic surfactant in grey water.

2. The adsorption filtration column filled with the modified oyster shells realizes the high-efficiency removal of anionic surfactant (LAS) in rural grey water, and keeps the long-term stable operation of the adsorption column.

3. The structure and the component characteristics of the oyster shells are fully exerted, waste is turned into wealth, and the resource utilization of the waste oyster shells is realized.

4. The method for synthesizing the nano zero-valent iron is environment-friendly, and has the advantages of no toxicity, no pollution, simpler operation process, low cost, reproducibility and the like compared with the traditional method.

4. The tea polyphenol has the functions of reduction and stabilization, and the in-situ synthesized nano zero-valent iron is more stable and has better particle dispersibility.

5. The iron reserves are abundant, the price is low and the magnetic recovery treatment is easy, so the investment cost for modifying the oyster shell by using the nano zero-valent iron is low, and the method has a certain economic value.

6. The modified oyster shell can effectively remove pollutants under the condition of neutral pH, and has wide application range.

7. The porous structure oyster shell after low-concentration acidification and high-temperature calcination is used as a carrier, and the prepared load type nano zero-valent iron has low biological toxicity and is beneficial to filter material hanging membrane in an adsorption column.

8. The treated outlet water of the grey water is used for irrigation or toilet flushing after reaching the reuse standard, and the difficulty of water supply can be reduced for water-deficient areas.

Drawings

The drawings of the invention are illustrated as follows:

FIG. 1 is a standard curve of sodium dodecylbenzenesulfonate of example 1;

FIG. 2 is a graph comparing the effect of sodium dodecylbenzenesulfonate adsorbed by unmodified and modified oyster shells in example 1;

FIG. 3 is a structural view of an experimental apparatus using an adsorption filtration column in example 2;

FIG. 4 is a graph comparing the LAS removal rate over time (days) for the effluent of two adsorption filtration columns of example 2.

In fig. 3, 1, a water storage bucket; 2. a peristaltic pump; 3. a stainless steel bracket; 4. a rotameter; 5. an adsorption column of unmodified oyster shell; 6. modified oyster shell adsorption column; 7. a water distribution area; 8-9 parts of perlite; 10. unmodified oyster shell; 11. modified oyster shells; 12-13, washing sand with water; 14. and (7) a water outlet.

Detailed Description

The invention is further illustrated by the following examples in conjunction with the accompanying drawings:

the modified oyster shell of the invention comprises oyster shell particles, the oyster shell particles are mixed in iron ion solution, under the protection of nitrogen, tea polyphenol extracted from dry green tea is used as a reducing agent, and ferric iron dispersed on the micropore surface of the oyster shell is reduced into nano zero-valent iron.

Example 1

The modified oyster shell of the embodiment is prepared by the following steps:

1. pretreatment of oyster shells: pulverizing natural Concha Ostreae (particle diameter of 5-10 cm) into Concha Ostreae with particle diameter of 1-2 cm, soaking in ultrapure water for 20 h, ultrasonic treating for 4 h, rinsing with ultrapure water for 4-6 times, oven drying at 105 deg.C for 24 h, and further pulverizing into Concha Ostreae particles (particle diameter of 2-4 mm) with 5-10 mesh.

Part of the obtained oyster shell particles are unmodified oyster shells and are used for a comparison test; one part is used as modified oyster shell raw material.

2. Increasing the aperture of the oyster shell: using 0.01 mol/L HNO to the modified oyster shell particle raw material₃Soaking for 30 min, calcining at 650 deg.C in muffle furnace for 45min, naturally cooling, and drying in constant temperature drying oven.

3. Extracting tea polyphenol: grinding dry green tea into 18-mesh dry green tea powder, weighing 22 g of dry green tea powder, dissolving in 440mL of 50% ethanol solution, shaking, sealing, heating in 80 deg.C water bath for 1 hr, magnetically stirring, vacuum filtering, and storing

4. In-situ synthesis of a novel filter material: weighing 40 g of the oyster shell granules prepared in thestep 2 and 100mL of 0.1mol/LFeCl₃•6H₂Mixing the O solution in a 1000 mL three-neck flask, uniformly mixing for 10 min by using a mechanical stirrer under the protection of nitrogen, setting the stirring speed at 290 r/min, measuring 300 mL of tea polyphenol extracting solution, pouring the tea polyphenol extracting solution into a constant pressure titration funnel, dripping the tea polyphenol extracting solution into the three-neck flask at the speed of 12.5 mL/min, and continuing stirring for 15 min after dripping.

5. Separation and cleaning: pouring the liquid in the three-mouth flask into a waste liquid barrel, leaving the solid modified oyster shell at the bottom of the flask, adding absolute ethyl alcohol, soaking for 15 min by ultrasound, and repeatedly cleaning with ultrapure water and absolute ethyl alcohol for 8 times.

6. And (3) drying treatment: and (4) putting the oyster shells prepared in the step (5) in a vacuum drying oven for 24 hours, setting the drying temperature to be 40 ℃, and preparing the oyster shells modified by the nano zero-valent iron.

7. And (4) storing the modified oyster shells prepared in the step (6) into a brown reagent bottle, and putting the reagent bottle into a constant-temperature drying oven for later use.

The standard curve of typical anionic surfactant sodium dodecyl benzene sulfonate in the grey water is determined, and the specific steps are as follows:

1) and preparing 100 mg/L sodium dodecyl benzene sulfonate standard use solution: weighing 25 mg of C₁₈H₂₉NaO₃S was dissolved in a 100mL beaker and transferred to a 250 mL volumetric flask and made to volume with ultra pure water.

2) And transferring 100 mg/L sodium dodecyl benzene sulfonate standard use solution of 0mL, 0.3 mL, 0.5 mL, 1.3mL, 2.1 mL and 2.5 mL respectively, fixing the volume in a 50 mL volumetric flask by using ultrapure water, adjusting the corresponding concentrations to be 0, 0.6, 1.0, 2.6, 4.2 and 5.0 mg/L respectively, adjusting the pH value to be 6-7, and preparing 0 mg/L-5.00 mg/L series standard solution.

3) And fluorescence intensity was measured at an excitation wavelength of 261 nm and an emission wavelength of 315 nm. As shown in FIG. 1, the LAS standard curve is plotted with the fluorescence intensity of 0mg/L of sodium dodecyl benzene sulfonate as ordinate and the mass concentration as abscissa, the regression equation is y = 96.977x-0.5388, and the linear correlation coefficient R is²=0.997。

Comparative testing of typical anionic surfactant sodium dodecylbenzene sulfonate in the removal of grey water:

preparing 20mg/L Sodium Dodecyl Benzene Sulfonate (SDBS) simulated wastewater: weighing 20mg of C₁₈H₂₉NaO₃S was dissolved in a 100mL beaker and transferred to a 1000 mL volumetric flask and made to volume with ultra pure water.

Weighing 5 parts of unmodified oyster shell and modified oyster shell according to 1 g each time, pouring the weighed 5 parts into different 50 mL conical flasks, adding 30 mL of prepared 20mg/L sodium dodecyl benzene sulfonate simulated wastewater respectively, rapidly sealing the conical flasks, oscillating at 25 ℃ and 210r/min, taking 10 mL of supernatant at intervals of 1 h, 12 h, 24 h, 36 h and 48 h, centrifuging at 11000 r/min and 4 ℃ for 20 min, filtering and separating impurities by using a 0.45 mu m microporous filter membrane, adjusting the pH value to be 6-7, and measuring the fluorescence intensity at an excitation wavelength of 261 nm and an emission wavelength of 315 nm.

The test result is shown in figure 2, and it is seen from figure 2 that the removal rate of the modified oyster shell to the sodium dodecylbenzene sulfonate in the simulated wastewater is as high as 90.72% (48 h), which is obviously higher than the removal rate of 45.01% of the unmodified oyster shell with the same particle size.

The contrast test shows that the modified oyster shell and the unmodified oyster shell simulate the wastewater removal effect of 10 mg/L Sodium Dodecyl Benzene Sulfonate (SDBS), and the same test mode is adopted, and the test result is as follows: the final removal rate of Sodium Dodecyl Benzene Sulfonate (SDBS) of unmodified oyster shells is 48.63%, and the final removal rate of modified oyster shells reaches 93.14%.

The contrast test of the modified oyster shell and the unmodified oyster shell simulates the wastewater removal effect of 30 mg/L Sodium Dodecyl Benzene Sulfonate (SDBS), and the same test mode is adopted, and the test result is as follows: the final removal rate of the sodium dodecyl benzene sulfonate by the unmodified oyster shell is 30.61 percent, and the final removal rate of the sodium dodecyl benzene sulfonate by the modified oyster shell reaches 83.53 percent. Compared with the detection result of sodium dodecyl benzene sulfonate simulated wastewater with the concentration of 10 mg/L and 20mg/L, the removal effect is reduced, which is mainly determined by the maximum adsorption quantity of the oyster shells, and the material reaches the adsorption saturation state at the concentration.

Example 2

The adsorption filtration column comprises the following components in structure: by high 500 mm, the internal diameter is made for 60 mm's organic glass pipe, and effective volume is 1.1L, and the filter material is filled in machine glass socle portion to the at least 10 cm department from the tube top, and the tube top is reserved has highly at least 10 cm's high space for peg graft annular water-locator and flourishing water, and machine glass socle portion is equipped with the delivery port, and the filter material is filled in the intraductal segmentation of machine glass, and the distribution of filter material is by supreme volume ratio according to in proper order down: washed sand, modified oyster shell or unmodified oyster shell and perlite =1:2: 1.

As shown in fig. 3, anadsorption column 5 of unmodified oyster shell and anadsorption column 6 of modified oyster shell are both vertically fixed on astainless steel bracket 3, theadsorption column 5 of unmodified oyster shell is filled with washed-outsand 12,unmodified oyster shell 10 andperlite 8 from bottom to top in turn, a water distribution area 7 is left at the top of a tube, and awater outlet 14 is arranged at the bottom; similarly, theabsorption column 6 of the modified oyster shell is filled with the washedsand 13, the modified oyster shell 11 and the perlite 9 from bottom to top in sequence, a water distribution area is reserved at the top of the tube, and a water outlet is arranged at the bottom of the tube. Thewater storage barrel 1 is connected in parallel with the water distribution pipe at the upper ends of theadsorption column 5 of the unmodified oyster shell and theadsorption column 6 of the modified oyster shell after passing through the hose and theperistaltic pump 2, and the branch pipes of theadsorption column 5 of the unmodified oyster shell and theadsorption column 6 of the modified oyster shell are respectively provided with arotameter 14.

Preparing simulated grey water, wherein the concentration is as follows: LAS 20mg/L, COD 150 mg/L, NH₃N12 mg/L, TN 20mg/L, TP2 mg/L. (wherein LAS represents an anionic surfactant, and the preparation method is the same as that of example 1. the sodium dodecylbenzenesulfonate is used)

Modified oyster shell and unmodified oyster shell are taken from example 1, the experiment process is that a peristaltic pump is used for continuously supplying water, the hydraulic retention time of the adsorption filtration column is 8 hours, and the LAS removal rate in the effluent of the adsorption filtration column is detected every day within 6 days. The change in LAS removal rate is shown in fig. 4, which shows from fig. 4: the removal rate of LAS by the two adsorption filtration columns is in a slow descending trend along with the time extension, compared with the adsorption column with the modified oyster shell, the adsorption column has the best removal effect, the highest removal rate is 84.15%, and the average removal rate in 6 days is 80.73%, while the adsorption column with the unmodified oyster shell has the highest removal rate of 41.02% and the average removal rate in 6 days is 36.49%.

The most important reason that the removal rate of the adsorption column to LAS is less than that of the adsorption experiment in theembodiment 1 is that the water distribution solute used in the adsorption process in theembodiment 1 is single and has no influence of other impurity ions, while the adsorption column uses simulated grey water and has complex composition, and chemical components in the simulated grey water can influence the adsorption effect of the filter material. Further, in example 1, the filter material was sufficiently contacted with the solution by the oscillation, and the adsorption effect was also affected.

Preparing simulated grey water with the concentration as follows:LAS 10 mg/L, COD 150 mg/L,NH₃n12 mg/L, TN 20mg/L and TP2 mg/L, the adsorption filtration device and the operation process are the same as those in the above, and the filter material synthesis steps and the simulated wastewater preparation method are the same as those in example 1. The detection result is as follows: the removal rate of LAS by the two adsorption filtration columns is in a slow descending trend along with the time extension, the average removal rate of the adsorption column of the modified oyster shell in 6 days is 82.46%, and the average removal rate of the adsorption column of the unmodified oyster shell in 6 days is 39.57%.

Preparing simulated grey water with the concentration as follows: LAS 30 mg/L, COD 150 mg/L, NH₃N12 mg/L, TN 20mg/L and TP2 mg/L, the adsorption filtration device and the operation process are the same as those in the above, and the filter material synthesis steps and the simulated wastewater preparation method are the same as those in example 1. The detection result is as follows: the removal rate of LAS by the two adsorption filtration columns is in slow decline with time, the average removal rate of the adsorption column of modified oyster shell in 6 days is 76.91%, and the average removal rate of the adsorption column of unmodified oyster shell in 6 days is 24.38%.

Claims (9)

1. A modified oyster shell comprises oyster shell particles, and is characterized in that: mixing Concha Ostreae granules in iron ion solution, and reducing ferric iron dispersed on microporous surface of Concha Ostreae into nanometer zero-valent iron with tea polyphenols extracted from dried green tea as reducing agent under nitrogen protection.

2. A method for preparing modified oyster shells as claimed in claim 1, which comprises the steps of:

step 1, oyster shell pretreatment: pulverizing natural Concha Ostreae into Concha Ostreae particles, soaking in ultrapure water, ultrasonic treating, oven drying, and further pulverizing and sieving dried Concha Ostreae;

step 2, increasing the aperture of the oyster shell: placing the mixture into a drying oven for later use after acidification and calcination;

step 3, extracting tea polyphenol: dissolving dried green tea in ethanol solution, heating, stirring, extracting and filtering in a water bath kettle to obtain tea polyphenol solution;

step 4, in-situ synthesis of the novel filter material: uniformly stirring the oyster shell granules prepared in the step 2 and an iron ion solution in a three-neck flask, then dripping the tea polyphenol solution extracted in the step 3 into the oyster shell granules at a constant speed by using a constant-pressure dropping funnel under the condition of nitrogen protection, and continuously stirring for 10-20 min after dripping;

step 5, separation and cleaning: separating solid modified oyster shells generated at the bottom of the three-neck flask from the solution, and washing with ultrapure water and absolute ethyl alcohol for multiple times;

and step 6, drying treatment: and (5) putting the oyster shells cleaned in the step (5) into a vacuum constant-temperature drying box to obtain the oyster shells modified by the nano zero-valent iron.

3. The method of claim 2, wherein: and (4) storing the modified oyster shells prepared in the step (6) into a brown reagent bottle, and putting the reagent bottle into a constant-temperature drying oven for later use.

4. The method according to claim 2 or 3, wherein: in the step 1, the primarily crushed oyster shells have a particle size of 1-2 cm, are soaked in ultrapure water for 20 h, ultrasonically treated for 4 h, and dried for 24 h, are further crushed into 5-10 mesh oyster shells with a particle size of 2-4 mm, and are placed in a drying oven for later use.

5. The method of claim 2, wherein: in step 2, HNO with the concentration of 0.01 mol/L is adopted₃HCl or H₂SO₄Soaking for 30 min for acidification and pore-forming, and calcining for 45min in a muffle furnace at the temperature of 650-850 ℃ to increase the pore diameter.

6. The method of claim 2, wherein: in the step 3, grinding the dry green tea into 18-mesh dry green tea powder, dissolving the dry green tea powder in 50% ethanol solution, extracting tea polyphenol at 80 ℃ for 1 h, wherein the adding ratio of the dry green tea powder to the ethanol solution is 1 g/20 mL, and performing magnetic stirring.

7. The method of claim 6, wherein: in step 4, the iron ion solution is FeCl₃•6H₂O, the concentration of the solution is 0.1mol/L, the product ratio of tea polyphenol to iron ion solution is 3: 1, the adding ratio of oyster shell particles to iron ion solution is 20 g/50 mL, the dripping speed of the tea polyphenol extracting solution is controlled at 12.5 mL/min, and the mechanical stirring speed in the synthetic reaction is 290 r/min.

8. The modified oyster shell of claim 1 for use in the removal of anionic surfactants in rural grey water.

9. The utility model provides an use requirement 1 modified oyster shell preparation adsorb filtration column, includes the organic glass pipe, the filter material is filled in machine glass socle portion to the at least 10 cm department from the tube top, and annular water-locator pegs graft at the machine glass mouth of pipe, is equipped with delivery port, characterized by in machine glass socle portion: the inside section of glass tube of machine is filled with the filter material, and the distribution of filter material is by supreme volume ratio according to in proper order down: washed sand, modified oyster shell or unmodified oyster shell and perlite =1:2: 1.

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