Zero-discharge recycling process and system for photovoltaic cell production wastewater

Abstract

The invention discloses a zero-discharge recycling process and system for photovoltaic cell production wastewater. The system comprises a first-stage reaction tank A, a first-stage reaction tank B, a first-stage reaction tank C, a first-stage flocculation tank, a second-stage reaction tank A, a second-stage reaction tank B, a second-stage flocculation tank, a third-stage reaction tank, a third-stage flocculation tank and an electro-adsorption module which are connected in sequence. According to the invention, the electro-adsorption technology is combined, so that the photovoltaic cell production wastewater can be efficiently purified; the ordered mesoporous carbon material with the large specific surface area is selected as the electrode plate material, the ordered mesoporous carbon material has the good adsorption capacity, after electrification, double electric layers can be formed on the surface of the adsorption material, diffusion layers of the double electric layers are compressed, the charge density is increased, the demanded quantity of counter ions is increased, and more ions are gathered to the double electric layers; under the action of electric field force, the migration rate of ions is increased, so that the ions are more easily adsorbed on the material; in addition, the adsorption capacity of the electrified adsorption material is 5-10 times larger than that of the non-electrified adsorption material.

Description

Technical Field

[0001] The present invention relates to the technical field of wastewater treatment, and particularly relates to a zero-discharge recycling process and system for photovoltaic cell production wastewater. Background Art

[0002] Traditional defluorination technologies mainly include adsorbent method, precipitation method, ion exchange method, membrane separation method, etc.

[0003] The adsorbent method adsorbs and removes fluoride ions in water by using specific adsorbents. Commonly used adsorbents include activated carbon, aluminum fluoride, iron fluoride, activated alumina, hydroxyapatite (bone char), etc. These adsorbents have a high affinity for fluorine and can effectively adsorb fluoride ions in water onto their surfaces to achieve the purpose of defluorination. Although activated carbon has a particularly large specific surface area, its pore size is also very large, and it is easy for fluoride ions to escape after entering the pores. Therefore, the adsorption capacity for fluoride ions is very low, and it cannot be regenerated. After adsorption saturation, it can only be discarded, resulting in high operating costs. The hydroxyapatite material has a high price, poor strength and is easy to break, complex operation, difficult management, fishy smell in the effluent, and even the possibility of ammonia nitrogen exceeding the standard. The continuous operation time of activated alumina is short, the regeneration time is long and complex, and the management is complex; the filter material is prone to caking, resulting in uneven water distribution and water collection, seriously affecting the service life; the effluent water quality is poor, and it can only reduce fluoride and cannot remove harmful substances such as chromaticity, turbidity, and heavy metal ions that sometimes coexist in the water body; it is afraid of coexisting phosphates in the water. Once the surface area of activated alumina is occupied by phosphates, the defluorination function will end.

[0004] The precipitation method adds chemical agents (such as aluminum hydroxide, calcium fluoride, barium fluoride, calcium hydroxide, magnesium hydroxide, etc.) to make the fluoride ions in water react with them to form insoluble precipitates, and then removes the fluoride ions from the water through the formation and precipitation process of the precipitates. The reaction time is long, and it takes a certain time to complete the chemical reaction and precipitation process. The sludge treatment is difficult, and the generated precipitates need subsequent treatment, which may increase the treatment cost and environmental burden. The treatment precision is poor. For high-concentration fluoride-containing wastewater, the treatment effect may not be ideal, and it is difficult for the effluent to meet the discharge standard.

[0005] The ion exchange method exchanges fluoride ions in water with other anions on the ion exchange resin to achieve the purpose of defluorination. Commonly used ion exchange resins include strongly basic resins and strongly acidic resins, etc. Limited water treatment capacity: suitable for treating small amounts of water, and may not be efficient enough for large-scale water treatment systems. The resin regeneration is complex. The resin needs to be regenerated regularly to restore its exchange capacity, and the regeneration process may be complex and costly. The management difficulty is large, and strict control of operating conditions and treatment effects is required to ensure the defluorination effect and water quality safety.

[0006] The membrane separation method realizes defluorination through the selective permeation of the membrane. Common membrane separation methods include reverse osmosis, nanofiltration, ultrafiltration, etc. The pore sizes of these membranes are relatively small, which can prevent the passage of fluoride ions, thereby removing fluoride ions from water. There is a large amount of concentrated water. A large amount of concentrated water will be generated during the membrane separation process, which needs to be treated again or discharged. The price of membrane modules is high. High-quality membrane modules are expensive, increasing the treatment cost. Membrane fouling and lifespan issues. Membranes are prone to fouling and damage, and need to be replaced or cleaned regularly, increasing the maintenance cost and time.

[0007] RO treated water, that is, water treated by RO (Reverse Osmosis) technology, although it has the effect of efficient water purification, also has some disadvantages. The RO reverse osmosis technology requires a large amount of energy to drive the water permeation process. This is because a certain pressure needs to be applied to the reverse osmosis membrane to permeate water molecules from a high-concentration solution to a low-concentration solution, and electrical energy or mechanical energy is consumed in this process. Therefore, the energy consumption of RO treated water is relatively high. RO treated water equipment involves precision mechanical and electronic components, so the maintenance and repair costs are relatively high. At the same time, as the core component, the lifespan of the reverse osmosis membrane is limited and needs to be replaced regularly. This not only increases the maintenance cost of the equipment, but also may affect the normal operation of the equipment and the water purification effect. RO treated water equipment has limited adaptability to water quality and temperature. If the water quality is too poor or the temperature is too high / low, it may affect the normal operation of the equipment and the water purification effect. Therefore, when using RO treated water equipment, it is necessary to pay attention to the changes in water quality and temperature and take corresponding measures for adjustment.

[0008] Traditional wastewater treatment technologies face problems such as complex systems, high operating costs, easy scaling and corrosion. Therefore, it is necessary to improve the existing technologies to provide more reliable solutions. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a zero-discharge and reuse process and system for photovoltaic cell production wastewater in view of the above-mentioned deficiencies in the prior art.

[0010] To solve the above technical problems, the technical solution adopted by the present invention is: In the first aspect of the present invention, a zero-discharge and reuse system for photovoltaic cell production wastewater is provided, including a first-stage reaction tank A, a first-stage reaction tank B, a first-stage reaction tank C, a first-stage flocculation tank, a second-stage reaction tank A, a second-stage reaction tank B, a second-stage flocculation tank, a third-stage reaction tank, a third-stage flocculation tank, and an electro-adsorption module connected in sequence.

[0011] Preferably, the system further includes a sludge thickening tank for concentrating the sludge generated in the first-stage flocculation tank, the second-stage flocculation tank, and the third-stage flocculation tank, and a sludge filter press for filtering the sludge concentrated by the sludge thickening tank.

[0012] Preferably, the supernatant of the first-stage flocculation tank enters the second-stage reaction tank A, the supernatant of the second-stage flocculation tank enters the third-stage reaction tank, and the supernatant of the third-stage flocculation tank enters the electro-adsorption module. The fresh water obtained after the treatment of the electro-adsorption module is reused as qualified discharge water, and the concentrated water is refluxed to the first-stage reaction tank A.

[0013] Preferably, the material of the electrode plate used in the electro-adsorption module is an ordered mesoporous carbon material, and the ordered mesoporous carbon material is prepared by the following method:

[0014] 1) Add P123 to ethanol to prepare a template agent solution. Add phenolic resin to the template agent solution, and then add hydrochloric acid as a catalyst, and react under heating and stirring;

[0015] 2) After the reaction, stand at room temperature for aging, pour the obtained solution into a mold, and perform curing treatment under heating;

[0016] 3) Heat and carbonize the product obtained in step 2) under the protection of an inert gas, immerse the obtained product in ethanol after cooling to room temperature, take it out, wash and dry it to constant weight to obtain a porous carbon material;

[0017] 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution, mix evenly, heat and activate the obtained mixture under the protection of an inert gas, wash it with ethanol after cooling to room temperature, and dry it to constant weight to obtain the ordered mesoporous carbon material.

[0018] Preferably, the ordered mesoporous carbon material is prepared by the following method:

[0019] 1) Add P123 to ethanol to prepare a template agent solution with a mass concentration of P123 of 2.5-10%. Add phenolic resin to the template agent solution, control the mass ratio of phenolic resin to P123 to be 2-8:1, and then add hydrochloric acid with a concentration of 0.25-1 mol / L as a catalyst. The mass of hydrochloric acid is 5-20% of P123, and react under stirring at 30-50°C and 200-800 rpm for 5-20 h;

[0020] 2) After the reaction, stand at room temperature for 6-24 h for aging, pour the obtained solution into a mold, and perform curing treatment at 50-70°C for 6-24 h;

[0021] 3) Heat and carbonize the product obtained in step 2) under nitrogen protection at 700-900°C for 3-12 h, immerse the obtained product in ethanol after cooling to room temperature, soak it for 12-48 h, take it out, wash and dry it to constant weight to obtain a porous carbon material;

[0022] 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution with a mass concentration of 15 - 60%, control the liquid - solid ratio to be 1.5 - 6, mix evenly, and then heat and activate the resulting mixture under nitrogen protection at 500 - 700 °C for 1 - 4 h. After cooling to room temperature, wash with ethanol and dry to constant weight to obtain the ordered mesoporous carbon material.

[0023] Preferably, the ordered mesoporous carbon material is prepared by the following method:

[0024] 1) Add P123 to ethanol to prepare a template agent solution with a mass concentration of 5% of P123. Add phenolic resin to the template agent solution, control the mass ratio of phenolic resin to P123 to be 4:1, and then add 0.5 mol / L hydrochloric acid as a catalyst. The mass of hydrochloric acid is 10% of P123, and react at 40 °C and 400 rpm with stirring for 10 h;

[0025] 2) After the reaction, let it stand at room temperature for 12 h for aging. Pour the resulting solution into a mold and cure it at 60 °C for 12 h;

[0026] 3) Heat - carbonize the product obtained in step 2) under nitrogen protection at 800 °C for 6 h. After cooling to room temperature, immerse the resulting product in ethanol, soak for 24 h, take it out, wash, and dry to obtain a porous carbon material;

[0027] 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution with a mass concentration of 30%, control the liquid - solid ratio to be 3, mix evenly, and then heat and activate the resulting mixture under nitrogen protection at 600 °C for 2 h. After cooling to room temperature, wash with ethanol and dry to constant weight to obtain the ordered mesoporous carbon material.

[0028] In the second aspect of the present invention, a zero - discharge recycling process for photovoltaic cell production wastewater is provided. It uses the above - mentioned system for wastewater treatment, and this process includes the following steps:

[0029] S1. Input the acid - containing wastewater and alkali - containing wastewater generated during the production of photovoltaic cells into the first - stage reaction tank A, add alkali to adjust the pH in the first - stage reaction tank A, stir and react, and then enter the first - stage reaction tank B; add acid to adjust the pH in the first - stage reaction tank B, stir and react, and then enter the first - stage reaction tank C; add a first flocculant to the first - stage reaction tank C, stir and react, and then the effluent enters the first flocculation tank; add a second flocculant to the first flocculation tank for flocculation and sedimentation;

[0030] S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A. Sodium aluminate is added to the secondary reaction tank A, and acid is added to the secondary reaction tank A to adjust the pH, followed by stirring for reaction. The effluent from the secondary reaction tank A enters the secondary reaction tank B. Na2CO3 is added to the secondary reaction tank B, and stirring for reaction is carried out. The effluent from the secondary reaction tank B enters the secondary flocculation tank. A second flocculant is added to the secondary flocculation tank for flocculation and sedimentation.

[0031] S3. The supernatant in the secondary flocculation tank enters the tertiary reaction tank. Ca(OH)2 is added to the tertiary reaction tank to adjust the pH, followed by stirring for reaction. The effluent from the tertiary reaction tank enters the tertiary flocculation tank. A second flocculant is added to the tertiary flocculation tank for flocculation and sedimentation.

[0032] S4. The supernatant in the tertiary flocculation tank enters the electro-adsorption module. The fresh water obtained after the treatment by the electro-adsorption module is reused as qualified discharged water, and the concentrated water obtained is recycled to the primary reaction tank A for cyclic treatment.

[0033] Among them, the sludge generated from flocculation and sedimentation in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained sludge cake is entrusted to an external party for treatment.

[0034] Preferably, the alkali added to the primary reaction tank A is a Ca(OH)2 solution with a mass concentration of 5 - 20%, and the acid is a H2SO4 solution with a mass concentration of 25 - 80%.

[0035] The first flocculant is polyaluminum chloride, and the second flocculant is polyacrylamide.

[0036] The acid added to the secondary reaction tank A is a HCl solution with a concentration of 0.25 - 1 mol / L.

[0037] Preferably, the process includes the following steps:

[0038] S1. The acid-containing wastewater and alkali-containing wastewater generated in the production process of photovoltaic cells are input into the primary reaction tank A. A Ca(OH)2 solution with a mass concentration of 5 - 20% is added to the primary reaction tank A to adjust the pH to 10 - 12, and after stirring for reaction for 5 - 30 min, it enters the primary reaction tank B. A H2SO4 solution with a mass concentration of 25 - 80% is added to the primary reaction tank B to adjust the pH to 8.5 - 9, and after stirring for reaction for 10 - 40 min, it enters the primary reaction tank C. Polyaluminum chloride with a concentration of 50 - 200 ppm is added to the primary reaction tank C, and after stirring for reaction for 5 - 20 min, then the effluent enters the primary flocculation tank. Polyacrylamide is added to the primary flocculation tank for flocculation and sedimentation.

[0039] S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A. Sodium aluminate is added to the secondary reaction tank A, and the addition amount of sodium aluminate is controlled to satisfy that the mass ratio of sodium aluminate to SiO2 in water is 1.5 - 6:1. A HCl solution with a concentration of 0.25 - 1 mol / L is added to the secondary reaction tank A to adjust the pH to 8 - 9, and stirring reaction is carried out for 15 - 60 min. The effluent from the secondary reaction tank A enters the secondary reaction tank B. A Na2CO3 solution with a mass concentration of 15 - 60% is added to the secondary reaction tank B, and the molar ratio of CO3 2- : Ca 2+ in water is controlled to be 1 - 4:1, and stirring reaction is carried out for 15 - 60 min. The effluent from the secondary reaction tank B enters the secondary flocculation tank. Polyacrylamide is added to the secondary flocculation tank for flocculation sedimentation;

[0040] S3. The supernatant in the secondary flocculation tank enters the tertiary reaction tank. A Ca(OH)2 solution with a mass concentration of 5 - 20% is added to the tertiary reaction tank to adjust the pH to 6 - 7, and stirring reaction is carried out for 15 - 60 min. The effluent from the tertiary reaction tank enters the tertiary flocculation tank. Polyacrylamide is added to the tertiary flocculation tank for flocculation sedimentation;

[0041] S4. The supernatant in the tertiary flocculation tank enters the electro - adsorption module. The fresh water obtained after the treatment of the electro - adsorption module is reused as qualified discharged water, and the concentrated water obtained is recycled to the primary reaction tank A for cyclic treatment;

[0042] Among them, the sludge generated by flocculation sedimentation in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained sludge cake is outsourced for treatment.

[0043] Preferably, the process includes the following steps:

[0044] S1. The acid - containing wastewater and alkali - containing wastewater generated in the production process of photovoltaic cell wafers are mixed and input into the primary reaction tank A. A Ca(OH)2 solution with a mass concentration of 10% is added to the primary reaction tank A to adjust the pH to 10 - 12, and after stirring reaction for 15 min, it enters the primary reaction tank B. A H2SO4 solution with a mass concentration of 50% is added to the primary reaction tank B to adjust the pH to 8.5 - 9, and after stirring reaction for 20 min, it enters the primary reaction tank C. Poly - aluminum chloride with a concentration of 100 ppm is added to the primary reaction tank C, and stirring reaction is carried out for 10 min, and then the effluent enters the primary flocculation tank. Polyacrylamide is added to the primary flocculation tank for flocculation sedimentation;

[0045] S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A. Sodium aluminate is added to the secondary reaction tank A, and the addition amount of sodium aluminate is controlled to satisfy that the mass ratio of sodium aluminate to SiO2 in water is 3:1. A HCl solution with a concentration of 0.5 mol / L is added to the secondary reaction tank A to adjust the pH to 8 - 9, and the mixture is stirred and reacted for 30 min. The effluent from the secondary reaction tank A enters the secondary reaction tank B. A Na2CO3 solution with a mass concentration of 30% is added to the secondary reaction tank B, and the molar ratio of CO3 2- : Ca 2+ is controlled to be 2:1, and the mixture is stirred and reacted for 30 min. The effluent from the secondary reaction tank B enters the secondary flocculation tank. Polyacrylamide is added to the secondary flocculation tank for flocculation and sedimentation;

[0046] S3. The supernatant in the secondary flocculation tank enters the tertiary reaction tank. A Ca(OH)2 solution with a mass concentration of 10% is added to the tertiary reaction tank to adjust the pH to 6 - 7, and the mixture is stirred and reacted for 30 min. The effluent from the tertiary reaction tank enters the tertiary flocculation tank. Polyacrylamide is added to the tertiary flocculation tank for flocculation and sedimentation;

[0047] S4. The supernatant in the tertiary flocculation tank enters the electro - adsorption module. The fresh water obtained after the treatment of the electro - adsorption module is used as qualified discharged water for reuse, and the concentrated water obtained is refluxed to the primary reaction tank A for cyclic treatment;

[0048] Among them, the sludge generated by flocculation and sedimentation in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained sludge cake is entrusted to an external party for treatment.

[0049] The beneficial effects of the present invention are as follows:

[0050] The present invention provides a zero - discharge and reuse process and system for photovoltaic cell production wastewater. By combining the electro - adsorption technology in the present invention, the high - efficiency purification of photovoltaic cell production wastewater can be realized;

[0051] The electro - adsorption technology, also known as the capacitive deionization technology, is a new type of water treatment technology that can realize water purification and desalination. It can effectively remove impurity ions in water without scaling under the premise of low energy consumption; it has the advantages of "multi - use of one water, cascade utilization", no external discharge of wastewater. Based on the increasingly strict environmental protection requirements, the electro - adsorption technology has the advantages of low energy consumption, low cost, and no secondary pollution. The investment in the electro - adsorption process device is slightly higher than that of the thermal method and membrane method process devices, but in the subsequent operation process, the chemical addition cost and membrane replacement cost are reduced; since the adsorption material selects inexpensive and easily available carbon materials as the main raw material, this material has good stability and does not need to be replaced frequently; and the electro - adsorption technology can remove the salts in water without adding chemicals, saving costs and avoiding unnecessary impurities. The electro - adsorption module itself does not produce new emissions, avoiding secondary pollution.

[0052] The present invention selects an ordered mesoporous carbon material with a relatively large specific surface area as the electrode plate material, which itself has a good adsorption capacity. After being energized, an electric double layer will be formed on the surface of the adsorption material. The diffusion layer of the electric double layer is compressed, the charge density increases, and the demand for counterions increases, causing more ions to gather in the electric double layer; under the action of the electric field force, the migration rate of ions increases, making it easier for ions to be adsorbed on the material; in addition, the adsorption capacity of the adsorption material after being energized is 5 to 10 times greater than that of the non-energized adsorption material. Description of the Drawings

[0053] Figure 1 It is a schematic structural diagram of a zero-discharge recycling system for photovoltaic cell production wastewater in Example 1;

[0054] Figure 2 It is a schematic structural diagram of the electro-adsorption module in Example 1;

[0055] Description of the Reference Numerals in the Drawings:

[0056] 1—Primary reaction tank A; 2—Primary reaction tank B; 3—Primary reaction tank C; 4—Primary flocculation tank; 5—Secondary reaction tank A; 6—Secondary reaction tank B; 7—Secondary flocculation tank; 8—Tertiary reaction tank; 9—Tertiary flocculation tank; 10—Electro-adsorption module; 11—Sludge thickening tank; 12—Sludge filter press; 101—Reaction vessel; 102—Cation exchange membrane; 103—Cathode plate; 104—Anion exchange membrane; 105—Anode plate; 106—Inlet; 107—Purified water outlet; 108—Concentrated water outlet. Detailed Embodiments

[0057] The following further describes the present invention in detail with reference to embodiments, so that those skilled in the art can implement it according to the description in the specification.

[0058] It should be understood that the terms such as "having", "comprising", and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0059] Unless otherwise specified, the test methods used in the following embodiments are all conventional methods. The materials, reagents, etc. used in the following embodiments can all be obtained from commercial sources unless otherwise specified. For those not indicating specific conditions in the following embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For those reagents or instruments not indicating the manufacturer, they are all conventional products that can be purchased commercially.

[0060] The present invention provides a zero-discharge recycling system for photovoltaic cell production wastewater, including a primary reaction tank A, a primary reaction tank B, a primary reaction tank C, a primary flocculation tank, a secondary reaction tank A, a secondary reaction tank B, a secondary flocculation tank, a tertiary reaction tank, a tertiary flocculation tank, and an electro-adsorption module connected in sequence.

[0061] In a preferred embodiment, the system further includes a sludge thickening tank for thickening the sludge generated in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank, and a sludge filter press for filtering the sludge thickened by the sludge thickening tank.

[0062] In a preferred embodiment, the supernatant of the primary flocculation tank enters the secondary reaction tank A, the supernatant of the secondary flocculation tank enters the tertiary reaction tank, the supernatant of the tertiary flocculation tank enters the electro-adsorption module, and the fresh water obtained after the treatment of the electro-adsorption module is reused as qualified discharged water, and the concentrated water is refluxed to the primary reaction tank A.

[0063] In a preferred embodiment, the material of the electrode plate used in the electro-adsorption module is an ordered mesoporous carbon material, and the ordered mesoporous carbon material is prepared by the following method:

[0064] 1) Add P123 to ethanol to prepare a template agent solution, add phenolic resin to the template agent solution, then add hydrochloric acid as a catalyst, and react under heating and stirring;

[0065] 2) After the reaction, stand at room temperature for aging, pour the obtained solution into a mold, and cure it under heating;

[0066] 3) Heat and carbonize the product obtained in step 2) under the protection of an inert gas, immerse the obtained product in ethanol after cooling to room temperature, take it out, wash it, and dry it to constant weight to obtain a porous carbon material;

[0067] 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution, mix it evenly, heat and activate the obtained mixture under the protection of an inert gas, wash it with ethanol after cooling to room temperature, and dry it to constant weight to obtain the ordered mesoporous carbon material.

[0068] In a preferred embodiment, the ordered mesoporous carbon material is prepared by the following method:

[0069] 1) Add P123 to ethanol to prepare a template agent solution with a mass concentration of P123 of 2.5-10%, add phenolic resin to the template agent solution, control the mass ratio of phenolic resin to P123 to be 2-8:1, then add hydrochloric acid with a concentration of 0.25-1 mol / L as a catalyst, the mass of hydrochloric acid is 5-20% of P123, and react at 30-50 °C and 200-800 rpm for 5-20 h under stirring;

[0070] 2) After the reaction, stand at room temperature for 6-24 h for aging, pour the obtained solution into a mold, and cure it at 50-70 °C for 6-24 h;

[0071] 3) Heat and carbonize the product obtained in step 2) under nitrogen protection at 700 - 900 °C for 3 - 12 h. After cooling to room temperature, immerse the obtained product in ethanol for 12 - 48 h, take it out, wash and dry it to constant weight to obtain the porous carbon material;

[0072] 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution with a mass concentration of 15 - 60%, control the liquid - solid ratio to be 1.5 - 6, mix evenly, and then heat and activate the obtained mixture under nitrogen protection at 500 - 700 °C for 1 - 4 h. After cooling to room temperature, wash it with ethanol and dry it to constant weight to obtain the ordered mesoporous carbon material.

[0073] In a preferred embodiment, the ordered mesoporous carbon material is prepared by the following method:

[0074] 1) Add P123 to ethanol to prepare a template agent solution with a mass concentration of 5% of P123. Add phenolic resin to the template agent solution, control the mass ratio of phenolic resin to P123 to be 4:1, then add 0.5 mol / L hydrochloric acid as a catalyst, and the mass of hydrochloric acid is 10% of P123. React at 40 °C and 400 rpm for 10 h;

[0075] 2) After the reaction, let it stand at room temperature for 12 h for aging. Pour the obtained solution into a mold and cure it at 60 °C for 12 h;

[0076] 3) Heat and carbonize the product obtained in step 2) under nitrogen protection at 800 °C for 6 h. After cooling to room temperature, immerse the obtained product in ethanol for 24 h, take it out, wash and dry it to obtain the porous carbon material;

[0077] 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution with a mass concentration of 30%, control the liquid - solid ratio to be 3, mix evenly, and then heat and activate the obtained mixture under nitrogen protection at 600 °C for 2 h. After cooling to room temperature, wash it with ethanol and dry it to constant weight to obtain the ordered mesoporous carbon material.

[0078] The present invention also provides a zero - discharge recycling process for the wastewater produced in the production of photovoltaic cell wafers. It uses the above - mentioned system for wastewater treatment, and this process includes the following steps:

[0079] S1. Input the acid - containing wastewater and alkali - containing wastewater generated in the production of photovoltaic cell wafers into the first - stage reaction tank A, add alkali to adjust the pH in the first - stage reaction tank A, stir and react, and then enter the first - stage reaction tank B; add acid to adjust the pH in the first - stage reaction tank B, stir and react, and then enter the first - stage reaction tank C; add the first flocculant to the first - stage reaction tank C, stir and react, and then the effluent enters the first flocculation tank; add the second flocculant to the first flocculation tank for flocculation and sedimentation;

[0080] S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A. Sodium aluminate is added to the secondary reaction tank A, and acid is added to the secondary reaction tank A to adjust the pH, followed by stirring for reaction; the effluent from the secondary reaction tank A enters the secondary reaction tank B. Na2CO3 is added to the secondary reaction tank B, followed by stirring for reaction; the effluent from the secondary reaction tank B enters the secondary flocculation tank. A second flocculant is added to the secondary flocculation tank for flocculation and sedimentation;

[0081] S3. The supernatant in the secondary flocculation tank enters the tertiary reaction tank. Ca(OH)2 is added to the tertiary reaction tank to adjust the pH, followed by stirring for reaction; the effluent from the tertiary reaction tank enters the tertiary flocculation tank. A second flocculant is added to the tertiary flocculation tank for flocculation and sedimentation;

[0082] S4. The supernatant in the tertiary flocculation tank enters the electro-sorption module. The fresh water obtained after the treatment by the electro-sorption module is reused as qualified discharged water, and the concentrated water obtained is recycled to the primary reaction tank A for cyclic treatment;

[0083] Among them, the sludge generated by flocculation and sedimentation in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained sludge cake is sent out for off-site treatment.

[0084] In a preferred embodiment, the alkali added to the primary reaction tank A is a Ca(OH)2 solution with a mass concentration of 5-20%, and the acid is a H2SO4 solution with a mass concentration of 25-80%;

[0085] The first flocculant is polyaluminum chloride, and the second flocculant is polyacrylamide;

[0086] The acid added to the secondary reaction tank A is a HCl solution with a concentration of 0.25-1 mol / L.

[0087] In a preferred embodiment, the process comprises the following steps:

[0088] S1. The acid-containing wastewater and alkali-containing wastewater generated in the production process of photovoltaic cell wafers are input into the primary reaction tank A. A Ca(OH)2 solution with a mass concentration of 5-20% is added to the primary reaction tank A to adjust the pH to 10-12, and after stirring for reaction for 5-30 min, it enters the primary reaction tank B; a H2SO4 solution with a mass concentration of 25-80% is added to the primary reaction tank B to adjust the pH to 8.5-9, and after stirring for reaction for 10-40 min, it enters the primary reaction tank C; polyaluminum chloride with a concentration of 50-200 ppm is added to the primary reaction tank C, and after stirring for reaction for 5-20 min, then the effluent enters the primary flocculation tank; polyacrylamide is added to the primary flocculation tank for flocculation and sedimentation;

[0089] S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A. Sodium aluminate is added to the secondary reaction tank A, and the addition amount of sodium aluminate is controlled to satisfy that the mass ratio of sodium aluminate to SiO2 in water is 1.5 - 6:1. A HCl solution with a concentration of 0.25 - 1 mol / L is added to the secondary reaction tank A to adjust the pH to 8 - 9, and stirring reaction is carried out for 15 - 60 min. The effluent from the secondary reaction tank A enters the secondary reaction tank B. A Na2CO3 solution with a mass concentration of 15 - 60% is added to the secondary reaction tank B, and the molar ratio of CO3 2- : Ca 2+ in water is controlled to be 1 - 4:1, and stirring reaction is carried out for 15 - 60 min. The effluent from the secondary reaction tank B enters the secondary flocculation tank. Polyacrylamide is added to the secondary flocculation tank for flocculation sedimentation;

[0090] S3. The supernatant in the secondary flocculation tank enters the tertiary reaction tank. A Ca(OH)2 solution with a mass concentration of 5 - 20% is added to the tertiary reaction tank to adjust the pH to 6 - 7, and stirring reaction is carried out for 15 - 60 min. The effluent from the tertiary reaction tank enters the tertiary flocculation tank. Polyacrylamide is added to the tertiary flocculation tank for flocculation sedimentation;

[0091] S4. The supernatant in the tertiary flocculation tank enters the electro - adsorption module. The fresh water obtained after the electro - adsorption module treatment is reused as qualified discharged water, and the concentrated water obtained is recycled to the primary reaction tank A for circular treatment;

[0092] Among them, the sludge generated by flocculation sedimentation in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained sludge cake is outsourced for treatment.

[0093] In a preferred embodiment, the process includes the following steps:

[0094] S1. The acid - containing wastewater and alkali - containing wastewater generated in the production process of photovoltaic cell wafers are input into the primary reaction tank A. A Ca(OH)2 solution with a mass concentration of 10% is added to the primary reaction tank A to adjust the pH to 10 - 12, and after stirring reaction for 15 min, it enters the primary reaction tank B. A H2SO4 solution with a mass concentration of 50% is added to the primary reaction tank B to adjust the pH to 8.5 - 9, and after stirring reaction for 20 min, it enters the primary reaction tank C. Poly aluminum chloride with a concentration of 100 ppm is added to the primary reaction tank C, and stirring reaction is carried out for 10 min, and then the effluent enters the primary flocculation tank. Polyacrylamide is added to the primary flocculation tank, and the addition concentration is 2 ppm, and flocculation sedimentation is carried out for 10 min;

[0095] S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A. Sodium aluminate is added to the secondary reaction tank A, and the addition amount of sodium aluminate is controlled to meet the mass ratio of sodium aluminate to SiO2 in water of 3:1. A 0.5 mol / L HCl solution is added to the secondary reaction tank A to adjust the pH to 8 - 9, and the mixture is stirred and reacted for 30 min. The effluent from the secondary reaction tank A enters the secondary reaction tank B. A 30% Na2CO3 solution by mass concentration is added to the secondary reaction tank B, and the molar ratio of CO3 2- :Ca 2+ in water is controlled to be 2:1, and the mixture is stirred and reacted for 30 min. The effluent from the secondary reaction tank B enters the secondary flocculation tank. Polyacrylamide is added to the secondary flocculation tank, and the addition concentration is 2 ppm, and the mixture is flocculated and settled for 10 min;

[0096] S3. The supernatant in the secondary flocculation tank enters the tertiary reaction tank. A 10% Ca(OH)2 solution by mass concentration is added to the tertiary reaction tank to adjust the pH to 6 - 7, and the mixture is stirred and reacted for 30 min. The effluent from the tertiary reaction tank enters the tertiary flocculation tank. Polyacrylamide is added to the tertiary flocculation tank, and the addition concentration is 2 ppm, and the mixture is flocculated and settled for 10 min;

[0097] S4. The supernatant in the tertiary flocculation tank enters the electro - adsorption module. The fresh water obtained after the treatment of the electro - adsorption module is used as qualified discharged water for reuse, and the concentrated water obtained is refluxed to the primary reaction tank A for cyclic treatment;

[0098] Among them, the sludge generated by flocculation and sedimentation in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained sludge cake is outsourced for treatment.

[0099] The above is the general concept of the present invention. The following provides detailed examples and comparative examples on this basis to further illustrate the present invention.

[0100] Example 1

[0101] A zero - discharge reuse system for photovoltaic cell production wastewater, comprising a primary reaction tank A (1), a primary reaction tank B (2), a primary reaction tank C (3), a primary flocculation tank (4), a secondary reaction tank A (5), a secondary reaction tank B (6), a secondary flocculation tank (7), a tertiary reaction tank (8), a tertiary flocculation tank (9), and an electro - adsorption module (10) connected in sequence, and a sludge treatment subsystem. The sludge treatment subsystem includes a sludge thickening tank 11 for concentrating the sludge generated in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank, and a sludge filter press 12 for pressure - filtering the sludge concentrated by the sludge thickening tank 11.

[0102] The supernatant of the primary flocculation tank enters the secondary reaction tank A, the supernatant of the secondary flocculation tank enters the tertiary reaction tank, and the supernatant of the tertiary flocculation tank enters the electro-adsorption module. The fresh water obtained after the treatment of the electro-adsorption module is reused as qualified discharged water, and the concentrated water is recycled to the primary reaction tank A.

[0103] In this embodiment, a set of sludge treatment subsystems are respectively configured for the primary flocculation tank, the secondary flocculation tank, and the tertiary flocculation tank. The sludge cakes generated by the three sets of sludge treatment subsystems are outsourced for treatment, and the generated filtrates flow into the next operation section respectively, that is: the filtrate in the sludge treatment subsystem corresponding to the primary flocculation tank enters the secondary reaction tank A, the filtrate in the sludge treatment subsystem corresponding to the secondary flocculation tank enters the tertiary reaction tank, and the filtrate in the sludge treatment subsystem corresponding to the tertiary flocculation tank enters the electro-adsorption module tank.

[0104] In this embodiment, the electro-adsorption module includes a reaction vessel 101, a cation exchange membrane 102 and a cathode plate 103 sequentially arranged in the reaction vessel 101 from the center to the left, an anion exchange membrane 104 and an anode plate 105 sequentially arranged in the reaction vessel 101 from the center to the right, a water inlet 106 located at the upper center of the reaction vessel 101, a purified water outlet 107 located at the lower center of the reaction vessel 101, and concentrated water outlets 108 located at both ends of the reaction vessel 101.

[0105] The working principle of the electro-adsorption module is as follows:

[0106] 1. Adsorption stage:

[0107] First, close the outlet. The wastewater enters the reaction vessel 101 from the water inlet 106. The cathode plate 103 and the anode plate 105 are respectively connected to the cathode and anode of an external power supply. Under the action of the electric field, the cations in the wastewater move to the left and are adsorbed by the cathode plate 103 on the left after passing through the cation exchange membrane 102, while the anions move to the right and are adsorbed by the anode plate 105 on the right after passing through the anion exchange membrane 104.

[0108] 2. Desorption stage:

[0109] After adsorption saturation, reverse-connect the cathode plate 103 and the anode plate 105, that is, the cathode plate 103 and the anode plate 105 are respectively connected to the anode and cathode of the external power supply. The cations adsorbed on the cathode plate 103 are desorbed into the concentrated water on the left, and the anions adsorbed on the anode plate 105 are desorbed into the concentrated water on the right. The concentrated water on the left and right is discharged from their respective concentrated water outlets 108 and recycled to the primary reaction tank A for cyclic treatment; the purified water with the removed anions and cations in the middle area is discharged from the purified water outlet 107 at the lower middle as qualified discharged water for reuse.

[0110] The electrode adsorption material is mainly carbon material, which has the advantages of large adsorption capacity, good regeneration effect, low price and easy availability. Commonly used electrode materials include activated carbon, graphene, carbon aerogel, etc. An excellent electrode adsorption material should have a large specific surface area, good chemical stability during normal operation, high ion mobility in the pore diameter, good conductivity of electrons in the electrode material, low contact resistance between the porous electrode and the current collector, good wettability, low cost and scalability, good processability, large specific surface area, and high biological inertness.

[0111] In this embodiment, the material of the electrode plate used in the electro-adsorption module is an ordered mesoporous carbon material, and the ordered mesoporous carbon material is prepared by the following method:

[0112] 1) Add P123 (polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer) to ethanol to prepare a template agent solution with a mass concentration of 5% of P123. Add phenolic resin (PF - 2A01, Jiangsu Sanmu Group) to the template agent solution, control the mass ratio of phenolic resin to P123 to be 4:1, and then add hydrochloric acid with a concentration of 0.5 mol / L as a catalyst. The mass of hydrochloric acid is 10% of P123, and react at 40 °C and 400 rpm for 10 h;

[0113] 2) After the reaction, let it stand at room temperature for 12 h for aging. Pour the obtained solution into a mold and cure it at 60 °C for 12 h;

[0114] 3) Heat and carbonize the product obtained in step 2) under nitrogen protection at 800 °C for 6 h. After cooling to room temperature, immerse the obtained product in ethanol, soak for 24 h, take it out, wash and dry to obtain a porous carbon material;

[0115] 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution with a mass concentration of 30%, control the liquid - solid ratio to be 3, mix evenly, and heat and activate the obtained mixture under nitrogen protection at 600 °C for 2 h. After cooling to room temperature, wash it with ethanol and dry to constant weight to obtain the ordered mesoporous carbon material.

[0116] Example 2

[0117] A zero - discharge recycling process for photovoltaic cell production wastewater uses the system of Example 1 for wastewater treatment. The treatment object in this example: photovoltaic cell production wastewater includes four streams of water, namely dilute acid, dilute alkali, concentrated acid, and concentrated alkali. The water quality after mixing is as follows:

[0118] Table 1

[0119]

[0120] This process includes the following steps:

[0121] S1. Input the acid-containing wastewater and alkali-containing wastewater generated in the production process of photovoltaic cells into the first-stage reaction tank A. Add a Ca(OH)₂ solution with a mass concentration of 10% to the first-stage reaction tank A to adjust the pH to 11. After stirring and reacting for 15 minutes, it enters the first-stage reaction tank B. Add a H₂SO₄ solution with a mass concentration of 50% to the first-stage reaction tank B to adjust the pH to 9. After stirring and reacting for 20 minutes, it enters the first-stage reaction tank C. Add polyaluminum chloride (PAC) with a concentration of 100 ppm to the first-stage reaction tank C, stir and react for 10 minutes, and then the effluent enters the first-stage flocculation tank. Add polyacrylamide (PAM) to the first-stage flocculation tank, with an addition concentration of 2 ppm. After the reaction forms flocs, flocculate and settle for 10 minutes, and the fluoride ion is reduced to below 20 mg / L.

[0122] S2. The supernatant in the first-stage flocculation tank enters the second-stage reaction tank A. Add sodium aluminate to the second-stage reaction tank A, and control the addition amount of sodium aluminate to satisfy that the mass ratio of sodium aluminate to SiO₂ in water is 3:1. Add a HCl solution with a concentration of 0.5 mol / L to the second-stage reaction tank A to adjust the pH to 8.5, and stir and react for 30 minutes. The effluent from the second-stage reaction tank A enters the second-stage reaction tank B. Add a Na₂CO₃ solution with a mass concentration of 30% to the second-stage reaction tank B, and control the molar ratio of CO₃ 2- :Ca 2+ in water to be 2:1, stir and react for 30 minutes. The effluent from the second-stage reaction tank B enters the second-stage flocculation tank. Add polyacrylamide to the second-stage flocculation tank, with an addition concentration of 2 ppm. After the reaction forms flocs, flocculate and settle for 10 minutes, and the silicon dioxide is reduced to below 10 mg / L, and the calcium ion concentration is reduced to below 5 mg / L.

[0123] S3. The supernatant in the second-stage flocculation tank enters the third-stage reaction tank. Add a Ca(OH)₂ solution with a mass concentration of 10% to the third-stage reaction tank to adjust the pH to 7, and stir and react for 30 minutes. The effluent from the third-stage reaction tank enters the third-stage flocculation tank. Add polyacrylamide to the third-stage flocculation tank, with an addition concentration of 2 ppm, flocculate and settle for 10 minutes, and the fluoride ion is reduced to below 2 mg / L.

[0124] S4. The supernatant in the third-stage flocculation tank enters the electro-adsorption module. The fresh water obtained after the electro-adsorption module treatment is reused as qualified effluent for discharge, and the concentrated water obtained is recycled to the first-stage reaction tank A for cyclic treatment.

[0125] Among them, the sludge generated by flocculation sedimentation in the primary flocculation tank, secondary flocculation tank, and tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor. The obtained sludge cake is outsourced for treatment, and the generated filtrate flows into the next operation section respectively, that is: the filtrate in the sludge treatment subsystem corresponding to the primary flocculation tank enters the secondary reaction tank A, the filtrate in the sludge treatment subsystem corresponding to the secondary flocculation tank enters the tertiary reaction tank, and the filtrate in the sludge treatment subsystem corresponding to the tertiary flocculation tank enters the electro-adsorption module tank.

[0126] In the reclaimed water treated in this example, the pH value is about 6.5, and all concentrations are reduced to below 0.5 mg / L, as shown in Table 2 below.

[0127] Table 2

[0128]

[0129] Comparative Example 1

[0130] The difference between this example and Example 2 is only that: the electrode of the electro-adsorption module in this example is a conventional carbon electrode, specifically: HPG-50 (high-purity graphite, diameter 5 mm), Shandong Bashan Graphite Factory.

[0131] The water quality of the reclaimed water treated in this example is as shown in Table 3 below:

[0132] Table 3

[0133]

[0134] It can be seen from the comparison of the test results in Table 3 with Table 2 that the ion removal efficiency of the electro-adsorption module with the electrode made of the ordered mesoporous carbon material prepared in Example 1 is significantly higher.

[0135] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily made. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to specific details.

Claims

1. A photovoltaic cell production wastewater zero-discharge reuse system, characterized in that: It includes a primary reaction tank A, a primary reaction tank B, a primary reaction tank C, a primary flocculation tank, a secondary reaction tank A, a secondary reaction tank B, a secondary flocculation tank, a tertiary reaction tank, a tertiary flocculation tank and an electric adsorption module which are connected in sequence.

2. The photovoltaic cell production wastewater zero-discharge reuse system according to claim 1 is characterized in that: The system also includes a sludge concentration tank for concentrating the sludge produced in the primary flocculation tank, the secondary flocculation tank and the tertiary flocculation tank, and a sludge filter press for filtering the sludge concentrated in the sludge concentration tank.

3. The photovoltaic cell production wastewater zero-discharge reuse system according to claim 2 is characterized in that: The supernatant of the primary flocculation tank enters the secondary reaction tank A, the supernatant of the secondary flocculation tank enters the tertiary reaction tank, the supernatant of the tertiary flocculation tank enters the electrosorption module, and the fresh water obtained after treatment by the electrosorption module is reused as qualified discharge water, and the concentrated water is returned to the primary reaction tank A.

4. The photovoltaic cell production wastewater zero-discharge reuse system according to claim 1 is characterized in that: The material of the electrode plate used in the electrosorption module is an ordered mesoporous carbon material, which is prepared by the following method: 1) P123 is added to ethanol to prepare a template solution, phenolic resin is added to the template solution, and then hydrochloric acid is added as a catalyst to react under heating and stirring; 2) After the reaction is completed, the mixture is aged at room temperature, and the obtained solution is poured into a mold and cured under heating; 3) heating the product obtained in step 2) under the protection of an inert gas for carbonization, cooling the product to room temperature, immersing the product in ethanol, taking it out, washing it, and drying it to a constant weight to obtain a porous carbon material; 4) Grinding the porous carbon material obtained in step 3) into powder, then adding it to a Na2CO3 solution, mixing it evenly, heating and activating the resulting mixture under the protection of an inert gas, cooling it to room temperature, washing it with ethanol, and drying it to constant weight to obtain the ordered mesoporous carbon material.

5. The photovoltaic cell production wastewater zero-discharge reuse system according to claim 4 is characterized in that: The ordered mesoporous carbon material is prepared by the following method: 1) P123 is added to ethanol to prepare a template solution with a mass concentration of 2.5-10% of P123, phenolic resin is added to the template solution, and the mass ratio of phenolic resin to P123 is controlled to be 2-8:1, and then 0.25-1 mol / L hydrochloric acid is added as a catalyst, and the mass of the hydrochloric acid is 5-20% of P123, and the reaction is carried out at 30-50° C. and 200-800 rpm for 5-20 hours; 2) After the reaction is completed, the mixture is aged at room temperature for 6-24 hours, and the obtained solution is poured into a mold and cured at 50-70° C. for 6-24 hours; 3) heating the product obtained in step 2) at 700-900° C. for carbonization for 3-12 h under nitrogen protection, cooling to room temperature, immersing the obtained product in ethanol for 12-48 h, taking out, washing and drying to constant weight to obtain a porous carbon material; 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution with a mass concentration of 15-60%, control the liquid-to-solid ratio to 1.5-6, mix well, heat the resulting mixture under nitrogen protection at 500-700°C for 1-4h, cool to room temperature, wash with ethanol, and dry to constant weight to obtain the ordered mesoporous carbon material.

6. The photovoltaic cell production wastewater zero-discharge reuse system according to claim 5 is characterized in that: The ordered mesoporous carbon material is prepared by the following method: 1) P123 was added to ethanol to prepare a template solution with a mass concentration of 5% of P123, phenolic resin was added to the template solution, and the mass ratio of phenolic resin to P123 was controlled to be 4:1, and then 0.5 mol / L hydrochloric acid was added as a catalyst, and the mass of the hydrochloric acid was 10% of P123, and the reaction was carried out at 40° C. and 400 rpm for 10 hours; 2) After the reaction is completed, the mixture is aged at room temperature for 12 hours, and the obtained solution is poured into a mold and cured at 60° C. for 12 hours; 3) The product obtained in step 2) is heated and carbonized at 800° C. for 6 h under nitrogen protection, and after cooling to room temperature, the obtained product is immersed in ethanol for 24 h, taken out, washed and dried to obtain a porous carbon material; 4) Grind the porous carbon material obtained in step 3) into powder, then add it to a Na2CO3 solution with a mass concentration of 30%, control the liquid-to-solid ratio to 3, mix well, heat the resulting mixture at 600°C for 2h under nitrogen protection, cool to room temperature, wash with ethanol, and dry to constant weight to obtain the ordered mesoporous carbon material.

7. A zero-discharge recycling process for photovoltaic cell production wastewater, characterized in that: The wastewater treatment is carried out using a system as described in any one of claims 1 to 6, and the process comprises the following steps: S1. The acidic wastewater and alkaline wastewater generated in the production process of photovoltaic cells are input into the primary reaction tank A, alkali is added to the primary reaction tank A to adjust the pH, and the wastewater is stirred and reacted before entering the primary reaction tank B; acid is added to the primary reaction tank B to adjust the pH, and the wastewater is stirred and reacted before entering the primary reaction tank C; the first flocculant is added to the primary reaction tank C, and the reaction is stirred, and then the effluent enters the primary flocculation tank; the second flocculant is added to the primary flocculation tank for flocculation and sedimentation; S2, the supernatant in the primary flocculation tank enters the secondary reaction tank A, sodium aluminate is added to the secondary reaction tank A, and acid is added to the secondary reaction tank A to adjust the pH, and the reaction is stirred; the effluent of the secondary reaction tank A enters the secondary reaction tank B, Na2CO3 is added to the secondary reaction tank B, and the reaction is stirred; the effluent of the secondary reaction tank B enters the secondary flocculation tank, and the second flocculant is added to the secondary flocculation tank for flocculation and sedimentation; S3, the supernatant in the secondary flocculation tank enters the tertiary reaction tank, Ca(OH)2 is added to the tertiary reaction tank to adjust the pH, and the reaction is stirred; the effluent of the tertiary reaction tank enters the tertiary flocculation tank, the second flocculant is added to the tertiary flocculation tank, and flocculation and sedimentation are carried out; S4, the supernatant in the tertiary flocculation tank enters the electrosorption module, the fresh water obtained after treatment by the electrosorption module is reused as qualified discharge water, and the concentrated water obtained is returned to the primary reaction tank A for cyclic treatment; Among them, the sludge produced by flocculation and sedimentation in the primary flocculation tank, the secondary flocculation tank, and the tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained mud cake is outsourced for treatment.

8. The photovoltaic cell production wastewater zero-discharge reuse process according to claim 7, characterized in that: The alkali added to the primary reaction tank A is a Ca(OH)2 solution with a mass concentration of 5-20%, and the acid is a H2SO4 solution with a mass concentration of 25-80%; The first flocculant is polyaluminium chloride, and the second flocculant is polyacrylamide; The acid added to the secondary reaction tank A is a HCl solution with a concentration of 0.25-1 mol / L.

9. The photovoltaic cell production wastewater zero-discharge reuse process according to claim 8, characterized in that: The process includes the following steps: S1. The acidic wastewater and alkaline wastewater generated in the production process of photovoltaic cells are input into the primary reaction tank A, and a Ca(OH)2 solution with a mass concentration of 5-20% is added to the primary reaction tank A to adjust the pH to 10-12, and the solution is stirred for reaction for 5-30 minutes before entering the primary reaction tank B; a H2SO4 solution with a mass concentration of 25-80% is added to the primary reaction tank B to adjust the pH to 8.5-9, and the solution is stirred for reaction for 10-40 minutes before entering the primary reaction tank C; polyaluminium chloride with a concentration of 50-200ppm is added to the primary reaction tank C, and the solution is stirred for reaction for 5-20 minutes, and then the effluent enters the primary flocculation tank; polyacrylamide is added to the primary flocculation tank for flocculation and sedimentation; S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A, sodium aluminate is added to the secondary reaction tank A, and the amount of sodium aluminate added is controlled to make the mass ratio of sodium aluminate to SiO2 in water be 1.5-6:1, and 0.25-1 mol / L HCl solution is added to the secondary reaction tank A to adjust the pH to 8-9, and the reaction is stirred for 15-60 minutes; the effluent of the secondary reaction tank A enters the secondary reaction tank B, and a Na2CO3 solution with a mass concentration of 15-60% is added to the secondary reaction tank B to control the CO3 2- :Ca 2+ The molar ratio is 1 to 4:1, and the reaction is stirred for 15 to 60 minutes; the effluent from the secondary reaction tank B enters the secondary flocculation tank, and polyacrylamide is added to the secondary flocculation tank for flocculation and sedimentation; S3, the supernatant in the secondary flocculation tank enters the tertiary reaction tank, a Ca(OH)2 solution with a mass concentration of 5-20% is added to the tertiary reaction tank to adjust the pH to 6-7, and the reaction is stirred for 15-60 minutes; the effluent of the tertiary reaction tank enters the tertiary flocculation tank, polyacrylamide is added to the tertiary flocculation tank, and flocculation and sedimentation are carried out; S4, the supernatant in the tertiary flocculation tank enters the electrosorption module, the fresh water obtained after treatment by the electrosorption module is reused as qualified discharge water, and the concentrated water obtained is returned to the primary reaction tank A for cyclic treatment; Among them, the sludge produced by flocculation and sedimentation in the primary flocculation tank, the secondary flocculation tank, and the tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained mud cake is outsourced for treatment.

10. The photovoltaic cell production wastewater zero-discharge reuse process according to claim 9, characterized in that: The process includes the following steps: S1. Mix the acidic wastewater and alkaline wastewater generated in the production process of photovoltaic cells and input them into the primary reaction tank A. Add a 10% Ca(OH)2 solution to the primary reaction tank A to adjust the pH to 10-12, stir and react for 15 minutes, and then enter the primary reaction tank B; add a 50% H2SO4 solution to the primary reaction tank B to adjust the pH to 8.5-9, stir and react for 20 minutes, and then enter the primary reaction tank C; add 100ppm polyaluminium chloride to the primary reaction tank C, stir and react for 10 minutes, and then the effluent enters the primary flocculation tank; add polyacrylamide to the primary flocculation tank for flocculation and sedimentation; S2. The supernatant in the primary flocculation tank enters the secondary reaction tank A, sodium aluminate is added to the secondary reaction tank A, and the amount of sodium aluminate added is controlled to make the mass ratio of sodium aluminate to SiO2 in water 3:1, and 0.5 mol / L HCl solution is added to the secondary reaction tank A to adjust the pH to 8-9, and the reaction is stirred for 30 minutes; the effluent of the secondary reaction tank A enters the secondary reaction tank B, and a Na2CO3 solution with a mass concentration of 30% is added to the secondary reaction tank B to control the CO3 2- :Ca 2+ The molar ratio is 2:1, and the reaction is stirred for 30 minutes; the effluent from the secondary reaction tank B enters the secondary flocculation tank, and polyacrylamide is added to the secondary flocculation tank for flocculation and sedimentation; S3, the supernatant in the secondary flocculation tank enters the tertiary reaction tank, a 10% Ca(OH)2 solution is added to the tertiary reaction tank to adjust the pH to 6-7, and the reaction is stirred for 30 minutes; the effluent from the tertiary reaction tank enters the tertiary flocculation tank, polyacrylamide is added to the tertiary flocculation tank, and flocculation and sedimentation are carried out; S4, the supernatant in the tertiary flocculation tank enters the electrosorption module, the fresh water obtained after treatment by the electrosorption module is reused as qualified discharge water, and the concentrated water obtained is returned to the primary reaction tank A for cyclic treatment; Among them, the sludge produced by flocculation and sedimentation in the primary flocculation tank, the secondary flocculation tank, and the tertiary flocculation tank is treated by a sludge thickening tank and a sludge compressor, and the obtained mud cake is outsourced for treatment.

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