Treatment method of solar cell concentrated alkali wastewater

Abstract

The invention relates to the technical field of waste water silicon removal treatment and silicon resource utilization, and discloses a solar cell concentrated alkali waste water treatment method which comprises the following steps: S1, collecting solar cell concentrated alkali waste water generated intermittently in an adjusting buffer pool, feeding the solar cell concentrated alkali waste water into a silicon system dissolving-out device through a lifting pump, adjusting the pH value of the waste water to 7.5-8.0, and carrying out ultrasonic treatment on the waste water; the mechanical stirring rotating speed is kept at 45-60 r / min, the reaction time is 10-15 min, and silicate ions are promoted to be converted into colloidal silicon; the method is suitable for zero discharge treatment of various high-concentration silicon-containing wastewater, is high in silicon removal effect and relatively low in comprehensive cost, is a low-cost and full-quantification silicon-containing wastewater treatment and recovery method, and adopts a technical route of silicon system dissolution, cascade material membrane, low-temperature evaporation and drying, resin adsorption, reverse osmosis, evaporative crystallization and drying, so that the method is suitable for large-scale industrial production. The problem that high-content silicon enters a follow-up wastewater zero discharge process, scaling is caused, and an evaporation system loses efficacy is solved, and silicon waste is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater desiliconization and silicon resource utilization, in particular to a method for treating concentrated alkaline wastewater from solar cells. Background Art

[0002] The production of solar cells is based on silicon wafers. Its main process flow includes texturing, pickling, phosphorus diffusion, etching, anti-reflective film coating, etc. In the production process, hydrofluoric acid, nitric acid, phosphorus oxychloride and isopropyl alcohol are usually used to clean silicon wafers to produce the following types of solar cell wastewater: concentrated alkaline wastewater, acid and alkali washing wastewater, hydrofluoric acid concentrated solution, hydrofluoric acid washing wastewater, acid waste gas treatment wastewater, etc. Among them, the acid and alkali washing wastewater, hydrofluoric acid concentrated solution, hydrofluoric acid washing wastewater and acid waste gas treatment wastewater have large water volumes. The main pollutants in the water are fluoride, COD, total nitrogen, etc., especially high-concentration fluoride, which is considered to be the characteristic pollutant of wastewater in this industry. The focus of pollutant removal is mostly on targeted consideration of fluoride removal processes.

[0003] Concentrated alkaline wastewater originates from the alkaline solution cleaning process. Its primary pollutants include silica, sodium hydroxide, and isopropyl alcohol. Although produced in small quantities, the wastewater contains very high concentrations of silica (5,000-10,000 mg / L) and COD (8,000-20,000 mg / L), and an alkaline pH (11-13.5). The current process for treating this wastewater involves mixing it with other acidic wastewaters for neutralization, typically to adjust the wastewater's pH. However, this method fails to consider the significant impact of high silica concentrations on subsequent water treatment systems.

[0004] As environmental protection requirements become increasingly stringent and industrial wastewater discharge standards gradually increase, zero wastewater discharge will become the future development direction. This is especially true when it comes to solar cell wastewater treatment, where zero discharge is required. If the silicon in the concentrated alkaline wastewater is not removed in advance, the high concentration of silicon in the evaporator will easily form a silicon scale during the evaporation and crystallization process, which is extremely difficult to clean. Over long-term operation, the silicon scale accumulates and adheres to the surface of the equipment, significantly reducing the heat exchange efficiency of the evaporation system. In severe cases, it can cause equipment blockage and system failure, directly affecting the normal safe production of the enterprise.

[0005] Silicon has a devastating impact on the stable operation of evaporative crystallization, so pretreatment is essential. Generally, the silicon content in evaporative crystallization processes should not exceed 20 mg / L. Currently, the main methods for removing silicon from wastewater include chemical coagulation, ion exchange, electrocoagulation, and adsorption. Calcium-magnesium desiliconizers, such as Ca(OH)2 and MgO, are commonly used in engineering. These desiliconizers are inefficient, consume a lot of reagents, and produce a lot of sludge. For concentrated alkaline wastewater from solar cells, especially those with very high silicon contents, the reagent consumption is enormous, and the operating costs are unacceptable. Adsorption is suitable for deep treatment of low-concentration silicon, but the regeneration and replacement costs of the adsorbent are high, and its effectiveness at treating high-concentration silicon is limited.

[0006] When treating solar cell wastewater for zero-discharge treatment, the concentrated alkaline wastewater must be treated for silicon removal by separation. Conventional technologies such as chemical and adsorption methods have certain problems with high-concentration silicon removal. Therefore, a treatment method for concentrated alkaline wastewater from solar cells is proposed. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for treating concentrated alkaline wastewater from solar cells to solve the problems raised in the above background technology.

[0008] To achieve the above object, the present invention provides the following technical solution: a method for treating concentrated alkaline wastewater from solar cells, comprising the following steps:

[0009] S1. Collect the intermittently generated concentrated alkaline wastewater from solar cells in a regulating buffer tank and pump it into a silicon-based dissolution device through a lifting pump. Adjust the pH value of the wastewater to 7.5-8.0, maintain a mechanical stirring speed of 45-60 r / min, and react for 10-15 minutes to promote the conversion of silicate ions into colloidal silicon.

[0010] S2, pumping the pretreated wastewater in S1 into a cascade material membrane device, and separating by multi-stage membrane filtration to obtain a high-silicon concentrate and a clear liquid;

[0011] S3, sending the high-silicon concentrated liquid into a low-temperature evaporation device, and concentrating it 2-4 times under the conditions of vacuum degree of -0.095MPa and temperature ≤55°C to obtain a high-concentration silicon evaporation residue;

[0012] S4. The silicon evaporation residue is dried in a first drying device at 100-600°C to produce dry silicon mud with a moisture content of ≤0.5%, which is then carbonized at medium to high temperatures and used as slag material or purified;

[0013] S5. The clear liquid produced by the step material membrane in S2 is further processed by a resin adsorption device. The resin exchange adopts a coated polymer resin material with a coating thickness of not less than 10 μm.

[0014] S6, the clear liquid after resin adsorption in S5 enters reverse osmosis treatment to separate into high brine and clear liquid, wherein the clear liquid meets the standards and is reused, and the high brine is further treated by an evaporation crystallization device to obtain crystalline salt;

[0015] S7. Processing the crystallized salt through a second drying device at 100-200° C. to obtain an industrial salt product having a moisture content of ≤0.5% and a sodium chloride content of ≥92%.

[0016] Preferably, in the above-mentioned S1, a heating module is provided on one side of the silicon-based dissolution device, the temperature control range of the heating module is 25-85°C, and the reaction time is 30-60min, so as to promote the generation of silicic acid.

[0017] As a preference, the above: when the silicon content of the wastewater exceeds 20000 mg / L, a flocculant is added to S1 to perform coagulation and sedimentation treatment in a sedimentation tank;

[0018] The amount of flocculant added is 0.0003%-0.005% of the wastewater mass.

[0019] Preferably, the above-mentioned: a sedimentation tank inclined pipe is installed on one side of the sedimentation tank, the installation angle of the sedimentation tank inclined pipe filler is 60°, and the rising flow rate is 0.3 mm / s.

[0020] Preferably, in the above-mentioned step S2, the cascade material membrane device includes a primary material membrane device, a secondary material membrane device and a tertiary material membrane device;

[0021] The pore size of the material membrane of the first-level material membrane device is 10000Da;

[0022] The pore size of the material membrane of the secondary material membrane device is 5000Da;

[0023] The pore size of the material membrane of the three-stage material membrane device is 1000Da;

[0024] The membrane material of the first-stage material membrane device, the second-stage material membrane device and the third-stage material membrane device is polyphenol ether.

[0025] As a preference, the above-mentioned material membrane has a single membrane area of 20-25m 2 , operating flux 25-45LMH, membrane thickness 120-150μm.

[0026] Preferably, in the above-mentioned step S3, the contact surface of the low-temperature evaporation device is made of titanium alloy, and the concentration rate is ≥90%.

[0027] Preferably, in the above-mentioned step S4, the drying time of the first drying device is 200-400 min, and the evaporation capacity is 1000-5000 kg / h.

[0028] Preferably, in the above-mentioned step S7, the rotation speed of the rotary disk of the second drying device is set to 75 rpm / s, the evaporation amount is 200-2000 kg / h, and the drying time is 480-600 min.

[0029] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects:

[0030] 1. The method of the present invention is suitable for zero-discharge treatment of various high-concentration silicon-containing wastewaters, has high silicon removal effect and low comprehensive cost. It is a low-cost, fully quantitative method for treating and recovering silicon-containing wastewater. It utilizes the technical route of "silicon dissolution, stepped material membrane, low-temperature evaporation + drying, resin adsorption, reverse osmosis, evaporation crystallization, and drying". First, it avoids high-content silicon from entering the subsequent wastewater zero-discharge process, which will cause scaling and lead to failure of the evaporation system. Secondly, it avoids the waste of silicon. Compared with similar silicon removal treatment technologies, it not only reduces the treatment cost, but also recovers dry silicon mud with certain economic value. After the organic matter is removed by medium and high temperature carbonization, it can be used as a slag material for resource utilization, or further purified and utilized according to the needs of downstream products.

[0031] 2. The method provided by the present invention adopts a cascade material membrane device to remove silicon from wastewater. Through the combination and coordinated treatment of multi-stage material membrane units with different pore sizes, the designed silicon removal rate of the entire system can reach more than 90%.

[0032] 3. The core silicon removal process of the present invention is based on the membrane method. Compared with the traditional silicon removal process that adopts chemical method and adds sodium aluminate or magnesium agent to remove silicon, the cost of using the agent is too high, the treatment efficiency is not stable, and a large amount of inorganic sludge will be generated. The use of cascade material membrane device technology does not require the addition of a large amount of chemical agents, and the treatment cost can be reduced to 1 / 5 of other methods, which reduces the treatment cost and is especially suitable for scenes with large water volumes.

[0033] 4. The present invention adopts membrane method to remove silicon. Compared with other methods, this treatment method is simpler, more efficient and stable to operate, and can be applied to large water quality fluctuations. It not only greatly improves the removal rate and stability of silicon, but also solves the silicon scale problem for back-end zero-emission treatment and reduces the difficulty of subsequent production wastewater treatment.

[0034] 5. The device described in the present invention is mature in industrialization and can be promoted as an engineering application. The method provided by the present invention is also applicable to other high-silicon-content concentrated alkaline wastewater generated by different battery production processes and industrial production wastewater generated in the silicon dioxide production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0036] Figure 1 is a process flow chart of the silicon recovery method of the present invention;

[0037] Figure 2 It is a process flow chart of the step material membrane device of the present invention. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0039] It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the conditions under which this application can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in this application without affecting the efficacy and purpose that can be achieved by this application.

[0040] Example

[0041] See also Figure 1-2 The present invention provides a technical solution: a method for treating concentrated alkaline wastewater from solar cells, comprising the following steps:

[0042] S1. Collect the intermittently generated concentrated alkaline wastewater from solar cells in a regulating buffer tank. Use a separate pipeline to collect and treat this concentrated alkaline wastewater separately. The overall principle of quality-based treatment is adopted, with homogenization and equalization. The wastewater is pumped into a silicon-based dissolution device via a lifting pump. Hydrochloric acid or dilute sulfuric acid is added and stirred to adjust the pH. The pH value of the wastewater is adjusted to 7.5-8.0. The pH of the original wastewater is 12. The mechanical stirring speed is maintained at 45-60 r / min, and the reaction time is 10-15 minutes. This promotes the conversion of silicate ions to colloidal silicon; reducing the solubility of silicon promotes the conversion of silicate ions to colloidal silicon, changes the silicon morphology, and increases the proportion of colloidal silicon and precipitated silicon in the wastewater. The amount of acid to be added is determined through small-scale experiments. Accurately dosing minimizes the cost of reagent input.

[0043] A heating module is installed on one side of the silicon dissolution unit. The temperature of the heating module is controlled within a range of 25-85°C, and the reaction time is 30-60 minutes to promote the formation of silicic acid. The optimal reaction temperature of the heating module is 55-65°C. This high temperature allows the precipitation of soluble silicon in the concentrated alkaline wastewater, converting it into colloidal or precipitated silicon, thereby improving the recovery rate of the material membrane at the back end. S1 is suitable for wastewater with a silicon content of no more than 20,000 mg / L. If the silicon content exceeds 20,000 mg / L, flocculants are added to S1 for coagulation and sedimentation in the sedimentation tank. The flocculant dosage is 0.0003%-0.005% of the wastewater mass. Flocculants include inorganic flocculants, microbial flocculants, and organic-inorganic composite additives. The wastewater can come from concentrated alkaline wastewater from solar cells or industrial wastewater generated during silica production. When multiple wastewater streams are present, the concentrated alkaline wastewater should not be mixed with other wastewaters for treatment; instead, separation treatment is preferred.

[0044] A sedimentation tank inclined pipe is installed on one side of the sedimentation tank. The installation angle of the sedimentation tank inclined pipe filler is 60°, and the rising flow rate is 0.3mm / s. The supernatant generated is collected and enters the cascade material membrane device for further treatment. The sludge is filtered through a plate and frame filter press to obtain silicon mud, which can be recovered as a by-product.

[0045] S2, pumping the pretreated wastewater in S1 into a cascade material membrane device, and separating by multi-stage membrane filtration to obtain a high-silicon concentrate and a clear liquid;

[0046] In the cascade material membrane device, the silicon concentration and type of the inlet and outlet water are first identified and set, and then single-stage, two-stage or multi-stage material membrane filtration is performed. The design recovery rate of the entire system is not less than 90%;

[0047] The cascade material membrane device includes a first-stage material membrane device, a second-stage material membrane device and a third-stage material membrane device;

[0048] The pore size of the material membrane of the first-stage material membrane device is 10000Da;

[0049] The pore size of the material membrane of the secondary material membrane device is 5000Da;

[0050] The pore size of the material membrane of the three-stage material membrane device is 1000Da;

[0051] The recovery rates for 10,000Da silicon are 95%, 5,000Da silicon are 97%, and 1,000Da silicon are 99%. The overall system silicon recovery rate is no less than 90%. Concentrate reflux is used within the membrane system to improve the recovery rate. Single-stage or multi-stage material membrane filtration can also be used, depending on the influent silicon concentration and effluent requirements.

[0052] The three-stage material membranes can be independent of each other and used separately, or the material membranes with the same pore size can be set as the first stage, the second stage, and the third stage in series, while the second and third stages are operated in parallel. The combination is flexible, and the pore size of the cascade material membrane is between ultrafiltration and nanofiltration.

[0053] The membrane material in the primary material membrane device, the secondary material membrane device and the tertiary material membrane device is polyphenol ether; the cascade material membrane element is prepared by a layer-by-layer self-assembly method on the membrane surface, and the self-assembled film has higher anti-scaling and anti-pollution properties.

[0054] The silicon recovery rate is 99%, and the concentrated solution reflux method is used in the membrane system to improve the recovery rate, such as Figure 2 The wastewater first passes through the primary material membrane device. After membrane separation and concentration, the clear liquid enters the intermediate water tank and the concentrate enters the concentrate tank. The concentrate in the primary concentrate storage tank further enters the secondary material membrane device. After membrane separation and concentration, the secondary concentrate and clear liquid are generated. The secondary concentrate enters the concentrate tank and is mixed and homogenized with the primary concentrate, and then enters the tertiary material membrane device. After membrane separation and concentration, the concentrated liquid finally enters the concentrate storage tank, and the clear liquid enters the clean water tank for storage.

[0055] The single membrane area of the material membrane is 20-25m 2 , operating flux 25-45LMH, membrane thickness 120-150μm, maximum operating pH range 1-12, step material membrane device operating pressure range 0.3-1.0Mpa, the operating pressure value is 0.7-0.8Mpa to achieve the best removal rate. When it exceeds 1.0MPa, the silicon recovery rate will gradually decrease, thereby affecting the removal effect.

[0056] When manufacturing the stepped material membrane elements, chemical grafting and electron beam radiation grafting are used to introduce vinyl sulfonic acid (VSA) and hydroxylamine-O-sulfonic acid (HOSA) into the membrane surface to prepare a modified membrane with sulfonic acid groups. This membrane has lower surface roughness, stronger hydrophilicity and negative charge, and has a higher retention rate, stronger resistance to silica scale and pollution without sacrificing permeability.

[0057] After membrane separation and concentration, the colloidal silica or precipitated silica is separated, the clear liquid enters the clear liquid tank, and the high-concentration concentrated liquid enters the concentrated liquid tank.

[0058] S3. Send the high-silicon concentrate to the low-temperature evaporation device and concentrate it 2-4 times under the conditions of vacuum degree of -0.095MPa and temperature ≤55℃ to obtain high-concentration silicon vapor residue; under low-pressure environment, the water evaporates rapidly, while the pollutants and impurities are concentrated and separated. The high-concentration silicon concentrate is transported to the low-temperature evaporation device through a pump, and the wastewater is evaporated and concentrated using negative pressure evaporation technology.

[0059] The contact surface of the low-temperature evaporation device is made of titanium alloy, with a concentration rate of ≥90%. Titanium alloy has excellent corrosion resistance. The clear liquid is converted into recycled water through other processes, and zero wastewater discharge treatment is achieved through the combination of other processes.

[0060] S4. The silicon vapor residue is passed through the first drying device at 100-600°C to produce dry silicon mud with a moisture content of ≤0.5%. The optimal temperature is 180-450°C. After medium-high temperature carbonization, it can be used as slag material or purified. The drying time of the first drying device is 200-400 minutes, and the evaporation rate is 1000-5000kg / h.

[0061] The first drying device is selected from one or a combination of disk type, drum type, flash type and fluidized bed type. The high-concentration silicon vapor residue produced by the low-temperature evaporation device is then passed through the first drying device to produce a dry silicon mud product.

[0062] S5. The clear liquid produced by the stepped material membrane in S2 is further treated by a resin adsorption device. The resin exchange adopts a coated polymer resin material with a coating thickness of not less than 10μm. Through the Donnan effect, the ionic form of silicon in water and the ion exchange characteristics of the strong base anion resin are utilized to pre-aggregate the ionic silicon, thereby further improving the filtration effect of the ionic silicon.

[0063] The clear liquid produced by the cascade material membrane is further treated by ion exchange resin and reverse osmosis process and then meets the standards for reuse, and the concentrated liquid enters the next treatment unit.

[0064] S6, the clear liquid after resin adsorption in S5 enters reverse osmosis treatment to separate into high brine and clear liquid, wherein the clear liquid meets the standards and is reused, and the high brine is further treated by an evaporation crystallization device to obtain crystalline salt;

[0065] S7. Processing the crystallized salt through a second drying device at 100-200° C., with the optimal temperature being 120-160° C., to obtain an industrial salt product having a moisture content of ≤0.5% and a sodium chloride content of ≥92%.

[0066] The reverse osmosis concentrate is processed through evaporation crystallization + drying device to obtain product salt, achieving zero emission treatment.

[0067] The rotating disk speed of the second drying device is set to 75rpm / s, the evaporation capacity is 200-2000kg / h, the drying time is 480-600min, and the drying device is selected from one or a combination of spray drying, self-disc drying, drum drying, flash drying and fluidized bed drying.

[0068] The following are examples of practical applications of the method of the present invention:

[0069] 1. The present invention was used to treat concentrated alkaline wastewater from a 10GW solar cell plant in Xinjiang, with a daily production volume of 300m3. 3 / d, the inlet silicon concentration is 6018.32mg / L, the equipment processing capacity is 15t / h, the operation time is 22h, and it is designed as a two-stage material membrane. The recovery rate of the first material membrane is 95%, and the recovery rate of the second material membrane is 97%. After treatment, the silicon concentration of the effluent is 472.41mg / L, and the operating flux is 28.38L / m 2 h, operating pressure is 0.72 MPa, actual total recovery rate is 92.17%, and annual stable operation time exceeds 330 days;

[0070] 2. Treat concentrated alkaline wastewater from a 20GW solar cell plant in Ningxia, with a daily production volume of 550m3. 3 / d, the inlet silicon concentration is 7052.15mg / L, the equipment processing capacity is 25t / h, the operation time is 22h, and it is designed as a three-stage material membrane. The recovery rate of the first-stage material membrane is 95%, the recovery rate of the second-stage material membrane is 97%, and the recovery rate of the third-stage material membrane is 99%. After treatment, the silicon concentration of the effluent is 441.63mg / L, and the operating flux is 27.95L / m 2 h, the operating pressure is 0.79 MPa, the actual total recovery rate is 93.74%, and the annual stable operation time exceeds 330 days.

[0071] In summary, the method of the present invention is suitable for zero-discharge treatment of various high-concentration silicon-containing wastewaters, has high silicon removal effect and low comprehensive cost. It is a low-cost, fully quantitative silicon-containing wastewater treatment and recovery method. It utilizes the "silicon dissolution, stepped material membrane, low-temperature evaporation + drying, resin adsorption, reverse osmosis, evaporation crystallization, drying" technical route. First, it avoids high-content silicon from entering the subsequent wastewater zero-discharge process, which will cause scaling and lead to failure of the evaporation system. Secondly, it avoids the waste of silicon. Compared with similar silicon removal treatment technologies, it not only reduces the treatment cost, but also recovers dry silicon mud with certain economic value. After the organic matter is removed by medium and high temperature carbonization, it can be used as a slag material for resource utilization, or further purified and utilized according to the needs of downstream products.

[0072] The method provided by the present invention adopts a cascade material membrane device to remove silicon from wastewater. Through the combination and coordinated treatment of multi-stage material membrane units with different pore sizes, the designed silicon removal rate of the entire system can reach more than 90%.

[0073] The core silicon removal process of the present invention is based on the membrane method. Compared with the traditional silicon removal process that adopts chemical method and adds sodium aluminate or magnesium agent to remove silicon, the cost of using the agent is too high, the treatment efficiency is not stable, and a large amount of inorganic sludge will be generated. The use of the cascade material membrane device technology does not require the addition of a large amount of chemical agents, and the treatment cost can be reduced to 1 / 5 of other methods, which reduces the treatment cost and is particularly suitable for scenarios with large water volumes.

[0074] The present invention adopts membrane method to remove silicon. Compared with other methods, this treatment method is simpler, more efficient and stable to operate, and can be applied to large water quality fluctuations. It not only greatly improves the silicon removal rate and stability, but also solves the silicon scale problem for back-end zero-emission treatment and reduces the difficulty of subsequent production wastewater treatment.

[0075] The device described in the present invention is mature in industrialization and can be promoted as an engineering application. The method provided by the present invention is also applicable to other high-silicon-content concentrated alkaline wastewater generated by different battery production processes and industrial production wastewater generated in the silica production process.

[0076] Those skilled in the art will appreciate that various combinations and / or combinations of features described in the various embodiments and / or claims of the present invention may be made, even if such combinations and / or combinations are not explicitly described in the present invention. In particular, various combinations and / or combinations of features described in the various embodiments and / or claims of the present invention may be made, without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

Claims

1. A method for treating concentrated alkaline wastewater from solar cells, characterized in that: The following steps are involved: S1. Collect the intermittently generated concentrated alkaline wastewater from solar cells in a regulating buffer tank and pump it into a silicon-based dissolution device through a lifting pump. Adjust the pH value of the wastewater to 7.5-8.0, maintain a mechanical stirring speed of 45-60 r / min, and react for 10-15 minutes to promote the conversion of silicate ions into colloidal silicon. S2, pumping the pretreated wastewater in S1 into a cascade material membrane device, and separating by multi-stage membrane filtration to obtain a high-silicon concentrate and a clear liquid; S3, sending the high-silicon concentrated liquid into a low-temperature evaporation device, and concentrating it 2-4 times under the conditions of vacuum degree of -0.095MPa and temperature ≤55°C to obtain a high-concentration silicon evaporation residue; S4. The silicon evaporation residue is dried in a first drying device at 100-600°C to produce dry silicon mud with a moisture content of ≤0.5%, which is then carbonized at medium to high temperatures and used as slag material or purified; S5. The clear liquid produced by the step material membrane in S2 is further processed by a resin adsorption device. The resin exchange adopts a coated polymer resin material with a coating thickness of not less than 10 μm. S6, the clear liquid after resin adsorption in S5 enters reverse osmosis treatment to separate into high brine and clear liquid, wherein the clear liquid meets the standards and is reused, and the high brine is further treated by an evaporation crystallization device to obtain crystalline salt; S7. Processing the crystallized salt through a second drying device at 100-200° C. to obtain an industrial salt product having a moisture content of ≤0.5% and a sodium chloride content of ≥92%.

2. The method for treating concentrated alkaline wastewater from solar cells according to claim 1, wherein: In S1, a heating module is provided on one side of the silicon-based dissolution device. The temperature control range of the heating module is 25-85°C, and the reaction time is 30-60 minutes to promote the generation of silicic acid.

3. The method for treating concentrated alkaline wastewater from solar cells according to claim 2, wherein: When the silicon content of wastewater exceeds 20,000 mg / L, flocculant is added to S1 to carry out coagulation and sedimentation treatment in the sedimentation tank; The amount of flocculant added is 0.0003%-0.005% of the wastewater mass.

4. The method for treating concentrated alkaline wastewater from solar cells according to claim 3, wherein: A sedimentation tank inclined pipe is installed on one side of the sedimentation tank, the installation angle of the sedimentation tank inclined pipe filler is 60°, and the rising flow rate is 0.3 mm / s.

5. The method for treating concentrated alkaline wastewater from solar cells according to claim 1, characterized in that: In S2, the cascade material membrane device includes a primary material membrane device, a secondary material membrane device and a tertiary material membrane device; The pore size of the material membrane of the first-level material membrane device is 10000Da; The pore size of the material membrane of the secondary material membrane device is 5000Da; The pore size of the material membrane of the three-stage material membrane device is 1000Da; The membrane material of the first-stage material membrane device, the second-stage material membrane device and the third-stage material membrane device is polyphenol ether.

6. The method for treating concentrated alkaline wastewater from solar cells according to claim 5, characterized in that: The single membrane area of the material membrane is 20-25m 2 , operating flux 25-45LMH, membrane thickness 120-150μm.

7. The method for treating concentrated alkaline wastewater from solar cells according to claim 1, characterized in that: In S3, the contact surface of the low-temperature evaporation device is made of titanium alloy, and the concentration rate is ≥90%.

8. The method for treating concentrated alkaline wastewater from solar cells according to claim 2, characterized in that: In S4, the drying time of the first drying device is 200-400 minutes, and the evaporation capacity is 1000-5000 kg / h.

9. The method for treating concentrated alkaline wastewater from solar cells according to claim 1, characterized in that: In S7, the rotation speed of the rotary disk of the second drying device is set to 75 rpm / s, the evaporation capacity is 200-2000 kg / h, and the drying time is 480-600 min.

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