A method of recycling photovoltaic cells

Abstract

The application provides a method for recycling photovoltaic cell pieces, and relates to the technical field of photovoltaic module recycling. In a liquid nitrogen environment, the photovoltaic cell pieces are crushed to obtain crushed cell pieces, the crushed cell pieces are screened and sorted to obtain sorted silicon wafers; the sorted silicon wafers and a deep eutectic solvent are mixed to perform leaching to obtain leached silicon wafers; the leached silicon wafers and an alkaline solution are mixed to perform micro-bubble alkali treatment to obtain alkali-treated silicon wafers; the alkali-treated silicon wafers, phosphoric acid and hydrogen peroxide are mixed to perform etching to obtain high-purity silicon wafers; and raw materials of the deep eutectic solvent include choline and lactic acid. The production process is simplified, and the production efficiency is improved.

Description

Technical Field

[0001] This application relates to the field of photovoltaic module recycling technology, and in particular to a method for recycling photovoltaic cells. Background Technology

[0002] Traditional photovoltaic cell recycling methods have many drawbacks. For example, pyrometallurgical methods are energy-intensive, and some chemical leaching methods use toxic and harmful substances such as cyanide and aqua regia, leading to significant pollution. These methods not only cause serious environmental pollution but also pose safety hazards. Furthermore, traditional recycling methods involve complex processes, resulting in low recycling efficiency, high costs, and difficulty in achieving ideal levels of silver recovery and silicon wafer purity.

[0003] Therefore, there is an urgent need to provide a method for recycling photovoltaic cells to solve the above problems. Summary of the Invention

[0004] The purpose of this application is to provide a method for recycling photovoltaic cells to solve the above-mentioned problems.

[0005] To achieve the above objectives, this application provides a method for recycling photovoltaic cells, comprising:

[0006] In a liquid nitrogen environment, photovoltaic cells are crushed to obtain crushed cells, which are then sieved and sorted to obtain sorted silicon wafers.

[0007] The sorted silicon wafers are mixed with a deep eutectic solvent and then leached to obtain leached silicon wafers.

[0008] The leached silicon wafer is mixed with an alkaline solution and subjected to microbubble alkaline treatment to obtain an alkaline-treated silicon wafer.

[0009] The alkaline-treated silicon wafer, phosphoric acid, and hydrogen peroxide are mixed and etched to obtain a high-purity silicon wafer.

[0010] The raw materials for the deep eutectic solvent include choline and lactic acid.

[0011] Optionally, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0012] A. The crushing temperature is -196℃ to -180℃, and the time is 15min to 30min;

[0013] B. The sieve mesh size for the sieving process is 0.1mm-5mm;

[0014] C. The magnetic field strength for sorting is 0.5T-2T, and the conveying speed is 0.5m / s-2m / s.

[0015] Optionally, the molar ratio of choline to lactic acid is 1-1.8:2-2.2.

[0016] Optionally, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0017] A. The leaching temperature is 35℃-55℃;

[0018] B. The leaching process also includes ultrasonication at a frequency of 18kHz-22kHz, a temperature of 40℃-50℃, and a duration of 1h-2h.

[0019] Optionally, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0020] A. The alkaline solution includes a sodium carbonate solution;

[0021] B. The pH value of the alkaline solution is 10-11;

[0022] C. The alkaline solution is recycled, with a recycling frequency of ≥15 times.

[0023] Optionally, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0024] A. The average diameter of the bubble clusters in the microbubble alkaline treatment process is 40μm-60μm;

[0025] B. The temperature of the microbubble alkali treatment is 20℃-30℃, and the time is 10min-30min.

[0026] Optionally, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0027] A. The volume ratio of the phosphoric acid to the hydrogen peroxide is 2.5-3.5:1; the mass concentration of the hydrogen peroxide is 10%-30%, and the mass concentration of the phosphoric acid is 40%-80%.

[0028] B. The etching time is 10 min-20 min.

[0029] Optionally, vacuum membrane distillation can be used to recover the eutectic solvent after leaching.

[0030] Optionally, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0031] A. The recovery rate of the recovered product is ≥92%;

[0032] B. During the recycling process, the generated waste gas is degraded by microorganisms to obtain degraded waste gas; the removal rate of volatile organic compounds in the degraded waste gas is ≥99.3%;

[0033] C. The distillation temperature of the vacuum membrane distillation method is 50℃-70℃, and the pressure is 1kPa-5kPa.

[0034] Optionally, the residual metal content on the surface of the high-purity silicon wafer is <50ppm.

[0035] Compared with the prior art, the beneficial effects of this application include:

[0036] The method for recycling photovoltaic cells provided in this application utilizes the embrittlement effect of photovoltaic cells at low temperatures to reduce energy consumption during the crushing process. Furthermore, the inert environment of liquid nitrogen effectively prevents oxidation of the metal components, crushing the photovoltaic cells into small-sized granular materials with unoxidized metal components. Preliminary screening is performed based on particle size differences to separate particles of different sizes. Then, efficient separation is achieved through sorting, realizing the efficient physical separation of silicon wafers, metals, and other components. A deep eutectic solvent is used to highly selectively dissolve the silver grid lines on the silicon wafer. Microbubble alkaline treatment is then employed to allow the bubble clusters to chemically react with the aluminum back surface field, achieving rapid stripping of the aluminum back surface field. After removing the aluminum back surface field, impurities on the silicon wafer surface are further reduced. A mixed solution of phosphoric acid and hydrogen peroxide is used for directional regeneration micro-etching of the silicon wafer surface, more effectively removing impurities and defects, clearing residual metal impurities, and ensuring that the metal residue on the silicon wafer surface meets the standards for solar-grade silicon. Attached Figure Description

[0037] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0038] Figure 1 This is a schematic diagram of the process for recycling photovoltaic cells provided in Example 1. Detailed Implementation

[0039] As used in this article:

[0040] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0041] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0042] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0043] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0044] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0045] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0046] This application provides a method for recycling photovoltaic cells, including:

[0047] In a liquid nitrogen environment, photovoltaic cells are crushed to obtain crushed cells, which are then sieved and sorted to obtain sorted silicon wafers.

[0048] It should be noted that after sorting, a mixed metal, including silver and copper, is obtained. In some embodiments, the mixed metal can be separated. For example, a chemical displacement method is used, in which the mixture is immersed in a silver nitrate solution, and copper reacts with silver nitrate to produce elemental silver and copper nitrate. After filtration, silver is obtained.

[0049] The sorted silicon wafers are mixed with a deep eutectic solvent and then leached to obtain leached silicon wafers.

[0050] The leached silicon wafer is mixed with an alkaline solution and subjected to microbubble alkaline treatment to obtain an alkaline-treated silicon wafer.

[0051] The alkaline-treated silicon wafer, phosphoric acid, and hydrogen peroxide are mixed and etched to obtain a high-purity silicon wafer.

[0052] The raw materials for the deep eutectic solvent include choline and lactic acid.

[0053] In some embodiments, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0054] A. The crushing temperature is -196℃ to -180℃, and the time is 15min to 30min;

[0055] Optionally, the crushing temperature can be any value between -196℃, -194℃, -192℃, -190℃, -188℃, -186℃, -184℃, -182℃, -180℃, or -196℃--180℃, and the time can be any value between 15min, 20min, 25min, 30min, or 15min-30min.

[0056] It is important to note that placing photovoltaic cells in a liquid nitrogen environment for crushing utilizes the embrittlement effect of materials at low temperatures, thereby reducing energy consumption during the crushing process. If low-temperature crushing is not performed first, the structure of the cells remains relatively intact, making it difficult to achieve effective separation of the components directly through screening and sorting. Furthermore, the metal components may oxidize during ordinary crushing, affecting the quality of subsequent metal recovery.

[0057] B. The sieve mesh size for the sieving process is 0.1mm-5mm;

[0058] Optionally, the mesh size of the sieve can be 0.1mm, 1mm, 5mm or any value between 0.1mm and 5mm;

[0059] C. The magnetic field strength for sorting is 0.5T-2T, and the conveying speed is 0.5m / s-2m / s.

[0060] Optionally, the sorting magnetic field strength can be any value between 0.5T, 1T, 1.5T, 2T or 0.5T-2T, and the conveying speed can be any value between 0.5m / s, 1m / s, 1.5m / s, 2m / s or 0.5m / s-2m / s.

[0061] In some embodiments, the molar ratio of choline to lactic acid is 1-1.8:2-2.2.

[0062] Optionally, the molar ratio of choline to lactic acid can be any value between 1:2, 1.5:2, 1.8:2, 1.5:2.2, or 1-1.8:2-2.2.

[0063] It is important to note that the choline-lactic acid system was chosen as the deep eutectic solvent. This system can achieve highly selective dissolution of silver grid lines in photovoltaic cells, reducing the impact on other components. Choline chloride and lactic acid form a low eutectic mixture through hydrogen bonding, which increases the dissolution rate of Ag by 4.3 times (compared to pure lactic acid). The carboxylic acid groups in lactic acid selectively chelate silver ions, and choline enhances the solvent polarity, promoting the dissociation of silver grid lines.

[0064] In some embodiments, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0065] A. The leaching temperature is 35℃-55℃;

[0066] Optionally, the leaching temperature can be any value between 35℃, 40℃, 45℃, 50℃, 55℃, or 35℃-55℃.

[0067] B. The leaching process also includes ultrasonication at a frequency of 18kHz-22kHz, a temperature of 40℃-50℃, and a duration of 1h-2h.

[0068] Optionally, the frequency of the ultrasound can be any value between 18kHz, 19kHz, 20kHz, 21kHz, 22kHz or 18kHz-22kHz, the temperature can be any value between 40℃, 45℃, 50℃ or 40℃-50℃, and the time can be any value between 1h, 1.5h, 2h or 1h-2h.

[0069] It should be noted that while ultrasound can enhance the metal leaching process by utilizing its cavitation and mechanical effects, if there is no prior crushing, screening, and sorting treatment, the ultrasonic field may not be able to fully exert its enhancing effect due to the inhomogeneity of the material, resulting in prolonged leaching time and increased energy consumption.

[0070] In some embodiments, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0071] A. The alkaline solution includes a sodium carbonate solution;

[0072] B. The pH value of the alkaline solution is 10-11;

[0073] Optionally, the pH value of the alkaline solution can be any value between 10, 10.5, 11, or 10-11.

[0074] C. The alkaline solution is recycled, with a recycling frequency of ≥15 times.

[0075] Optionally, the number of cycles can be 15, 20, 25, or any number of cycles greater than or equal to 15.

[0076] In some embodiments, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0077] A. The average diameter of the bubble clusters in the microbubble alkaline treatment process is 40μm-60μm;

[0078] Optionally, the average diameter of the bubble clusters during the microbubble alkaline treatment process can be 40 μm, 50 μm, 60 μm or any value between 40 μm and 60 μm;

[0079] B. The temperature of the microbubble alkali treatment is 20℃-30℃, and the time is 10min-30min.

[0080] Optionally, the temperature for microbubble alkali treatment can be any value between 20℃, 25℃, 30℃ or 20℃-30℃, and the time can be any value between 10min, 20min, 30min or 10min-30min.

[0081] It is important to note that using sodium carbonate solution at room temperature to chemically react the bubble clusters with the aluminum back field achieves rapid stripping of the aluminum back field. Compared with the traditional NaOH process, this method reduces the corrosiveness of silicon by 80%.

[0082] In some embodiments, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0083] A. The volume ratio of phosphoric acid to hydrogen peroxide is 2.5-3.5:1; the mass concentration of hydrogen peroxide is 10%-30%, and the mass concentration of phosphoric acid is 40%-80%.

[0084] Optionally, the volume ratio of phosphoric acid to hydrogen peroxide can be any value between 2.5:1, 3:1, 3.5:1, or 2.5-3.5:1; the mass concentration of hydrogen peroxide can be any value between 10%, 20%, 30%, or 10%-30%; and the mass concentration of phosphoric acid can be any value between 40%, 50%, 60%, 70%, 80%, or 40%-80%.

[0085] It should be noted that the mixed solution of phosphoric acid and hydrogen peroxide has a high selective etching ability for metal impurities (such as silver and aluminum) on the surface of silicon wafers. It can effectively remove metal residues on the surface of silicon wafers, making the metal residue on the surface of silicon wafers less than 50 ppm, which meets the standard for solar-grade silicon wafers. At the same time, the etching rate of the silicon substrate is low, avoiding silicon wafer loss caused by excessive etching.

[0086] B. The etching time is 10 min-20 min.

[0087] Optionally, the etching time can be any value between 10 min, 15 min, 20 min, or 10 min and 20 min.

[0088] In some embodiments, vacuum membrane distillation is used to recover the eutectic solvent after leaching.

[0089] In some embodiments, the method for recycling photovoltaic cells satisfies at least one of the following conditions:

[0090] A. The recovery rate of the recovered product is ≥92%;

[0091] Optionally, the recovery rate can be any value of 92%, 93%, 94%, 95%, 96%, or ≥92%;

[0092] B. During the recycling process, the generated waste gas is degraded by microorganisms to obtain degraded waste gas; the removal rate of volatile organic compounds in the degraded waste gas is ≥99.3%;

[0093] Optionally, the removal rate of volatile organic compounds can be any value of 99.3%, 99.4%, 99.6%, 99.7%, 99.9%, or ≥99.3%;

[0094] C. The distillation temperature of the vacuum membrane distillation method is 50℃-70℃, and the pressure is 1kPa-5kPa.

[0095] Optionally, the distillation temperature of the vacuum membrane distillation method can be any value between 50℃, 60℃, 70℃ or 50℃-70℃, and the pressure can be any value between 1kPa, 2kPa, 3kPa, 4kPa, 5kPa or 1kPa-5kPa.

[0096] It is important to note that improving the utilization rate of eutectic solvents can reduce production costs.

[0097] In some embodiments, the residual metal content on the surface of the high-purity silicon wafer is <50ppm.

[0098] Optionally, the amount of residual metal on the surface of the high-purity silicon wafer can be any value of 45ppm, 40ppm, 30ppm, 20ppm or <50ppm.

[0099] It should be noted that the method for recycling photovoltaic cells in this application reduces 2-3 processes compared to traditional methods, simplifies the production process, and improves production efficiency. The low-temperature crushing, dynamic ultrasonic strengthening, and closed-loop recycling system used for energy-efficient utilization achieve energy conservation and consumption reduction. The various processes are interconnected and mutually influential, together forming a complete, efficient, and environmentally friendly method for recycling photovoltaic cells. The implementation of each step is aimed at achieving the goals of high-efficiency recycling, high-purity silicon wafer and metal recovery, low energy consumption, low cost, and low environmental pollution.

[0100] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0101] Example 1

[0102] This embodiment provides a method for recycling photovoltaic cells, including:

[0103] S1. Low-temperature crushing: The photovoltaic cells to be recycled are placed in a specially designed low-temperature container, and liquid nitrogen is introduced to rapidly reduce the temperature inside the container to the liquid nitrogen temperature (-180℃). This temperature is maintained for a period of time (15 minutes) to allow the cells to become fully brittle. Then, the crushing equipment is started to crush the cells.

[0104] S2. Screening and sorting: The crushed battery cells are conveyed to the intelligent vibrating screen (screen mesh size is 1mm) to perform preliminary screening according to particle size. The screened material enters the rare earth permanent magnet eddy current separator. By adjusting the magnetic field strength (1T) and the material conveying speed (1m / s), the metal and silicon wafers are efficiently separated.

[0105] S3, Immersion: The silicon wafer obtained in step S2 is placed in a deep eutectic solvent (molar ratio of choline and lactic acid 1:2), stirred in a constant temperature water bath at 45°C, and an ultrasonic device with a frequency of 20kHz is turned on at the same time for 1.5 hours to obtain the leached silicon wafer.

[0106] S4. Microbubble alkali treatment: Prepare a sodium carbonate solution with a pH of 10.5, inject it into a reaction vessel equipped with a micro / nano bubble generator, place the leachated silicon wafer into the reaction vessel, start the micro / nano bubble generator to generate a bubble group with an average diameter of 50μm, react at 25℃ for 20min to obtain the alkali-treated silicon wafer.

[0107] S5. Etching: After alkaline treatment, the silicon wafer is placed in an etching tank containing a mixed solution of phosphoric acid and hydrogen peroxide (the volume ratio of phosphoric acid and hydrogen peroxide is 3:1, where the mass concentration of hydrogen peroxide is 20% and the mass concentration of phosphoric acid is 60%) for surface micro-etching. After etching for 1 hour, a high-purity silicon wafer is obtained.

[0108] S6: Solvent Regeneration: Vacuum membrane distillation is used to recover the eutectic solvent that has undergone 15 leachings. The distillation temperature is 60℃ and the pressure is 2.5kPa. The recovery rate is greater than 92%. A three-stage bio-trickling filter is used to collect the waste gas generated during the recovery process. Through the degradation of microorganisms, the removal efficiency of volatile organic compounds can reach 99.3%, and the emissions meet EPA standards.

[0109] The process for recycling photovoltaic cells is as follows: Figure 1 As shown.

[0110] Example 2

[0111] The difference from Example 1 is that the molar ratio of choline to lactic acid in the eutectic solvent is 1:1.

[0112] Example 3

[0113] The difference from Example 1 is that the volume ratio of phosphoric acid to hydrogen peroxide in the phosphoric acid-hydrogen peroxide mixed solution is 3:2.

[0114] Comparative Example 1

[0115] The difference from Example 1 is that the crushing is carried out at room temperature.

[0116] Comparative Example 2

[0117] The difference from Example 1 is that no screening or sorting is performed.

[0118] Comparative Example 3

[0119] The difference from Example 1 is that no choline is added to the eutectic solvent.

[0120] Comparative Example 4

[0121] The difference from Example 1 is that no lactic acid is added to the eutectic solvent.

[0122] Comparative Example 5

[0123] The difference from Example 1 is that the lactic acid in the eutectic solvent is replaced with oxalic acid.

[0124] Comparative Example 6

[0125] The difference from Example 1 is that sodium carbonate is replaced with sodium hydroxide.

[0126] Comparative Example 7

[0127] The difference from Example 1 is that phosphoric acid is not added during etching.

[0128] Comparative Example 8

[0129] The difference from Example 1 is that hydrogen peroxide is not added during etching.

[0130] Comparative Example 9

[0131] The difference from Example 1 is that the phosphoric acid-hydrogen peroxide mixture used during etching is replaced with an HF solution.

[0132] The silicon wafers prepared in the above embodiments and comparative examples were tested for metal residue. The specific test results are shown in Table 1.

[0133] Table 1 Metal Residue Test

[0134] Test components Metal residue / ppm Example 1 Ag < 5, Al < 5, Cu < 3, Fe < 3 Example 2 Ag < 10, Al < 10, Cu < 5, Fe < 5 Example 3 Ag < 4, Al < 4, Cu < 2, Fe < 2 Comparative Example 1 Ag<100,Al<100,Cu<60,Fe<60 Comparative Example 2 Ag<10000, Al<10000, Cu<600, Fe<600 Comparative Example 3 Ag<50,Al<50,Cu<25,Fe<25 Comparative Example 4 Ag<50,Al<50,Cu<25,Fe<25 Comparative Example 5 Ag < 20, Al < 20, Cu < 8, Fe < 8 Comparative Example 6 Ag<40,Al<40,Cu<10,Fe<25 Comparative Example 7 Ag<40,Al<40,Cu<10,Fe<25 Comparative Example 8 Ag<800,Al<800,Cu<300,Fe<450 Comparative Example 9 Ag<60,Al<50,Cu<20,Fe<50

[0135] analyze:

[0136] As shown in Table 1, Examples 1-3 can effectively remove impurities and defects from the surface of silicon wafers, eliminate residual metal impurities, and ensure that the amount of residual metal on the surface of silicon wafers meets the standards for solar-grade silicon.

[0137] In contrast, Comparative Example 1 was crushed at room temperature, and the metal oxide layer on the surface affected subsequent processing.

[0138] In Comparative Example 3, without the addition of choline, the eutectic solvent resulted in a significant decrease in metal leaching efficiency due to the weakening of the hydrogen bond network, the reduction in acidity and oxidizing ability, and the decrease in coordination selectivity. Consequently, the metal residue (PPM) on the silicon wafer was generally increased.

[0139] Comparative Example 4: No lactic acid was added. Lactic acid can optimize the viscosity and conductivity of DES and improve electrodeposition efficiency. After removing lactic acid, the coating density decreased, the metal grains coarsened, and the residual amount increased.

[0140] Comparative Example 5 replaced lactic acid in the eutectic solvent with oxalic acid, and its metal removal effect was significantly worse than that of the choline-lactic acid system. This proves that in the eutectic solvent system, not any organic acid + choline can achieve the effect of the choline-lactic acid system. Furthermore, the oxalic acid system is particularly suitable for scenarios that require efficient dissolution of oxides or reduction of high-valence metals, but attention should be paid to controlling the potential corrosion of the silicon substrate by the acid.

[0141] Comparative Example 6 showed that replacing sodium carbonate with sodium hydroxide resulted in an increase in residue levels.

[0142] In Comparative Example 7, the absence of phosphoric acid in the etching process leads to a significant increase in the amount of residual metal impurities (such as Fe and Al) on the silicon wafer due to residual silicon nitride and insufficient acidity.

[0143] In Comparative Example 8, the absence of hydrogen peroxide during etching resulted in an increase in the PPM of metal ions.

[0144] Comparative Example 9, by replacing the phosphoric acid-hydrogen peroxide mixture during etching with an HF solution, resulted in Fe... 2+ The decrease in complexation efficiency proves that not all oxidants can achieve the etching effect of the phosphoric acid-hydrogen peroxide mixture in this application.

[0145] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0146] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for recycling photovoltaic cells, characterized in that, include: In a liquid nitrogen environment, photovoltaic cells are crushed to obtain crushed cells, which are then sieved and sorted to obtain sorted silicon wafers. The sorted silicon wafers are mixed with a deep eutectic solvent and then leached to obtain leached silicon wafers. The leached silicon wafer is mixed with an alkaline solution and subjected to microbubble alkaline treatment to obtain an alkaline-treated silicon wafer. The alkaline-treated silicon wafer, phosphoric acid, and hydrogen peroxide are mixed and etched to obtain a high-purity silicon wafer. The raw materials for the deep eutectic solvent include choline and lactic acid.

2. The method for recycling photovoltaic cells according to claim 1, characterized in that, At least one of the following conditions must be met: A. The crushing temperature is -196℃ to -180℃, and the time is 15min to 30min; B. The sieve mesh size for the sieving process is 0.1mm-5mm; C. The magnetic field strength for sorting is 0.5T-2T, and the conveying speed is 0.5m / s-2m / s.

3. The method for recycling photovoltaic cells according to claim 1, characterized in that, The molar ratio of choline to lactic acid is 1-1.8:2-2.

2.

4. The method for recycling photovoltaic cells according to claim 1, characterized in that, At least one of the following conditions must be met: A. The leaching temperature is 35℃-55℃; B. The leaching process also includes ultrasonication at a frequency of 18kHz-22kHz, a temperature of 40℃-50℃, and a duration of 1h-2h.

5. The method for recycling photovoltaic cells according to claim 1, characterized in that, At least one of the following conditions must be met: A. The alkaline solution includes a sodium carbonate solution; B. The pH value of the alkaline solution is 10-11; C. The alkaline solution is recycled, with a recycling frequency of ≥15 times.

6. The method for recycling photovoltaic cells according to claim 1, characterized in that, At least one of the following conditions must be met: A. The average diameter of the bubble clusters in the microbubble alkaline treatment process is 40μm-60μm; B. The temperature of the microbubble alkali treatment is 20℃-30℃, and the time is 10min-30min.

7. The method for recycling photovoltaic cells according to claim 1, characterized in that, At least one of the following conditions must be met: A. The volume ratio of the phosphoric acid to the hydrogen peroxide is 2.5-3.5:1; the mass concentration of the hydrogen peroxide is 10%-30%, and the mass concentration of the phosphoric acid is 40%-80%. B. The etching time is 10 min-20 min.

8. The method for recycling photovoltaic cells according to claim 1, characterized in that, The eutectic solvent after leaching was recovered using vacuum membrane distillation.

9. The method for recycling photovoltaic cells according to claim 8, characterized in that, At least one of the following conditions must be met: A. The recovery rate of the recovered product is ≥92%; B. During the recycling process, the generated waste gas is degraded by microorganisms to obtain degraded waste gas; the removal rate of volatile organic compounds in the degraded waste gas is ≥99.3%; C. The distillation temperature of the vacuum membrane distillation method is 50℃-70℃, and the pressure is 1kPa-5kPa.

10. The method for recycling photovoltaic cells according to any one of claims 1-9, characterized in that, The residual metal content on the surface of the high-purity silicon wafer is <50ppm.

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