Method for extracting high-purity copper-indium-gallium-selenium powder from retired copper-indium-gallium-selenium photovoltaic cell

Abstract

The invention belongs to the field of new energy solid waste recycling, and particularly relates to a method for extracting high-purity copper-indium-gallium-selenium powder from a decommissioned copper-indium-gallium-selenium photovoltaic cell, which comprises the following steps: (1) pretreating the decommissioned copper-indium-gallium-selenium photovoltaic cell to obtain a cell sheet material; (2) mixing alkali liquor with benzyl alcohol and hydrogen peroxide; contacting the cut battery sheet material with the mixed solution and leaching; (3) carrying out ultrasonic treatment on a liquid-solid mixture obtained by leaching, then taking out a substrate, a wire and a resin film with clean surfaces and partially broken EVA from the solution, and leaving black copper indium gallium selenium powder in the solution; (4) filtering the obtained solution containing the copper-indium-gallium-selenium powder to obtain leachate and filter residues; and carrying out post-treatment on filter residues to obtain high-purity copper indium gallium selenium powder. According to the method, the quality and purity of the recovered copper indium gallium selenium powder can be improved, the high recovery rate is guaranteed, and efficient utilization of the retired copper indium gallium selenium photovoltaic cell is achieved.

Description

Method for extracting high-purity copper indium gallium selenide (CIGS) powder from decommissioned CIGS photovoltaic cells Technical Field

[0001] This invention belongs to the field of new energy solid waste recycling, specifically involving a method for extracting high-purity copper indium gallium selenide powder from decommissioned copper indium gallium selenide photovoltaic cells. Background Technology

[0002] With the rapid development of the photovoltaic industry, a large number of retired photovoltaic cells are generated. Copper indium gallium selenide (CIGS) thin-film photovoltaic cells, as a type of photovoltaic cell, produce a large amount of solid waste containing CIGS after retirement. To facilitate the sustainable utilization of metals such as copper, indium, gallium, and selenium, it is necessary to find a suitable method to recycle CIGS powder from the waste. The key step in recovering CIGS powder is processing the molybdenum backplate and ethylene-vinyl acetate polymer (EVA) binder on the back electrode. In existing technologies, the main technical route for extracting CIGS powder is: first, crushing the battery raw materials into powder, then using acid leaching, and combining this with distillation, pyrometallurgical refining, and extraction processes to obtain high-purity CIGS powder or the corresponding elemental metal.

[0003] Current technologies for extracting copper indium gallium selenide (CIGS) powder all employ a crushing followed by acid leaching as the first step. This approach is only suitable for decommissioned CIGS photovoltaic cells with glass substrates and cannot be applied to decommissioned flexible CIGS thin-film photovoltaic cells with stainless steel substrates. Furthermore, the recovered powder may contain trace amounts of EVA impurities. When decommissioned CIGS photovoltaic cells contain stainless steel substrates, acid leaching will leach iron from the stainless steel into the solution, making subsequent processes for recovering copper, indium, and gallium more difficult. On the other hand, existing methods do not readily yield CIGS alloy powder directly, limiting the potential for further utilization of the recovered product.

[0004] Therefore, it is necessary to continue researching methods for extracting copper indium gallium selenide (CIGS) powder from decommissioned CIGS photovoltaic cells. Summary of the Invention

[0005] The purpose of this invention is to solve the technical problem that existing technologies cannot extract high-purity (e.g., higher than 98%) copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells in a simple and high-recovery-rate (e.g., higher than 95%) manner. This invention provides a method for extracting high-purity CIGS powder from retired CIGS photovoltaic cells, which can not only process retired flexible CIGS photovoltaic cells with stainless steel backsheets, but also improve the quality and purity of the recovered CIGS powder while ensuring a high recovery rate, thus achieving efficient utilization of retired CIGS photovoltaic cells.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a method for extracting high-purity copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells, comprising the following steps: (1) pretreatment: after pretreatment of the retired CIGS photovoltaic cells, a battery sheet material is obtained; (2) leaching with a mixed solution: benzyl alcohol and hydrogen peroxide are added sequentially to a prepared alkaline solution to obtain a mixed solution; the battery sheet material obtained in step (1) is leached in contact with the mixed solution; wherein, during leaching, 100-200 cells are treated per 1 L of mixed solution. g (e.g., 120g, 150g, 180g) of decommissioned copper indium gallium selenide photovoltaic cell sheet material; (3) Separation: The liquid-solid mixture obtained from the leaching in step (2) is ultrasonically treated, and then the clean substrate, wires, resin film and partially broken EVA are taken out from the solution, while the black copper indium gallium selenide powder remains in the solution; (4) Filtration: The solution containing copper indium gallium selenide powder obtained in step (3) is filtered to obtain leaching liquid and filter residue; then the filter residue is washed and dried to obtain high-purity copper indium gallium selenide powder.

[0007] According to the method provided by the present invention, in some embodiments, the pretreatment in step (1) includes: removing the plastic encapsulation material of the decommissioned copper indium gallium selenide photovoltaic cell and cutting the cell into sheet materials.

[0008] Step (1) can remove impurities from the encapsulation material on the battery, and controlling the size of the sheet material is beneficial to improving the efficiency of the reaction in the subsequent leaching process.

[0009] According to the method provided by the present invention, in some embodiments, the size of the battery sheet material in step (1) is 5-10 cm. 2 For example, 5.5cm 2 6cm 2 7cm 2 8cm 2 9cm 2 .

[0010] According to the method provided by the present invention, in some embodiments, the alkaline solution in step (2) is selected from an aqueous solution of sodium hydroxide or an aqueous solution of potassium hydroxide.

[0011] In some implementations, the concentration of the alkaline solution in step (2) is 0.5-1.0 mol / L (e.g., 0.55 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L, 0.8 mol / L, 0.85 mol / L, 0.9 mol / L).

[0012] In some implementations, the volume ratio of alkali solution: benzyl alcohol: hydrogen peroxide in the mixed solution in step (2) is (10-20):(3-5):1; for example, the volume ratio of alkali solution: hydrogen peroxide is 12:1, 14:1, 15:1, 16:1, 18:1; the volume ratio of benzyl alcohol: hydrogen peroxide is 3.5:1, 4:1, 4.5:1.

[0013] The preparation process of the mixed solution in step (2) of this article can be as follows: First, add a certain amount of sodium hydroxide solid to deionized water to form an alkaline solution of a certain concentration; then add a certain amount of benzyl alcohol under stirring, disperse it evenly and maintain stirring, then add hydrogen peroxide at a rate of 100 drops / minute, and maintain stirring for 5 minutes after the addition is completed to obtain the mixed solution.

[0014] According to the method provided by the present invention, in some embodiments, the leaching process conditions in step (2) include: leaching at 50-80°C (e.g., 55°C, 60°C, 65°C, 70°C, 75°C) with air introduced, and the leaching time is 1-4 h (e.g., 1.5h, 2h, 2.5h, 3h, 3.5h).

[0015] According to the method provided by the present invention, in some embodiments, the time for ultrasound treatment in step (3) is 10-30 minutes, for example, 12 minutes, 14 minutes, 15 minutes, 18 minutes, 20 minutes, 24 minutes, 25 minutes, or 28 minutes.

[0016] According to the method provided by the present invention, in some embodiments, the method further includes the following steps: (5) recycling and reuse of leachate: recycling the leachate obtained after filtration in step (4) and returning it to step (2) for leaching with the battery sheet material cut in step (1).

[0017] The leachate obtained after filtration in step (4) is still strongly alkaline, and the main ions contained in the solution are sodium ions and molybdenum ions. The pH value of the leachate is measured to ensure that the pH value is maintained at around 13.5. The solution can then be used repeatedly 5 times to leach the battery sheet material cut in step (1). When the molybdenum concentration in the leachate reaches 5-10 mol / L (e.g., 6 mol / L, 8 mol / L, 9 mol / L), it can be electrolyzed or reduced to recover the molybdenum element. After evaporation and condensation, benzyl alcohol can be recovered.

[0018] According to the method provided by the present invention, in some embodiments, the method further includes the following steps: (6) post-processing of copper indium gallium selenide powder: the high-purity copper indium gallium selenide powder obtained after filtration in step (4) is stored under dry conditions and reused in the production process of copper indium gallium selenide photovoltaic cells, or the metal elements are recovered and separated (such as using acid leaching, oxidative roasting, extraction, reduction and other methods to recover high-quality copper, indium, gallium and selenium metals from the powder).

[0019] Compared to existing technologies, the beneficial effects of this invention are at least as follows: This invention utilizes a leaching method combining alkaline leaching, benzyl alcohol-assisted swelling, and hydrogen peroxide-accelerated oxidation to efficiently extract high-purity copper indium gallium selenide (CIGS) powder. Furthermore, the combination of leaching and ultrasound allows for the efficient recovery of CIGS powder from decommissioned CIGS photovoltaic cells. Compared to existing processing methods, this method offers advantages such as fewer impurities in the recovered product, higher recovery efficiency, and a simpler process. Additionally, the mixed solution (leaching liquid) used in the leaching process can be recycled at least five times, which helps save on process costs. Detailed Implementation

[0020] To provide a detailed understanding of the technical features and content of this invention, preferred embodiments will be described in more detail below. While preferred embodiments of the invention are described in the examples, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0021] In this article, some terms are defined as follows: Leaching: a separation technique that uses a solvent (such as water, acid, alkali, salt solution, etc.) to dissolve certain target components in a solid reactant and transfer them to the liquid phase; Oxidative roasting: a process of heat treatment of solid materials in a high-temperature and aerobic environment to change the chemical composition of the materials; Extraction: a separation method that uses the difference in solubility of a solute in two immiscible solvents to transfer the solute from one liquid phase to another; Reduction: a chemical process that uses a reducing agent to reduce the oxidation state of elements in a target substance, converting it into an element or a low oxidation state compound.

[0022] In some embodiments of the present invention, a method for extracting high-purity copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells includes the following steps: (1) Pretreatment: removing the plastic encapsulation material from the retired CIGS photovoltaic cells and cutting the cells into approximately 5-10 cm pieces. 2 (For example, 6cm) 2 7cm 2 8cm 2 9cm 2(1) Sheet material; (2) Mixed solution leaching: Prepare a solution with a concentration of 0.5-1.0 mol / L (e.g., 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.85 mol / L). A 0.9 mol / L alkali solution (such as sodium hydroxide aqueous solution) is prepared, and benzyl alcohol (liquid, analytical grade) and 5% hydrogen peroxide are added sequentially according to specific steps to form a mixed solution; wherein, the volume ratio of alkali solution (such as sodium hydroxide aqueous solution), benzyl alcohol and hydrogen peroxide is 10-20:3-5:1; the volume ratio of alkali solution (such as sodium hydroxide aqueous solution) to hydrogen peroxide can be, for example, 12:1, 14:1, 15:1, 16:1, 18:1; the volume ratio of benzyl alcohol and hydrogen peroxide can be, for example, 3.5:1, 4:1, 4.5:1; a certain amount of the mixed solution is measured, and the decommissioned copper indium gallium selenide photovoltaic cell sheet material obtained in step (1) is put into the mixed solution, and air is introduced at 50-80℃ (for example, 55℃, 60℃, 70℃, 75℃) for leaching, and the leaching time is 1-4 h (e.g., 1.5h, 2h, 2.5h, 3h, 3.5h); wherein, during leaching, 100-200 g of decommissioned copper indium gallium selenide photovoltaic cells are treated per 1 L of mixed solution; (3) Separation: After the reaction is completed, the liquid-solid mixture obtained by leaching is sonicated for 10-30 minutes (e.g., 12 minutes, 15 minutes, 18 minutes, 20 minutes, 25 minutes, 28 minutes), and then the clean substrate, wires, resin film and partially broken EVA can be taken out from the solution, while the black copper indium gallium selenide powder remains in the mixed solution; (4) Filtration: The mixed solution containing copper indium gallium selenide powder obtained by separation is filtered using filtration and washing equipment to obtain leaching liquid and filter residue; then the filter residue is filtered. After washing and drying, high-purity copper indium gallium selenide powder is obtained; (5) Recycling and reuse of leachate: The leachate obtained after filtration in step (4) is still strongly alkaline, and the main ions contained in the solution are sodium ions and molybdenum ions; The pH value of the leachate is measured to ensure that its pH value is maintained at 13-14 (such as around 13.5), and then it is recycled and used in step (2) to leach the retired copper indium gallium selenide photovoltaic cell sheet material; The leaching step of recycling and using in step (2) is repeated 5 times. When the molybdenum element concentration in the leachate reaches 5-10 mol / L, the mixed solution can be electrolyzed or reduced to recover the molybdenum element. After evaporation and condensation, benzyl alcohol can be recovered; (6) Subsequent processing of copper indium gallium selenide powder: The obtained high-purity copper indium gallium selenide powder is stored under dry conditions. It can be reused in the production process of copper indium gallium selenide photovoltaic cells, or high-quality copper, indium, gallium and selenium metals can be recovered from the powder by acid leaching, oxidative roasting, extraction, reduction and other methods.

[0023] In the pretreatment process, impurities in the encapsulation materials contained in decommissioned copper indium gallium selenide photovoltaic cells can be removed, and controlling the size of the sheet material is beneficial to improving the reaction efficiency in the subsequent leaching process.

[0024] During the leaching process, sodium hydroxide reacts with the oxide film on the surface of molybdenum to form soluble sodium molybdate. At this time, elemental Mo is exposed in the solution. The addition of hydrogen peroxide can accelerate its oxidation rate, allowing it to quickly form a new oxide film and continue to react with the sodium hydroxide solution. In addition, benzyl alcohol in the mixed solution can swell the EVA in the decommissioned copper indium gallium selenide battery, improving the leaching efficiency.

[0025] In this invention, (1) a leaching method consisting of alkaline leaching, benzyl alcohol organic solvent-assisted swelling, and hydrogen peroxide-accelerated oxidation can efficiently extract high-purity copper indium gallium selenide (CIGS) powder. Compared with existing methods, this invention can effectively process molybdenum backsheets and is applicable to retired CIGS flexible photovoltaic cells with stainless steel backsheets. (2) After leaching, ultrasonic and filtration processes are combined to extract metal powder from retired CIGS photovoltaic cells, significantly improving the powder recovery rate. (3) The mixed solution used in the leaching process can be recycled at least 5 times, which helps to save the cost of the process.

[0026] The copper indium gallium selenide (CIGS) powder extracted by this invention has high purity, reaching 99% or higher. Furthermore, the iron and molybdenum impurities in the powder can be controlled to within 0.1%. Using acid leaching, high-purity CIGS powder cannot be obtained, as the leachate contains over 50% iron, manganese, and molybdenum impurities, hindering subsequent metal separation. In addition, the method of this invention results in minimal raw material loss. By combining it with ultrasonic processing, the recovery rate of CIGS powder can be consistently maintained at 95% or higher, compared to only around 50% without ultrasonic treatment. Moreover, the recovered leachate can be reused up to five times in the leaching process, reducing the consumption of mixed solutions and saving on process costs.

[0027] Unless otherwise specified in the examples, the conditions should be performed under standard conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the examples are assumed to be commercially available.

[0028] Example 1: A method for extracting high-purity copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells, comprising the following steps: (1) Pretreatment: removing the plastic encapsulation material from the retired CIGS photovoltaic cells and cutting the cells into approximately 5cm pieces. 2(2) Mixed solution leaching: Prepare a sodium hydroxide aqueous solution with a concentration of about 0.85 mol / L, then add benzyl alcohol (liquid, analytical grade) under stirring, disperse evenly and maintain stirring, then add 5% hydrogen peroxide at a rate of 100 drops / minute to form a mixed solution; in this mixed solution, the volume ratio of sodium hydroxide aqueous solution, benzyl alcohol and hydrogen peroxide is 10:3:1; take a certain amount of the prepared mixed solution, put the cut retired copper indium gallium selenide photovoltaic cell sheet material into the mixed solution, and leach it by passing air at 80°C for 1 h; among which, 100 mol / L of mixed solution is treated during leaching. g retired copper indium gallium selenide photovoltaic cell sheet material; (3) Separation: After the reaction is completed, the liquid-solid mixture obtained by leaching is ultrasonically treated for 20 minutes. Then, the clean substrate, wire, resin film and some broken EVA are taken out from the solution. The black copper indium gallium selenide powder remains in the mixed solution; (4) Filtration: The mixed solution containing copper indium gallium selenide powder obtained in step (3) is filtered using a filtration and washing device to obtain leaching solution and filter residue. After washing and drying the filter residue, high-purity copper indium gallium selenide powder is obtained; (5) Recycling and reuse of leaching solution: The leaching solution obtained after filtration is still strongly alkaline. The main ions it contains are sodium ions and molybdenum ions. The pH value of the leaching solution is measured to ensure that the pH value is maintained at 13.5. Then, the leaching solution can be used repeatedly 5 times to leach retired copper indium gallium selenide photovoltaic cell sheet material. When the molybdenum element concentration in the leaching solution reaches 5 mol / L, the mixed solution is electrolyzed or reduced to recover molybdenum element. After evaporation and condensation, benzyl alcohol can be recovered.

[0029] In this embodiment, the purity of the recovered copper indium gallium selenide (CIGS) powder can reach 99.2%, and the content of iron and molybdenum impurities in the powder can be controlled within 0.1 wt%; the recovery rate of CIGS powder is 98%.

[0030] The ICP test results of high-purity copper indium gallium selenide (CIGS) powder are as follows: Cu content: 19.8%; In content: 24.7%; Ga content: 6.4%; Se content: 48.3%; the balance is impurities.

[0031] The obtained high-purity copper indium gallium selenide (CIGS) powder can be stored under dry conditions and reused in the production process of CIGS photovoltaic cells.

[0032] Example 2: A method for extracting high-purity copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells, comprising the following steps: (1) Pretreatment: removing the plastic encapsulation material from the retired CIGS photovoltaic cells and cutting the cells into approximately 10cm pieces. 2(2) Leaching of mixed solution: Prepare a sodium hydroxide aqueous solution with a concentration of about 0.85 mol / L, then add benzyl alcohol (liquid, analytical grade) under stirring, disperse evenly and maintain stirring, then add 5% hydrogen peroxide at a rate of 100 drops / minute to form a mixed solution; in this mixed solution, the volume ratio of sodium hydroxide aqueous solution, benzyl alcohol and hydrogen peroxide is 20:5:1; take a certain amount of the prepared mixed solution, put the cut retired copper indium gallium selenide photovoltaic cell sheet material into the mixed solution, and leach it by passing air at 50°C for 4 hours; among which, 150 mol / L of mixed solution is treated during leaching. g retired copper indium gallium selenide photovoltaic cell sheet material; (3) Separation: After the reaction, the liquid-solid mixture obtained by leaching is ultrasonically treated for 30 minutes. Then, the clean substrate, wire, resin film and some broken EVA are taken out from the solution. The black copper indium gallium selenide powder remains in the mixed solution; (4) Filtration: The mixed solution containing copper indium gallium selenide powder obtained in step (3) is filtered using a filtration and washing device to obtain leaching solution and filter residue. After washing and drying the filter residue, high-purity copper indium gallium selenide powder is obtained; (5) Recycling and reuse of leaching solution: The leaching solution obtained after filtration is still strongly alkaline. The main ions it contains are sodium ions and molybdenum ions. The pH value of the leaching solution is measured to ensure that the pH value is kept at 13. Then, the leaching solution can be used repeatedly 5 times to leach retired copper indium gallium selenide photovoltaic cell sheet material. When the molybdenum element concentration in the leaching solution reaches 10 mol / L, the mixed solution is electrolyzed or reduced to recover molybdenum element. After evaporation and condensation, benzyl alcohol can be recovered.

[0033] In this embodiment, the purity of the recovered copper indium gallium selenide (CIGS) powder can reach 99.8%, and the content of iron and molybdenum impurities in the powder can be controlled within 0.1%; the recovery rate of CIGS powder is 97%.

[0034] The ICP test results of high-purity copper indium gallium selenide (CIGS) powder are as follows: Cu content: 20.2%; In content: 24.0%; Ga content: 6.8%; Se content: 48.8%; the balance is impurities.

[0035] The obtained high-purity copper indium gallium selenide (CIGS) powder can be stored under dry conditions and reused in the production process of CIGS photovoltaic cells.

[0036] Example 3: A method for extracting high-purity copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells, comprising the following steps: (1) Pretreatment: removing the plastic encapsulation material from the retired CIGS photovoltaic cells and cutting the cells into approximately 7cm pieces. 2(2) Leaching of mixed solution: Prepare a sodium hydroxide aqueous solution with a concentration of about 0.85 mol / L, then add benzyl alcohol (liquid, analytical grade) under stirring, disperse evenly and maintain stirring, then add 5% hydrogen peroxide at a rate of 100 drops / minute to form a mixed solution; in this mixed solution, the volume ratio of sodium hydroxide aqueous solution, benzyl alcohol and hydrogen peroxide is 15:4:1; take a certain amount of the prepared mixed solution, put the cut retired copper indium gallium selenide photovoltaic cell sheet material into the mixed solution, and leach it by passing air at 65°C for 2 hours; among which, 200 mol / L of mixed solution is treated per 1 L of leaching solution. g retired copper indium gallium selenide photovoltaic cell sheet material; (3) Separation: After the reaction is completed, the liquid-solid mixture obtained by leaching is ultrasonically treated for 10 minutes. Then, the clean substrate, wire, resin film and some broken EVA can be taken out from the solution. The black copper indium gallium selenide powder remains in the mixed solution; (4) Filtration: The mixed solution containing copper indium gallium selenide powder obtained in step (3) is filtered using a filtration and washing device to obtain leaching solution and filter residue. After washing and drying the filter residue, high-purity copper indium gallium selenide powder is obtained; (5) Recycling and reuse of leaching solution: The leaching solution obtained after filtration is still strongly alkaline. The main ions it contains are sodium ions and molybdenum ions. The pH value of the leaching solution is measured to ensure that the pH value is kept at 14. Then, the leaching solution can be used repeatedly 5 times to leach retired copper indium gallium selenide photovoltaic cell sheet material. When the molybdenum element concentration in the leaching solution reaches 6 mol / L, the mixed solution is electrolyzed or reduced to recover molybdenum element. After evaporation and condensation, benzyl alcohol can be recovered.

[0037] In this embodiment, the purity of the recovered copper indium gallium selenide (CIGS) powder can reach 99.7%, and the content of iron and molybdenum impurities in the powder can be controlled within 0.1%; the recovery rate of CIGS powder is 95%.

[0038] The ICP test results of high-purity copper indium gallium selenide (CIGS) powder are as follows: Cu content: 19.8%; In content: 24.3%; Ga content: 6.7%; Se content: 49.1%; the balance is impurities.

[0039] The obtained high-purity copper indium gallium selenide (CIGS) powder can be stored under dry conditions and reused in the production process of CIGS photovoltaic cells.

[0040] Comparative Example 1: A method for extracting copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells, comprising the following steps: (1) Pretreatment: removing the plastic encapsulation material from the retired CIGS photovoltaic cells and cutting the cells into approximately 5cm pieces. 2(2) Solution leaching: Prepare a sodium hydroxide aqueous solution with a concentration of about 0.85 mol / L, put the cut retired copper indium gallium selenide photovoltaic cell sheet material into the solution, and leach at 80°C for 1 h; wherein, each 1 L of mixed solution can treat 100 g retired copper indium gallium selenide photovoltaic cell sheet material; (3) Separation: After the reaction is completed, the liquid-solid mixture obtained by leaching is ultrasonically treated for 20 minutes. Then, the clean substrate, wires, resin film and some broken EVA are taken out from the solution. The black copper indium gallium selenide powder remains in the mixed solution; (4) Filtration: The mixed solution containing copper indium gallium selenide powder obtained in step (3) is filtered using a filtration and washing device to obtain leaching solution and filter residue. After washing and drying the filter residue, high-purity copper indium gallium selenide powder is obtained; (5) Recycling and reuse of leaching solution: The leaching solution obtained after filtration is still strongly alkaline. The main ions it contains are sodium ions and molybdenum ions. The pH value of the leaching solution is measured to ensure that the pH value is maintained at 13.5. Then, the leaching solution can be used repeatedly 5 times to leach retired copper indium gallium selenide photovoltaic cell sheet material. When the molybdenum element concentration in the leaching solution reaches 5 mol / L, the mixed solution is electrolyzed or reduced to recover molybdenum element.

[0041] In this comparative example, since hydrogen peroxide and benzyl alcohol were not added during the leaching process, the recovered powder contained more non-metallic element impurities and molybdenum element impurities. The purity of the recovered copper indium gallium selenide powder was only 78.5%, and the recovery rate of copper indium gallium selenide powder was 95%.

[0042] Comparative Example 2: A method for extracting copper indium gallium selenide (CIGS) powder from retired CIGS photovoltaic cells, comprising the following steps: (1) Pretreatment: removing the plastic encapsulation material from the retired CIGS photovoltaic cells and cutting the cells into approximately 5cm pieces. 2(2) Mixed solution leaching: Prepare a sodium hydroxide aqueous solution with a concentration of about 0.85 mol / L, then add benzyl alcohol (liquid, analytical grade) under stirring, disperse evenly and maintain stirring, then add 5% hydrogen peroxide at a rate of 100 drops / minute to form a mixed solution; in this mixed solution, the volume ratio of sodium hydroxide aqueous solution, benzyl alcohol and hydrogen peroxide is 10:3:1; take a certain amount of the prepared mixed solution, put the cut retired copper indium gallium selenide photovoltaic cell sheet material into the mixed solution, and leach it by passing air at 80°C for 1 h; among which, 100 mol / L of mixed solution is treated during leaching. g retired copper indium gallium selenide photovoltaic cell sheet material; (3) Separation: After the reaction is completed, the substrate, wires, resin film and some broken EVA are taken out from the solution of the liquid-solid mixture obtained by leaching. The black copper indium gallium selenide powder is still left in the mixed solution. At this time, it is found that there are a lot of black substances remaining on the surface of the substrate; (4) Filtration: The mixed solution containing copper indium gallium selenide powder obtained in step (3) is filtered using a filtration and washing device to obtain leaching solution and filter residue; after washing and drying the filter residue, high-purity copper indium gallium selenide powder is obtained; (5) Recycling and reuse of leaching solution: The leaching solution obtained after filtration is still strongly alkaline. The main ions it contains are sodium ions and molybdenum ions; the pH value of the leaching solution is measured to ensure that its pH value is kept at 13.5. Then the solution can be used repeatedly 5 times to leach retired copper indium gallium selenide photovoltaic cell sheet material. When the molybdenum element concentration in the leaching solution reaches 5 mol / L, the mixed solution is electrolyzed or reduced to recover molybdenum element. After evaporation and condensation, benzyl alcohol can be recovered.

[0043] In this comparative example, although the purity of the recovered copper indium gallium selenide powder can reach 99.2% and the content of iron and molybdenum impurities in the powder can be controlled within 0.1%, the recovery rate of copper indium gallium selenide powder is only about 20%, since ultrasonic treatment is not used.

[0044] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the spirit of the invention.

Claims

1. A method for extracting high-purity copper indium gallium selenide (CIGS) powder from decommissioned CIGS photovoltaic cells, characterized in that, The process includes the following steps: (1) Pretreatment: After pretreatment of the retired copper indium gallium selenide photovoltaic cell, a cell sheet material is obtained; (2) Leaching of mixed solution: Benzyl alcohol and hydrogen peroxide are added to the prepared alkaline solution in sequence to obtain a mixed solution; the cell sheet material obtained in step (1) is leached in contact with the mixed solution; wherein, 100-200 g of retired copper indium gallium selenide photovoltaic cell sheet material is treated per 1 L of mixed solution during leaching; (3) Separation: The liquid-solid mixture obtained from leaching in step (2) is ultrasonically treated, and then the clean substrate, wires, resin film and partially broken EVA are taken out from the solution, while the black copper indium gallium selenide powder remains in the solution; (4) Filtration: The solution containing copper indium gallium selenide powder obtained in step (3) is filtered to obtain leachate and filter residue; the filter residue is then washed and dried to obtain high-purity copper indium gallium selenide powder.

2. The method according to claim 1, characterized in that, The pretreatment in step (1) includes: removing the plastic encapsulation material of the retired copper indium gallium selenide photovoltaic cell and cutting the cell into sheet materials.

3. The method according to claim 1, characterized in that, The size of the battery sheet material in step (1) is 5-10 cm. 2 .

4. The method according to claim 1, characterized in that, The alkaline solution in step (2) is selected from sodium hydroxide aqueous solution or potassium hydroxide aqueous solution.

5. The method according to claim 1, characterized in that, The concentration of the alkaline solution in step (2) is 0.5-1.0 mol / L.

6. The method according to claim 1, characterized in that, In the mixed solution described in step (2), the volume ratio of alkali solution: benzyl alcohol: hydrogen peroxide is (10-20): (3-5):

1.

7. The method according to claim 1, characterized in that, The leaching process conditions in step (2) include: leaching at 50-80℃ with air introduced, and leaching time of 1-4 h.

8. The method according to claim 1, characterized in that, The ultrasonic treatment in step (3) takes 10-30 minutes.

9. The method according to claim 1, characterized in that, The method further includes the following steps: (5) recycling and reuse of leachate: the leachate obtained after filtration in step (4) is recycled and returned to step (2) for leaching with the battery sheet material cut in step (1).

10. The method according to any one of claims 1-9, characterized in that, The method further includes the following steps: (6) Post-processing of copper indium gallium selenide powder: the high-purity copper indium gallium selenide powder obtained after filtration in step (4) is stored under dry conditions and reused in the production process of copper indium gallium selenide photovoltaic cells, or the metal elements are recovered and separated.