Environment-friendly method for recycling retired crystalline silicon solar cell panel

Abstract

The invention discloses a green method for recycling a retired crystalline silicon solar cell panel, and belongs to the technical field of solid waste resourceful treatment. After the retired crystalline silicon solar cell panel is subjected to high-temperature pyrolysis, tempered glass, an aluminum frame, a copper-lead-tin solder and a crystalline silicon solar cell piece are obtained; the crystalline silicon solar cell is put into the heated mixed molten salt of sodium hydroxide and potassium hydroxide for alkaline leaching treatment, then heating treatment and cooling are carried out, and after the steps, namely salt etching, silver and silicon cells are obtained; after the copper-lead-tin solder is heated, oxidized and dissolved, a copper strip and a lead-tin coating are obtained; and soaking the lead-tin coating in a NaOH solution, and carrying out electro-deposition treatment to obtain copper, lead, tin and tin dioxide. Metal such as silicon and silver is recovered by a green method, and separation is driven by a salt etching method and a copper-lead-tin solder only by using an alkaline solution, so that the influence on the environment is small, toxic chemical substances and secondary pollution are eliminated, and the recovery treatment difficulty is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of solid waste resource treatment, and specifically relates to a green method for recycling and treating retired crystalline silicon solar panels. Background Art

[0002] With the increasingly severe global warming situation and the depletion of fossil fuels, clean energy such as solar energy, wind energy, biomass energy, geothermal energy, etc. has attracted more and more attention. As an environmentally friendly and high-conversion power generation device, solar cells have developed rapidly around the world in recent years. Since crystalline silicon solar cells were developed earlier, the technology is mature, and the conversion rate is high, they have the largest market share. Retired crystalline silicon solar panels are a valuable urban mineral resource, from which materials can be extracted to re-manufacture photovoltaic modules to achieve material recycling.

[0003] At present, the research on photovoltaic module recycling is still in its infancy. Traditional recycling processes (such as organic dissolution, strong acid dissolution, extraction separation, etc.) will produce a lot of secondary pollution. In addition, in the process of recycling silicon and silver, one challenge is that silver is usually dissolved in nitric acid, which is volatile and highly oxidizing. The acidic dissolution process will produce toxic nitrogen oxides and waste liquid. Another challenge is to remove SiN in phosphoric acid or HNO3-HF-CH3COOH solution. x , which also produces chemical waste, toxic nitrogen oxides and hydrofluoric acid. Hydrofluoric acid is volatile and highly toxic, posing a safety risk to operators. Therefore, it is particularly necessary and important to develop a non-toxic and environmentally friendly green method to recycle silicon, silver and other metals from retired crystalline silicon solar panels.

[0004] In view of the technical problems of insufficient high-value utilization of existing retired crystalline silicon solar panels and environmental pollution caused by the recycling process, it is urgent to find a non-toxic and environmentally friendly green recycling method. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a green method for recycling and processing retired crystalline silicon solar panels, so as to solve the technical problems existing in the prior art of insufficient high-value utilization of retired crystalline silicon solar panels and environmental pollution caused by the recycling process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention discloses a green method for recycling and treating retired crystalline silicon solar panels, comprising the following steps: 1) After high-temperature pyrolysis of retired crystalline silicon solar panels, tempered glass, aluminum frames, copper-lead-tin solder and crystalline silicon solar cells are obtained; 2) placing the crystalline silicon solar cell obtained in step 1) into a heated mixed molten salt of sodium hydroxide and potassium hydroxide for alkaline leaching, then heating and cooling, and obtaining silver and silicon solar cells after sufficient salt corrosion; 3) heating and oxidizing the copper-lead-tin solder obtained in step 1) to dissolve it, thereby obtaining a copper strip and a lead-tin coating; 4) The lead-tin coating obtained in step 3) is immersed in a NaOH solution and subjected to an electrodeposition treatment to obtain copper, lead, tin and tin dioxide.

[0007] Preferably, in step 2), the mass ratio of crystalline silicon solar cell sheet to mixed molten salt of sodium hydroxide and potassium hydroxide is (6-10):1.

[0008] Further preferably, in step 1), the high temperature pyrolysis conditions are: heating at 500-600° C. for 2-4 h under nitrogen or argon.

[0009] Preferably, in step 2), in the mixed molten salt of sodium hydroxide and potassium hydroxide, the concentration of sodium hydroxide is 16-42wt%, and the concentration of potassium hydroxide is 22-58wt%.

[0010] Preferably, in step 2), the heating temperature of the mixed molten salt of sodium hydroxide and potassium hydroxide is 180-220°C.

[0011] Preferably, in step 2), the alkali leaching treatment time is 1-3 seconds.

[0012] Preferably, in step 2), the heating treatment conditions are: continuous heating at 180-300° C. for 5-300 seconds.

[0013] Preferably, in step 2), the cooling condition is: cooling in 2-10° C. cold water for 20-40 min to room temperature.

[0014] Preferably, in step 3), the conditions for heating and oxidative dissolution are: oxidation at 300-600° C. for 10-60 min.

[0015] Preferably, in step 4), the conditions for the electrodeposition treatment are: temperature of 90° C., immersion in a 40-50wt% sodium hydroxide solution for 5-10 min; cathode current of lead is 1.2-1.4V, and cathode current of tin is 1.4-1.8V.

[0016] Compared with the prior art, the present invention has the following beneficial effects: A green method for recycling and treating retired crystalline silicon solar panels. The method not only realizes the resource utilization and high-value utilization of retired crystalline silicon solar panels by recycling aluminum frames, tempered glass, silicon wafers, silver and copper in the panels, but also provides an environmentally friendly green method for recycling and treating the retired crystalline silicon solar panels. The green method for recycling and treating retired crystalline silicon solar panels disclosed in the present invention increases the added value of the product. After high-temperature pyrolysis, tempered glass, aluminum frames, copper-lead-tin solder and crystalline silicon solar cells can be obtained in one step, which can be directly classified and recycled, and the added value of the recycled materials is increased. Silicon, silver and other metals are recycled by a green method. The salt etching method and the recycling of copper-lead-tin solder only use alkaline solutions to drive separation, which has little impact on the environment and eliminates toxic chemicals and secondary pollution. The difficulty of recycling and treatment is reduced. Tempered glass and aluminum frames that can be directly recycled are obtained through one-time pyrolysis, and then copper-lead-tin solder and crystalline silicon solar cells are processed step by step. The recycling process is simple and the operation is convenient and feasible. The tail gas is harmless, and the tail gas generated during the high-temperature heat treatment process is incinerated to prevent secondary pollution and protect the environment. The method of the present invention uses a combination of heat treatment technology and salt etching to achieve the recycling of retired crystalline silicon solar cell panels, glass recovery and silicon wafer separation, as well as the recycling of valuable metals and silicon wafers. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a technical roadmap for the green method of recycling and treating retired crystalline silicon solar panels in Example 1 of the present invention. DETAILED DESCRIPTION

[0018] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 creative work should fall within the scope of protection of the present invention.

[0019] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0020] The present invention is further described in detail below in conjunction with the accompanying drawings: A green method for recycling and processing retired crystalline silicon solar panels, comprising the following steps: 1) First, 15-20kg of retired crystalline silicon solar panels are placed in a closed heating device and heated at a temperature range of 500-600°C in an inert atmosphere (nitrogen or argon) for 2-4 hours; tempered glass, aluminum frame, copper-lead-tin solder and 6-8kg of crystalline silicon solar cells are obtained; 2) Place 800-1000g of a mixed molten salt of sodium hydroxide and potassium hydroxide into an alumina crucible and heat it to 180-220°C in a muffle furnace; 3) The crystalline silicon solar cell obtained after the heat treatment in step 1) is placed in the mixed molten salt heated in step 2) and immersed for 1-3 seconds to completely wet the crystalline silicon solar cell; 4) After the alkali leaching treatment in step 3), the crystalline silicon solar cell is immediately taken out from the molten salt, placed in an alumina crucible, the crucible is placed in a muffle furnace, and heated at 180-300°C for 5-300s; 5) taking out the crystalline silicon solar cell treated in step 4) from the furnace, and immersing it in 2-10°C cold water to cool it down to room temperature for 20-40 minutes; 6) placing the copper-lead-tin solder obtained in step 1) into a muffle furnace and oxidizing it in air at 300-600° C. for 10-60 min; 7) The copper-lead-tin solder oxidized in step 6) is immersed in a 40-50wt% NaOH solution at 90°C for 20-40 minutes; 8) Continue to recover the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) by electrodeposition, and soak the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in 40-50wt% sodium hydroxide solution for 5-10 minutes at 90°C and with the cathode current of lead at 1.2-1.4V and the cathode current of tin at 1.4-1.8V.

[0021] After pyrolysis in step 1), the tempered glass, aluminum frame, copper-lead-tin solder and crystalline silicon solar cell are completely separated, the plastic parts such as the back panel are reduced to ashes through heat treatment, and the exhaust gas is incinerated in an incinerator and then discharged; after the heating equipment is cooled, the tempered glass and aluminum frame are sorted for recycling.

[0022] In step 3), the concentration of sodium hydroxide is 16-42wt%, and the concentration of potassium hydroxide is 22-58wt%; the mass ratio of crystalline silicon solar cell: mixed molten salt of sodium hydroxide and potassium hydroxide is (6-10):1.

[0023] In step 5), after the above-mentioned alkaline immersion treatment, heating and cooling, i.e., salt etching, silicon nitride, silicon dioxide and aluminum oxide can be selectively dissolved, so that the surface salt is completely dissolved in water, thereby achieving the separation of the silver wire and the silicon wafer.

[0024] In step 6), the lead-tin coating on the surface of the copper-lead-tin solder is completely converted into lead oxide and tin dioxide.

[0025] In step 7), the lead oxide and tin dioxide are completely dissolved in the sodium hydroxide solution, and the copper strip is recovered.

[0026] In step 8), the solubility of lead oxide and tin dioxide is 99.6 g·L -1 and 0.058 g·L -1 Since the solubility of lead oxide is much higher than that of tin dioxide, it can be electrodeposited as lead, and part of the tin dioxide dissolved in the solution can be deposited as tin; most of the tin is recovered in the form of tin dioxide. Therefore, the solder is recovered as copper, lead, tin and tin dioxide.

[0027] Example 1 A green method for recycling and processing retired crystalline silicon solar panels, comprising the following steps: 1) 15kg of retired crystalline silicon solar panels were placed in an RX3 series-18KW box-type tempering resistance furnace and heated at 540℃ for 3h in a nitrogen atmosphere; tempered glass, aluminum frame, copper-lead-tin solder and 6kg crystalline silicon solar cells; 2) 800 g of a mixed molten salt of sodium hydroxide and potassium hydroxide (16 wt% sodium hydroxide, 22 wt% potassium hydroxide) was placed in an alumina crucible and heated to 200 °C in a muffle furnace; 3) placing the crystalline silicon solar cell obtained after the heat treatment in step 1) above into the mixed molten salt heated in step (2) and soaking for 2 seconds to completely soak the crystalline silicon solar cell; 4) After the alkali leaching treatment in step 3), the crystalline silicon solar cell is immediately taken out from the molten salt, placed in an alumina crucible, the crucible is placed in a muffle furnace, and heated at 200°C for 90 seconds; 5) taking out the crystalline silicon solar cell processed in step 4) from the furnace and immersing it in 5°C cold water to cool it down to room temperature for 30 minutes; 6) placing the copper-lead-tin solder obtained in step 1) into a muffle furnace and oxidizing it in air at 500° C. for 1 h to obtain a copper strip and a lead-tin coating; 7) The copper-lead-tin solder oxidized in step 6) is immersed in a 45wt% sodium hydroxide solution at 90°C for 30 minutes; 8) Continue to recover the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) by electrochemical deposition. Put the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) into a 45wt% sodium hydroxide solution for 6 minutes at 90°C and a cathode current of 1.4V for lead and 1.8V for tin.

[0028] See also Figure 1 This is a technical roadmap for the green method of recycling and treating retired crystalline silicon solar panels in Example 1 of the present invention; as can be seen from the figure, after high-temperature pyrolysis of retired crystalline silicon solar panels, tempered glass, aluminum frames, copper-lead-tin solder and crystalline silicon solar cells are obtained; the crystalline silicon solar cells are placed in a mixed molten salt of heated sodium hydroxide and potassium hydroxide for alkaline leaching treatment, followed by heating treatment and cooling, and after the above steps, i.e., salt etching, silver and silicon cells are obtained; copper-lead-tin solder is heated, oxidized and dissolved to obtain copper strips and lead-tin coatings; the lead-tin coating is immersed in a NaOH solution and subjected to electrodeposition treatment to obtain copper, lead, tin and tin dioxide. The green method is used to recycle metals such as silicon and silver. The salt etching method and the recovery of copper-lead-tin solder only use alkaline solutions to drive separation, which has little impact on the environment, eliminates toxic chemicals and secondary pollution, and reduces the difficulty of recycling.

[0029] Example 2 A green method for recycling and processing retired crystalline silicon solar panels, comprising the following steps: 1) Put 18kg of retired crystalline silicon solar panels into the RX3 series-18KW box-type tempering resistance furnace and heat them at 540℃ for 3h in a nitrogen atmosphere; obtain tempered glass, aluminum frame, copper-lead-tin solder and 7kg of crystalline silicon solar cells; 2) 900 g of a mixed molten salt of sodium hydroxide and potassium hydroxide (42 wt% sodium hydroxide, 58 wt% potassium hydroxide) was placed in an alumina crucible and heated to 200° C. in a muffle furnace; 3) The crystalline silicon solar cell obtained after the heat treatment in step 1) is placed in the mixed molten salt heated in step 2) and immersed for 2 seconds to make the crystalline silicon solar cell completely wetted; 4) After the alkali leaching treatment in step 3), the crystalline silicon solar cell is immediately taken out from the molten salt, placed in an alumina crucible, the crucible is placed in a muffle furnace, and heated at 200°C for 90 seconds; 5) taking out the crystalline silicon solar cell processed in step 4) from the furnace and immersing it in 5°C cold water to cool it down to room temperature for 30 minutes; 6) placing the copper-lead-tin solder obtained in step 1) into a muffle furnace and oxidizing it in air at 500° C. for 1 h; 7) The copper-lead-tin solder oxidized in step 6) is immersed in a 45wt% sodium hydroxide solution at 90°C for 30 minutes; 8) Continue to recover the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) by electrochemical deposition. The lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) are placed in a 45 wt % sodium hydroxide solution for 6 min at 90° C. and with a cathode current of 1.4 V for lead and a cathode current of 1.8 V for tin.

[0030] The recovery rates of silicon, silver, etc. recovered in Example 1-2 were tested, and the results are shown in Table 1: Table 1 Recovery rate of silicon, silver and other components recovered in Example 1 (wt.%)

[0031] As can be seen from Table 1, the method provided by the present invention can achieve high added value recovery of metals and non-metals from crystalline silicon solar cell panels. At the same time, the preparation method is simple, the raw material source is abundant and the cost is low, and it has the advantages of high efficiency and environmental friendliness.

[0032] Example 3 A green method for recycling and processing retired crystalline silicon solar panels, comprising the following steps: 1) Put 18kg of retired crystalline silicon solar panels into the RX3 series-18KW box-type tempering resistance furnace and heat them at 500℃ for 4h in a nitrogen atmosphere; obtain tempered glass, aluminum frame, copper-lead-tin solder and 7kg of crystalline silicon solar cells; 2) Place 1000 g of a mixed molten salt of sodium hydroxide and potassium hydroxide (32 wt% sodium hydroxide, 40 wt% potassium hydroxide) into an alumina crucible and heat to 180° C. in a muffle furnace; 3) The crystalline silicon solar cell obtained after the heat treatment in step 1) is placed in the mixed molten salt heated in step 2) and immersed for 3 seconds to make the crystalline silicon solar cell completely wetted; 4) After the alkali leaching treatment in step 3), the crystalline silicon solar cell is immediately taken out from the molten salt, placed in an alumina crucible, the crucible is placed in a muffle furnace, and heated at 180°C for 300s; 5) taking out the crystalline silicon solar cell treated in step 4) from the furnace and immersing it in 2°C cold water to cool it down to room temperature for 40 minutes; 6) placing the copper-lead-tin solder obtained in step 1) into a muffle furnace and oxidizing it in air at 300° C. for 50 min; 7) The copper-lead-tin solder oxidized in step 6) is immersed in a 40wt% sodium hydroxide solution at 90°C for 20 minutes; 8) Continue to recover the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) by electrochemical deposition, and place the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) in a 40wt% sodium hydroxide solution for 5 minutes at 90°C and with a cathode current of 1.4V for lead and a cathode current of 1.8V for tin; obtain copper, lead, tin and tin dioxide.

[0033] Example 4 A green method for recycling and processing retired crystalline silicon solar panels, comprising the following steps: 1) Put 20kg of retired crystalline silicon solar panels into the RX3 series-18KW box-type tempering resistance furnace and heat them at 600℃ for 2h in a nitrogen atmosphere; obtain tempered glass, aluminum frame, copper-lead-tin solder and 8kg of crystalline silicon solar cells; 2) 800 g of a mixed molten salt of sodium hydroxide and potassium hydroxide (20 wt% sodium hydroxide, 25 wt% potassium hydroxide) was placed in an alumina crucible and heated to 220° C. in a muffle furnace; 3) The crystalline silicon solar cell obtained after the heat treatment in step 1) is placed in the mixed molten salt heated in step 2) and immersed for 1 second to make the crystalline silicon solar cell completely wetted; 4) After the alkali leaching treatment in step 3) above, the crystalline silicon solar cell is immediately taken out from the molten salt, placed in an alumina crucible, the crucible is placed in a muffle furnace, and heated at 300°C for 5 seconds; 5) taking out the crystalline silicon solar cell treated in step 4) from the furnace, and immersing it in 10° C. cold water to cool it down to room temperature for 20 minutes; 6) placing the copper-lead-tin solder obtained in step 1) into a muffle furnace and oxidizing it in air at 600° C. for 10 min; 7) The copper-lead-tin solder oxidized in step 6) is immersed in a 50wt% sodium hydroxide solution at 90°C for 40 minutes; 8) Continue to recover the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) by electrochemical deposition. The lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) are placed in a 50 wt% sodium hydroxide solution for 10 min at 90° C. and with a cathode current of 1.2 V for lead and a cathode current of 1.4 V for tin.

[0034] Example 5 A green method for recycling and processing retired crystalline silicon solar panels, comprising the following steps: 1) Put 18kg of retired crystalline silicon solar panels into the RX3 series-18KW box-type tempering resistance furnace and heat them at 550℃ for 2.5h in a nitrogen atmosphere; obtain tempered glass, aluminum frame, copper-lead-tin solder and 6kg of crystalline silicon solar cells; 2) Place 1000 g of a mixed molten salt of sodium hydroxide and potassium hydroxide (40 wt% sodium hydroxide, 50 wt% potassium hydroxide) into an alumina crucible and heat to 210 °C in a muffle furnace; 3) The crystalline silicon solar cell obtained after the heat treatment in step 1) is placed in the mixed molten salt heated in step 2) and immersed for 2 seconds to make the crystalline silicon solar cell completely wetted; 4) After the alkali leaching treatment in step 3) above, the crystalline silicon solar cell is immediately taken out from the molten salt, placed in an alumina crucible, the crucible is placed in a muffle furnace, and heated at 220°C for 100 seconds; 5) taking the crystalline silicon solar cell treated in step 4) out of the furnace and immersing it in 6°C cold water to cool it down to room temperature for 25 minutes; 6) placing the copper-lead-tin solder obtained in step 1) into a muffle furnace and oxidizing it in air at 400° C. for 40 minutes; 7) The copper-lead-tin solder oxidized in step 6) is immersed in a 45wt% sodium hydroxide solution at 90°C for 25 minutes; 8) Continue to recover the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) by electrochemical deposition. At 90° C., with the cathode current of lead being 1.3 V and the cathode current of tin being 1.6 V, the lead oxide and tin dioxide dissolved in the sodium hydroxide solution in step 7) are placed in a 45 wt % sodium hydroxide solution for 7 min.

[0035] The green method for recycling and treating retired crystalline silicon solar panels disclosed in the present invention has at least the following advantages: (1) The method of the present invention increases the added value of the product: tempered glass, aluminum frame, copper-lead-tin solder and crystalline silicon solar cell can be obtained in one step after high-temperature pyrolysis, which can be directly classified and recycled, thereby increasing the added value of the recycled materials.

[0036] (2) Recycling of metals such as silicon and silver using green methods: Both salt etching and the recycling of copper, lead, and tin solder use only alkaline solutions to drive separation, which has less impact on the environment and eliminates toxic chemicals and secondary pollution.

[0037] (3) The difficulty of recycling is reduced: tempered glass and aluminum frames that can be directly recycled are obtained through a single pyrolysis process, and then the copper-lead-tin solder and crystalline silicon solar cells are processed step by step. The recycling process is simple and the operation is convenient and feasible.

[0038] (4) Harmless treatment of tail gas: The tail gas generated during the high-temperature heat treatment process is incinerated to prevent secondary pollution and protect the environment.

[0039] (5) The method of the present invention uses a combination of heat treatment technology and salt etching to achieve the recycling of retired crystalline silicon solar panel frames, glass and silicon wafers, as well as the recycling of valuable metals and silicon wafers.

[0040] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A green method for recycling retired crystalline silicon solar panels, characterized in that: The following steps are involved: 1) After high-temperature pyrolysis of retired crystalline silicon solar panels, tempered glass, aluminum frames, copper-lead-tin solder and crystalline silicon solar cells are obtained; 2) placing the crystalline silicon solar cell obtained in step 1) into a heated mixed molten salt of sodium hydroxide and potassium hydroxide for alkaline leaching, then heating and cooling, and obtaining silver and silicon solar cells after sufficient salt corrosion; 3) heating and oxidizing the copper-lead-tin solder obtained in step 1) to dissolve it, thereby obtaining a copper strip and a lead-tin coating; 4) The lead-tin coating obtained in step 3) is immersed in a NaOH solution and subjected to an electrodeposition treatment to obtain copper, lead, tin and tin dioxide.

2. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 2), the mass ratio of the crystalline silicon solar cell sheet to the mixed molten salt of sodium hydroxide and potassium hydroxide is (6-10):

1.

3. The green method for recycling retired crystalline silicon solar panels according to claim 2, characterized in that: In step 1), the high temperature pyrolysis conditions are: heating at 500-600° C. for 2-4 hours under nitrogen or argon.

4. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 2), in the mixed molten salt of sodium hydroxide and potassium hydroxide, the concentration of sodium hydroxide is 16-42wt%, and the concentration of potassium hydroxide is 22-58wt%.

5. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 2), the heating temperature of the mixed molten salt of sodium hydroxide and potassium hydroxide is 180-220°C.

6. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 2), the alkali leaching treatment time is 1-3s.

7. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 2), the heating treatment conditions are: continuous heating at 180-300° C. for 5-300 seconds.

8. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 2), the cooling condition is: cooling in 2-10° C. cold water for 20-40 minutes to room temperature.

9. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 3), the conditions for the heating oxidation dissolution are: oxidation at 300-600° C. for 10-60 min.

10. The green method for recycling retired crystalline silicon solar panels according to claim 1, characterized in that: In step 4), the conditions of the electrodeposition treatment are: temperature of 90° C., immersion in 40-50wt% sodium hydroxide solution for 5-10 min; cathode current of lead is 1.2-1.4V, and cathode current of tin is 1.4-1.8V.

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