Method for efficiently extracting and recycling valuable components from waste solar cell fragments

Abstract

The invention belongs to the technical field of photovoltaic module recycling, and discloses a method for efficiently extracting and recovering valuable components from waste solar cell fragments, which comprises the following steps: firstly, carrying out aluminum removal leaching by using chlorate, then carrying out silver extraction leaching by using a choline chloride / ethylene glycol / water / mixture as a silver leaching solvent, and finally, carrying out high-efficiency recycling on the valuable components. Diluting the silver leaching solution to obtain silver chloride with relatively high purity; and finally, carrying out silicon nitride removal leaching through a hydrogen fluoride solution to obtain a high-purity silicon-containing material. By the adoption of the method, the aluminum removal rate reaches up to 97% or above, the non-silver nitrate leaching solvent is adopted, the purity of obtained silver chloride is larger than 97%, the silicon material with the purity larger than 99% is finally obtained, and efficient, economical and environment-friendly comprehensive extraction and recovery of the waste solar cell fragments are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic module recycling, and particularly relates to a method for efficiently extracting and recycling valuable components from waste solar cell fragments. Background Art

[0002] In recent years, global photovoltaic modules are about to enter the large-scale retirement stage. If such a huge amount of solid waste resources are not recycled and treated in time, it will lead to serious problems such as resource waste and environmental pollution. Therefore, the recycling of retired photovoltaic modules has gradually attracted attention.

[0003] Currently, for the comprehensive recycling and development of photovoltaic modules, people have also carried out a lot of research work. Among them, mainly more disassembly, fragmentation and sorting research have been done on the disassembly of the frames and junction boxes of waste photovoltaic modules, the removal of EVA glue, the recycling of glass, and the removal of backsheets. After the waste photovoltaic modules are disassembled, fragmented and sorted, solar photovoltaic cell fragments with higher purity can be obtained. The main valuable components in solar cells are metallurgical silicon and metallic silver, and there is also a certain amount of metallic aluminum. Among them, silver has a high economic recycling value, accounting for more than 40% of the total recycling value of the entire photovoltaic module. Therefore, how to remove metallic aluminum from silicon wafers, efficiently recycle metallic silver, and obtain metallurgical silicon with higher purity is of great significance.

[0004] Chinese Patent Document CN115786713A discloses a method for recycling silver and aluminum in solar panels. Through a heat treatment system, an acid leaching system, a silver chloride precipitation system, and a crude silver powder recovery system, a mixed solution of methanesulfonic acid and hydrogen peroxide is used to leach silver and aluminum from waste solar panels. Chinese Patent Document CN118531221A discloses a method for recycling silver from photovoltaic panels. Using choline chloride as a leaching agent, a sufficient corrosion reaction is carried out on the silver and aluminum on the surface of waste photovoltaic panels. After the silver and aluminum on the surface of the photovoltaic panels are leached, filtration is carried out. The leaching residue is subjected to secondary leaching, the leaching solution is concentrated, the obtained concentrated solution is purified, ammonia water is added to quickly remove the base metal aluminum therein, and then filtration is carried out on it. Hydrochloric acid is added to the filtrate to obtain a precipitate of silver chloride at a relatively fast rate, and finally industrial-grade hydrazine hydrate is used as a reducing agent to obtain a sponge silver product.

[0005] Chinese Patent Document CN110404944A discloses a device for separating, purifying and recycling battery materials in crystalline silicon photovoltaic modules, mainly using sodium hydroxide to remove aluminum, nitric acid to leach silver, and hydrofluoric acid to remove silicon nitride.

[0006] Chinese Patent Document CN208912062U proposes a recycling device for waste photovoltaic cells, which is used to leach silver from waste photovoltaic cell powder by nitric acid. By adding waste photovoltaic cell powder and pure water into a reaction kettle, stirring evenly through a stirring component, and then adding nitric acid through an acid inlet pipe, the hydrogen generated during the reaction is discharged through a hydrogen separator to avoid explosion caused by excessive hydrogen content. The oxygen supplement component is used to convert the waste gas generated during the nitric acid leaching reaction into nitric acid, reducing acid consumption. Pressurized leaching is adopted to improve the metal leaching effect. This device can only recycle silver in the battery cells, and its structure is complex. The silver recovery rate needs to be verified. Chinese Patent Document CN107746960A respectively proposes methods for recycling aluminum in battery cells by using hydrochloric acid and sodium hydroxide solution, and separating and recycling silver in battery cells by using nitric acid and sodium sulfide. This patent only provides recycling methods and does not introduce corresponding separation and recycling devices. Most of the above patent documents use traditional leaching methods such as acids and alkalis for aluminum removal and silver extraction. The traditional methods have high acid and alkali concentrations, large consumption, and difficult wastewater treatment. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the above background technology, and provide a more efficient, economical and environmentally friendly method for comprehensive recycling and utilization of valuable metals from solar cells.

[0008] To solve the above technical problem, the technical solution proposed by the present invention is: A method for efficiently extracting and recycling valuable components from waste solar cell fragments, comprising the following steps: (1) Adding waste solar cell fragments into a chloride salt solution for aluminum removal leaching, and filtering to obtain filter residue 1 containing silver and silicon; Aluminum will form a dense Al2O3 oxide film (with a thickness of about 2 - 10 nm) in the air. Cl - has strong corrosiveness and can destroy the film through the following reaction: Al2O3 + 6Cl - + H2O → 2Al(OH)3 + 6Cl - → 2AlCl3 + 3H2O; Cl - adsorbs on the surface of Al2O3 and forms a stable [AlCl4] 3+ complex ion with Al - to weaken the binding force between the oxide film and the substrate, accelerate the film layer shedding, and the effect is more obvious under the action of heating and ultrasonic assistance. AlCl3 will hydrolyze in water: AlCl3 + 3H2O → Al(OH)3 + 3HCl; The generated HCl further promotes the dissolution of alumina, forming an autocatalytic cycle; (2) Dissolve choline chloride or calcium chloride in a solvent, heat and stir. After obtaining a transparent liquid, add an oxidant, heat and stir to dissolve to form a homogeneous liquid (deep eutectic solvent (DES)), and prepare a silver leaching solvent; (3) Add the filter residue 1 obtained in step (1) to the silver leaching solvent for silver leaching. After liquid-solid separation, a silver-containing filtrate 2 and a silicon material filter residue 2 removing aluminum and silver are obtained; Reaction principle: The oxidant oxidizes metallic silver (Ag 0 ) to silver ions (Ag + ), such as ferric chloride: Ag + FeCl → AgCl + FeCl2; The generated AgCl is insoluble in water and will cover the silver surface to hinder the reaction (which needs to be solved through complexation). As a component of the deep eutectic solvent (DES), choline chloride promotes the reaction in the following ways: a. Provide a high concentration of Cl - , choline chloride decomposes to release Cl - , which combines with AgCl to form soluble complexes (such as \[AgCl2\] - , \[AgCl3\] 2- etc.): AgCl + Cl- → [AgCl2] - , this process breaks the passivation layer of AgCl and continuously dissolves silver; b. The highly polar and low-volatile solvent formed by the choline chloride - FeCl3 system enhances ion migration and reaction activity. Compared with traditional acid leaching (nitric acid or cyanide), DES is more environmentally friendly and has low corrosivity; (4) Dilute the filtrate 2 obtained in step (3) with water, stir and then filter. The obtained filter residue 3 is silver chloride precipitate; In the undiluted DES system, DES forms a highly polar environment through hydrogen bonding, which can stabilize the complexation form of Ag + . The low viscosity of DES allows Ag + and Cl - to migrate freely, maintaining the dynamic equilibrium of AgCl2 - . After adding a large amount of water, the hydrogen bond structure of DES is destroyed, the polarity of the system is reduced, resulting in a decrease in the solubility of AgCl - . After dilution, the activity coefficient of the solution increases, the interaction between ions weakens, and the activity coefficients of Ag + and Cl - increase, and the actual concentration exceeds the solubility product (Ksp(AgCl) = 1.8×10 -10 , triggering the precipitation of AgCl.

[0009] (5) Add the silicon material filter residue 2 obtained in step (3) to a hydrofluoric acid solution for silicon nitride removal leaching. The filter residue 4 obtained after filtration is a silicon-containing material.

[0010] In the above method, preferably, in step (1), the waste solar cell fragments are solar cell silicon wafer scraps separated by disassembling, crushing, and sorting photovoltaic panels. By mass percentage, they contain 1.01% silver, 91.92% silicon, and 6.41% aluminum. The chloride salt includes at least one of ferric chloride, copper chloride, aluminum chloride, and calcium chloride. Further preferably, the chloride salt is aluminum chloride.

[0011] Preferably, in step (1), the aluminum removal leaching is carried out by means of heating mechanical stirring or ultrasonic treatment. The temperature of the aluminum removal leaching is 30 - 80°C, and the time is 3 - 30 min. Further preferably, the temperature of the aluminum removal leaching is 40 - 60°C, and the time is 5 - 15 min.

[0012] Preferably, in step (2), the solvent is water or ethylene glycol. The molar ratio of calcium chloride (CaCl2·6H2O) to ethylene glycol is 1:1 - 2, the molar ratio of choline chloride to ethylene glycol is 1:2 - 3, and the molar ratio of choline chloride to water is 1:2 - 4. Further preferably, the molar ratio of calcium chloride (CaCl2·6H2O) to ethylene glycol is 1:1, the molar ratio of choline chloride to ethylene glycol is 1:2, and the molar ratio of choline chloride to water is 1:4. The temperature of the heating and stirring is 40 - 60°C.

[0013] Preferably, in step (2), the oxidant is at least one of ferric chloride, copper chloride, ferric nitrate, and copper nitrate. The dosage of the oxidant is 0.2 - 1 mol / L. Further preferably, the dosage of the oxidant is 0.4 - 0.8 mol / L.

[0014] Preferably, in step (3), the silver extraction leaching is carried out by means of heating mechanical stirring or ultrasonic treatment. The temperature of the silver extraction leaching is 30 - 80°C, and the time is 2 - 30 min.

[0015] Preferably, in step (4), the dilution multiple of adding water is 7 - 15 times. Further preferably, the dilution multiple of adding water is 9 - 12 times.

[0016] Preferably, in step (5), the concentration of the hydrofluoric acid solution is 1 - 10%. Further preferably, the concentration of the hydrofluoric acid solution is 2 - 6%.

[0017] Preferably, in step (5), the silicon nitride removal leaching is carried out by means of heating and mechanical stirring or ultrasonic treatment. The temperature of the silicon nitride removal leaching is 50-80 °C, and the time is 20-90 min.

[0018] Preferably, the filtrate 1 obtained after filtration in step (1) is an aluminum chloride leaching solution; the filtrate 3 obtained after filtration in step (4) is returned to step (3) for recycling as a silver leaching solvent, and the filtrate 4 obtained after filtration in step (5) is returned to step (5) for recycling in silicon nitride removal leaching.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the method of the present invention, the aluminum removal rate is as high as over 97%. Using a non-silver nitrate leaching solvent, the purity of the obtained silver chloride is greater than 97%, the silver recovery rate is greater than 97%, and silicon materials with a purity greater than 99% and a recovery rate greater than 92% are obtained, realizing the efficient, economic, and environmentally friendly comprehensive extraction and recovery of waste solar cell fragments.

[0020] (2) The present invention preferentially removes aluminum using a chloride solution, avoiding the use of high-concentration alkali / acid for aluminum leaching, effectively reducing the environmental impact of acid / alkali, and also avoiding the leaching of irrelevant metals during acid leaching of aluminum, reducing subsequent separation steps.

[0021] (3) Using a mixed non-nitric acid leaching system of choline chloride / ethylene glycol / calcium chloride / water, silver enters the solution in the form of a complex, and silver chloride precipitates by adding water for dilution, developing a new method for silver leaching and extraction, avoiding the adverse effects brought by using nitric acid to leach silver.

[0022] (4) In the process of removing the blue silicon nitride antireflection film of waste solar cell fragments, the method of heating with a low-concentration hydrofluoric acid solution is adopted, avoiding the disadvantage of easy volatilization of a high-concentration hydrofluoric acid solution and improving safety.

[0023] (5) Ultrasonic-assisted leaching is adopted in the process, greatly improving the leaching rates of aluminum, silver, and hydrofluoric acid. The leaching time of aluminum can be less than 10 min, the silver leaching time is less than 30 min, and the silicon nitride removal rate can also be lower than 30 min. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 is the process flow chart of the present invention. Detailed implementation manners

[0026] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and meticulously in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all the professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0028] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0029] The waste solar cell fragments used in the following examples are the silicon wafer scraps of solar cells separated by disassembling, crushing and sorting photovoltaic panels. By mass percentage, they contain 1.01% silver, 91.92% silicon, and 6.41% aluminum.

[0030] Example 1: A method for efficiently extracting and recovering valuable components from waste solar cell fragments, as Figure 1 shown, includes the following steps: (1) Add the silicon wafer scraps of solar cells into a prepared reaction device of 0.5 mol / L aluminum chloride solution for stirring leaching. The reaction temperature is 50 °C and the reaction time is 10 min. When the reaction ends, filter to obtain filtrate 1 (aluminum chloride leaching solution) and residue 1 (silver- and silicon-containing material); (2) Add the prepared silver leaching solvent (by molar ratio choline chloride: water = 1:4, ferric chloride 0.5 mol / L) to residue 1. The reaction temperature is 60 °C. After fully stirring for 15 min, perform liquid-solid separation to obtain filtrate 2 (silver-containing solution) and residue 2 (aluminum- and silver- and silicon-free material); (3) Dilute filtrate 2 with 10 times the volume of distilled water and stir for 40 min, then filter and dry to obtain residue 3 (silver chloride powder); the recovery rate of this diluted silver is 99.3%; (4) Add residue 2 to the prepared 4% hydrofluoric acid solution. The reaction temperature is 60 °C. After stirring for 1 h, filter to remove silicon nitride and obtain high-purity silicon material.

[0031] After testing, the final aluminum leaching rate is 98.3%, the silver leaching rate is 97.5%, the purity of silver chloride is 99.4%, the silicon content of the silicon material is 99.3%, and the silicon recovery rate is 92.5%.

[0032] Example 2: A method for efficiently extracting and recovering valuable components from waste solar cell fragments, asFigure 1 As shown in the figure, it includes the following steps: (1) Add the scrap of solar cell silicon wafers into the prepared reaction device of 0.5 mol / L aluminum chloride solution and carry out ultrasonic leaching. The reaction temperature is 50 °C and the reaction time is 5 min. When the reaction ends, filter to obtain filtrate 1 (aluminum chloride leaching solution) and residue 1 (silver- and silicon-containing material); (2) Add the prepared silver leaching solvent (choline chloride: ethylene glycol = 1:2 in molar ratio, 0.5 mol / L iron nitrate) to residue 1, carry out ultrasonic reaction, with the reaction temperature of 50 °C. After reacting for 10 min, carry out liquid-solid separation to obtain filtrate 2 (silver-containing solution) and residue 2 (aluminum- and silver- and silicon-free material); (3) Dilute filtrate 2 with 10 times its volume of distilled water and stir for 40 min, then filter and dry to obtain residue 3 (silver chloride powder); the silver recovery rate of this dilution is 99.2%; (4) Add residue 2 into the prepared 5% hydrofluoric acid solution, with the reaction temperature of 60 °C. Stir for 1 h and then filter to remove silicon nitride and obtain high-purity silicon material.

[0033] After testing, the final aluminum leaching rate is 97.6%, the silver leaching rate is 98.2%, the purity of silver chloride is 99.6%, the silicon content in the silicon material is 99.5%, and the silicon recovery rate is 93.2%.

[0034] Example 3: A method for efficiently extracting and recovering valuable components from waste solar cell fragments, as Figure 1 shown in the figure, includes the following steps: (1) Add the scrap of solar cell silicon wafers into the prepared reaction device of 0.6 mol / L ferric chloride solution and carry out stirring leaching. The reaction temperature is 50 °C and the reaction time is 20 min. When the reaction ends, filter to obtain filtrate 1 (aluminum chloride leaching solution) and residue 1 (silver- and silicon-containing material); (2) Add the prepared silver leaching solvent (calcium chloride CaCl₂·6H₂O: ethylene glycol = 1:1 in molar ratio, 0.6 mol / L copper nitrate) to residue 1, carry out ultrasonic reaction, with the reaction temperature of 50 °C. After reacting for 10 min, carry out liquid-solid separation to obtain filtrate 2 (silver-containing solution) and residue 2 (aluminum- and silver- and silicon-free material); (3) Dilute filtrate 2 with 10 times its volume of distilled water and stir for 40 min, then filter and dry to obtain residue 3 (silver chloride powder); the silver recovery rate of this dilution is 99.6%; (4) Add residue 2 into the prepared 4% hydrofluoric acid solution, with the reaction temperature of 60 °C. Stir ultrasonically for 25 min and then filter to remove silicon nitride and obtain high-purity silicon material.

[0035] After testing, the final aluminum leaching rate is 98.6%, the silver leaching rate is 98.3%, the purity of silver chloride is 99.3%, the silicon content of high-purity silicon material is 99.4%, and the silicon recovery rate is 92.8%.

[0036] Example 4: A method for efficiently extracting and recycling valuable components from waste solar cell fragments, as Figure 1 shown, includes the following steps: (1) Add the crushed silicon wafers of solar cells into a prepared reaction device of 0.5 mol / L aluminum chloride solution for ultrasonic leaching. The reaction temperature is 50°C and the reaction time is 10 min. When the reaction ends, filter to obtain filtrate 1 (aluminum chloride leaching solution) and filter residue 1 (silver- and silicon-containing material); (2) Add the prepared silver leaching solvent (choline chloride: water = 1:4 in molar ratio, 0.5 mol / L copper chloride) to filter residue 1, and carry out ultrasonic reaction. After the reaction temperature is 50°C and the reaction is carried out for 10 min, perform liquid-solid separation to obtain filtrate 2 (silver-containing solution) and filter residue 2 (aluminum- and silver-free silicon material); (3) Stir and dilute filtrate 2 with 10 times its volume of distilled water, stir for 40 min, filter and dry to obtain filter residue 3 (silver chloride powder); the silver recovery rate of this dilution is 99.5%; (4) Add filter residue 2 to the prepared 4% hydrofluoric acid solution, react at a temperature of 60°C, stir for 40 min and then filter to obtain high-purity silicon material.

[0037] After testing, the final aluminum leaching rate is 98%, the silver leaching rate is 98.5%, the purity of silver chloride is 99.6%, the silicon content of high-purity silicon material is 99.1%, and the silicon recovery rate is 93.2%.

Claims

1. A method for efficiently extracting and recycling valuable components from waste solar cell fragments, characterized in that, It includes the following steps: (1) Add waste solar cell fragments into a chloride salt solution for aluminum removal leaching, and after filtration, obtain filter residue 1 containing silver and silicon; (2) Dissolve choline chloride or calcium chloride in a solvent, heat and stir, and after obtaining a transparent liquid, add an oxidant, heat and stir to dissolve to form a homogeneous liquid, and prepare a silver leaching solvent; (3) Add the filter residue 1 obtained in step (1) into the silver leaching solvent for silver extraction leaching, and after liquid-solid separation, obtain filtrate 2 containing silver and silicon material filter residue 2 free of aluminum silver; (4) Dilute the filtrate 2 obtained in step (3) with water, stir and then filter, and the obtained filter residue 3 is silver chloride precipitate; (5) Add the silicon material filter residue 2 obtained in step (3) into a hydrofluoric acid solution for silicon nitride removal leaching, and after filtration, the obtained filter residue 4 is silicon-containing material.

2. The method according to claim 1, characterized in that, In step (1), the waste solar cell fragments are solar cell silicon wafer scraps separated by disassembling, crushing and sorting photovoltaic panels. By mass percentage, it contains 0.2 - 1.1% silver, 78 - 94.0% silicon, and 3.0 - 7.0% aluminum; the chloride salt includes at least one of ferric chloride, copper chloride, aluminum chloride and calcium chloride.

3. The method according to claim 1, wherein In step (1), the aluminum removal leaching is carried out by means of heating mechanical stirring or ultrasonic treatment, the temperature of the aluminum removal leaching is 30 - 80 °C, and the time is 3 - 30 min.

4. The method according to claim 1, wherein In step (2), the solvent is water or ethylene glycol, the molar ratio of calcium chloride to ethylene glycol is 1:1 - 2, the molar ratio of choline chloride to ethylene glycol is 1:2 - 3, and the molar ratio of choline chloride to water is 1:2 - 4; the temperature of the heating and stirring is 40 - 60 °C.

5. The method according to claim 1, wherein In step (2), the oxidant is at least one of ferric chloride, copper chloride, ferric nitrate, copper nitrate, and the dosage of the oxidant is 0.2 - 1 mol / L.

6. The method according to claim 1, wherein In step (3), the silver extraction leaching is carried out by means of heating mechanical stirring or ultrasonic treatment, the temperature of the silver extraction leaching is 30 - 80 °C, and the time is 2 - 30 min.

7. The method according to claim 1, characterized in that, In step (4), the dilution multiple of adding water is 7 - 15 times.

8. The method according to claim 1, wherein In step (5), the mass concentration of the hydrofluoric acid solution is 1 - 10%.

9. The method according to claim 1, characterized in that, In step (5), the silicon nitride removal leaching is carried out by means of heating mechanical stirring or ultrasonic treatment, the temperature of the silicon nitride removal leaching is 50 - 80 °C, and the time is 20 - 90 min.

10. The method according to any one of claims 1-9, characterized in that, The filtrate 1 obtained after filtration in step (1) is aluminum chloride leaching solution; the filtrate 3 obtained after filtration in step (4) is returned to step (3) for recycling as silver leaching solvent, and the filtrate 4 obtained after filtration in step (5) is returned to step (5) for recycling silicon nitride removal leaching.

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