A method for recovering silver in photovoltaics with thiosulfate
Patent Information
- Application Number
- CN202611271949.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-20
- Publication Date
- 2026-09-25
AI Technical Summary
以上浸出剂对银的选择性较差，对设备防腐性能要求严苛，且易造成生态环境压力
本发明以配位化合物（配位化合物+添加剂）为催化氧化剂，利用硫代硫酸盐自身可控分解的特性，实现了退役晶硅光伏电池中银组分的高效选择性浸出。
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Abstract
Description
Technical Field
[0001] This invention relates to the field of recycling waste photovoltaic resources, specifically to a method for recovering silver from photovoltaic materials using thiosulfate. Background Technology
[0002] Crystalline silicon solar cells, as the core component of photovoltaic modules, are mainly composed of silver wires and high-purity silicon, and have significant recycling value.
[0003] Current silver extraction technologies for photovoltaic modules mostly employ acid-base leaching processes: the leaching agent is primarily nitric acid, but composite systems composed of citric acid, ammonia, and hydrogen peroxide are also used, with the alkali being either molten or a high-concentration NaOH / KOH. These leaching agents exhibit poor selectivity for silver, impose stringent requirements on equipment corrosion resistance, and easily create environmental pressure.
[0004] Furthermore, traditional silver extraction processes generally follow a "leaching-precipitation-precipitation dissolution-reduction" route, which is lengthy and complex. Other research utilizes molten alkali to selectively etch silicon dioxide, silicon, and silicon nitride at the silver-silicon interface, allowing for the direct recovery of intact silver wires. However, this technology is only applicable to unbroken whole solar cells and cannot be matched with the mainstream processes for dismantling and breaking existing photovoltaic modules, thus limiting its application. Summary of the Invention
[0005] This invention provides a method for recovering silver from photovoltaic cells using thiosulfate. The silver leaching agent of this invention achieves efficient and selective leaching of silver components from decommissioned crystalline silicon photovoltaic cells.
[0006] This invention provides a method for recovering silver, comprising the following steps: Retired photovoltaic cells are immersed in a silver leaching agent to obtain a leachate; The silver leaching agent comprises thiosulfate, coordination compound and water.
[0007] Preferably, the thiosulfate includes one or more of Na2S2O3, K2S2O3 and (NH4)2S2O3; The concentration of the thiosulfate is 0.08 ~ 0.15 mol / L.
[0008] Preferably, the molar ratio of the thiosulfate to the coordination compound is (2~10):1; the coordination compound includes one or more of copper-based coordination compounds, iron-based coordination compounds, cobalt-based coordination compounds, and nickel-based coordination compounds.
[0009] Preferably, the molar ratio of metal to ligand in the coordination compound is 1:(1~6).
[0010] Preferably, the ligands in the copper-based coordination compound include one or more of ammonia, polyamine organic ligands, and carboxylic acid organic ligands; The ligands in the iron-based coordination compound include one or more of oxalic acid, ethylenediaminetetraacetic acid, tartaric acid, and cyanide ions; The ligands in the cobalt-based coordination compound include ammonia; The ligands in the nickel-based coordination compound include ammonia.
[0011] Preferably, the silver leaching agent further includes additives, which include one or more of thiourea, ethylenediaminetetraacetic acid, amino acids, triethanolamine, carboxymethyl cellulose, and sodium humate; the concentration of the additives is 0~20 mmol / L.
[0012] Preferably, the pH value of the silver leaching agent is 7-10.
[0013] Preferred options also include: The leachate was allowed to stand to produce a precipitate, and then the resulting system was filtered to obtain a filter cake. The filter cake was dried and roasted in sequence to obtain elemental silver.
[0014] Preferably, the leaching temperature is 25~30℃, the leaching time is 10~150 min, the leaching is carried out under stirring conditions, and the stirring speed is 250~300 rpm; The liquid-solid ratio of the retired photovoltaic cell to the silver leaching agent is (2~5):1.
[0015] Preferably, the roasting temperature is 700~800℃ and the time is 1~2h.
[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention uses coordination compounds (coordination compounds + additives) as catalytic oxidants and takes advantage of the controllable decomposition characteristics of thiosulfate to achieve efficient and selective leaching of silver components in decommissioned crystalline silicon photovoltaic cells.
[0017] The method for recovering silver in this invention can achieve efficient and selective leaching and precipitation recovery of silver in one step. The leaching agent is green and environmentally friendly, the process is short, and it is applicable to crystalline silicon battery fragments or powders, with strong industrial adaptability. Attached Figure Description
[0018] Figure 1 This is a schematic diagram illustrating the process of recycling silver from retired photovoltaic cells as an example. Detailed Implementation
[0019] This invention provides a method for recovering silver, comprising the following steps: Retired photovoltaic cells are immersed in a silver leaching agent to obtain a leachate; The silver leaching agent comprises thiosulfate, coordination compound and water.
[0020] The silver leaching agent provided by the present invention includes thiosulfate; the concentration of the thiosulfate is preferably 0.08~0.15 mol / L, and in specific embodiments of the present invention it can be 0.09 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L or 1.4 mol / L; the thiosulfate preferably includes one or more of Na2S2O3, K2S2O3 and (NH4)2S2O3.
[0021] The silver leaching agent provided by this invention comprises a coordination compound; the molar ratio of the thiosulfate to the coordination compound is preferably (2~10):1, and in specific embodiments of this invention, it can be 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1; the coordination compound preferably comprises one or more of copper-based coordination compounds, iron-based coordination compounds, cobalt-based coordination compounds, and nickel-based coordination compounds; the ligand in the copper-based coordination compound preferably comprises one or more of ammonia, polyamine organic ligands, and carboxylic acid organic ligands; when the ligand is ammonia, the copper-based coordination compound is preferably tetraamminecopper sulfate; the polyamine organic ligand preferably comprises ethyl... One or more of diamine, diethylenetriamine, and triethylenetetramine; the carboxylic acid organic ligand preferably includes one or more of oxalic acid, citric acid, malic acid, and tartaric acid; the ligand in the iron-based coordination compound includes one or more of oxalic acid, ethylenediaminetetraacetic acid, tartaric acid, and cyanide ions; when the ligand in the iron-based coordination compound is a cyanide ion, the iron-based coordination compound is preferably potassium ferricyanide; the ligand in the nickel-based coordination compound preferably includes ammonia; the nickel-based coordination compound preferably includes hexaamminenickel sulfate; the ligand in the cobalt-based coordination compound preferably includes ammonia; the cobalt-based coordination compound preferably includes hexaamminecobalt sulfate and / or hexaamminecobalt trichloride.
[0022] In this invention, the molar ratio of metal to ligand in the coordination compound is preferably 1:(1~6), and in specific embodiments of this invention it can be 1:2, 1:3, 1:4 or 1:5.
[0023] The silver leaching agent provided by this invention preferably further includes additives, the concentration of which is preferably 0-20 mmol / L. In specific embodiments of this invention, the concentration can be 1 mmol / L, 2 mmol / L, 3 mmol / L, 4 mmol / L, 5 mmol / L, 6 mmol / L, 7 mmol / L, 8 mmol / L, 9 mmol / L, 10 mmol / L, 11 mmol / L, 12 mmol / L, 13 mmol / L, 14 mmol / L, 15 mmol / L, 16 mmol / L, 17 mmol / L, 18 mmol / L, or 19 mmol / L. The additives preferably include one or more of thiourea, ethylenediaminetetraacetic acid, amino acids, triethanolamine, carboxymethyl cellulose, and sodium humate. Thiourea and amino acids can improve the leaching efficiency of silver by synergistic leaching with thiosulfate, while other additives can coordinate with the metal to regulate the leaching system potential, thereby achieving controlled decomposition of thiosulfate.
[0024] The preferred pH value of the silver leaching agent provided by the present invention is 7 to 10, and in specific embodiments of the present invention it can be 8 or 9.
[0025] The leachate was allowed to stand to produce a precipitate, and then the resulting system was filtered to obtain a filter cake. The filter cake was dried and roasted in sequence to obtain elemental silver.
[0026] In this invention, the liquid-solid ratio of the retired photovoltaic cell to the silver leaching agent is preferably (2~5):1, and in specific embodiments of this invention it can be 3:1 or 4:1; the retired crystalline silicon cell preferably includes retired crystalline silicon cell fragments or retired crystalline silicon cell powder.
[0027] After obtaining the leachate, the present invention preferably allows the leachate to stand to produce a precipitate, and then filters the resulting system to obtain a filter cake.
[0028] In this invention, the leaching temperature is 25~30℃ and the leaching time is 10~150 min. In specific embodiments of this invention, the leaching time can be 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min, 110 min, 120 min, 130 min or 20 min. The leaching is preferably carried out under stirring conditions, and the stirring speed is preferably 250~300 rpm.
[0029] After obtaining the filter cake, the present invention preferably dries and calcines the filter cake in sequence to obtain elemental silver.
[0030] In this invention, the roasting temperature is preferably 700~800℃ and the roasting time is preferably 1~2h. In specific embodiments of this invention, the roasting temperature can be 720℃, 750℃ or 780℃ and the roasting time can be 1.2h, 1.5h or 1.8h.
[0031] The following detailed description of the method for recovering silver from photovoltaic cells using thiosulfate provided by the present invention, with reference to specific embodiments, should not be construed as limiting the scope of protection of the present invention.
[0032] Figure 1 This is a schematic diagram illustrating the process of recycling silver from retired photovoltaic cells as an example.
[0033] Unless otherwise specified, the thiosulfate used in the following examples and Comparative Example 3 is sodium thiosulfate, with a concentration of 0.1 mol / L. The molar ratio of thiosulfate to catalytic oxidant is 5:1, the molar ratio of metal to ligand in the catalytic oxidant is 1:6, and the pH of the silver leaching agent aqueous solution is 8. The leaching conditions are 25°C, 300 rpm, 120 min, and a liquid-to-solid ratio of 2.5:1. After leaching, the solution is filtered, and the resulting silver leaching solution is allowed to stand for 4 h to precipitate. The resulting filter cake is then dried and calcined at 750°C for 1.5 h.
[0034] Table 1. Elemental composition (wt%) of decommissioned photovoltaic cells
[0035] Unit g / t. Comparative Example 1 (1) Prepare 100 mL of 15wt% nitric acid solution and add 10 g of decommissioned crystalline silicon battery fragments. The liquid-solid ratio is 10:1.
[0036] (2) Immerse for 120 min at 60℃ and 300 rpm.
[0037] (3) Determine the concentrations of Ag, Si, Al and Mg in the leachate, calculate the leaching rate, and examine the selectivity.
[0038] Table 2 lists the leaching rates of Ag, Si, Al, and Mg after leaching for 120 min.
[0039] Table 2. Leaching rates of Ag, Si, Al, and Mg after 120 min of leaching.
[0040] The results of multiple parallel experiments obtained using the above steps are as follows: when silver is leached from crystalline silicon solar cells using a 15wt% nitric acid solution, the leaching rate of silver is 94.32% after 120 minutes. At the same time, the leaching rates of Al and Mg are also above 90%, indicating poor selectivity for silver.
[0041] Comparative Example 2 (1) Prepare 100 mL of 20wt% sodium hydroxide solution and add 10 g of decommissioned crystalline silicon battery fragments. The liquid-solid ratio is 10:1.
[0042] (2) Immerse for 20 min at 60℃ and 300 rpm.
[0043] (3) Collect the detached silver wires by sieving and calculate the Ag recovery rate; determine the concentrations of Si, Al and Mg in the alkaline solution, calculate the leaching rate, and investigate the loss of other components by this method.
[0044] Table 3 lists the Ag recovery rate and the leaching rates of Si, Al, and Mg after leaching for 40 min.
[0045] Table 3. Recovery rate of Ag and leaching rates of Si, Al, and Mg after leaching for 40 min.
[0046] The results of multiple parallel experiments using the above steps are as follows: when using 20wt% sodium hydroxide solution to recover silver from crystalline silicon solar cells, the silver recovery rate reached 98.92% after 20 minutes. The leaching rates of Si and Mg were low, while the leaching rate of Al was high. In addition, due to the small size of the retired crystalline silicon solar cell fragments, the silver recovery process is complicated.
[0047] Comparative Example 3 (1) Prepare 100 mL aqueous solutions with 0.02 mol / L copper glycinate, nickel glycinate, cobalt glycinate or iron glycinate as catalytic oxidants, 0.03 mmol / L thiourea as additives, and 0.1 mol / L sodium thiosulfate as silver leaching agent. Adjust the pH of the aqueous solution to 10 and add 40 g of decommissioned crystalline silicon battery fragments.
[0048] (2) The silver leaching rate was calculated by leaching for 120 min at 25℃ and 300 rpm. The Ag concentration of the leachate in different systems was measured.
[0049] Table 4 lists the silver leaching rates under different catalytic oxidant systems after leaching for 120 min.
[0050] Table 4. Silver leaching rate under different catalytic oxidant systems after leaching for 120 min.
[0051] The results of multiple parallel experiments obtained using the above steps are as follows: when using copper glycinate, nickel glycinate, cobalt glycinate, and iron glycinate as catalytic oxidants for leaching for 120 min, the silver leaching rates were 61.29%, 43.37%, 25.12%, and 1.98%, respectively, all of which were relatively low.
[0052] Example 1 (1) Prepare 100 mL of aqueous solution with 0.02 mol / L potassium ferricyanide as catalytic oxidant, 0.03 mmol / L thiourea as additive, and 0.1 mol / L sodium thiosulfate as silver leaching agent. Adjust the pH of the aqueous solution to 8 and add 40 g of decommissioned crystalline silicon battery fragments.
[0053] (2) Using the above leaching conditions and operating procedures, the concentrations of Ag, Si, Al and Mg in the leachate were measured, the leaching rate was calculated, and the selectivity was examined.
[0054] (3) The obtained Ag2S powder was roasted under the above conditions, the obtained solid was collected, and the silver recovery rate was calculated.
[0055] Table 5 lists the leaching rates of Ag, Si, Al, and Mg after leaching for 120 min.
[0056] Table 5. Leaching rates of Ag, Si, Al, and Mg after 120 min of leaching.
[0057] The results of multiple parallel experiments obtained using the above steps are as follows: using the leaching system of Example 1 for 120 min, the silver leaching rate was 99.46%, with almost no other ions leached, indicating high selectivity for silver. The silver recovery rate after calcination was above 99.9%. Comparison of Tables 2 and 3 shows that compared with acid-base leaching, the thiosulfate leaching system has advantages such as high silver recovery rate, environmental friendliness, and simple process. Moreover, the coordination compound used in this example is a preferred coordination compound.
[0058] Example 2 (1) A 100 mL aqueous solution was prepared using a system of 0.02 mol / L copper sulfate and 0.12 mol / L ammonia water as the catalytic oxidant, 0.03 mmol / L sodium ethylenediaminetetraacetate as the additive, and 0.1 mol / L sodium thiosulfate as the silver leaching agent. The pH of the aqueous solution was adjusted to 8, and 40 g of decommissioned crystalline silicon battery powder was added.
[0059] (2) Using the above leaching conditions and operating procedures, the concentrations of Ag, Si, Al and Mg in the leachate were measured, the leaching rate was calculated, and the selectivity was examined.
[0060] (3) The obtained Ag2S powder was roasted under the above conditions, the obtained solid was collected, and the silver recovery rate was calculated.
[0061] Table 6 lists the leaching rates of Ag, Si, Al, and Mg after leaching for 120 min.
[0062] Table 6. Leaching rates of Ag, Si, Al, and Mg after 120 min of leaching.
[0063] The results of multiple parallel experiments obtained using the above steps are as follows: using the leaching system of Example 2 for 120 min, the silver leaching rate was 99.65%, with almost no other ions leached, indicating high selectivity for silver. The silver recovery rate after calcination was over 99.9%. Comparing Tables 2 and 3, it can be seen that compared with acid-base leaching, the thiosulfate leaching system has advantages such as high silver recovery rate, environmental friendliness, and simple process. Moreover, the coordination compound used in this example is a preferred coordination compound.
[0064] Example 3 (1) Prepare 100 mL of aqueous solution with 0.02 mol / L hexaamminecobalt trichloride as catalytic oxidant and 0.1 mol / L sodium thiosulfate as leaching agent, adjust the pH of the aqueous solution to 8, and add 40 g of decommissioned crystalline silicon battery fragments.
[0065] (2) Using the above leaching conditions and operating procedures, the concentrations of Ag, Si, Al and Mg in the leachate were measured, the leaching rate was calculated, and the selectivity was examined.
[0066] (3) The obtained Ag2S powder was roasted under the above conditions, the obtained solid was collected, and the silver recovery rate was calculated.
[0067] Table 7 lists the leaching rates of Ag, Si, Al, and Mg after leaching for 120 min.
[0068] Table 7. Leaching rates of Ag, Si, Al, and Mg after 120 min of leaching.
[0069] The results of multiple parallel experiments obtained using the above steps are as follows: using the leaching system of Example 3 for 120 min, the silver leaching rate was 95.18%, with almost no other ions leached, indicating high selectivity for silver. The silver recovery rate after calcination was over 99%. Comparison of Tables 2 and 3 shows that compared with acid-base leaching, the thiosulfate leaching system has advantages such as high silver recovery rate, environmental friendliness, and simple process. Furthermore, the coordination compound used in this example is a preferred coordination compound.
[0070] Example 4 (1) Using a system of 0.02 mol / L nickel sulfate and 0.12 mol / L ammonia as the catalytic oxidant and 0.1 mol / L sodium thiosulfate as the leaching agent, prepare 100 mL of aqueous solution, adjust the pH of the aqueous solution to 8, and add 40 g of decommissioned crystalline silicon battery powder.
[0071] (2) Using the above leaching conditions and operating procedures, the concentrations of Ag, Si, Al and Mg in the leachate were measured, the leaching rate was calculated, and the selectivity was examined.
[0072] (3) The obtained Ag2S powder was roasted under the above conditions, the obtained solid was collected, and the silver recovery rate was calculated.
[0073] Table 8 lists the leaching rates of Ag, Si, Al, and Mg after leaching for 120 min.
[0074] Table 8. Leaching rates of Ag, Si, Al, and Mg after 120 min of leaching.
[0075] The results of multiple parallel experiments obtained using the above steps are as follows: using the leaching system of Example 4 for 120 min, the silver leaching rate was 97.07%, with almost no other ions leached, indicating high selectivity for silver. The silver recovery rate after calcination was over 99%. Comparison of Tables 2 and 3 shows that compared with acid-base leaching, the thiosulfate leaching system has advantages such as high silver recovery rate, environmental friendliness, and simple process. Furthermore, the coordination compound used in this example is a preferred coordination compound.
[0076] Furthermore, compared to Comparative Example 3, the catalytic oxidant used in Examples 1-4 was more effective. This indicates that the catalytic oxidant used in the examples was a preferred catalytic oxidant.
[0077] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for recovering silver, characterized in that, Includes the following steps: Retired photovoltaic cells are immersed in a silver leaching agent to obtain a leachate; The silver leaching agent comprises thiosulfate, coordination compound and water.
2. The method according to claim 1, characterized in that, The thiosulfate includes one or more of Na2S2O3, K2S2O3 and (NH4)2S2O3; The concentration of the thiosulfate is 0.08 ~ 0.15 mol / L.
3. The method according to claim 1, characterized in that, The molar ratio of the thiosulfate to the coordination compound is (2~10):1; the coordination compound includes one or more of copper-based coordination compounds, iron-based coordination compounds, cobalt-based coordination compounds, and nickel-based coordination compounds.
4. The method according to claim 1 or 3, characterized in that, The molar ratio of metal to ligand in the coordination compound is 1:(1~6).
5. The method according to claim 3, characterized in that, The ligands in the copper-based coordination compounds include one or more of ammonia, polyamine organic ligands, and carboxylic acid organic ligands; The ligands in the iron-based coordination compound include one or more of oxalic acid, ethylenediaminetetraacetic acid, tartaric acid, and cyanide ions; The ligands in the cobalt-based coordination compound include ammonia; The ligands in the nickel-based coordination compound include ammonia.
6. The method according to claim 1, characterized in that, The silver leaching agent also includes additives, which include one or more of thiourea, ethylenediaminetetraacetic acid, amino acids, triethanolamine, carboxymethyl cellulose and sodium humate; the concentration of the additives is 0~20 mmol / L.
7. The method according to claim 1, characterized in that, The pH value of the silver leaching agent is 7-10.
8. The method according to claim 1, characterized in that, Also includes: The leachate was allowed to stand to produce a precipitate, and then the resulting system was filtered to obtain a filter cake. The filter cake was dried and roasted in sequence to obtain elemental silver.
9. The method according to claim 1, characterized in that, The leaching temperature is 25~30℃, the time is 10~150min, and the leaching is carried out under stirring conditions at a stirring speed of 250~300 rpm. The liquid-solid ratio of the retired photovoltaic cell to the silver leaching agent is (2~5):
1.
10. The method according to claim 8, characterized in that, The roasting temperature is 700~800℃ and the time is 1~2h.