A method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemical regulation of eutectic solvents

Abstract

This invention discloses a method for the recovery and regeneration of elemental silver from waste photovoltaic panels based on electrochemical regulation of a eutectic solvent, belonging to the field of resource recycling technology for waste photovoltaic modules. The method involves mixing choline chloride and ethylene glycol, heating and stirring to form a eutectic solvent, and then adding anhydrous copper chloride to prepare a chloride-rich leachate. Waste photovoltaic panel cells are placed in the chloride-rich leachate and heated under forced convection stirring to oxidize elemental silver, which then enters the liquid phase as complexed ions. After the reaction, solid-liquid separation yields pure silicon wafers and the silver-rich leachate. Deionized water is added to the silver-rich leachate to precipitate silver chloride, and after solid-liquid separation, silver chloride precipitate is obtained. The washed silver chloride is precipitated in a sodium thiosulfate solution containing sodium sulfite to form a stable electrolyte. Electrodeposition is then performed on the electrolyte to deposit elemental silver on the cathode, achieving optimal matching of effective ionic conductivity and realizing efficient and green extraction of elemental silver and lossless solvent recycling.

Description

Technical Field

[0001] This invention belongs to the field of waste photovoltaic panel recycling technology, specifically relating to a method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemical regulation of eutectic solvent. Background Technology

[0002] Solar energy, as an important renewable and clean energy source, has been widely developed and applied. With the increasing service life of photovoltaic modules, the number of waste photovoltaic panels continues to grow. If these waste photovoltaic panels are not disposed of properly, the heavy metals and other components they contain may adversely affect the soil and water environment. At the same time, waste photovoltaic panels also contain valuable elements such as silver, aluminum, and silicon, which have high resource utilization value. While silver content is relatively low, its value is high; efficient recycling of silver not only has significant economic implications but also helps reduce the energy consumption and environmental burden of primary silver mining.

[0003] Currently, the main methods for recycling metals from waste photovoltaic panels include pyrometallurgy and hydrometallurgy. Pyrometallurgy typically separates metallic and non-metallic components through high-temperature treatment, but it suffers from high energy consumption, large equipment investment, and the potential generation of harmful gases. Hydrometallurgy offers higher recycling efficiency and has been widely used in related recycling processes. However, traditional hydrometallurgy is mostly carried out in aqueous solutions, usually requiring the use of strong acids, strong alkalis, or strong oxidants. The leaching process may also generate harmful gases, increasing reagent consumption and raising the costs of subsequent environmental treatment and equipment.

[0004] Deep eutectic solvents (DES), as a type of green solvent system developed in recent years, can significantly reduce the melting point of the system through hydrogen bonding interactions between components. These solvents are characterized by simple preparation, wide availability of raw materials, low cost, wide liquidus temperature range, good thermal stability, and tunable molecular structure, thus showing promising application prospects in the field of precious metal recovery.

[0005] However, existing silver recovery technologies based on eutectic solvents for waste photovoltaic panels still have certain shortcomings. For example, the invention patent with publication number CN 119433192 A, entitled "A Eutectic Solvent and a Method for Separating and Recovering Metals from Waste Crystalline Silicon Photovoltaic Panels," discloses a eutectic solvent recovery method using betaine hydrochloride as a hydrogen bond acceptor and ethylene glycol as a hydrogen bond donor, with a molar ratio of 1:5 to 1:12. Although this method reduces the macroscopic viscosity of the system by increasing the proportion of hydrogen bond donors, the reduced effective ion concentration affects the system's charge transport capacity, thus hindering the kinetic improvement of leaching and subsequent electrolysis processes. Therefore, developing a eutectic solvent silver recovery method that balances leaching capacity, electrochemical activity, and recyclability remains of great significance. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention provides a method for the recovery and regeneration of elemental silver from waste photovoltaic panels based on electrochemical control of a eutectic solvent. This method achieves the leaching, precipitation, regeneration, and electrodeposition recovery of elemental silver from waste photovoltaic panels by controlling the eutectic solvent system and leaching conditions, while also considering the recycling of the solvent system.

[0007] This invention is achieved through the following technical solution: A method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemical regulation of eutectic solvents, specifically including the following steps: Step 1: Mix choline chloride and ethylene glycol in a molar ratio of 1:(1.5~3.5), heat and stir to form a eutectic solvent, then add anhydrous copper chloride to obtain a chlorine-rich leachate. Step 2: Place the waste crystalline silicon photovoltaic cell into a chlorine-rich leaching solution and heat it under forced convection stirring to oxidize the elemental silver and allow it to enter the liquid phase in the form of complexed ions. After the reaction is completed, the solid and liquid are separated to obtain the pure silicon wafer substrate after silver removal and the silver-rich leaching solution. Step 3: Add deionized water to the silver-rich leachate to precipitate the formed silver chloride precipitate. After solid-liquid separation, obtain silver chloride precipitate and copper-containing filtrate. Then, evaporate and dehydrate the copper-containing filtrate to obtain the chlorine-rich leachate. Step 4: Dissolve the washed silver chloride precipitate in a sodium thiosulfate solution containing sodium sulfite to form a stable electrolyte. Then, electrodeposit the electrolyte to deposit elemental silver on the cathode, thus completing the recycling and regeneration of elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvent.

[0008] A further improvement of the present invention is that: Step 1: Choline chloride and ethylene glycol are stirred at 70-90°C for 1-3 hours under drying conditions to obtain the eutectic solvent.

[0009] In step 1, the concentration of anhydrous copper chloride in the chlorine-rich leachate is 0.1–0.5 mol / L.

[0010] Step 2 involves applying forced convection stirring at 70–90°C with a rotation speed ≥500 rpm.

[0011] Step 2: Heat for 60-90 minutes under forced convection stirring.

[0012] In step 3, the volume of deionized water added is 1 to 3 times the volume of the silver-rich leachate, and the evaporation and dehydration are carried out by vacuum rotary evaporation at 60°C.

[0013] The sodium thiosulfate solution in step 4 has a concentration of 0.5~2.0 mol / L, and the sodium sulfite has a concentration of 0.05~0.20 mol / L.

[0014] In step 4, electrodeposition is performed in constant current mode with a current of 0.01–0.04 A. The cathode material for electrodeposition is selected from titanium sheets, graphite sheets, or silver sheets, and the anode material is selected from titanium sheets, platinum sheets, or graphite rods.

[0015] The chlorine-rich leachate obtained in step 3 can be recycled up to 10 times, with the silver leaching rate maintained at over 96.15% per cycle.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This invention relates to a method for the recovery and regeneration of elemental silver from waste photovoltaic panels based on electrochemical regulation of a eutectic solvent. The thermal-convection coupling condition helps to weaken interfacial mass transfer limitations, improving the silver dissolution rate and recovery efficiency, and giving the silver dissolution process stronger surface chemical reaction control characteristics. Compared with traditional formulations that reduce viscosity by adding excessive hydrogen bond donors, this invention has better overall performance in terms of silver recovery rate, recycling, and process greenness. Existing technologies typically introduce additional precipitants during the precipitation stage to cause copper ions to precipitate, resulting in the oxidant being unable to be reused in the system. This invention changes the system polarity by adding deionized water to the silver-rich leachate, causing silver to preferentially precipitate as silver chloride, while the copper-containing filtrate can be restored to a copper-containing eutectic solvent that can be reused for leaching after evaporation and dehydration. Cyclic experiments show that after 10 consecutive uses, the single silver leaching rate can still be maintained above 96.15%, thereby reducing the need for oxidant and solvent replenishment. This invention dissolves the obtained silver chloride precipitate in a solution containing sodium thiosulfate and sodium sulfite to form an electrolyte, and then obtains elemental silver by constant current electrodeposition. The silver-poor electrolyte after electrodeposition can be used to dissolve subsequent silver chloride precipitates, thereby reducing the consumption of fresh solvent in the purification stage and reducing waste liquid discharge.

[0017] Furthermore, electrochemical evaluation determined that a 1:2 ratio of choline chloride to ethylene glycol was optimal. Although this system has a slightly higher viscosity, it possesses a high effective ionic conductivity, which can mitigate the migration hindrance caused by high viscosity to some extent. Attached Figure Description

[0018] Figure 1 This is the full-component infrared spectrum characterization of the eutectic solvent (DES) in Example 1 of the present invention.

[0019] Figure 2 The NMR characterization images are of the eutectic solvent (DES) structures with different molar ratios in Example 1 of this invention.

[0020] Figure 3a This is a thermal stability analysis diagram of the eutectic solvent (DES) in Example 1 of the present invention.

[0021] Figure 3b This is a thermal stability analysis diagram of the eutectic solvent (DES) in Example 2 of the present invention.

[0022] Figure 4a1 This is a SEM image of the silicon solar cell before reaction in Example 1 of the present invention at 100 μm. Figure 4a2 This is a SEM image of the silicon solar cell after reaction in Example 1 of the present invention at 100 μm.

[0023] Figure 4b1 This is an EDSSi test image of the silicon solar cell before reaction in Example 1 of the present invention at 100 μm.

[0024] Figure 4b2 This is an EDSSi test image of the silicon solar cell after reaction in Example 1 of the present invention at 100 μm.

[0025] Figure 4c1 This is a EDSAg test image of the silicon solar cell before reaction in Example 1 of the present invention at 100 μm.

[0026] Figure 4c2 This is an EDSAg test image of the silicon solar cell after reaction in Example 1 of the present invention at 100 μm.

[0027] Figure 4d1 This is an EDSAl test image of the silicon solar cell at 100 μm before reaction in Example 1 of the present invention.

[0028] Figure 4d2 This is an EDS Al test image of the silicon solar cell after reaction in Example 1 of the present invention at 100 μm.

[0029] Figure 5 This is an electrodeposition curve diagram of Embodiment 1 of the present invention.

[0030] Figure 6 This is an X-ray diffraction (XRD) pattern of the electrodeposition product obtained in Example 1 of the present invention.

[0031] Figure 7 This is a temperature-viscosity line graph of two eutectic solvents (DES) with different molar ratios in Example 2 of the present invention.

[0032] Figure 8 This is a temperature-conductivity line graph for two different molar ratios of eutectic solvent (DES) in Example 2 of the present invention.

[0033] Figure 9 The CV test graphs are for DES with different oxidant types in Comparative Example 1 and Example 3 of this invention.

[0034] Figure 10 The silver recovery kinetic curves of two DES under different conditions in Comparative Example 1 and Example 3 of this invention are shown.

[0035] Figure 11 The figures show the silver recovery kinetics curves of the Cu-DES system under different oxidant concentrations.

[0036] Figure 12 This is a Tafel rate curve of the Cu-DES system in Example 7 of the present invention.

[0037] Figure 13 This is a graph showing the silver recovery rate of DES after 10 cycles in Example 8 of the present invention.

[0038] Figure 14 This is the DES infrared spectrum obtained by 10 cycles in Embodiment 8 of the present invention.

[0039] Figure 15 This is a SEM image of the elemental silver deposited in Example 9 of the present invention. Detailed Implementation

[0040] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0041] This invention provides a low-melting-point solvent with high electrochemical activity, composed of a hydrogen bond acceptor and a hydrogen bond donor, wherein the hydrogen bond acceptor is choline chloride and the hydrogen bond donor is ethylene glycol; the molar ratio of the two is 1:(1.5-3.5), and the solvent is stirred for 1.5-2.5 h under drying conditions at 70-90°C.

[0042] Furthermore, the optimal molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:2. This ratio breaks with the conventional experience of blindly increasing the hydrogen bond donor to dilute and reduce viscosity. Electrochemical evaluation results show that, at this ratio, although the system has a relatively high macroscopic viscosity, it still exhibits good electrical conductivity, which is beneficial for subsequent silver leaching and electrodeposition recovery.

[0043] Furthermore, anhydrous copper chloride (CuCl2) is added as an oxidant to the eutectic solvent at the same temperature to prepare a leachate; wherein the concentration of divalent copper ions is 0.1-0.5 mol / L, preferably 0.3 mol / L.

[0044] This invention breaks through the traditional method of selecting oxidants based solely on trial and error. By electrochemically evaluating the standard electrode potential difference between silver and various oxidants in a specific eutectic solvent (DES) system, it confirms the effectiveness of divalent copper ions (Cu). 2+The oxidation process mediated by this method not only has a suitable driving force but also exhibits excellent coordination stability and process reproducibility. Furthermore, this invention clearly defines the concentration range of divalent copper ions in the leachate. Reaction kinetic analysis revealed that in the preferred 1:2 system, when the oxidant concentration is between 0.1 and 0.5 mol / L, Cu ions diffusing to the solid-liquid interface... 2+ The concentration gradient directly determines the leaching rate; however, when the concentration reaches or exceeds 0.5 mol / L, the kinetic gain exhibits significant diminishing marginal returns due to the high viscosity of the DES system.

[0045] This invention also provides a method for recovering and regenerating silver from waste crystalline silicon photovoltaic panels using the above-mentioned eutectic solvent, comprising the following steps: Step 1: Mix the above leachate with the dismantled waste crystalline silicon photovoltaic cells, and apply forced convection stirring (speed ≥ 500 rpm) at 70–90℃ for 60–90 min. Utilize fluid dynamics to overcome the system's viscosity resistance, oxidize the metallic silver, and [AgCl] x ] 1-x (Where x is 2, 3, or 4) The complexed ions enter the liquid phase. After the reaction, the mixture is separated into solid and liquid phases to obtain a clean solid substrate with the silver layer completely removed, and a silver-rich leaching solution (volume denoted as V). 1-3 V of water is added to the silver-rich leaching solution to precipitate silver chloride. Deionized water is used as the antisolvent to break the complexation equilibrium, causing silver to precipitate as silver chloride. The temperature is kept consistent with the leaching reaction temperature for 60-90 min. The silver chloride precipitate is obtained by filtration. Step 2: After washing the silver chloride precipitate obtained in Step 1, dissolve it in a mixed solution of sodium thiosulfate and sodium sulfite, where the concentration of sodium thiosulfate is 0.5~2.0 mol / L and the concentration of sodium sulfite is 0.05~0.20 mol / L. This completes the complexation and redissolution, forming the mother liquor for electrolysis. Simultaneously, the aqueous leachate after silver removal (silver chloride) in Step 1 is dehydrated by vacuum rotary evaporation at 60℃ to remove water and restore the system to its initial leachate state. This completes the leaching-precipitation-dehydration process, making it ready for direct use in subsequent photovoltaic panel leaching.

[0046] Step 3: After filtering the mother electrolyte obtained in Step 2, the solution is introduced into an electrolytic cell for in-situ electrodeposition for 0.75~3.0 h. The current is controlled within the selective deposition range (preferably 0.01 A ~ 0.04 A) to selectively reduce the silver complex to elemental silver at the cathode. After electrodeposition, the silver-poor electrolyte is recycled back to this step to dissolve the next batch of silver chloride. The cathode material is selected from titanium sheets, graphite sheets, or silver sheets; the anode material is selected from titanium sheets, platinum sheets, or graphite rods. After electrodeposition, the cathode is removed and the elemental silver is stripped off. After multiple rinsing and drying, high-purity elemental silver is obtained. Step 4: After step 3 is completed, the silver-poor electrolyte is collected. Infrared characterization was performed on the original DES, the aqueous intermediate from step 2, and the regenerated DES. The results showed that the water-related characteristic absorption peaks in the aqueous intermediate were significantly weakened or disappeared in the regenerated DES; simultaneously, the main characteristic absorption peaks corresponding to the original DES were still present in the regenerated DES, and no significant new characteristic peaks appeared. These results indicate that the evaporation dehydration process can effectively remove the introduced water while preserving the main structural features of the eutectic solvent system. Although the solvent color darkened slightly after multiple thermal cycles, the regenerated DES can still be used for subsequent silver leaching. After 10 consecutive leaching-precipitation-dehydration cycles of steps 1-2, the single-cycle silver recovery rate of this system can still be maintained above 96.15%.

[0047] Example 1: This embodiment aims to verify the actual operating effect under optimal electrochemical control parameters.

[0048] Step 1: Pure choline chloride (ChCl) and ethylene glycol (EG) are mixed at the optimal molar ratio of 1:2 and continuously stirred at 80°C for 2 hours under drying conditions to form a homogeneous and transparent eutectic solvent. Anhydrous copper chloride (CuCl2) is added to this system to achieve a concentration of 0.3 mol / L, and stirring continues at the same temperature until dissolved, thus preparing divalent copper (CuCl2). 2 + Chlorine-rich leachate mediated by ( ). Infrared spectral results ( Figure 1 The results showed that the main absorption peak of the obtained eutectic solvent broadened and shifted slightly compared to the pure component, indicating a strong interaction between the components. NMR results ( Figure 2 The results showed that the characteristic proton signals in the eutectic solvent shifted relative to the pure component, indicating that choline chloride and ethylene glycol had formed a new eutectic solvent system. Thermogravimetric analysis results ( Figure 3a , Figure 3b The results showed that the system did not undergo significant thermal decomposition at 80℃, but weight loss increased at higher temperatures. Therefore, 80℃ was selected as the preferred temperature that balances system stability and process efficiency.

[0049] Step 2: Add 5 g of waste crystalline silicon photovoltaic cells (with backsheets removed) to the above leachate, and stir the mixture at 80°C and 500 rpm for 60 min. Samples were taken at fixed time intervals during the reaction, and the silver content in the leachate was determined using ICP-OES. The results showed that the silver content in the liquid phase continuously increased with the reaction time, reaching its highest value at 60 min; based on the liquid phase silver content, the silver leaching rate reached 99.5% under these conditions at 60 min. Furthermore, Figure 4a1 , Figure 4a2 The SEM shown Figure 4b1 , Figure 4b2 , Figure 4c1 , Figure 4c2 , Figure 4d1 , Figure 4d2 The EDS results show that before the reaction, obvious silver grid lines were observed on the surface of the solar cell, and the Ag element signal was clearly distributed; after the reaction, the surface silver grid lines basically disappeared, the Ag element signal was significantly weakened, and the morphology of the silicon substrate was not significantly damaged. This indicates that under the above conditions, silver can be efficiently leached while the silicon substrate remains basically intact.

[0050] Step 3: The solid-liquid mixture from Step 2 is filtered while hot to separate the silicon wafer and the silver-rich leaching solution. Twice the volume of deionized water is added to the silver-rich leaching solution. This abrupt change in liquid phase polarity disrupts the equilibrium of the silver chloride complex, causing silver to precipitate completely as white silver chloride (AgCl). After the secondary solid-liquid separation, the resulting filtrate contains intact divalent copper oxidant. The filtrate is then dehydrated by vacuum rotary evaporation at 60°C, restoring the regenerated copper-containing eutectic solvent to its initial activity.

[0051] Step 4: Dissolve the washed AgCl precipitate in a mixed aqueous solution of 1.0 mol / L sodium thiosulfate and 0.1 mol / L sodium sulfite. Introduce this electrolyte into a two-electrode electrolytic cell (pure titanium cathode, platinum anode), and electrodeposit at a constant current of 0.02 A for 1.5 h. The resulting electrodeposition curve is shown below. Figure 5 As shown. Figure 5 The results show that under constant current conditions, the electrolytic cell voltage changes with the deposition process, which can be used to characterize the silver deposition process. The cathode was removed and the spongy deposits were peeled off. XRD analysis was performed. Figure 6 This indicates that the product obtained is elemental silver with a face-centered cubic structure.

[0052] Example 2: This example is used to demonstrate that the optimal molar ratio of choline chloride to ethylene glycol is 1:2 as specified in this invention.

[0053] Two eutectic solvents with molar ratios of 1:2 and 1:3 were prepared, respectively. The test results... Figure 7 The results show that the macroscopic viscosity of the 1:2 system is higher than that of the 1:3 system, but... Figure 8 Contrary to expectations, the 1:2 system exhibits significantly better electrical conductivity than the lower viscosity 1:3 system. Arrhenius model fitting reveals that the 1:2 system possesses a significantly higher pre-exponential factor. This confirms that the 1:2 formulation, with its abundant effective carrier concentration, thermodynamically compensates for the migration hindrance caused by high viscosity, providing charge transport assurance for subsequent silver leaching.

[0054] Example 3 and Comparative Example 1 were used to compare the suitability of different oxidants in the same eutectic solvent system. Except that the oxidants were set to 0.3 mol / L CuCl2 (Example 3) and 0.3 mol / L FeCl3 (Comparative Example 1), the other eutectic solvent preparation conditions and leaching conditions were the same as in Example 1.

[0055] Cyclic voltammetry test results ( Figure 9 The results showed that both systems exhibited significant redox responses, but their electrochemical response characteristics differed, indicating that different oxidants exhibited different electrochemical behaviors in this eutectic solvent. The silver recovery kinetics curves obtained after a leaching reaction at 80℃ and 500rpm for 180 min are shown below. Figure 10 As shown in the figure, the silver recovery rate of the CuCl2 system is higher than that of the FeCl3 system; the average silver recovery rate of the FeCl3 system is only 55.16%, and the data fluctuates significantly. This indicates that in the chlorine-rich eutectic solvent system described in this invention, CuCl2 is more conducive to obtaining a stable silver leaching effect than FeCl3.

[0056] Examples 4-6: This set of examples verifies the regulatory effect of oxidant (CuCl2) concentration on recovery efficiency, supporting the limitation of 0.1 M to 0.5 M. The conditions are consistent with step 2 of Example 1, and the results are as follows. Figure 11 As shown.

[0057] Example 4 (0.1 M system): The oxidant concentration gradient at the solid-liquid interface was insufficient, and the kinetics were severely sluggish. After 180 min, the recovery rate was only 30.62%.

[0058] Example 5 (0.3 M system): The kinetics were significantly improved, and the recovery rate reached 72.66% at 180 min, showing excellent linear dissolution characteristics.

[0059] Example 6 (0.5 M system): The recovery rate reached 69.38% at 120 min and the final recovery rate was 75.13% at 180 min.

[0060] Example 7: Pure silver sheets were treated with the leachate of Example 1 under static conditions at room temperature (approximately 25°C). Due to the extremely high bulk viscosity leading to huge mass transfer resistance, the silver recovery rate was less than 10% after 180 min of reaction. Figure 12 The results show that in the Cu-DES system, the corrosion current density of silver at 80℃ and 500 rpm is significantly higher than that at room temperature, increasing from approximately 0.37 mA / cm² to approximately 6.04 mA / cm², an increase of about 16 times. Combined with the apparent activation energy of 43.2 kJ / mol obtained from kinetic calculations, it can be concluded that the dissolution process of silver under this thermo-convection coupling condition exhibits stronger surface chemical reaction control characteristics.

[0061] Example 8: The regenerated copper-containing eutectic solvent from Example 1, after rotary evaporation and dehydration, was poured back into the reactor without adding any copper chloride, and waste crystalline silicon photovoltaic cells were added. A closed-loop leaching-precipitation-dehydration cycle was performed 10 times consecutively under the conditions of Example 1. ICP testing showed that ( Figure 13 After 10 cycles, the average silver leaching rate remained stable at over 96.15%. Infrared testing showed that the main structure of DES did not change significantly. Figure 14 ).

[0062] Examples 9-11 were used to investigate the effects of different constant current conditions on silver deposition time and the morphology of the deposited products. Except for the electrodeposition current being adjusted to 0.01 A, 0.03 A, and 0.04 A, respectively, the other conditions were the same as step 4 of Example 1. During the constant current deposition process, the electrolytic cell voltage naturally varied with the deposition process; this voltage change was recorded only as a process response and was not considered a necessary control parameter of this invention.

[0063] Example 9 (0.01 A): Due to the low current, the silver deposition rate was slow, and the deposition time was 3.0 h. The resulting silver deposit was relatively dense and exhibited a relatively uniform sponge-like porous structure. Figure 15 ).

[0064] Example 10 (0.03 A): The deposition rate was significantly improved, and the time required to complete deposition was 1.0 h.

[0065] Example 11 (0.04 A): Under higher current conditions, the silver deposition time was further reduced to 0.75 h.

Claims

1. A method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemical regulation of eutectic solvents, characterized in that, Includes the following steps: S1, choline chloride and ethylene glycol are mixed in a molar ratio of 1:(1.5~3.5), heated and stirred to form a eutectic solvent, and then anhydrous copper chloride is added to obtain a chlorine-rich leachate; S2, the waste crystalline silicon photovoltaic cell is placed in a chlorine-rich leaching solution and heated under forced convection stirring to oxidize the elemental silver and enter the liquid phase in the form of complex ions. After the reaction is completed, solid and liquid are separated to obtain the pure silicon wafer substrate after silver removal and the silver-rich leaching solution. S3, add deionized water to the silver-rich leachate to precipitate silver as silver chloride precipitate. After solid-liquid separation, silver chloride precipitate and copper-containing filtrate are obtained. The copper-containing filtrate is then evaporated and dehydrated to obtain the chlorine-rich leachate. S4, the washed silver chloride precipitate is dissolved in a sodium thiosulfate solution containing sodium sulfite to form an electrolyte. Then, the electrolyte is electrodeposited to deposit elemental silver on the cathode, thus completing the recycling and regeneration of elemental silver from waste photovoltaic panels based on electrochemical regulation of the eutectic solvent.

2. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 1, characterized in that, S1. Choline chloride and ethylene glycol are stirred at 70-90°C for 1-3 hours under drying conditions to obtain the eutectic solvent.

3. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 1, characterized in that, In S1, the concentration of anhydrous copper chloride in the chlorine-rich leachate is 0.1–0.5 mol / L.

4. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 1, characterized in that, S2 is reacted under forced convection stirring at 70–90°C with a rotation speed ≥500 rpm.

5. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 1, characterized in that, S2 is heated for 60-90 minutes under forced convection stirring.

6. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 1, characterized in that, The silver-poor electrolyte obtained after S4 electrodeposition is used to dissolve silver chloride in place of the sodium thiosulfate solution containing sodium sulfite.

7. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 6, characterized in that, The volume of deionized water added in S3 is 1 to 3 times the volume of the silver-rich leachate; the evaporation and dehydration are carried out by vacuum rotary evaporation at 60°C.

8. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 1, characterized in that, The sodium thiosulfate solution in S4 has a concentration of 0.5~2.0 mol / L, and the sodium sulfite has a concentration of 0.05~0.20 mol / L.

9. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 1, characterized in that, Electrodeposition in S4 employs a constant current mode with a current of 0.01–0.04 A; The cathode material for electrodeposition is selected from titanium sheets, graphite sheets, or silver sheets, and the anode material is selected from titanium sheets, platinum sheets, or graphite rods.

10. The method for recovering and regenerating elemental silver from waste photovoltaic panels based on electrochemically controlled eutectic solvents according to claim 6, characterized in that, The chlorine-rich leachate in S3 can be continuously recycled up to 10 times, with a single silver leaching rate maintained at over 96.15%.

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