A method for improving the leaching of aluminum electrodes in photovoltaic cells

Abstract

The application discloses a method for improving aluminum electrode leaching in photovoltaic cell pieces, comprising (1) crushing waste photovoltaic cell pieces to obtain crushed materials; (2) configuring an alkaline leaching solution added with a silicon inhibitor, and placing the crushed materials into the alkaline leaching solution for leaching; and after reaction is completed, filtering and separating to obtain an aluminum leaching solution; wherein the silicon inhibitor is one or more of EDTA, nitrate and nitrite of sodium and potassium. By adding the silicon inhibitor while leaching the alkaline solution, the leaching effect of the aluminum electrode in the cell pieces is improved, and the adverse effect of silicon leaching when the alkaline solution leaches the aluminum electrode is reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of new energy solid waste resource recycling, and particularly relates to a method for improving the leaching of aluminum electrodes in photovoltaic cells, especially a method for preparing aluminum electrodes with high efficiency and high purity leaching. BACKGROUND

[0002] Under the background of global energy transformation, photovoltaic technology is widely praised for its clean and renewable characteristics. However, with the rapid development of the photovoltaic industry, the disposal of waste photovoltaic modules has gradually become an environmental challenge that cannot be ignored. Especially for the recovery of aluminum, it not only concerns the recycling of resources, but also involves the overall situation of environmental protection and sustainable development.

[0003] Photovoltaic modules are mainly composed of glass, aluminum frame, silicon wafer and back plate, etc. Among them, aluminum as an important structural material, its recycling value cannot be ignored. However, the current recycling of photovoltaic modules faces multiple difficulties. First, there is a lack of efficient recycling technology. Traditional physical sorting methods are difficult to accurately separate aluminum from other materials, resulting in low recovery efficiency; chemical leaching and other methods can improve the recovery rate, but the cost is high and may cause secondary pollution. Second, the economic incentive mechanism is insufficient. Because the cost of recycling is higher than the cost of new aluminum materials, combined with the limited demand for recycled aluminum in the market, recycling enterprises lack enough motivation to carry out large-scale recycling. Third, public awareness is weak. Many people lack awareness of the importance of photovoltaic module recycling, resulting in a large number of waste modules being discarded or buried at will, causing resource waste and environmental pollution.

[0004] The global aluminum resource exploration and processing process has high energy consumption and heavy pollution. Extracting aluminum from waste photovoltaic modules not only can alleviate the dependence on primary aluminum ore resources, but also can significantly reduce environmental impact. According to the statistics of the International Aluminum Association, recycling one ton of waste aluminum material can save about 95% of energy consumption and reduce more than 90% of greenhouse gas emissions. Therefore, strengthening the recycling and utilization of aluminum elements in waste photovoltaic modules has important significance for promoting the development of circular economy and protecting natural resources.

[0005] In addition, the waste photovoltaic silicon cell contains Al, Al2O3, Si, Si3N4, Ag, Cu, Pb and other substances, and the components are complex. The silicon content of the waste cell is the highest (about 90%), and the aluminum content is more than 5%. Studies have shown that the cost of using silicon cell to purify and prepare high-purity silicon is much lower than that of extracting silicon from quartz sand. Therefore, in order to realize the recycling of silicon resources, the waste photovoltaic silicon cell must be de-aluminized and purified. At present, in the field of de-aluminum and aluminum resource utilization of waste photovoltaic silicon cells, the amphoteric characteristics of aluminum are often used to remove aluminum in the cell by acid (HCl, H2SO4 and HNO3) or alkali (NaOH and KOH) leaching, and then neutralization and precipitation to form Al(OH)3 to realize the recovery of aluminum resources. As for the acid leaching to remove aluminum, the passivation reaction of aluminum is easy to occur with oxidizing acid (H2SO4 and HNO3), and the formed aluminum oxide film will prevent the further dissolution of aluminum, resulting in the difficulty to achieve high removal rate of aluminum, and the dissolution of silver will also occur, reducing the yield of silver in the subsequent process. The use of HCl leaching can avoid the passivation of aluminum and the dissolution of silver, so HCl is often used to remove aluminum impurities in waste cells. However, HCl is volatile during the HCl leaching process, resulting in a poor operating environment. In addition, the co-dissolution reaction of coexisting metals in the cell is easy to occur during the acid leaching to remove aluminum, which leads to the difficulty in subsequent separation and recovery, and the direct addition of alkali for neutralization and recovery will cause the co-precipitation of other metals, resulting in low purity of Al(OH)3 prepared.

[0006] The use of alkaline solution to leach aluminum can effectively avoid the co-dissolution problem of other metals, so the alkali method is often used as the first step of cell purification in the present research. The alkali solution has high de-aluminum efficiency, and the removal rate can reach more than 99%, while the dissolution of Si will occur, but the composition of the leaching solution is NaOH-NaAlO2-Na2SiO3-H2O system. For the recovery and utilization of aluminum resources after alkali de-aluminum, Al(OH)3 products are often obtained by direct neutralization and precipitation, but little attention is paid to the problem of impurity silicon in aluminum products caused by the side reaction of silicon dissolution during the leaching process. During the above-mentioned acid neutralization process of alkaline leaching solution, Al(OH)3 precipitate and aluminum-silicon co-precipitation to form sodium aluminum silicate precipitate will occur at the same time, which is the reason for the excessive silicon impurities in the aluminum hydroxide product; and if the alkali solution is adjusted to reduce the leaching of silicon during the leaching process, it will also lead to low leaching efficiency of aluminum.

[0007] CN118419959A discloses a method for preparing pseudo-boehmite from waste photovoltaic silicon cells, which first uses alkaline solution to enter the cell, and then obtains a solution containing sodium aluminate after solid-liquid separation, and then adds a desiliconizing agent (one or both of a calcium-containing compound and a magnesium-containing compound) to obtain a sodium aluminate solution with low silicon content, and finally adds acid to precipitate to obtain pseudo-boehmite. However, this method still needs to prepare a sodium aluminate solution containing silicon by alkali dissolution, and then selectively precipitate the silicon to relatively improve the purity of aluminum, which is complex in operation.

[0008] Therefore, developing a new method for recycling aluminum resources from waste photovoltaic silicon solar cells to reduce the adverse effects of silicon leaching on aluminum would be of great significance in addressing the coexistence problem of silicon. Summary of the Invention

[0009] The purpose of this invention is to provide a method for improving the leaching of aluminum electrodes in photovoltaic cells, so as to reduce the adverse effects of silicon on aluminum leaching.

[0010] To achieve the above objectives, the present invention adopts the following technical solution:

[0011] A method for improving the leaching of aluminum electrodes in photovoltaic cells, the method comprising:

[0012] (1) Crush the waste photovoltaic cells to obtain crushed material;

[0013] (2) Prepare an alkaline leaching solution with added silicon inhibitor, put the pulverized material into it for leaching, and filter and separate it after the reaction is completed to obtain aluminum leaching solution; wherein, the silicon inhibitor is one or more of EDTA, sodium nitrite and sodium nitrate.

[0014] In step (1) of the present invention, the waste photovoltaic cells are crushed to facilitate subsequent leaching. Preferably, the waste photovoltaic cells are crushed to a size of 50 mesh or larger, such as 100 mesh or 200 mesh. It is understood in the art that smaller particles are more conducive to leaching.

[0015] In a preferred embodiment, in step (1), before crushing, the waste photovoltaic cells are cleaned, for example, the waste photovoltaic cells are ultrasonically cleaned to remove dirt, filtered and then placed in a blower dryer to dry the moisture.

[0016] In step (2) of this invention, aluminum in the pulverized material is leached using a prepared alkaline leaching solution containing a silicon inhibitor to obtain a sodium aluminate leaching solution. Leaching aluminum from photovoltaic cells using alkaline solutions is well-known in the art. In some embodiments, the alkali in the alkaline leaching solution is sodium hydroxide or potassium hydroxide, with a concentration of 0.5-2.5 mol / L, preferably 1-2 mol / L, such as 1.5 mol / L. In some embodiments, the leaching temperature can be 10-35°C, such as 15, 20, or 30°C, preferably 15-25°C, as lower temperatures are beneficial for inhibiting silicon leaching. Preferably, during leaching, the liquid-to-solid mass ratio is 8-15:1, such as 10:1 or 12:1.

[0017] In one embodiment, the silicon inhibitor is one or more of sodium and potassium nitrates and nitrites, such as sodium nitrite, sodium nitrate, potassium nitrate, and potassium nitrite; preferably, the molar ratio of silicon inhibitor to alkali in the leachate is (0.1-2):10, such as 0.2:10, 0.5:10, 0.8:10, or 1.5:10, more preferably (0.4-1):10.

[0018] Research has found that leaching metallic aluminum with sodium hydroxide solution at low temperatures, while simultaneously adding directional precipitants such as sodium nitrite or sodium nitrate, allows silicon in the solution to leach out in solid form, accelerates the aluminum reaction rate, and achieves efficient leaching while reducing the silicon content in the solution. This ultimately achieves highly efficient aluminum leaching with a leaching rate exceeding 97%, with aluminum hydroxide purity exceeding 98%, and the generated byproduct sodium silicate purity exceeding 90%. The entire cleaning solution remains pollution-free. In short, it offers multiple benefits, as detailed below:

[0019] (1) Promotes aluminum dissolution: Increases the alkalinity of the solution. Sodium nitrite dissociates into sodium ions and nitrite ions in water. These sodium ions can enhance the alkalinity of the solution, increase the degree of dissociation of sodium hydroxide, thereby providing more hydroxide ions and accelerating the aluminum dissolution reaction.

[0020] (2) Formation of soluble aluminates and stabilization of aluminates: Under strongly alkaline conditions, aluminum reacts with sodium hydroxide to form sodium aluminate, which is a soluble aluminate. The presence of sodium nitrite helps maintain the high alkalinity of the solution, making sodium aluminate more stable and reducing aluminum precipitation.

[0021] (3) Ionic effect: The ions dissociated from sodium nitrite can change the ionic strength and activity of the solution, reduce the activity of aluminum, and make aluminum more likely to exist in the solution in ionic form, thereby accelerating the leaching rate of aluminum.

[0022] (4) Formation of insoluble silicate compounds: Sodium nitrite can react with silicate ions in solution to form insoluble silicates, such as sodium silicate. These silicates are not easily dissolved, thereby reducing the leaching of silicon.

[0023] (5) pH and ionic strength: Sodium nitrite can reduce the solubility of silicon by affecting the pH and ionic strength of the solution. Both highly alkaline environments and high ionic strength are unfavorable for the dissolution of silicon.

[0024] (6) In the technical solution of the present invention, the final purity of aluminum hydroxide is above 99%, and no waste is generated during recycling, which can realize industrial production.

[0025] In one embodiment, the silicon inhibitor is EDTA (ethylenediaminetetraacetic acid). Studies have found that by adding EDTA, it can complex with the leached silicon during leaching to form a silica colloid, thereby facilitating separation from the leachate.

[0026] Preferably, the concentration of EDTA in the leachate is 0.1-0.3 mol / L, for example, 0.2 mol / L.

[0027] In some implementations, a membrane filtration system is used in step (2), for example, a membrane with a pore size of 0.05-0.2 μm, such as 0.1 μm, for solid-liquid separation and silica colloid retention.

[0028] In a preferred embodiment, step (2) employs a gradient cooling leaching process, with the temperature decreasing by 1-4°C, for example, 2 or 3°C, every 10 minutes, for a total leaching time of 50-60 minutes; preferably, the final leaching temperature is stabilized at 8-12°C, for example, 10°C.

[0029] It is understood in the art that the aluminum leached by the present invention can be further processed and utilized. In some embodiments, the method of the present invention further includes step (3): adding hydrochloric acid to the aluminum leaching solution to carry out a precipitation reaction, filtering and drying after the reaction is completed to obtain solid aluminum hydroxide; furthermore, the solid aluminum hydroxide can be subjected to multiple low-temperature washings to improve purity, wherein the first low-temperature washing temperature is 15-25℃, the second low-temperature washing temperature is 10-15℃, and the lower temperature is more conducive to the dissolution and elution of sodium silicate as an impurity. The washed solid aluminum hydroxide can be calcined at high temperature to obtain solid alumina, for example, at a calcination temperature of 1000-1200℃ and a calcination time of 2-3 hours. At the same time, it is understood in the art that the silicon by-product separated in step (2) can also be washed and recycled.

[0030] Preferably, the leaching and washing are carried out under stirring, for example at a stirring rate of 200 r / min.

[0031] Compared with the prior art, the present invention has the following advantages:

[0032] This invention improves the leaching effect of aluminum electrodes in solar cells by adding a silicon inhibitor during alkaline leaching, and also produces valuable byproducts. It solves the problem of simultaneous silicon leaching during alkaline leaching of aluminum electrodes, not only improving the purity of the downstream aluminum product but also enabling the preparation of valuable byproducts. Specifically, the aluminum leaching rate can reach over 97%, the aluminum product purity can reach over 98%, and the generated byproduct sodium silicate has a purity greater than 90%. The entire leaching process is pollution-free, and no solid waste is generated. Attached Figure Description

[0033] Figure 1This is a flowchart illustrating one embodiment of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0035] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to these ranges or values, such as values ​​±10% of the endpoint values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. Without conflict, the embodiments and features described in this application can be combined with each other.

[0036] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion, 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 explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0037] In the following examples and comparative examples, the solar cells used contain 0.053% Ag and 0.053% Al. Unless otherwise specified, all percentages mentioned in this invention are by mass.

[0038] Example 1

[0039] (1) The waste photovoltaic cells are ultrasonically cleaned to remove dust and dry the moisture. They are then ground and passed through a 50-mesh sieve (Taylor standard sieve) to obtain pulverized material.

[0040] (2) Prepare a leaching solution with a sodium hydroxide concentration of 1 mol / L and a sodium nitrite addition ratio of 0.5:10 to sodium hydroxide concentration; leach the pulverized material in a water bath at a temperature maintained at 20°C (liquid-solid mass ratio of 8:1) for 30 min, and filter to obtain aluminum leaching solution.

[0041] (3) Add hydrochloric acid to the aluminum leaching solution to maintain the pH value of the solution at about 7, and allow precipitation for 2 hours. After the reaction, filter and dry to obtain solid aluminum hydroxide. Then, perform two low-temperature water washes to improve the purity. The first low-temperature wash is at 15°C and the second low-temperature wash is at 10°C (the stirring rate during the above leaching and washing is 100 r / min). After washing, filter and dry to store as solid.

[0042] Experiments have shown that this method can produce high-purity aluminum hydroxide solid. ICP testing shows that the aluminum leaching rate (the proportion of aluminum in the total aluminum in the aluminum leaching solution) is over 97%, the purity of aluminum hydroxide is over 99%, the silicon impurity content is less than 0.3%, and the purity of the generated byproduct sodium silicate is greater than 90% after cleaning.

[0043] Example 2

[0044] (1) The waste photovoltaic cells are ultrasonically cleaned to remove dust and dry the moisture. They are then ground and passed through a 50-mesh sieve (Taylor standard sieve) to obtain pulverized material.

[0045] (2) Prepare a leaching solution with a sodium hydroxide concentration of 1.5 mol / L and a sodium nitrite addition ratio of 1:10 to sodium hydroxide concentration; leach the pulverized material in a water bath at a temperature maintained at 25°C (liquid-solid mass ratio of 10:1) for 30 min, and filter to obtain aluminum leaching solution.

[0046] (3) Add hydrochloric acid to the aluminum leaching solution to maintain the pH value of the solution at about 7, and allow precipitation for 2 hours. After the reaction, filter and dry to obtain solid aluminum hydroxide. Then, perform two low-temperature water washes to improve the purity. The first low-temperature wash is at 15°C and the second low-temperature wash is at 10°C (the stirring rate during the above leaching and washing is 100 r / min). After washing, filter and dry to store as solid.

[0047] Experiments revealed that this method achieves a high aluminum leaching rate, but the purity of the aluminum hydroxide solid is relatively low. This is because excessive addition of sodium nitrite accelerates the reaction in the solution, causing more aluminum and silicon to react and form solids that do not remain in the solution. ICP testing showed that the aluminum leaching rate was over 97%, the aluminum hydroxide purity was 92%, and the silicon impurity content was approximately 4%.

[0048] Example 3

[0049] (1) The waste photovoltaic cells are ultrasonically cleaned to remove dust and dry the moisture. They are then ground and passed through a 50-mesh sieve (Taylor standard sieve) to obtain pulverized material.

[0050] (2) Prepare a leaching solution with a sodium hydroxide concentration of 1.0 mol / L and a sodium nitrite addition ratio of 0.75:10 to sodium hydroxide concentration; leach the pulverized material (liquid-solid mass ratio of 15:1) in a water bath at a temperature maintained at 25°C for 30 min, and filter to obtain an aluminum leaching solution.

[0051] (3) Add hydrochloric acid to the aluminum leaching solution to maintain the pH value of the solution at about 7, and allow precipitation for 2 hours. After the reaction, filter and dry to obtain solid aluminum hydroxide. Then, perform two low-temperature water washes to improve the purity. The first low-temperature wash is at 15°C and the second low-temperature wash is at 10°C (the stirring rate during the above leaching and washing is 100 r / min). After washing, filter and dry to store as solid.

[0052] Experiments revealed that this method achieves a high aluminum leaching rate, but the purity of the aluminum hydroxide solid is relatively low. This is because excessive sodium nitrite addition accelerates the reaction in the solution, causing more aluminum and silicon to react and form solids that do not remain in the solution. ICP testing showed that the aluminum leaching rate was over 96%, the aluminum hydroxide purity was 95%, and the silicon impurity content was approximately 3%.

[0053] Example 4

[0054] (1) The waste photovoltaic cells are ultrasonically cleaned to remove dust and dry the moisture. They are then ground and passed through a 50-mesh sieve (Taylor standard sieve) to obtain pulverized material.

[0055] (2) Prepare a leaching solution with a sodium hydroxide concentration of 1 mol / L and a sodium nitrate addition ratio of 0.1:10 to sodium hydroxide concentration; leach the pulverized material in a water bath at a temperature maintained at 25°C (liquid-solid mass ratio of 10:1) for 30 min, and filter to obtain aluminum leaching solution.

[0056] (3) Add hydrochloric acid to the aluminum leaching solution to maintain the pH value of the solution at about 7, and allow precipitation for 2 hours. After the reaction, filter and dry to obtain solid aluminum hydroxide. Then, perform two low-temperature water washes to improve the purity. The first low-temperature wash is at 15°C and the second low-temperature wash is at 10°C (the stirring rate during the above leaching and washing is 100 r / min). After washing, filter and dry to store as solid.

[0057] Experiments revealed that this method resulted in a low aluminum leaching rate and low purity of the aluminum hydroxide solid. This was because the amount of sodium nitrite added was small, resulting in only a small amount of silicon reacting to form a solid. ICP analysis showed an aluminum leaching rate of 94%, an aluminum hydroxide purity of 95%, and a silicon impurity content of approximately 4%.

[0058] Example 5

[0059] The difference from Example 1 is that sodium nitrite is replaced with an equimolar amount of potassium nitrite. Everything else is the same as in Example 1.

[0060] Experiments have shown that this method can produce high-purity aluminum hydroxide solid. ICP testing revealed that the aluminum leaching rate is over 97%, the aluminum hydroxide purity is 98.5%, and the silicon impurity content is less than 1%.

[0061] Comparative Example 1

[0062] The difference from Example 1 is that sodium nitrite is not added in step (2). The rest is the same as in Example 1.

[0063] Experiments revealed that this method resulted in a low aluminum leaching rate and low purity of the aluminum hydroxide solid. This is because silicon leaches out along with aluminum in the alkaline solution and remains in the solution. ICP analysis showed that the leached aluminum content was approximately 92.5%, the aluminum hydroxide purity was 93.5%, and the silicon impurity content was around 5%.

[0064] Example 6

[0065] (1) The waste photovoltaic cells are ultrasonically cleaned to remove dust and dry the moisture. They are then ground and passed through a 120-mesh sieve (Taylor standard sieve) to obtain pulverized material.

[0066] (2) Prepare a leaching solution with a sodium hydroxide concentration of 1.5 mol / L and an EDTA concentration of 0.2 mol / L. When leaching the pulverized material (liquid-solid mass ratio of 10:1), the initial temperature is 20℃, the temperature is gradually reduced to 10℃, the leaching time is 55 min, and the aluminum leaching solution is obtained by filtration.

[0067] (3) Add hydrochloric acid to the aluminum leaching solution to maintain the pH value of the solution at around 7, and allow precipitation for 2 hours. After the reaction, filter and dry to obtain solid aluminum hydroxide. Then, perform two low-temperature water washes to improve the purity. The first low-temperature wash is at 15℃ and the second low-temperature wash is at 10℃ (the stirring rate during the above leaching and washing is 100r / min). After washing, perform high-temperature calcination to obtain solid alumina. The calcination temperature is 1000-1200℃ and the calcination time is 2-3 hours.

[0068] Experiments have shown that this method can yield high-purity solid alumina. ICP analysis revealed that the alumina purity was 99.6%, the silicon content was 0.08%, and the aluminum recovery rate was 98.5%.

[0069] Example 7

[0070] The difference from Example 6 is that the temperature is kept stable at 20°C during leaching in step (2). The rest is the same as in Example 6.

[0071] Experiments have shown that this method can yield high-purity solid alumina. ICP analysis revealed that the alumina purity was 99.1%, the silicon content was 0.1%, and the aluminum recovery rate was 97.8%.

[0072] Example 8

[0073] The difference from Example 6 is that in step (2), the temperature is kept stable at 10°C during leaching. The rest is the same as in Example 6.

[0074] Experiments revealed that this method can yield high-purity solid alumina. ICP analysis showed an alumina purity of 99.6% and a silicon content of 0.08%. However, due to the low reaction temperature, the aluminum recovery rate was only 85%.

[0075] Example 9

[0076] The difference from Example 6 is that in step (2), the EDTA concentration is 0.1 mol / L, the initial temperature during leaching is 25°C, the temperature is gradually reduced to 12°C, and the leaching time is 50 min. The rest is the same as in Example 6.

[0077] Experiments have shown that this method can yield high-purity solid alumina. ICP analysis revealed that the alumina purity was 99.1%, the silicon content was 0.1%, and the aluminum recovery rate was 98.8%.

[0078] Example 10

[0079] The difference from Example 6 is that in step (2), the EDTA concentration is 0.3 mol / L, the initial temperature during leaching is 18°C, the temperature is gradually reduced to 8°C, and the leaching time is 60 min. The rest is the same as in Example 6.

[0080] Experiments have shown that this method can yield high-purity solid alumina. ICP analysis revealed that the alumina purity was 99.6%, the silicon content was 0.08%, and the aluminum recovery rate was 96.5%.

[0081] As can be seen from the above examples / comparative examples, the present invention improves the leaching effect of aluminum electrodes in battery cells by adding silicon inhibitors during alkaline leaching, and produces valuable byproducts. This solves the problem of simultaneous silicon leaching during alkaline leaching of aluminum electrodes, not only improving the purity of downstream aluminum products, but also realizing the preparation of valuable byproducts.

Claims

1. A method for improving the leaching of aluminum electrodes in photovoltaic cells, the method comprising: (1) The waste photovoltaic cells are crushed to obtain crushed material; (2) Prepare an alkaline leaching solution with added silicon inhibitor, put the pulverized material into it for leaching, and filter and separate it after the reaction is completed to obtain aluminum leaching solution; wherein, the silicon inhibitor is one or more of EDTA, sodium and potassium nitrates and nitrites; Wherein, when the silicon inhibitor is one or more of sodium nitrate, potassium nitrate, sodium nitrite and potassium nitrite, the molar concentration ratio of silicon inhibitor to alkali in the alkaline leachate is (0.1-2):10; When the silicon inhibitor is EDTA, its concentration in the alkaline leachate is 0.1-0.3 mol / L.

2. The method according to claim 1, characterized in that, The alkali in the alkaline leachate is sodium hydroxide or potassium hydroxide, with a concentration of 0.5-2.5 mol / L.

3. The method according to claim 1, characterized in that, The alkali in the alkaline leachate is sodium hydroxide or potassium hydroxide, with a concentration of 1-2 mol / L.

4. The method according to claim 2, characterized in that, During leaching, the liquid-to-solid mass ratio is 8-15:

1.

5. The method according to any one of claims 1-4, characterized in that, The leaching temperature in step (2) is 15-25℃.

6. The method according to any one of claims 1-4, characterized in that, The silicon inhibitor is one or more of sodium nitrate, potassium nitrate, sodium nitrite, and potassium nitrite, and the molar ratio of silicon inhibitor to alkali in the alkaline leachate is (0.4-1):

10.

7. The method according to claim 1, characterized in that, In step (2), a membrane filtration system with a membrane pore size of 0.1 μm is used for solid-liquid separation and silica colloid retention.

8. The method according to any one of claims 1-4, characterized in that, In step (2), a gradient cooling leaching process is adopted, with the temperature decreasing by 1-4℃ every 10 minutes, and the total leaching time is 50-60 minutes.

9. The method according to claim 8, characterized in that, In step (2), the final leaching temperature is stabilized at 8-12℃.

10. The method according to any one of claims 1-4 and 9, characterized in that, In step (1), the waste photovoltaic cells are crushed to a mesh size of 50 or higher.

11. The method according to claim 10, characterized in that, In step (1), the waste photovoltaic cells are cleaned before crushing.

12. The method according to any one of claims 1-4, 9 and 11, characterized in that, The method further includes step (3): adding hydrochloric acid to the aluminum leaching solution to carry out a precipitation reaction, filtering and drying after the reaction is completed to obtain solid aluminum hydroxide.

13. The method according to claim 12, characterized in that, The aluminum hydroxide solid is subjected to multiple low-temperature cleanings to improve its purity, wherein the first low-temperature cleaning is performed at a temperature of 15-25°C and the second low-temperature cleaning is performed at a temperature of 10-15°C.

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