A combined treatment method for removing multi-metal impurities and organic residues in photovoltaic cutting silicon sludge

Abstract

The application discloses a combined treatment method for removing multi-metal impurities and organic residues in photovoltaic cutting silicon sludge, and belongs to the technical field of photovoltaic waste resource utilization and new energy material preparation, and comprises the following steps: pretreating the photovoltaic waste silicon sludge, performing high-temperature hydrogen-argon heat treatment, performing acid leaching after cooling, and then performing washing and drying, so that the removal of silicon dioxide and metal inclusions in the photovoltaic silicon sludge is completed. The application combines high-temperature heat treatment and wet acid leaching, and fully plays the synergistic effect of heat treatment and acid leaching. The removal rate of metal impurities and the purity of silicon are significantly improved, the consumption of acid liquid and the corrosion of silicon particles are reduced, and the silicon material recovery rate is improved. The process flow of the application is simple, the equipment requirement is low, the continuous production is suitable, and the application can be widely applied to the fields of lithium ion battery silicon-based negative electrode material, high-purity silicon powder and photovoltaic silicon resource recycling and the like.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic waste resource utilization and new energy material preparation technology, and particularly relates to a combined treatment method for removing polymetallic impurities and organic residues from photovoltaic cutting silicon mud. Background Technology

[0002] With the rapid development of the photovoltaic industry, a large amount of silicon sludge waste is generated during the slicing processes of monocrystalline and polycrystalline silicon. Silicon sludge mainly originates from diamond wire cutting, slurry cutting, and silicon wafer grinding. Its main component is high-purity silicon particles, accompanied by metal wear particles, silicon surface oxide layers, organic cutting fluid residues, and small amounts of inorganic salts and other impurities. Since silicon sludge still contains a large amount of high-value silicon resources, realizing the resource utilization and high-value utilization of silicon sludge has become an important research direction in the fields of photovoltaic circular economy and new energy materials.

[0003] Currently, silica sludge recovery mainly employs processes such as magnetic separation, acid washing, alkaline washing, and flotation. Magnetic separation can remove some ferromagnetic impurities, but it struggles to remove metal oxides and non-magnetic metal impurities coated on the surface of silicon particles. Acid washing can remove free metals and some metal oxides, but for metal inclusions coated or embedded in the surface of silicon particles, the acid solution struggles to fully contact the impurity interface, resulting in low removal efficiency. Furthermore, it requires high acid concentrations and long leaching times, increasing acid consumption and potentially causing silicon particle loss. Alkaline washing is primarily used to remove some surface oxide layers, but the alkaline solution also has a corrosive effect on the silicon matrix, easily leading to a reduction in silicon particle size and a decrease in recovery rate.

[0004] Furthermore, photovoltaic silicon sludge, when exposed to air and wet processing environments for extended periods, typically forms a dense silica oxide layer on the surface of silicon particles. This oxide layer not only reduces the purity of the silicon material but also readily coats or fixes metallic impurities such as iron, aluminum, copper, nickel, and calcium onto the silicon particle surface, forming stable metal inclusion structures. These inclusions hinder the diffusion of acid into the interior, making it difficult for traditional wet pickling to adequately remove deep impurities, thus affecting the purity and electrochemical performance of the final silicon material. For silicon-based anode materials in lithium-ion batteries, residual metallic impurities can induce side reactions, accelerating the formation of the solid electrolyte interphase (SEI) film and irreversible lithium-ion consumption; while a thicker surface oxide layer reduces the conductivity and initial coulombic efficiency of the silicon particles, thus necessitating deep impurity removal treatment.

[0005] In recent years, heat treatment-assisted impurity removal technology has gradually attracted attention. Existing research shows that high-temperature heat treatment under a hydrogen-containing protective atmosphere can effectively reduce metal oxides such as iron, copper, and nickel to elemental metals, weakening their bonding strength with silicon particles. Simultaneously, a high-temperature argon-hydrogen atmosphere can promote defect formation, porosity, and interface activation in the oxide layer structure on the silicon particle surface, enhancing the penetration of subsequent acid solutions into the oxide layer and inclusions, thus significantly improving the impurity removal effect. However, most existing technologies treat heat treatment as a standalone process step, lacking a systematic process design for the synergistic removal of surface oxide layers and metal inclusions in silicon sludge. Insufficient research on the synergistic mechanism between heat treatment and subsequent acid leaching results in room for further improvement in metal impurity removal rate, silicon recovery rate, and process stability.

[0006] Therefore, providing a method that can fully utilize a high-temperature argon-hydrogen mixed atmosphere to reduce metal oxides and activate the interface of the oxide layer on the surface of silicon particles, and then combine it with acid leaching to achieve efficient and synergistic removal of silica and metal inclusions, is of great significance for improving the purity of silicon mud, reducing acid consumption, reducing silicon loss, and realizing the high-value utilization of photovoltaic silicon mud. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention proposes a combined treatment method for removing polymetallic impurities and organic residues from photovoltaic cutting silicon mud.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge includes the following steps: The photovoltaic waste silica sludge is pretreated by high-temperature hydrogen-argon heat treatment, cooled and then acid leached, followed by washing and drying, which completes the removal of polymetallic impurities and organic residues from the photovoltaic silica sludge.

[0009] Beneficial effects: This invention utilizes an argon-hydrogen mixed atmosphere to perform high-temperature heat treatment on silica sludge. Under the action of the reducing atmosphere, the metal oxides such as iron, copper, and nickel in the silica sludge are reduced to their corresponding metals. At the same time, it promotes the reduction, interface activation, and structural loosening of the oxide layer on the surface of silicon particles, weakening the bonding strength between the oxide layer and metal inclusions and the silicon matrix. Subsequently, an acid leaching process is used to deeply remove impurities from the heat-treated silica sludge, allowing the acid to penetrate more fully to the surface of silicon particles and the interface of inclusions, achieving efficient removal of metal impurities and activated oxide layers. Meanwhile, the organic impurities are all water-soluble organic substances such as PEG, and the acid leaching process can remove organic residues simultaneously, thereby obtaining high-purity silicon materials.

[0010] Preferably, the photovoltaic waste silicon sludge is derived from the waste silicon sludge generated during the production of monocrystalline or polycrystalline silicon by diamond wire cutting, with a particle size of 0.1-100μm. The impurities contained therein include one or more of the following metal elements: iron, aluminum, copper, nickel, calcium, and magnesium, which exist in the form of elemental or oxide.

[0011] Preferably, the atmosphere for the high-temperature hydrogen-argon heat treatment is an Ar / H2 mixed gas, wherein the hydrogen gas fraction is 3-20%.

[0012] Preferably, the high-temperature hydrogen-argon heat treatment is performed at a temperature of 600-1100℃ for a time of 0.5-6 hours.

[0013] Preferably, the cooling is performed under a protective atmosphere to below 100°C.

[0014] Preferably, the leaching reagent used in the acid leaching includes an acid or an acid and a complexing agent; Preferably, the acid includes one or more of hydrochloric acid, nitric acid, sulfuric acid, and organic acids; The complexing agent includes one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, citric acid, and oxalic acid.

[0015] Preferably, the concentration of the acid is 3% to 30%; The mass concentration of the complexing agent is 1% to 20%; Preferably, the acid leaching temperature is 20-90℃ and the time is 0.5-8h.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: This invention organically combines high-temperature heat treatment with wet acid leaching, fully leveraging the synergistic effects of both methods. On one hand, the high-temperature argon-hydrogen mixed atmosphere effectively reduces metal oxides in silicon sludge, transforming them from a stable oxidized state to a metallic state and reducing their bonding strength with silicon particles. On the other hand, the high temperature causes numerous microcracks, lattice defects, and a loose structure in the oxide layer on the silicon particle surface, enhancing the wetting and penetration capabilities of the acid solution at the interface between the oxide layer and the metal inclusions. This ensures more thorough subsequent acid leaching, significantly improving the removal rate of metal impurities and silicon purity, reducing acid consumption and silicon particle corrosion, and increasing silicon material recovery rate. The process of this invention is simple, requires minimal equipment, and is suitable for continuous production. It can be widely applied in fields such as lithium-ion battery silicon-based anode materials, high-purity silicon powder, and photovoltaic silicon resource recycling. Detailed Implementation

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 are within the scope of protection of the present invention.

[0018] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to specific embodiments.

[0019] An embodiment of the present invention provides a combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge, comprising the following steps: The photovoltaic waste silica sludge is pretreated by high-temperature hydrogen-argon heat treatment, cooled and then acid leached, followed by washing and drying, which completes the removal of polymetallic impurities and organic residues from the photovoltaic silica sludge.

[0020] This invention utilizes an argon-hydrogen mixed atmosphere to perform high-temperature heat treatment on silica sludge. Under the action of the reducing atmosphere, the metal oxides such as iron, copper, and nickel in the silica sludge are reduced to their corresponding metals. At the same time, it promotes the defect formation, interface activation, and structural loosening of the oxide layer on the surface of silicon particles, weakening the bonding strength between the oxide layer and metal inclusions and the silicon matrix. Subsequently, an acid leaching process is used to deeply remove impurities from the heat-treated silica sludge, allowing the acid to penetrate more fully to the surface of silicon particles and the interface of inclusions, achieving efficient removal of metal impurities and activated oxide layers, thereby obtaining high-purity silicon materials.

[0021] In a preferred embodiment, the photovoltaic waste silicon sludge is derived from the waste silicon sludge generated during the production of monocrystalline or polycrystalline silicon by diamond wire cutting. The particle size is 0.1-100μm, and the metal elements contained in the impurities include one or more of iron, aluminum, copper, nickel, calcium, and magnesium. The above metal elements exist in the form of elemental substances or oxides.

[0022] In a preferred embodiment, the pretreatment includes one or more of magnetic separation, ultrasonic dispersion, sieving, degreasing, and pyrolysis.

[0023] In a preferred embodiment, the atmosphere for the high-temperature hydrogen-argon heat treatment is an Ar / H2 mixed gas, wherein the hydrogen gas fraction is 3-20%.

[0024] In a preferred embodiment, the high-temperature hydrogen-argon heat treatment is performed at a temperature of 600-1100°C for a duration of 0.5-6 hours.

[0025] In a preferred embodiment, the cooling is performed by cooling to below 100°C under a protective atmosphere.

[0026] In a preferred embodiment, the leaching reagent used for acid leaching includes an acid or an acid and a complexing agent; In a preferred embodiment, the acid includes one or more of hydrochloric acid, nitric acid, sulfuric acid, and organic acids; The complexing agent includes one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, citric acid, and oxalic acid.

[0027] In a preferred embodiment, the concentration of the acid is 3% to 30%; The mass concentration of the complexing agent is 1% to 20%; In a preferred embodiment, the acid leaching temperature is 20-90°C and the time is 0.5-8 hours.

[0028] Unless otherwise specified, all raw materials used in the embodiments of this invention were purchased through commercial channels; Among them, photovoltaic waste silicon sludge is taken from the silicon sludge produced by photovoltaic wafer cutting, and its chemical composition includes Si powder, metal residues and their oxides, organic lubricant PEG, etc.

[0029] Unless otherwise specified, room temperature or normal temperature in the embodiments of the present invention refers to 25±3℃.

[0030] Example 1 A combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge includes the following steps: (1) Take 1000 g of photovoltaic waste silicon sludge generated during the cutting of photovoltaic monocrystalline silicon. After thorough washing with deionized water, dry it under vacuum at 80 ℃ for 12 h to remove residual cutting fluid and moisture from the surface. Place the dried waste silicon sludge in a quartz boat and put it into a tube furnace. Remove the air from the furnace under the protection of high-purity argon. When the oxygen content drops below 100 ppm, introduce a mixture of 5% hydrogen and 95% argon as a protective atmosphere. Heat the furnace to 700 ℃ at a heating rate of 5 ℃ / min and hold for 2 h for heat treatment. This reduces the iron oxides, copper oxides, and nickel oxides in the waste silicon sludge and promotes the formation of defect structures and loose interfaces on the surface oxide layer of silicon particles. After the heat treatment, continue to cool the sample to below 100 ℃ while maintaining the argon-hydrogen mixed atmosphere. Take out the sample to obtain the heat-treated silicon sludge.

[0031] (2) The heat-treated silica mud was added to a 10% hydrochloric acid solution and stirred and leached at 60 °C for 2 h. After acid leaching, the filtrate was repeatedly washed with deionized water until the pH of the filtrate was close to neutral. Then it was vacuum filtered and dried at 80 °C for 12 h to obtain the purified silica mud.

[0032] Example 2 A combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge includes the following steps: (1) Take 1000 g of photovoltaic waste silicon sludge generated during the cutting of photovoltaic monocrystalline silicon. After thorough washing with deionized water, dry it under vacuum at 80 ℃ for 12 h to remove residual cutting fluid and moisture from the surface. Place the dried waste silicon sludge in a quartz boat and put it into a tube furnace. Remove the air from the furnace under the protection of high-purity argon. When the oxygen content drops below 100 ppm, introduce a mixture of 10% hydrogen and 90% argon as a protective atmosphere. Heat the furnace to 850 ℃ at a heating rate of 8 ℃ / min and hold for 3 h for heat treatment. This reduces the iron oxides, copper oxides, and nickel oxides in the waste silicon sludge. The higher temperature and higher hydrogen concentration further promote the conversion of metal oxides to the metallic state and enhance the interfacial activation of the oxide layer on the surface of silicon particles, so that the metal particles wrapped inside the oxide layer are gradually exposed to the particle surface. After the heat treatment, continue to cool to room temperature while maintaining the argon-hydrogen mixed atmosphere. Take out the sample to obtain the heat-treated silicon sludge.

[0033] (2) The heat-treated silica mud was added to a mixed solution of 8% hydrochloric acid and 2% citric acid and stirred and leached at 70 °C for 3 h. Citric acid can further complex metal ions such as iron, aluminum and calcium, and improve the migration ability of metal impurities. After washing, vacuum filtration and drying at 80 °C for 12 h, the purified silica mud was obtained.

[0034] Example 3 A combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge includes the following steps: (1) Take 1000 g of photovoltaic waste silicon sludge generated during the cutting of photovoltaic monocrystalline silicon. After thorough washing with deionized water, dry it under vacuum at 80 ℃ for 12 h to remove residual cutting fluid and moisture from the surface. Place the dried waste silicon sludge in a quartz boat and put it into a tube furnace. Remove the air from the furnace under the protection of high-purity argon. When the oxygen content drops below 100 ppm, introduce a mixture of 15% hydrogen and 85% argon as a protective atmosphere. Heat the furnace to 950 ℃ at a heating rate of 10 ℃ / min and hold for 1.5 h for heat treatment. This reduces the iron oxides, copper oxides, and nickel oxides in the waste silicon sludge and promotes the formation of defect structures and loose interfaces on the surface oxide layer of silicon particles. A large number of nanoscale interface defects and microcracks are formed on the surface of silicon particles, which significantly improves the subsequent acid penetration efficiency. After the heat treatment, continue to cool to room temperature while maintaining the argon-hydrogen mixed atmosphere. Take out the sample to obtain the heat-treated silicon sludge.

[0035] (2) The heat-treated silica mud was added to a mixed solution of 5% hydrochloric acid and 2% oxalic acid and stirred and leached at 80 °C for 3 h. Oxalic acid can form a stable complex with iron ions, which accelerates the removal of residual iron impurities. After repeated washing with deionized water and drying at 80 °C for 12 h, the purified silica mud was obtained.

[0036] Comparative Example 1 The only difference from Example 1 is that, instead of high-temperature argon-hydrogen heat treatment, a 10% hydrochloric acid solution was directly used for leaching at 60 °C for 2 hours. All other process steps and parameters are the same as in Example 1, specifically including the following steps: 1000 g of photovoltaic waste silicon sludge generated during the cutting of photovoltaic monocrystalline silicon was thoroughly washed with deionized water and then vacuum dried at 80℃ for 12 h to remove residual cutting fluid and moisture from the surface. The dried waste silicon sludge was then added to a 10% hydrochloric acid solution and leached with stirring at 60℃ for 2 h. After acid leaching, the sludge was repeatedly washed with deionized water until the pH of the filtrate was close to neutral. The filtrate was then vacuum filtered and dried at 80℃ for 12 h to obtain purified silicon sludge.

[0037] Comparative Example 2 The only difference from Example 1 is that the high-temperature argon-hydrogen heat treatment conditions are: heating to 300°C at a heating rate of 5°C / min and holding at that temperature for 3 hours, specifically including the following steps: (1) Take 1000 g of photovoltaic waste silicon sludge generated during the cutting of photovoltaic monocrystalline silicon. After thorough washing with deionized water, dry it under vacuum at 80 ℃ for 12 h to remove residual cutting fluid and moisture from the surface. Place the dried waste silicon sludge in a quartz boat and put it into a tube furnace. Remove the air from the furnace under the protection of high-purity argon. When the oxygen content drops below 100 ppm, introduce a mixture of 5% hydrogen and 95% argon as a protective atmosphere. Heat the furnace to 300 ℃ at a heating rate of 5 ℃ / min and hold for 3 h for heat treatment. This reduces the iron oxides, copper oxides, and nickel oxides in the waste silicon sludge and promotes the formation of defect structures and loose interfaces on the surface oxide layer of silicon particles. After the heat treatment, continue to cool the sample to below 100 ℃ while maintaining the argon-hydrogen mixed atmosphere. Take out the sample to obtain the heat-treated silicon sludge.

[0038] (2) The heat-treated silica mud was added to a 10% hydrochloric acid solution and stirred and leached at 60 °C for 2 h. After acid leaching, the filtrate was repeatedly washed with deionized water until the pH of the filtrate was close to neutral. Then it was vacuum filtered and dried at 80 °C for 12 h to obtain the purified silica mud.

[0039] Comparative Example 3 The only difference from Example 1 is that the protective atmosphere during the heat treatment process does not include hydrogen; only argon is introduced as the protective atmosphere. Specifically, the process includes the following steps: (1) Take 1000 g of photovoltaic waste silicon sludge generated during the cutting of photovoltaic monocrystalline silicon. After thorough washing with deionized water, dry it under vacuum at 80 ℃ for 12 h to remove residual cutting fluid and moisture from the surface. Place the dried waste silicon sludge in a quartz boat and put it into a tube furnace. Remove the air from the furnace under the protection of high-purity argon. When the oxygen content drops below 100 ppm, continue to introduce argon as a protective atmosphere. Heat the furnace to 700 ℃ at a heating rate of 5 ℃ / min and hold for 2 h for heat treatment. After the heat treatment, continue to cool the furnace to below 100 ℃ while maintaining the argon atmosphere. Take out the sample to obtain the heat-treated silicon sludge.

[0040] (2) The heat-treated silica mud was added to a 10% hydrochloric acid solution and stirred and leached at 60 °C for 2 h. After acid leaching, the filtrate was repeatedly washed with deionized water until the pH of the filtrate was close to neutral. Then it was vacuum filtered and dried at 80 °C for 12 h to obtain the purified silica mud.

[0041] Comparative Example 4 The only difference from Example 1 is that the protective atmosphere during the heat treatment process is replaced with nitrogen, specifically including the following steps: (1) Take 1000 g of photovoltaic waste silicon sludge generated during the cutting of photovoltaic monocrystalline silicon. After thorough washing with deionized water, dry it under vacuum at 80 ℃ for 12 h to remove residual cutting fluid and moisture from the surface. Place the dried waste silicon sludge in a quartz boat and put it into a tube furnace. Remove the air from the furnace under the protection of high-purity argon. When the oxygen content drops below 100 ppm, introduce nitrogen gas as a protective atmosphere and heat it to 700 ℃ at a heating rate of 5 ℃ / min and hold for 2 h for heat treatment. After the heat treatment, continue to cool it to below 100 ℃ while maintaining the nitrogen atmosphere. Take out the sample to obtain the heat-treated silicon sludge.

[0042] (2) The heat-treated silica mud was added to a 10% hydrochloric acid solution and stirred and leached at 60 °C for 2 h. After acid leaching, the filtrate was repeatedly washed with deionized water until the pH of the filtrate was close to neutral. Then it was vacuum filtered and dried at 80 °C for 12 h to obtain the purified silica mud.

[0043] Technical effects: 1. Oxygen content and heavy metal impurity removal rate The levels of heavy metal impurities, oxygen content, and silicon purity in the purified silica mud obtained in Examples 1-3 and Comparative Examples 1-4 were detected using ICP, and the impurity removal rate was calculated. The results are shown in Table 1. Table 1 As can be seen, in Comparative Example 1, because the silicon particle surface still has a relatively complete oxide layer and coating structure, the acid solution has difficulty penetrating into the interior of the oxide layer, resulting in the metal impurities wrapped on the silicon particle surface not being fully dissolved, and only some of the free metal particles exposed on the particle surface are removed.

[0044] 2. Organic residue removal rate The levels of residual organic impurities in the purified silica mud obtained in Examples 1-3 and Comparative Examples 1-4 were detected using the TGA method, and the impurity removal rate was calculated. The results are shown in Table 2. Table 2 As can be seen, in Comparative Example 1, because the silicon particle surface still has a relatively complete oxide layer and coating structure, the acid solution has difficulty penetrating into the interior of the oxide layer, resulting in the organic matter wrapped on the silicon particle surface not being fully dissolved, and only some of the organic matter exposed on the particle surface being removed.

[0045] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge, characterized in that, Includes the following steps: The photovoltaic waste silica sludge is pretreated by high-temperature hydrogen-argon heat treatment, cooled and then acid leached, followed by washing and drying, which completes the removal of polymetallic impurities and organic residues from the photovoltaic silica sludge.

2. The combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge according to claim 1, characterized in that, The photovoltaic waste silicon sludge comes from the waste silicon sludge generated during the production of monocrystalline or polycrystalline silicon by diamond wire cutting. The particle size is 0.1-100μm, and the metal elements contained in the impurities include one or more of iron, aluminum, copper, nickel, calcium, and magnesium.

3. The combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge according to claim 1, characterized in that, The atmosphere for the high-temperature hydrogen-argon heat treatment is an Ar / H2 mixed gas, wherein the hydrogen gas fraction is 3-20%.

4. The combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge according to claim 1, characterized in that, The high-temperature hydrogen-argon heat treatment is performed at a temperature of 600-1100℃ for a time of 0.5-6 hours.

5. The combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge according to claim 1, characterized in that, The cooling is performed under a protective atmosphere to below 100°C.

6. The combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge according to claim 1, characterized in that, The leaching reagents used in the acid leaching include acids or acids and complexing agents.

7. The combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge according to claim 6, characterized in that, The acid includes one or more of hydrochloric acid, nitric acid, sulfuric acid, and organic acids; The complexing agent includes one or more of ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid, citric acid, and oxalic acid.

8. The combined treatment method for removing multi-metallic impurities and organic residues from photovoltaic cutting silicon sludge according to claim 1, characterized in that, The acid leaching temperature is 20-90℃, and the time is 0.5-8h.

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