Method for reducing oxygen content of photovoltaic silicon sludge

Abstract

The invention discloses a method for reducing the oxygen content of photovoltaic silicon sludge, which comprises the following steps: adding photovoltaic silicon sludge into a pickling solution which is an ammonium fluoride solution or a mixed solution of ammonium fluoride and hydrochloric acid, stirring for reaction, separating a solid product, washing the solid product with water, and drying to obtain purified silicon particles; the mass ratio of the photovoltaic silicon sludge to the pickling solution is 1: (10-60); the concentration of the ammonium fluoride solution is 0.5-10 mol / L, and in the mixed solution of ammonium fluoride and hydrochloric acid, the concentration of ammonium fluoride is 0.5-10 mol / L, and the concentration of hydrochloric acid is 0.5-5 mol / L. According to the method, the steps of acid pickling solution adding, stirring reaction, solid product separation, water washing and drying are carried out, the steps are relatively simple and easy to implement, and meanwhile, the oxygen content of the photovoltaic silicon sludge is effectively reduced in combination with control over the adding amount and concentration of the acid pickling solution in the reaction process.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon material recycling and utilization, and relates to a method for reducing the oxygen content of photovoltaic silicon mud. Background Art

[0002] As the output of photovoltaic modules increases year by year, the amount of silicon mud produced by diamond wire cutting in the production of silicon wafers, the core component of photovoltaic modules, increases year by year. The increasing amount of silicon mud may cause huge waste of resources and serious environmental pollution. At present, photovoltaic silicon mud is used to prepare high-purity silicon, silicon-containing alloys, electrode materials and hydrogen production materials. However, in the diamond wire silicon wafer cutting, due to the high local temperature during cutting, a layer of silicon dioxide oxide layer is formed on the surface of the cut silicon particles. Conventional physical separation methods cannot effectively remove the silicon oxide layer, which reduces the purity of the silicon particles separated from the silicon mud and greatly limits the recycling and reuse of photovoltaic silicon mud.

[0003] Chinese patents CN103373731B and CN102642837B introduce the process of smelting polysilicon through multiple purifications. Chinese patent CN105692624B uses thermal reduction to generate industrial silicon. Chinese patent application CN106082234A uses a medium frequency furnace to add slag agent for smelting. However, these prior arts use multiple and complicated processes and are unable to effectively remove metal impurities and the surface layer of silicon dioxide. They are not only costly, but also cause serious secondary pollution to the environment, resulting in excessive loss and waste of raw materials. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a method for reducing the oxygen content of photovoltaic silicon mud, thereby solving the technical problem that the prior art cannot effectively remove metal impurities in photovoltaic silicon mud and the surface layer of silicon dioxide.

[0005] The present invention is achieved through the following technical solutions: A method for reducing the oxygen content of photovoltaic silicon mud comprises the following steps: adding photovoltaic silicon mud to a pickling solution, wherein the pickling solution is an ammonium fluoride solution or a mixed solution of ammonium fluoride and hydrochloric acid, stirring for reaction, separating a solid product, washing the solid product with water, and drying to obtain purified silicon particles; the mass ratio of the photovoltaic silicon mud to the pickling solution is 1:(10-60); the concentration of the ammonium fluoride solution is 0.5-10 mol / L, and in the mixed solution of ammonium fluoride and hydrochloric acid, the concentration of ammonium fluoride is 0.5-10 mol / L, and the concentration of hydrochloric acid is 0.5-5 mol / L.

[0006] Preferably, during the stirring reaction, the stirring rate is 100-1000 r / min, the reaction temperature is 5-40° C., and the reaction time is 5-30 min.

[0007] Preferably, after the stirring reaction, when the solid reaction product is separated, the separation method is vacuum filtration.

[0008] Preferably, during the vacuum filtration process, the vacuum degree is less than 1000 Pa and the filtration time is 10 to 30 minutes.

[0009] Preferably, when the solid product is washed with water, it is washed 3 to 4 times.

[0010] Preferably, the drying process is specifically performed by vacuum drying at room temperature. Preferably, during the vacuum drying process, the vacuum degree is less than 1000 Pa and the processing time is 0.5 to 12 hours.

[0011] Preferably, the photovoltaic silicon mud includes elemental silicon, silicon oxide, metal and non-metal impurities and water-based cutting fluid.

[0012] A photovoltaic silicon mud is treated by the above method, and the oxygen content in the photovoltaic silicon mud after the treatment is as low as 1.31%.

[0013] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention discloses a method for reducing the oxygen content of photovoltaic silicon mud. By using ammonium fluoride solution or a mixed solution of ammonium fluoride and hydrochloric acid as a pickling liquid, the pickling liquid can react chemically with silicon dioxide to generate soluble silicate or silicon tetrafluoride, and then remove the silicon dioxide layer through a washing process. At the same time, it can effectively react with metal impurities in photovoltaic silicon mud, further improving the purity of silicon particles. The selectivity of this chemical reaction is high, and the effective removal of impurities can be ensured. In the method, the mass ratio of photovoltaic silicon mud to the pickling liquid is 1: (10~60), and at the same time, the concentration of the ammonium fluoride solution is 0.5~10 mol / L. In the mixed solution of ammonium fluoride and hydrochloric acid, the concentration of ammonium fluoride is 0.5~10 mol / L, and the concentration of hydrochloric acid is 0.5~5 mol / L, which ensures sufficient contact and reaction between the pickling liquid and the photovoltaic silicon mud. A higher pickling liquid ratio helps to accelerate the reaction process and improve the efficiency of removing metal impurities and silicon dioxide. The method comprises adding a pickling solution, and then performing stirring reaction, separating solid products, washing with water and drying steps. These steps are relatively simple and easy to implement. At the same time, combined with the control of the amount of pickling solution added and the concentration during the reaction process, the oxygen content of the photovoltaic silicon mud is effectively reduced.

[0014] Furthermore, another inventive point of the present invention is that during the stirring reaction, the stirring rate is 100-1000 r / min, the reaction temperature is 5-40°C, and the reaction time is 5-30min. First, the stirring rate is within the range of 100-1000 r / min, which can ensure that the pickling solution and the photovoltaic silicon mud are fully mixed and accelerate the rate of the chemical reaction. A higher stirring rate helps to break the diffusion barrier between the reactants and promote effective contact between the reactant molecules, thereby improving the reaction efficiency; secondly, the reaction temperature is within the range of 5-40°C, which not only avoids the side reactions and material degradation that may be caused by excessively high temperatures, but also ensures that the chemical reaction can proceed smoothly. This temperature range helps to maintain the stability of the reaction system while reducing energy consumption and safety hazards. The temperature is higher than 40°C, which increases the oxygen content on the surface of the product, which is not conducive to the purification process. In addition, the reaction time is controlled within 5-30min, which not only ensures that the reaction can be fully carried out, but also avoids the increase in energy consumption and the decrease in product quality that may be caused by too long a reaction time. By precisely controlling the stirring rate, reaction temperature and reaction time, the reaction process can be optimized and the occurrence of side reactions can be reduced, thereby obtaining a purer and higher quality silicon particle product. This helps to improve the efficiency of removing oxygen from silicon mud. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0016] Figure 1 This is a schematic diagram of the process of reducing the oxygen content of photovoltaic silicon mud according to the present invention; Figure 2 This is a comparison chart of the oxygen content of silicon particles obtained in Examples 1 to 3 of the present invention; Figure 3 TEM test images of untreated photovoltaic silicon mud and silicon particles obtained in Example 3; Figure 4 This is a comparison chart of the oxygen content in silicon particles obtained in Examples 3 and 6 and Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0018] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0019] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0020] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0021] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0022] like Figure 1 As shown, the present invention provides a method for reducing the oxygen content of photovoltaic silicon mud, comprising the following steps: adding photovoltaic silicon mud to an acid washing liquid, wherein the acid washing liquid is an ammonium fluoride solution or a mixed solution of ammonium fluoride and hydrochloric acid, stirring the reaction at a stirring rate of 100-1000 r / min and a temperature of 5-40°C for 5-30 minutes, separating the solid product by vacuum filtration, wherein during the vacuum filtration process, the vacuum degree is less than 1000Pa, and the filtration time is 10-30 minutes, after filtration, and washing the solid product with water for 3-4 times, and performing vacuum drying treatment at room temperature, wherein during the vacuum drying treatment process, the vacuum degree is less than 1000Pa, and the treatment time is 0.5-12 hours, to obtain purified silicon particles; the mass ratio of the photovoltaic silicon mud to the acid washing liquid is 1:(10-60); the concentration of the ammonium fluoride solution is 0.5-10 mol / L, and the concentration of ammonium fluoride in the mixed solution of ammonium fluoride and hydrochloric acid is 0.5-10 mol / L, the concentration of hydrochloric acid is 0.5~5 mol / L. The photovoltaic silicon mud includes elemental silicon, silicon oxide, metal and non-metal impurities and water-based cutting fluid.

[0023] The photovoltaic silicon mud in the present invention comes from the solid waste silicon mud generated during the diamond wire cutting process of silicon wafers, the core component of photovoltaic modules.

[0024] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0025] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0026] Example 1 This embodiment provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare a 1.35 mol / L ammonium fluoride solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 20°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0027] By testing the oxygen content before and after the pickling treatment of photovoltaic silicon mud, it was found that the original oxygen content of the photovoltaic silicon mud was 6.03%. The oxygen content of the photovoltaic silicon mud pickled by this method was reduced to 4.43%, and the oxygen removal rate was 26.53%.

[0028] Example 2 This embodiment provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare a 2.7 mol / L ammonium fluoride solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 20°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0029] By testing the oxygen content before and after the pickling treatment of photovoltaic silicon mud, it was found that the original oxygen content of photovoltaic silicon mud was 6.03%. The oxygen content of photovoltaic silicon mud pickled by this method was reduced to 3.12%, and the oxygen removal rate was 48.26%.

[0030] Example 3 This embodiment provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare 2.7 mol / L ammonium fluoride solution and 1.12 mol / L hydrochloric acid solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 20°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0031] By testing the oxygen content before and after the pickling treatment of photovoltaic silicon mud, it was found that the original oxygen content of photovoltaic silicon mud was 6.03%. The oxygen content of photovoltaic silicon mud pickled by this method was reduced to 1.31%, and the oxygen removal rate was 78.3%.

[0032] Example 4 This embodiment provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare a 1.35 mol / L ammonium fluoride solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 30°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0033] By testing the oxygen content before and after the pickling treatment of photovoltaic silicon mud, it was found that the original oxygen content of photovoltaic silicon mud was 6.03%. The oxygen content of photovoltaic silicon mud pickled by this method was reduced to 3.87%, and the oxygen removal rate was 35.82%.

[0034] Example 5 This embodiment provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare a 1.35 mol / L ammonium fluoride solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:20, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 40°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0035] By testing the oxygen content before and after the pickling treatment of photovoltaic silicon mud, it was found that the original oxygen content of the photovoltaic silicon mud was 6.03%. The oxygen content of the photovoltaic silicon mud pickled by this method was reduced to 5.3%, and the oxygen removal rate was 12.17%.

[0036] Example 6 This embodiment provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare 2.7 mol / L ammonium fluoride solution and 1.12 mol / L hydrochloric acid solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 40°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0037] By testing the oxygen content before and after the pickling treatment of photovoltaic silicon mud, it was found that the original oxygen content of photovoltaic silicon mud was 6.03%. The oxygen content of photovoltaic silicon mud pickled by this method was reduced to 4.77%, and the oxygen removal rate was 20.88%.

[0038] Comparative Example 1 This comparative example provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare a 1.35 mol / L ammonium fluoride solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 50°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0039] Through the detection of oxygen content before and after pickling treatment of photovoltaic silicon mud, it can be known that the original oxygen content of photovoltaic silicon mud is 6.03%. The oxygen content of photovoltaic silicon mud pickled by this method has not decreased but increased, and the oxygen content is 12.83%.

[0040] Comparative Example 2 This comparative example provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare a 2.7 mol / L ammonium fluoride solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 50°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0041] Through the detection of oxygen content before and after pickling treatment of photovoltaic silicon mud, it can be known that the original oxygen content of photovoltaic silicon mud is 6.03%. The oxygen content of photovoltaic silicon mud pickled by this method has not decreased but increased, and the oxygen content is 29.47%.

[0042] Comparative Example 3 This comparative example provides a method for reducing the oxygen content of photovoltaic silicon mud, the method comprising the following steps: (1) Use a polytetrafluoroethylene beaker to prepare 2.7 mol / L ammonium fluoride solution and 1.12 mol / L hydrochloric acid solution to obtain an acid wash solution; (2) Mixing photovoltaic silicon mud and pickling solution in a mass ratio of 1:40, and then pouring the photovoltaic silicon mud into a polytetrafluoroethylene beaker to obtain a mixed solution of photovoltaic silicon mud and pickling solution; (3) Place the polytetrafluoroethylene beaker containing the mixed solution in a magnetic stirring device at a stirring rate of 600 r / min, a temperature of 60°C, and a duration of 30 min to obtain a mixed solution after the reaction is completed; (4) Pour the reaction mixture into a Buchner funnel connected to a vacuum filtration device and equipped with filter paper, and filter out the acid wash solution by the first filtration; then add pure water to the Buchner funnel for washing, and repeat the washing process 3 to 4 times to obtain pure silicon particles containing water on the filter paper; (5) The pure silicon particles containing water and the filter paper are placed in a vacuum drying oven and dried at room temperature to obtain silicon particles with low oxygen content.

[0043] Through the detection of oxygen content before and after pickling treatment of photovoltaic silicon mud, it can be known that the original oxygen content of photovoltaic silicon mud is 6.03%. The oxygen content of photovoltaic silicon mud pickled by this method has not decreased but increased, and the oxygen content is 25.85%.

[0044] Figure 2 The oxygen content of silicon particles obtained from photovoltaic silicon mud in Examples 1 to 3 of the present invention is compared to investigate the effects of different pickling solution concentrations and types on the oxygen content of photovoltaic silicon mud. Figure 2 It can be seen that when the concentration of ammonium fluoride solution increases, the oxygen content of photovoltaic silicon mud decreases significantly; when the concentration of ammonium fluoride solution remains unchanged and the hydrochloric acid solution is introduced, the oxygen content of photovoltaic silicon mud further decreases.

[0045] Figure 3 The TEM test images of untreated photovoltaic silicon mud and silicon particles obtained in Example 3 show that the silicon dioxide layer on the surface of silicon particles in the photovoltaic silicon mud is significantly reduced after being cleaned with a mixed solution of ammonium fluoride and hydrochloric acid.

[0046] Figure 2 and Figure 3 The feasibility of the method for reducing the oxygen content of photovoltaic silicon mud described in the present invention is confirmed.

[0047] Figure 4 The oxygen content in silicon particles obtained in Examples 3 and 6 and Comparative Example 3 of the present invention is compared, and the effect of different stirring temperatures on oxygen removal is investigated. Figure 4 It can be seen that when the stirring temperature increases from 20°C to 40°C, the oxygen content in the photovoltaic silicon mud increases significantly, but it still has a deoxygenation effect. When the temperature further increases to 60°C, the oxidation rate of silicon in the photovoltaic silicon mud is greater than the removal rate of silicon oxide, and the oxygen content increases significantly. Therefore, too high a temperature is not conducive to the control of the oxygen content on the surface of silicon particles.

[0048] Example 7 A method for reducing the oxygen content of photovoltaic silicon mud comprises the following steps: adding photovoltaic silicon mud to a pickling solution, wherein the pickling solution is an ammonium fluoride solution, stirring the reaction for 30 minutes at a stirring rate of 100 r / min and a temperature of 5°C, separating a solid product by vacuum filtration, wherein during the vacuum filtration process, the vacuum degree is less than 1000Pa, and the filtration time is 10 minutes, and after the filtration, the solid product is washed with water for 3 times, and vacuum dried at room temperature, wherein during the vacuum drying process, the vacuum degree is less than 1000Pa, and the treatment time is 0.5h, to obtain purified silicon particles; the mass ratio of the photovoltaic silicon mud to the pickling solution is 1:10; and the concentration of the ammonium fluoride solution is 0.5 mol / L.

[0049] Example 8 A method for reducing the oxygen content of photovoltaic silicon mud comprises the following steps: adding photovoltaic silicon mud to a pickling solution, wherein the pickling solution is a mixed solution of ammonium fluoride and hydrochloric acid, stirring the mixture at a stirring rate of 1000 r / min and a temperature of 40°C for a reaction of 5 minutes, separating a solid product by vacuum filtration, wherein during the vacuum filtration, the vacuum degree is less than 1000 Pa, and the filtration time is 30 minutes, and after the filtration, washing the solid product with water for 4 times, performing a vacuum drying treatment at room temperature, wherein during the vacuum drying treatment, the vacuum degree is less than 1000 Pa, and the treatment time is 12 hours, to obtain purified silicon particles; the mass ratio of the photovoltaic silicon mud to the pickling solution is 1:60; in the mixed solution of ammonium fluoride and hydrochloric acid, the concentration of ammonium fluoride is 10 mol / L, and the concentration of hydrochloric acid is 5 mol / L.

[0050] Example 9 A method for reducing the oxygen content of photovoltaic silicon mud comprises the following steps: adding photovoltaic silicon mud to a pickling solution, stirring the mixed solution of ammonium fluoride and hydrochloric acid at a stirring rate of 500 r / min and a temperature of 30°C for reaction for 20 minutes, separating solid products by vacuum filtration, wherein during the vacuum filtration process, the vacuum degree is less than 1000 Pa, and the filtration time is 20 minutes, and after the filtration, washing the solid product with water for 3 times, performing vacuum drying treatment at room temperature, wherein during the vacuum drying treatment process, the vacuum degree is less than 1000 Pa, and the treatment time is 8 hours, to obtain purified silicon particles; the mass ratio of the photovoltaic silicon mud to the pickling solution is 1:40; in the mixed solution of ammonium fluoride and hydrochloric acid, the concentration of ammonium fluoride is 8 mol / L, and the concentration of hydrochloric acid is 2 mol / L.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for reducing the oxygen content of photovoltaic silicon mud, characterized in that: The photovoltaic silicon mud is added to the pickling liquid, wherein the pickling liquid is an ammonium fluoride solution or a mixed solution of ammonium fluoride and hydrochloric acid. After stirring for reaction, the solid product is separated, and the solid product is washed with water and dried to obtain purified silicon particles. The mass ratio of the photovoltaic silicon mud to the pickling liquid is 1:(10~60); the concentration of the ammonium fluoride solution is 0.5~10 mol / L, and in the mixed solution of ammonium fluoride and hydrochloric acid, the concentration of ammonium fluoride is 0.5~10 mol / L, and the concentration of hydrochloric acid is 0.5~5 mol / L.

2. A method for reducing the oxygen content of photovoltaic silicon mud according to claim 1, characterized in that: During the stirring reaction, the stirring rate is 100-1000 r / min, the reaction temperature is 5-40° C., and the reaction time is 5-30 min.

3. A method for reducing the oxygen content of photovoltaic silicon mud according to claim 1, characterized in that: After stirring the reaction, the solid product of the reaction is separated by vacuum filtration.

4. A method for reducing the oxygen content of photovoltaic silicon mud according to claim 3, characterized in that: During the vacuum filtration process, the vacuum degree is less than 1000 Pa and the filtration time is 10 to 30 minutes.

5. The method for reducing the oxygen content of photovoltaic silicon mud according to claim 1, characterized in that: When the solid product is washed with water, wash it 3 to 4 times.

6. A method for reducing the oxygen content of photovoltaic silicon mud according to claim 1, characterized in that: The drying process is specifically to perform vacuum drying at room temperature.

7. A method for reducing the oxygen content of photovoltaic silicon mud according to claim 6, characterized in that: During the vacuum drying process, the vacuum degree is less than 1000 Pa and the processing time is 0.5 to 12 hours.

8. A method for reducing the oxygen content of photovoltaic silicon mud according to claim 1, characterized in that: The photovoltaic silicon mud comprises elemental silicon, silicon oxide, metal and non-metal impurities and water-based cutting fluid.

9. A photovoltaic silicon mud, characterized in that: The photovoltaic silicon mud is treated by the method described in any one of claims 1 to 8, and the oxygen content in the photovoltaic silicon mud after the treatment is as low as 1.31%.

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