A method of beneficiating silicon in a slurry of silicon cuttings by staged flotation

Abstract

The present application relates to a kind of segmented flotation enrichment silicon in silicon cutting waste slurry, belong to silicon secondary resources comprehensive utilization technical field.The present application breaks through the reagent selection of " cationic collector flotation silicon " for the existing direct flotation using dodecylamine and kerosene double reagent system, uses sodium oleate as single collector, and directly carries out flotation to low solid content silicon cutting waste slurry under natural pH=6~8 condition;While based on the variation law of silicon enrichment rate in flotation kinetics, the flotation process is divided into fast enrichment section and slow enrichment section for two-stage segmented control, and the total silicon recovery rate reaches more than 92.8%.The present application uses single sodium oleate, eliminates the defects of cationic collector foam viscous difficult filtration and kerosene flammable, and realizes the quantitative management of flotation process by segmented flotation control, shortens the flotation time.

Description

Technical Field

[0001] This invention relates to a method for enriching silicon in silicon cutting waste slurry by segmented flotation, belonging to the field of comprehensive utilization technology of silicon secondary resources. Background Technology

[0002] Diamond wire cutting is currently the mainstream cutting process for solar-grade monocrystalline silicon. However, this cutting process generates a large amount of silicon cutting waste slurry with low solids content, and approximately 25% to 30% of the total mass of high-purity silicon, namely micro-nano-level elemental silicon, is lost into the silicon cutting waste slurry. Since the initial nominal purity of micro-nano-level elemental silicon can reach 6N level, it has extremely high recycling value.

[0003] Currently, there are the following main technical routes for recovering silicon from silicon cutting waste slurry: Category 1: Flocculation-Filtration-Drying-Crushing Route. This technical route is currently the most widely used process in industrial applications. Its recycling process is as follows: First, flocculants are added to the cutting waste slurry with low solid content to cause silicon micropowder to agglomerate and settle. Then, solid-liquid separation is carried out through a plate and frame filter press. The filter cake is then dried and dehydrated to obtain solid blocks, commonly known as "silicon mud". Finally, the dried silicon mud blocks are crushed and screened to obtain primary silicon powder products. This technical route has the following defects: (1) Flocculants introduce organic or inorganic impurities, increasing the difficulty of subsequent purification; (2) The filtration process is inefficient and has a long processing cycle. Micro-nano silicon particles are easily oxidized; (3) The drying and crushing processes are repeated and generate dust pollution; (4) The silicon oxidation loss is large throughout the process, and the recovery rate is low.

[0004] Category Two: Direct Flotation Recovery Route. In recent years, our research team has attempted to directly apply flotation technology to the recovery of silicon from low-solids-content silicon cutting waste slurry. Our invention patent application, CN117839874A, describes a method for recovering silicon from crystalline silicon cutting waste slurry using flotation. It proposes using dodecylamine and kerosene as a combined collector for direct flotation of the primary slurry, achieving a silicon recovery rate of up to 98.2%, providing important technical verification for the direct flotation recovery of silicon cutting waste slurry. However, this technology still has the following technical shortcomings in practical applications: (1) Inherent defects of the reagent system. Dodecylamine is a cationic collector, which produces viscous foam with excessive foam stability, making defoaming difficult after flotation. The silica concentrate entrained in the foam is difficult to filter and dewater, increasing the cost of subsequent processing. At the same time, the optimal ratio of dodecylamine to kerosene needs to be frequently adjusted according to the fluctuations in the quality of the waste slurry, increasing the complexity of process control. In addition, kerosene is a flammable chemical, posing a fire and explosion hazard.

[0005] (2) The flotation control method relies on experience. This method uses a fixed flotation time of 24 minutes, which is an optimal value determined by experiments, but no quantitative control method based on the inherent laws of the flotation process has been established. The flotation endpoint depends on the operator's experience in judging the foam state. The flotation effect varies greatly between different operators and different batches, and the process stability is difficult to guarantee.

[0006] (3) Processing efficiency needs to be improved. The flotation time is relatively long, which takes up a lot of equipment time in actual production. Shortening the flotation time while ensuring the recovery rate is of great significance to improving production efficiency. Summary of the Invention

[0007] To address the shortcomings of existing direct flotation methods using a dual-reagent system of dodecylamine and kerosene, such as the difficulty in defoaming viscous foam, the safety hazard of kerosene's flammability, and the reliance on empirically determined flotation time and lack of quantitative control, this invention proposes a segmented flotation method for enriching silicon in silicon cutting waste slurry. This method overcomes the limitations of traditional cationic collector flotation of silicon by using sodium oleate as a single collector, directly flotating low-solids silicon cutting waste slurry under natural pH conditions of 6-8. Furthermore, based on the silicon enrichment rate variation law in flotation kinetics, the flotation process is divided into a rapid enrichment stage and a slow enrichment stage for two-stage segmented control, achieving a total silicon recovery rate of over 92.8%. This invention uses sodium oleate alone, eliminating the defects of cationic collectors such as viscous foam that is difficult to filter and kerosene's flammability. Simultaneously, segmented flotation control enables quantitative management of the flotation process, shortening the flotation time.

[0008] A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Fresh, untreated silicon cutting waste slurry with low solid content is stirred evenly and added to the flotation cell; the solid component in the silicon cutting waste slurry is micro-nano silicon particles; the silicon cutting waste slurry with low solid content has not undergone any flocculation, sedimentation, pressure filtration or drying pretreatment. (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry for 1 to 3 minutes at a pH of 6 to 8 to make the slurry evenly dispersed; (3) Add the collector sodium oleate solution to the silicon cutting waste slurry and stir for 3-8 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain the hydrophobic modified silicon slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5-6 L / min for rapid enrichment flotation for 6-8 min, and then air is introduced at a flow rate of 2-4 L / min for slow enrichment flotation for 10-20 min; during the rapid enrichment flotation stage, a batch of silica-enriched foam is collected every 1-2 min; during the slow enrichment flotation stage, a batch of silica-enriched foam is collected every 4-8 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate.

[0009] In step (1), the solid content of the silicon cutting waste slurry is 0.5~5wt%, the average particle size of silicon particles is 0.3~1μm, and the total content of metal impurities in the silicon cutting waste slurry is not higher than 1000ppmw.

[0010] Preferably, the volume ratio of water to silicon cutting waste slurry in step (2) is 0.1~0.5:1.

[0011] Preferably, the concentration of sodium oleate solution in step (3) is 2~5wt%, and the amount of sodium oleate solution added is 80~200mL / L based on the volume of silicon cutting waste slurry.

[0012] Preferably, the grade of the silicon concentrate in step (5) is 85~90wt%.

[0013] This invention organically combines the chemical adsorption mechanism of sodium oleate on silicon surfaces with segmented flotation quantitative control, forming a technical chain of "reagent selection → interfacial interaction → process control." This achieves a recovery rate of over 92.8% within a minimum of 16 minutes. The technical principles of this invention cover three aspects: silicon particle surface characteristics, the chemical adsorption mechanism of sodium oleate, and segmented flotation control. (1) Surface characteristics of silicon particles: During the cutting and slurry storage process, water molecules spontaneously adsorb onto the silicon surface, and with the formation of Si-O bonds, an amorphous SiO2 oxide film with a thickness of nanometers is formed on the surface of silicon particles, which changes the surface properties of silicon particles from hydrophobic elemental silicon to silicon dioxide surface with a certain degree of hydrophilicity; This surface characteristic determines that fatty acid collectors (such as sodium oleate) are suitable for flotation and extraction of silicon particles in silicon cutting waste slurry; (2) Chemical adsorption mechanism of sodium oleate: Sodium oleate hydrolyzes in aqueous solution to generate oleate ions (OL). - The O atom at the polar carboxyl head of the oleate ion can spontaneously form new chemical bonds such as O-Si with the Si atoms on the surface of the silicon particle, and new interface state energy levels appear in the band structure, thus resulting in chemisorption. After chemisorption is completed, the nonpolar long carbon chain of the oleate ion faces outward and forms a hydrophobic film on the surface of the silicon particle, enabling the silicon particle to selectively attach to the surface of the bubble and enter the foam layer, thereby achieving separation from water and hydrophilic impurities. (3) Segmented flotation control: Since the enrichment rate of silicon in the flotation process exhibits a two-stage characteristic of "fast at the beginning and slow at the end", the enrichment rate of silicon is the fastest in the first 6 to 8 minutes, which can contribute more than 70% of the total recovery rate; and then the enrichment rate slows down significantly. The physicochemical essence of this rule is that the silicon particle concentration is high in the early stage of flotation, the reagent adsorption is not saturated, and the probability of bubble collision is high, while in the later stage, the rate slows down due to the reduction of easily floatable particles, the decrease of reagent concentration, and the decrease of collision probability. Therefore, this invention divides the flotation process into a fast enrichment stage and a slow enrichment stage for quantitative control, realizing the leap from "experience judgment" to "quantitative control" in the flotation process.

[0014] The beneficial effects of this invention are: (1) The reagent system of the present invention is simplified from "two reagents" to "single reagent", which solves the inherent defects of cationic collectors; the anionic collector sodium oleate is used to replace the two reagent system, and hydrophobic modification is achieved by chemical adsorption of oleate ions on the silicon surface. This not only ensures the feasibility of flotation, but also eliminates the defect of viscous foam of cationic collectors, while avoiding the use of flammable kerosene and improving production safety. (2) The flotation control of this invention is upgraded from "experience judgment" to "quantitative control". Based on the flotation dynamics law, the flotation process is divided into a fast enrichment section and a slow enrichment section for segmented control, realizing the quantitative management of the flotation process, eliminating the uncertainty caused by the subjective judgment of the operator, and improving the process reproducibility and stability. (3) The processing efficiency of the present invention is significantly improved: while ensuring a recovery rate of over 92.8%, the total flotation time is reduced to a minimum of 16 minutes; (4) The present invention achieves the synergistic technical effect of "short process - single reagent - segmented control": it organically integrates three technical innovations: direct flotation eliminates pretreatment, simplifies the reagent system with a single sodium oleate reagent, and quantitative management of segmented flotation control, forming a complete "short process - single reagent - segmented control" technical solution, which has significant improvements in three dimensions: the degree of process simplification, the degree of reagent system simplification, and the controllability of the flotation process. Detailed Implementation

[0015] The present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0016] Example 1: The fresh, untreated low-solids silicon cutting waste slurry in this example was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano silicon particles with a solid content of 2.11 wt% and an average particle size of 0.52 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 7.2 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.25:1. (3) Add the collector sodium oleate solution (concentration of 2wt%) to the silicon cutting waste slurry and stir for 5 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 200mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5 L / min for rapid enrichment flotation for 6 min, and then air is introduced at a flow rate of 3.3 L / min for slow enrichment flotation for 10 min; during the rapid enrichment flotation stage, a batch of silica-enriched foam is collected every 2 min; during the slow enrichment flotation stage, a batch of silica-enriched foam is collected every 5 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 85.2 wt%, and the silicon recovery rate is 92.8%.

[0017] Example 2: In this example, the fresh, untreated silicon cutting waste slurry with low solids content was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano silicon particles with a solid content of 2.11 wt% and an average particle size of 0.52 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 7.4 for 1 minute to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.25:1. (3) Add the collector sodium oleate solution (concentration of 5wt%) to the silicon cutting waste slurry and stir for 8 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 100mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 6 L / min for rapid enrichment flotation for 8 min, and then air is introduced at a flow rate of 3 L / min for slow enrichment flotation for 12 min; during the rapid enrichment flotation stage, a batch of silica enriched foam is collected every 1 min; during the slow enrichment flotation stage, a batch of silica enriched foam is collected every 4 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 85.2 wt%, and the silicon recovery rate is 94.6%.

[0018] Example 3: In this example, the fresh, untreated silicon cutting waste slurry with low solids content was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano silicon particles with a solid content of 2.11 wt% and an average particle size of 0.52 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 7.1 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.25:1. (3) Add the collector sodium oleate solution (concentration of 3wt%) to the silicon cutting waste slurry and stir for 5 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 150mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5 L / min for rapid enrichment flotation for 7 min, and then air is introduced at a flow rate of 2 L / min for slow enrichment flotation for 12 min; during the rapid enrichment flotation stage, a batch of silica enriched foam is collected every 1 min; during the slow enrichment flotation stage, a batch of silica enriched foam is collected every 4 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 86.9 wt%, and the silicon recovery rate is 93.2%.

[0019] Example 4: In this example, the fresh, untreated silicon cutting waste slurry with low solids content was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano silicon particles with a solid content of 2.11 wt% and an average particle size of 0.52 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 7.8 for 3 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.4:1. (3) Add the collector sodium oleate solution (concentration of 5wt%) to the silicon cutting waste slurry and stir for 3min to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain the hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 80mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5 L / min for rapid enrichment flotation for 6 min, and then air is introduced at a flow rate of 3 L / min for slow enrichment flotation for 12 min; during the rapid enrichment flotation stage, a batch of silica enriched foam is collected every 2 min; during the slow enrichment flotation stage, a batch of silica enriched foam is collected every 4 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 89.3 wt%, and the silicon recovery rate is 94.7%.

[0020] Example 5: In this example, the fresh, untreated silicon cutting waste slurry with low solids content was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano silicon particles with a solid content of 2.11 wt% and an average particle size of 0.52 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 6.8 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.15:1. (3) Add the collector sodium oleate solution (concentration of 2wt%) to the silicon cutting waste slurry and stir for 5 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 200mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5 L / min for rapid enrichment flotation for 8 min, and then air is introduced at a flow rate of 3 L / min for slow enrichment flotation for 16 min; during the rapid enrichment flotation stage, a batch of silica enriched foam is collected every 2 min; during the slow enrichment flotation stage, a batch of silica enriched foam is collected every 4 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 87.3 wt%, and the silicon recovery rate is 93.1%.

[0021] Example 6: The fresh, untreated low-solids silicon cutting waste slurry in this example was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment; the solid components in the silicon cutting waste slurry were micro-nano-sized silicon particles, with a solid content of 3.5 wt% and an average particle size of 0.8 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 7.5 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.3:1. (3) Add the collector sodium oleate solution (concentration of 2wt%) to the silicon cutting waste slurry and stir for 5 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 180mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5.5 L / min for rapid enrichment flotation for 8 min, and then air is introduced at a flow rate of 3.3 L / min for slow enrichment flotation for 16 min; during the rapid enrichment flotation stage, a batch of silica-enriched foam is collected every 2 min; during the slow enrichment flotation stage, a batch of silica-enriched foam is collected every 4 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 89.8 wt%, and the silicon recovery rate is 94.7%.

[0022] Example 7: In this example, the fresh, untreated silicon cutting waste slurry with low solids content was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano-sized silicon particles with a solid content of 1 wt% and an average particle size of 0.8 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 7.0 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.20:1. (3) Add the collector sodium oleate solution (concentration of 2wt%) to the silicon cutting waste slurry and stir for 5min to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain the hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 80mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 6 L / min for rapid enrichment flotation for 8 min, and then air is introduced at a flow rate of 2 L / min for slow enrichment flotation for 16 min; during the rapid enrichment flotation stage, a batch of silica enriched foam is collected every 1 min; during the slow enrichment flotation stage, a batch of silica enriched foam is collected every 4 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 88.73 wt%, and the silicon recovery rate is 92.9%.

[0023] Example 8: In this example, the fresh, untreated silicon cutting waste slurry with low solids content was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano-sized silicon particles with a solid content of 1 wt% and an average particle size of 0.8 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 6.9 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.20:1. (3) Add the collector sodium oleate solution (concentration of 2wt%) to the silicon cutting waste slurry and stir for 5 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 150mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 6 L / min for rapid enrichment flotation for 8 min, and then air is introduced at a flow rate of 2 L / min for slow enrichment flotation for 16 min; during the rapid enrichment flotation stage, a batch of silica enriched foam is collected every 2 min; during the slow enrichment flotation stage, a batch of silica enriched foam is collected every 8 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 86.4 wt%, and the silicon recovery rate is 93.4%.

[0024] Example 9: In this example, the fresh, untreated silicon cutting waste slurry with low solids content was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment. The solid components in the silicon cutting waste slurry were micro-nano-sized silicon particles with a solid content of 5.0 wt% and an average particle size of 0.8 μm. The total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 6.7 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.15:1. (3) Add the collector sodium oleate solution (concentration of 3wt%) to the silicon cutting waste slurry and stir for 5 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 120mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5 L / min for rapid enrichment flotation for 6 min, and then air is introduced at a flow rate of 2 L / min for slow enrichment flotation for 15 min; during the rapid enrichment flotation stage, a batch of silica enriched foam is collected every 1 min; during the slow enrichment flotation stage, a batch of silica enriched foam is collected every 5 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate grade is 89.5 wt%, and the silicon recovery rate is 93.5%.

[0025] Example 10: The fresh, untreated low-solids silicon cutting waste slurry in this example was not subjected to any flocculation, sedimentation, pressure filtration, or drying pretreatment; the solid components in the silicon cutting waste slurry were micro-nano silicon particles, with a solid content of 2.11 wt% and an average particle size of 0.52 μm; the total content of metal impurities in the silicon cutting waste slurry was less than 1000 ppmw. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, the specific steps of which are as follows: (1) Directly stir the fresh, untreated silicon cutting waste slurry with low solid content evenly and add it to the flotation cell; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry at pH 6.8 for 2 minutes to make the slurry evenly dispersed; the volume ratio of water to silicon cutting waste slurry is 0.15:1. (3) Add the collector sodium oleate solution (concentration of 2wt%) to the silicon cutting waste slurry and stir for 5min to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain a hydrophobic modified silicon slurry; the amount of sodium oleate solution added is 120mL / L based on the volume of the silicon cutting waste slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5 L / min for rapid enrichment flotation for 8 min, and then air is introduced at a flow rate of 3.3 L / min for slow enrichment flotation for 20 min; during the rapid enrichment flotation stage, a batch of silica-enriched foam is collected every 1 min; during the slow enrichment flotation stage, a batch of silica-enriched foam is collected every 4 min. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate; In this embodiment, the silicon concentrate has a grade of 88.7 wt% and a silicon recovery rate of 93.9%.

[0026] The specific embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for enriching silicon in silicon cutting waste slurry by segmented flotation, characterized in that, The specific steps are as follows: (1) Fresh, untreated silicon cutting waste slurry with low solid content is stirred evenly and added to a flotation cell; the solid component in the silicon cutting waste slurry is micro-nano silicon particles; (2) Add water to the silicon cutting waste slurry in the flotation cell and adjust the slurry for 1 to 3 minutes at a pH of 6 to 8 to make the slurry evenly dispersed; (3) Add the collector sodium oleate solution to the silicon cutting waste slurry and stir for 3-8 minutes to allow the sodium oleate to fully react with the silicon particles in the silicon cutting waste slurry to obtain the hydrophobic modified silicon slurry. (4) Air is introduced into the hydrophobic modified silica slurry at a flow rate of 5-6 L / min for rapid enrichment flotation for 6-8 min, and then air is introduced at a flow rate of 2-4 L / min for slow enrichment flotation for 10-20 min; during the rapid enrichment flotation stage, a batch of silica enrichment foam is collected every 1-2 min. During the slow enrichment flotation stage, a batch of silicon enrichment foam is collected every 4 to 8 minutes. (5) The silicon enrichment foam is filtered and dried to obtain silicon concentrate.

2. The method for enriching silicon in silicon cutting waste slurry by segmented flotation according to claim 1, characterized in that: Step (1) The solid content in the silicon cutting waste slurry is 0.5~5wt%, the average particle size of silicon particles is 0.3~1μm, and the total content of metal impurities in the silicon cutting waste slurry is not higher than 1000ppmw.

3. The method for enriching silicon in silicon cutting waste slurry by segmented flotation according to claim 1, characterized in that: In step (2), the volume ratio of water to silicon cutting waste slurry is 0.1~0.5:

1.

4. The method for enriching silicon in silicon cutting waste slurry by segmented flotation according to claim 1, characterized in that: In step (3), the concentration of sodium oleate solution is 2~5wt%, and the amount of sodium oleate solution added is 80~200mL / L based on the volume of silicon cutting waste slurry.

5. The method for enriching silicon in silicon cutting waste slurry by segmented flotation according to claim 1, characterized in that: Step (5) The grade of the silicon concentrate is 85~90wt%.