A method for regulating the settling behavior of particles to achieve rapid solid-liquid separation of silicon cutting waste slurry

Abstract

The present application relates to a method for regulating the settling behavior of particles to realize the rapid solid-liquid separation of silicon cutting waste slurry, belonging to the technical field of photovoltaic solid waste silicon resource utilization. In view of the technical bottleneck that the micro-nano silicon particles in the silicon cutting waste slurry are difficult to settle and separate due to the too low initial solid content (1%~4%) and the strong negative surface electric property (Zeta potential about-35mV) leading to the dominant electrostatic repulsion, based on the theoretical law of "solid content dominant settling rate", a hierarchical regulation strategy is constructed. The present application increases the solid content through pre-concentration, greatly increases the collision probability of micro-nano silicon particles from a macroscopic point of view; adjusts the pH of the slurry to neutralize the surface charge to eliminate the electrostatic repulsion, and triggers spontaneous agglomeration from a microscopic point of view; for the residual ultra-fine particles, a cationic flocculating agent is added to increase the particle size of the secondary particles through bridging, so that they are converted into easily settled large flocs with "sufficient size, sufficient solid content and neutralized surface charge", and the solid silicon sediment is obtained through direct gravity settling.

Description

Technical Field

[0001] This invention relates to a method for rapidly separating solid and liquid components from silicon cutting waste slurry by regulating particle settling behavior, belonging to the field of photovoltaic solid waste silicon resource utilization technology. Background Technology

[0002] During the single-crystal silicon wafer cutting process, approximately 30% of the 6N-grade high-purity silicon material is lost in the cutting fluid in the form of micro- and nano-fine particles, forming a large amount of silicon cutting waste slurry. It is estimated that for every 1GW of silicon wafers cut, more than 40,000 cubic meters of waste slurry are generated, of which the silicon content is only 1-4%, and the remainder consists of water, cutting fluid, and a small amount of metallic impurities (Al, Fe, Ni, Ca, Mg, etc.). This waste slurry has the following characteristics: (1) The silicon particles are very small (0.1-10μm) and exhibit significant Brownian motion; (2) The silicon particles have a strong negative charge on their surface (Zeta potential of about -35mV), and there is electrostatic repulsion between the particles, forming a highly stable dispersion system; (3) The natural settling speed is extremely slow, making it difficult to settle and separate quickly; (4) As the whole process recycling cycle is extended, the oxide layer on the surface of the silicon particles continues to thicken, increasing the difficulty of subsequent purification, impurity removal, and deoxidation.

[0003] Currently, the mainstream industrial process for treating silicon cutting waste slurry is: waste slurry collection → pH adjustment → flocculation → plate and frame filtration, ultimately producing silicon cutting waste with a water content of approximately 50%, commonly known as "silicon mud." This process has the following technical shortcomings: (1) Silicon oxidation loss due to pressure filtration. The existing process uses pressure filtration to dewater the flocculated slurry, producing silicon mud with a water content of about 50%. Although the nominal purity of silicon in the silicon cutting waste slurry is extremely high, during the pressure filtration and subsequent drying process, the ultrafine silicon particles come into full contact with water and air, and the surface oxide layer continuously thickens (up to 5~10nm), resulting in the oxidation of some silicon and reducing the final silicon recovery rate and purity.

[0004] (2) Flocculants introduce metallic impurities, reducing silicon purity and increasing purification difficulty. Existing processes mostly use conventional flocculants (such as polyaluminum chloride, polyferric sulfate, etc.) to promote solid-liquid separation. These flocculants contain metallic elements such as aluminum and iron, which remain in the silicon deposits during flocculation, causing secondary metallic impurity contamination. At the same time, the organic polymer chains of flocculants may coat the surface of silicon particles, forming a physical barrier that hinders the effective contact between the acid and the surface of silicon particles during subsequent acid washing and purification, reducing impurity removal efficiency and increasing purification difficulty.

[0005] (3) There are safety hazards in the storage process. The silica mud produced by plate and frame filter press has a moisture content of about 50%, but there is still a potential danger of exothermic oxidation during the stacking and transportation process. It is highly flammable and may cause dust pollution, posing a safety threat to the production site.

[0006] (4) There are redundant steps in the process flow. In the subsequent metallurgical process of recycling and purification, the silica mud still needs to be crushed, dehydrated and clumped, which not only increases equipment investment and energy consumption, but also prolongs the processing cycle.

[0007] Therefore, there is an urgent need to develop a method for direct and efficient solid-liquid separation of silicon cutting waste slurry, eliminating the need for pressure filtration, reducing silicon oxidation loss, avoiding the introduction of metal impurities by flocculants, improving silicon recovery rate and purity, and eliminating safety hazards. Summary of the Invention

[0008] To address the problems of difficult solid-liquid separation, slow sedimentation rate, reliance on pressure filtration for dehydration, metal impurity contamination introduced by flocculants, low silicon recovery rate, high oxygen content, and low actual purity in existing silicon cutting waste slurry technologies, this invention proposes a method for rapid solid-liquid separation of silicon cutting waste slurry by regulating particle sedimentation behavior. Based on the theoretical principle that "solid content dominates sedimentation rate," a graded regulation strategy is constructed. Through the synergistic effect of "pre-concentration regulation - acid adjustment and agglomeration - flocculation enhancement - graded sedimentation," the sedimentation characteristics of silicon particles are fundamentally transformed, enabling efficient solid-liquid separation to be achieved solely through gravity sedimentation. The silicon recovery rate can reach over 90%, and the water content is below 45%, providing process support for the efficient resource utilization of photovoltaic silicon waste.

[0009] A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: Silicon cutting waste slurry is pre-concentrated until the solid content is increased to 5~10% to macroscopically increase the probability of particle collision, thus obtaining pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add acidic solution to the pre-concentrated slurry to adjust the pH to 1~3, so that the absolute value of the Zeta potential drops below 5mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and separate by static separation to obtain the upper suspension and the lower first-stage silica deposit. (3) Flocculation enhancement: Cationic flocculant solution is added to the upper suspension. Through bridging, the micro and nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining flocculation-enhanced slurry. (4) Graded sedimentation: The flocculated and enhanced slurry is allowed to stand and undergo gravity sedimentation to obtain the second-level silicon deposit at the bottom. The first-level silicon deposit and the second-level silicon deposit are combined to form silicon enrichment.

[0010] Preferably, the solid content of the silicon cutting waste slurry in step (1) is 1~4%, the surface Zeta potential is -35±3mV, and the initial pH is 5~8.

[0011] Preferably, the acidic solution in step (2) is sulfuric acid or hydrochloric acid.

[0012] Preferably, in step (3), when the particle size of the fine silica particles in the upper suspension is >0.6μm, the cationic flocculant is cationic polyacrylamide; when the particle size of the fine silica particles in the upper suspension is ≤0.6μm, the cationic flocculant is cationic polyacrylamide-polydiallyldimethylammonium chloride composite flocculant.

[0013] More preferably, the cationic polyacrylamide-polydiallyldimethylammonium chloride composite flocculant contains 0.2 to 1.5 wt% polydiallyldimethylammonium chloride.

[0014] Preferably, the amount of cationic flocculant added in step (3) is 0.1~1.0 g / L.

[0015] The mechanism by which this invention regulates particle settling behavior to achieve rapid solid-liquid separation of silicon cutting waste slurry: (I) Physicochemical nature of the difficulty in settling silicon particles: Micro-nano silicon particles in silicon cutting waste slurry have the following characteristics: (1) Silicon hydroxyl groups are formed on the particle surface due to hydration. When pH>2, the hydroxyl groups dissociate and release H. + (1) The particle surface is strongly negatively charged (Zeta potential is about -35mV), and there is significant electrostatic repulsion between particles to form a highly stable dispersion system; (2) The slurry has extremely low solid content, large particle spacing, significant Brownian motion, and the driving force of gravity sedimentation is insufficient to overcome thermal motion; (3) The specific surface area of ​​the fine particles is huge, and the surface hydration film is firm, which hinders effective collision and aggregation between particles.

[0016] (II) Macroscopic Mechanism of Pre-Concentration Regulation: Based on Stokes sedimentation theory and the Richardson-Zaki modified equation, solid content is the decisive factor affecting the settling rate of particle groups. When the solid content increases from 32% per particle, the settling time can increase by 10%. 6 More than double. Pre-concentration increases the solid content from 1%~4% to 5%~10%, macroscopically reducing the particle spacing and increasing the collision frequency, changing the particle settling pattern from "isolated and dispersed settling" to "particle cluster settling", creating a concentration basis for subsequent micro-control.

[0017] (III) Microscopic mechanism of acid-regulating aggregation: Under strongly acidic conditions (pH=1~3), H + A large amount of adsorption occurs on the surface of silicon particles, neutralizing the negative charge and reducing the absolute value of the Zeta potential to below 5mV. At this point, the electrostatic repulsion between particles is significantly weakened, and the particles spontaneously aggregate and rapidly settle under the dominance of van der Waals attraction.

[0018] (iv) Bridging mechanism of flocculation enhancement: After acidification and agglomeration, the residual ultrafine particles in the upper suspension are still difficult to settle effectively due to their extremely small mass and huge specific surface area. Cationic flocculants work through a dual action of charge neutralization and polymer bridging: the cationic groups of CPAM neutralize the residual negative charge on the particle surface, while its long molecular chains form "bridging" connections between different particles, linking the fine particles into large flocs that are tens to hundreds of times larger in size, thus transforming them into large flocs that are easy to settle.

[0019] (V) Synergistic mechanism of graded sedimentation: Through the three-step synergistic process of "pre-concentration to macroscopically increase solid content → acid adjustment and agglomeration to microscopically eliminate electrostatic repulsion → flocculation to strengthen bridging and increase size", the sedimentation characteristics of particles undergo a fundamental change: the size is large enough, the solid content is high enough, and the surface charge has been neutralized, so that efficient solid-liquid separation can be achieved by gravity sedimentation alone, achieving the technical effect of silicon recovery rate >90% and water content <45%.

[0020] The beneficial effects of this invention are: (1) Based on the "solid content-dominated" law of silicon particle sedimentation behavior, this invention constructs a graded control strategy: Based on Stokes sedimentation theory and the natural sedimentation law of silicon particles in silicon cutting waste slurry, a graded control strategy of "pre-concentration control-acidification agglomeration-flocculation enhancement-graded sedimentation" is proposed to change the sedimentation characteristics of silicon particles from "difficult to settle" to "easy to settle", and achieve a technical breakthrough of efficient solid-liquid separation by gravity sedimentation alone; (2) This invention avoids the contamination of metal impurities introduced by flocculants and ensures the purity of silicon: The cationic flocculant used is cationic polyacrylamide or cationic polyacrylamide-polydiallyldimethylammonium chloride composite flocculant, which does not contain metal elements such as aluminum and iron, thus avoiding secondary metal impurity contamination caused by conventional flocculants (such as polyaluminum chloride, polyferric sulfate, etc.) from the source; the spontaneous agglomeration and sedimentation of most silicon particles are achieved in advance through the "acid adjustment and agglomeration" step, which greatly reduces the amount of flocculant used in the subsequent process and further reduces the risk of purity decline due to flocculant residue; (3) The present invention significantly reduces the moisture content and improves the silicon recovery rate: the moisture content of the silicon enrichment is less than 45%, which is significantly better than the 50% moisture content of the existing process. After the complete three-step synergistic regulation, the total silicon recovery rate can reach more than 90%. (4) The present invention eliminates the pressure filtration step, simplifies the process flow, and by strengthening gravity sedimentation, solid-liquid separation can be completed in the sedimentation stage. The obtained silicon deposit can be directly dried and used for subsequent purification without the need for pressure filtration. This not only reduces equipment investment and energy consumption, but also shortens the processing cycle and reduces production costs. (5) The process of this invention is simple, time-saving, and safe: the process is carried out directly in the slurry state, and maintaining a low pH value in the slurry state can inhibit the oxidation of silicon particles, eliminating the need for pressure filtration, avoiding silicon oxidation loss during pressure filtration and drying, and shortening the processing cycle. At the same time, since there is no need for pressure filtration and long-term stacking, the safety risks of exothermic oxidation or even spontaneous combustion are reduced. Detailed Implementation

[0021] 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.

[0022] Example 1: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -32.9mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain an upper suspension and a lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.65 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.34 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 42.3%, and the silicon recovery rate was 90.5%.

[0023] Example 2: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -34.5mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain an upper suspension and a lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.65 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.34 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 40.9%, and the silicon recovery rate was 92.3%.

[0024] Example 3: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -36.5mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.72 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.68 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 44.1%, and the silicon recovery rate was 91.3%.

[0025] Example 4: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -35.7mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.72 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.34 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 42.7%, and the silicon recovery rate was 91.7%.

[0026] Example 5: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -37.2mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain an upper suspension and a lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.45 μm; (3) Flocculation enhancement: A cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) is added to the upper suspension. Through bridging, the micro-nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of the cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) added is 0.34 g / L, and the polydiallyl dimethyl ammonium chloride accounts for 0.24 wt% in the cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant; (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 41.9%, and the silicon recovery rate was 92.1%.

[0027] Example 6: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -35.6mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain an upper suspension and a lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.59 μm; (3) Flocculation enhancement: A cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) is added to the upper suspension. Through bridging, the micro and nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry. The amount of the cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) added is 0.68 g / L, and polydiallyl dimethyl ammonium chloride accounts for 0.705 wt% in the cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 43.3%, and the silicon recovery rate was 94.6%.

[0028] Example 7: The solid content of the silicon cutting waste slurry in this example is 1.15%, the surface Zeta potential is -35.2mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (2 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.75 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.34 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 40.6%, and the silicon recovery rate was 92.1%.

[0029] Example 8: The solid content of the silicon cutting waste slurry in this example is 1.15%, the surface Zeta potential is -33.7mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 5.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: An acidic solution (a sulfuric acid solution with a concentration of 1 mol / L) is added to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, triggering spontaneous agglomeration and sedimentation. After standing and separation, an upper suspension and a lower first-stage silica deposit are obtained; the average particle size of the fine silica particles in the upper suspension is 0.18 μm. (3) Flocculation enhancement: A cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) is added to the upper suspension. Through bridging, the micro and nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculated enhanced slurry. The amount of the cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) added is 0.34 g / L, and polydiallyl dimethyl ammonium chloride accounts for 1.2 wt% in the cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 43.5%, and the silicon recovery rate was 90.7%.

[0030] Example 9: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -34.1mV, and the initial pH is 6.9; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is pre-concentrated by ceramic membrane filtration until the solid content is increased to 7.5% to macroscopically improve the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L hydrochloric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.64 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.34 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 43.9%, and the silicon recovery rate was 94.1%.

[0031] Example 10: The solid content of the silicon cutting waste slurry in this example is 1.15%, the surface Zeta potential is -34.6mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is pre-concentrated by ceramic membrane filtration until the solid content is increased to 8.0% to macroscopically improve the particle collision probability and obtain pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (2 mol / L hydrochloric acid solution) to the pre-concentrated slurry to adjust the pH to 1.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.67 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.34 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 43.2%, and the silicon recovery rate was 93.1%.

[0032] Example 11: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -34.8mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is pre-concentrated by ceramic membrane filtration until the solid content is increased to 6.5% to macroscopically improve the particle collision probability and obtain pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1 mol / L hydrochloric acid solution) to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.48 μm; (3) Flocculation enhancement: A cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) is added to the upper suspension. Through bridging, the micro-nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculated enhanced slurry. The amount of the cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) added is 0.51 g / L, and polydiallyl dimethyl ammonium chloride accounts for 0.8 wt% in the cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 42.7%, and the silicon recovery rate was 93.4%.

[0033] Example 12: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -35.3mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is pre-concentrated by ceramic membrane filtration until the solid content is increased to 8.0% to macroscopically improve the particle collision probability and obtain pre-concentrated slurry; (2) Acid adjustment and agglomeration: An acidic solution (a sulfuric acid solution with a concentration of 1 mol / L) is added to the pre-concentrated slurry to adjust the pH to 2.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, triggering spontaneous agglomeration and sedimentation. After standing and separation, an upper suspension and a lower first-stage silica deposit are obtained; the average particle size of the fine silica particles in the upper suspension is 0.20 μm. (3) Flocculation enhancement: A cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) is added to the upper suspension. Through bridging, the micro-nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculated enhanced slurry. The amount of the cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) added is 0.85 g / L, and the polydiallyl dimethyl ammonium chloride accounts for 1.2 wt% in the cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 44.6%, and the silicon recovery rate was 92.7%.

[0034] Example 13: The solid content of the silicon cutting waste slurry in this example is 3.5%, the surface Zeta potential is -35.1mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 9.0% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1.5 mol / L sulfuric acid solution) to the pre-concentrated slurry to adjust the pH to 2.5, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain an upper suspension and a lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 2.50 μm; (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension. Through bridging, the micro and nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.26 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 41.2%, and the silicon recovery rate was 92.8%.

[0035] Example 14: The solid content of the silicon cutting waste slurry in this example is 3.8%, the surface Zeta potential is -34.3mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 8.5% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (1.2 mol / L hydrochloric acid solution) to the pre-concentrated slurry to adjust the pH to 2.8, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.55 μm; (3) Flocculation enhancement: A cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) is added to the upper suspension. Through bridging, the micro-nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculated enhanced slurry. The amount of the cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) added is 0.18 g / L, and polydiallyl dimethyl ammonium chloride accounts for 0.5 wt% in the cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 42.5%, and the silicon recovery rate was 91.7%.

[0036] Example 15: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -35.2mV, and the initial pH is 5.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is pre-concentrated by ceramic membrane filtration until the solid content is increased to 7.0% to macroscopically improve the particle collision probability and obtain pre-concentrated slurry; (2) Acid adjustment and agglomeration: An acidic solution (a sulfuric acid solution with a concentration of 1.8 mol / L) is added to the pre-concentrated slurry to adjust the pH to 2.9, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, triggering spontaneous agglomeration and sedimentation. After standing and separation, an upper suspension and a lower first-stage silica deposit are obtained; the average particle size of the fine silica particles in the upper suspension is 0.62 μm. (3) Flocculation enhancement: Cationic flocculant (cationic polyacrylamide) is added to the upper suspension to cause the micro and nano particles in the suspension to flocculate and grow through bridging, and transform them into large flocs that are easy to settle, thus obtaining a flocculation-enhanced slurry; the amount of cationic flocculant (cationic polyacrylamide) added is 0.34 g / L. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 42.2%, and the silicon recovery rate was 92.5%.

[0037] Example 16: The solid content of the silicon cutting waste slurry in this example is 2.3%, the surface Zeta potential is -34.7mV, and the initial pH is 6.5; A method for rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, comprising the following specific steps: (1) Pre-concentration control: The silicon cutting waste slurry is centrifuged and pre-concentrated until the solid content is increased to 7.5% to macroscopically increase the probability of particle collision, thus obtaining a pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add an acidic solution (2.0 mol / L hydrochloric acid solution) to the pre-concentrated slurry to adjust the pH to 3.0, so that the absolute value of the Zeta potential drops below 5 mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and let it stand to separate to obtain the upper suspension and the lower first-stage silica deposit; the average particle size of the fine silica particles in the upper suspension is 0.42 μm; (3) Flocculation enhancement: A cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) is added to the upper suspension. Through bridging, the micro-nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining a flocculated enhanced slurry. The amount of the cationic flocculant (cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant) added is 0.42 g / L, and polydiallyl dimethyl ammonium chloride accounts for 0.6 wt% in the cationic polyacrylamide-polydiallyl dimethyl ammonium chloride composite flocculant. (4) Staged sedimentation: The flocculation-enhanced slurry was allowed to settle at room temperature to obtain the second-stage silica deposit at the bottom. The first-stage silica deposit and the second-stage silica deposit were combined to form silica enrichment. In this embodiment, the water content of the silicon enrichment was 42.8%, and the silicon recovery rate was 92.7%.

[0038] 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 rapidly separating solids and liquids from silicon cutting waste slurry by regulating particle settling behavior, characterized in that, The specific steps are as follows: (1) Pre-concentration control: Silicon cutting waste slurry is pre-concentrated until the solid content is increased to 5~10% to obtain pre-concentrated slurry; (2) Acid adjustment and agglomeration: Add acidic solution to the pre-concentrated slurry to adjust the pH to 1~3, so that the absolute value of the Zeta potential drops below 5mV to eliminate the electrostatic repulsion between particles, trigger spontaneous agglomeration and sedimentation, and separate by static separation to obtain the upper suspension and the lower first-stage silica deposit. (3) Flocculation enhancement: Cationic flocculant solution is added to the upper suspension. Through bridging, the micro and nano particles in the suspension flocculate and grow, transforming into large flocs that are easy to settle, thus obtaining flocculation-enhanced slurry. (4) Graded sedimentation: The flocculated and enhanced slurry is allowed to stand and undergo gravity sedimentation to obtain the second-level silicon deposit at the bottom. The first-level silicon deposit and the second-level silicon deposit are combined to form silicon enrichment.

2. The method for rapid solid-liquid separation of silicon cutting waste slurry by regulating particle settling behavior according to claim 1, characterized in that: Step (1) The solid content of the silicon cutting waste slurry is 1~4%, the surface Zeta potential is -35±3mV, and the initial pH is 5~8.

3. The method for rapid solid-liquid separation of silicon cutting waste slurry by regulating particle settling behavior according to claim 1, characterized in that: Step (2) The acidic solution is sulfuric acid or hydrochloric acid.

4. The method for rapid solid-liquid separation of silicon cutting waste slurry by regulating particle settling behavior according to claim 1, characterized in that: In step (3), when the particle size of fine silica particles in the upper suspension is >0.6μm, the cationic flocculant is cationic polyacrylamide; when the particle size of fine silica particles in the upper suspension is ≤0.6μm, the cationic flocculant is cationic polyacrylamide-polydiallyldimethylammonium chloride composite flocculant.

5. The method for rapid solid-liquid separation of silicon cutting waste slurry by regulating particle settling behavior according to claim 4, characterized in that: In the cationic polyacrylamide-polydiallyldimethylammonium chloride composite flocculant, polydiallyldimethylammonium chloride accounts for 0.2~1.5 wt%.

6. The method for rapid solid-liquid separation of silicon cutting waste slurry by regulating particle settling behavior according to claim 1, characterized in that: Step (3) The amount of cationic flocculant added is 0.1~1.0g / L.