Method for preparing high-purity silicon powder and titanium dioxide based on chlorinated waste brine quenched slag

Abstract

The application relates to the technical field of solid waste resource utilization, and discloses a method for preparing high-purity silicon powder and titanium dioxide based on chlorination waste brine quenching slag, which comprises the following steps: S1, drying and ball milling treatment of the molten salt chlorination waste brine quenching slag to obtain pretreated materials; S2, magnetic separation of the pretreated materials to obtain non-magnetic mixed materials; S3, oxidative roasting of the non-magnetic mixed materials to obtain decarburized solid materials; S4, acid leaching, filtering and washing of the decarburized solid materials to obtain silicon-rich filter cakes and titanium-rich filtrate; S5, drying, grinding and airflow classification of the silicon-rich filter cakes to obtain silicon powder, and hydrolysis reaction of the titanium-rich filtrate after adding a hydrolysis agent and heating, filtration of metatitanic acid filter cakes and calcination and dehydration to obtain titanium dioxide. Through the scheme, the comprehensive recovery rate of silicon and titanium resources and the product added value are improved, and the solid waste emission and environmental pollution are effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of solid waste resource utilization technology, and in particular to a method for preparing high-purity silicon micro powder and titanium dioxide based on quenched slag from chlorinated waste brine. Background Technology

[0002] Titanium tetrachloride (TiCl4), as an important intermediate product in the titanium industry chain, has been widely used in its preparation process, particularly through molten salt chlorination, due to its advantages of low production cost and high product quality. However, this process generates a large amount of hazardous waste, such as waste salt and waste brine. Improper handling can easily lead to serious environmental pollution problems, thus hindering the further promotion and application of molten salt chlorination technology and the high-value utilization of primary titanium ore resources.

[0003] To address the aforementioned issues, various treatment and resource utilization solutions for molten salt chlorination waste salt and waste brine have been proposed in existing technologies. For example, by water quenching, oxidation to remove impurities, magnesium removal, and brine reuse, valuable components such as iron, magnesium, manganese, and sodium chloride can be recovered and utilized, thus solving the problem of waste brine resource utilization to a certain extent. However, a large amount of insoluble solid residue (i.e., water-quenched slag) is still generated during the water quenching process of waste brine. This type of water-quenched slag typically contains about 20%–40% silicon dioxide (SiO2), 10%–20% titanium dioxide (TiO2), and 10%–20% elemental carbon (C), as well as small amounts of chlorine and insoluble impurities such as iron, aluminum, calcium, and magnesium. Currently, the above-mentioned water-quenched slag is mostly disposed of by stockpiling or landfilling, which not only occupies land resources but also wastes valuable components, failing to achieve effective resource recovery and utilization.

[0004] On the other hand, in the field of silicon material and silicon micropowder preparation, existing technologies have developed various process routes, including high-temperature melting, plasma methods, chemical precipitation, and sol-gel methods. However, most of these methods rely on natural quartz as the silicon source and require the use of high-purity carbon reducing agents, resulting in high raw material costs, complex process flows, and difficulties in impurity removal. For low-grade silicon-, titanium-, and carbon-containing composite solid waste materials derived from molten salt chlorination processes, existing technologies lack a systematic process capable of achieving multi-component synergistic separation, purification, and graded utilization, especially in the high-value preparation of silicon components into silicon micropowder or silicon materials, where there are still significant shortcomings.

[0005] For the process of recovering water-quenched slag, existing technologies have proposed several improvement schemes, such as: Patent document CN202410906765.5 discloses a method for recovering Ti from quenched slag of chlorinated waste brine, which adopts a technical route of acid washing, water washing, pulping, aeration cyclone, membrane filtration and plate and frame filter press to recover Ti and C; Patent document CN202211692489.4 discloses a method for leaching TiO2 from molten salt chlorination slag. The method involves thoroughly mixing and stirring the molten salt chlorination slag with water to dissolve it, separating the filter residue, washing and drying the filter cake, calcining it, and then gravity separating it to obtain TiO2 concentrate. Patent document CN202511881922.2 discloses a method for recovering Si, C and TiO2 from quenched slag of chlorinated waste brine. The method involves hydrolysis, pressure filtration and washing, acid dissolution and reduction, fluidized bed and hydrocyclone treatment to recover Si, C and TiO2.

[0006] However, the above technologies may only be aimed at titanium resource recycling and do not involve the high-value utilization of silicon. Even if they involve multi-component recycling, there is still room for improvement in terms of process integration, high purification of silicon components, and product added value.

[0007] Therefore, for the Si, Ti, and C-containing composite water-quenched slag generated during molten salt chlorination, there is an urgent need to develop a process that can achieve efficient separation and high-value utilization of multiple components, especially to achieve high-purity recovery of silicon and preparation of high-value-added silicon micropowder or silicon materials, while also taking into account the resource utilization of components such as titanium dioxide, thereby improving the comprehensive utilization level of solid waste and reducing environmental pollution. This has important engineering application value and practical significance. Summary of the Invention

[0008] In view of this, the present invention proposes a method for preparing high-purity silicon micro powder and titanium dioxide based on quenched slag from chlorinated waste brine, which improves the comprehensive recovery rate of Si and Ti resources and the added value of products, and effectively reduces solid waste discharge and environmental pollution.

[0009] To achieve the above objectives, embodiments of the present invention provide a method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine, specifically including the following steps: S1, the quenching slag from molten salt chloride wastewater is dried and ball-milled to obtain pretreated material; S2, the pretreated material is subjected to magnetic separation to obtain a non-magnetic mixture; S3, the non-magnetic mixture is oxidized and roasted to obtain decarburized solids; S4, the decarbonized solids are acid-leached, filtered and washed to obtain a silica-rich filter cake and a titanium-rich filtrate; S5. The silica-rich filter cake is dried, ground, and air-separated to obtain silica powder. The titanium-rich filtrate is added to a hydrolyzing agent and heated to carry out a hydrolysis reaction. After filtration, a metatitanic acid filter cake is obtained and then calcined to dehydrate it to obtain titanium dioxide.

[0010] According to one embodiment of the present invention, in step S1, the quenching slag of molten salt chlorination waste brine is ball-milled to less than or equal to 200 mesh. The composition of the quenching slag of molten salt chlorination waste brine, by mass percentage, includes: SiO2 20-40%, TiO2 10-20%, C 10-20%, Cl ≤1%, Fe+Al+Ca+Mg ≤20%, and the balance being water and unavoidable impurities.

[0011] According to one embodiment of the present invention, in step S2, the magnetic separation includes wet high-intensity magnetic separation with a magnetic field strength of 8000~15000Gs.

[0012] According to one embodiment of the present invention, in step S3, the oxidative calcination temperature is 450~650℃ and the time is 0.5~3h.

[0013] According to one embodiment of the present invention, in step S4, acid leaching includes a first acid leaching step and a second acid leaching step. In the first acid leaching step, the decarbonized solid is leached with a first mixed acid including hydrochloric acid and sulfuric acid, and then filtered to obtain filter residue. In the second acid leaching step, the filter residue is leached with a second mixed acid including hydrochloric acid, sulfuric acid and hydrofluoric acid, and then filtered and washed until the pH value is 6.0~8.0 to obtain a silica-rich filter cake and a titanium-rich filtrate.

[0014] According to one embodiment of the present invention, in step S4, the volume ratio of hydrochloric acid to sulfuric acid in the first mixed acid is (2~3):1, the total hydrogen ion concentration in the first mixed acid is 3~5 mol / L, the solid-liquid ratio of the first acid leaching step is 1:(3~5) g / L, the leaching temperature is 70~85℃, and the leaching time is 2~3h.

[0015] According to one embodiment of the present invention, in step S4, the volume ratio of hydrochloric acid, sulfuric acid and hydrofluoric acid in the second mixed acid is (3~5):(1~2):(0.05~0.2), the total hydrogen ion concentration in the second mixed acid is 1~4 mol / L, the solid-liquid ratio of the second acid leaching step is 1:(3~8) g / L, the leaching temperature is 60~95℃, and the leaching time is 1~4h.

[0016] According to one embodiment of the present invention, in step S5, the particle size of the silicon micro powder is D50 = 1~10μm, and the purity of SiO2 in the silicon micro powder is greater than or equal to 99%.

[0017] According to one embodiment of the present invention, in step S5, the hydrolysing agent includes one or more of boric acid, ammonium sulfate, ammonia, and urea, the pH value of the hydrolysis reaction is 2.0~4.0, the hydrolysis temperature is 80~100℃, and the hydrolysis time is 2~4h.

[0018] According to one embodiment of the present invention, in step S5, the calcination temperature is 500~850℃, the calcination time is 2~5h, and the purity of titanium dioxide is greater than or equal to 90%.

[0019] This invention has at least the following beneficial technical effects: By sequentially performing a multi-step synergistic treatment on the quenched slag of chlorinated wastewater, including drying and ball milling, magnetic separation for impurity removal, oxidative roasting for decarburization, and acid leaching for separation, it achieves efficient decoupling and targeted enrichment of Si, Ti, and C-containing composite solid waste that was originally difficult to utilize. Based on this, high-purity silicon micropowder is prepared by drying, grinding, and air-flow classification of the silicon-rich components, and the titanium-rich components are converted into titanium dioxide through hydrolysis and calcination. This not only significantly improves the comprehensive recovery rate and added value of silicon and titanium resources, but also effectively reduces solid waste emissions and environmental pollution. It overcomes the problems of existing technologies that only focus on the recovery of a single element or insufficient utilization of silicon resources, achieving high-value and clean utilization of waste resources. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0021] Figure 1 A flowchart of an embodiment of the method for preparing high-purity silicon micro powder and titanium dioxide based on quenched slag from chlorinated waste brine provided by the present invention; Figure 2 This is a schematic diagram of an embodiment of the preparation of high-purity silicon micropowder provided by the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0023] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0024] This invention proposes a method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine. For example... Figure 1 As shown, the method includes the following steps S1 to S5: S1, the quenching slag from molten salt chloride wastewater is dried and ball-milled to obtain pretreated material; S2, the pretreated material is subjected to magnetic separation to obtain a non-magnetic mixture; S3, the non-magnetic mixture is oxidized and roasted to obtain decarburized solids; S4, the decarbonized solids are acid-leached, filtered and washed to obtain a silica-rich filter cake and a titanium-rich filtrate; S5. The silica-rich filter cake is dried, ground, and air-separated to obtain silica micropowder. The titanium-rich filtrate is added to a hydrolyzing agent and heated to carry out a hydrolysis reaction. After filtration, a metatitanic acid filter cake is obtained and then calcined to dehydrate it to obtain TiO2.

[0025] According to one embodiment of the present invention, in step S1, the quenching slag from molten salt chlorination wastewater originates from the water quenching slag produced as a byproduct of the "quenching of molten salt chlorination wastewater—oxidation and impurity removal—magnesium removal—brine reuse" process. This water quenching slag, by mass percentage, contains 20-40% SiO2, 10-20% TiO2, 10-20% elemental C, ≤1% Cl, and small amounts of insoluble substances such as Fe, Al, Ca, and Mg, wherein Fe+Al+Ca+Mg≤20%, and the remainder is water and unavoidable impurities, with a moisture content of 15-25%. The present invention, through... Figure 2 The technical route shown is used to prepare the water-quenched slag into high-purity silicon micropowder and TiO2.

[0026] According to an embodiment of the present invention, in step S1, the drying and ball milling of the quenched slag from molten salt chlorination wastewater can be achieved by the following method: the quenched slag is first dried to remove some moisture, then coarsely crushed using a crushing device, and then ground to the required fineness using a ball mill, such as ball milling to ≤200 mesh, to obtain the pretreated material.

[0027] According to one embodiment of the present invention, in step S2, the magnetic separation can be performed using a wet high-intensity magnetic separation method. The pretreated material is prepared into a slurry of a certain concentration, and then separated by a high-intensity magnetic separator under a set magnetic field strength to remove magnetic iron impurities, resulting in a non-magnetic mixture. The main purpose of magnetic separation is to remove Fe impurities to improve the purity of the final product. For example, wet high-intensity magnetic separation under a magnetic field strength of 8000~15000 Gs can achieve an iron removal rate of over 95%.

[0028] According to one embodiment of the present invention, in step S3, the purpose of oxidative calcination is to remove elemental carbon from the non-magnetic mixture. The non-magnetic mixture is placed in an oxidizing atmosphere and calcined at high temperature, causing the carbon to be converted into carbon dioxide gas and escape, yielding a decarburized solid. The calcination temperature and time need to be properly controlled to avoid the loss of silicon and titanium. For example, oxidative calcination at 450~650℃ for 0.5~3 h can achieve a carbon removal rate of over 96%.

[0029] According to one embodiment of the present invention, in step S4, the acid leaching employs a two-step acid leaching method, including a first-step acid leaching and a second-step acid leaching, to achieve efficient separation of Fe, Al, Ca, Mg, Si, and Ti. Specifically: Step 1: Acid leaching. The decarbonized solids are leached using a first mixed acid of hydrochloric acid and sulfuric acid. The volume ratio of hydrochloric acid to sulfuric acid in the first mixed acid can be (2~3):1, the total hydrogen ion concentration of the first mixed acid is 3~5 mol / L, the solid-liquid ratio of the first mixed acid is 1:(3~5) g / L, the leaching temperature is 70~85℃, and the leaching time is 2~3 hours. The purpose of this step is to dissolve most of the Ca, Mg, and Al, while controlling Si loss to be less than 1% and Ti loss to be less than 1%. After the first leaching, the solution is filtered. The resulting filtrate is waste acid containing Ca, Mg, and Al, which can be used to recover aluminum compounds and metal salts through reduction, precipitation, concentration, and crystallization processes, achieving full component utilization. The resulting filter residue is then used for the second acid leaching step.

[0030] The second step, acid leaching, involves leaching the filter residue obtained in the first step using a second mixed acid mixture of hydrochloric acid, sulfuric acid, and hydrofluoric acid. The volume ratio of hydrochloric acid, sulfuric acid, and hydrofluoric acid in the second mixed acid mixture is (3~5):(1~2):(0.05~0.2), the total hydrogen ion concentration is 1~4 mol / L, the solid-liquid ratio is 1:(3~8) g / L, the leaching temperature is 60~95℃, and the leaching time is 1~4 h. A small amount of hydrofluoric acid is added to break the Si-O bonds in the silicate, releasing the trapped metal impurities, and also facilitating the dissolution of Ti. After leaching, the residue is filtered and washed until neutral (pH 6.0~8.0), yielding a silica-rich filter cake and a titanium-rich filtrate.

[0031] It should be noted that the titanium-rich filtrate after the second step of acid leaching contains Ti and fluoride ions, and conventional hydrolysis methods are insufficient to completely precipitate Ti. Therefore, in step S5, the titanium-rich filtrate is hydrolyzed using a heating and synergistic hydrolysis agent. The hydrolysis agent is selected from one or more of boric acid, ammonium sulfate, ammonia, and urea. Hydrolysis is achieved as follows: the titanium-rich filtrate is heated to 80-100°C, the hydrolysis agent is added, and the final pH is adjusted to 2.0-4.0. Hydrolysis is carried out for 2-4 hours to disrupt the stability of the fluorine-titanium complex, allowing Ti to precipitate completely in the form of metatitanic acid. The metatitanic acid filter cake is obtained by filtration. After thorough washing to remove surface-adsorbed impurities, it is calcined at 500-850°C for 2-5 hours to dehydrate, yielding high-purity TiO2. Under this method, the titanium hydrolysis rate can reach over 95%. The waste acid generated after hydrolysis (mainly hydrochloric acid and sulfuric acid) can be recycled back to the acid leaching process in step S4.

[0032] According to one embodiment of the present invention, in step S5, the silicon micropowder is prepared by drying a silicon-rich filter cake to remove residual moisture, then grinding it using an ultrafine grinding device, and finally classifying it using an air classifier to obtain high-purity silicon micropowder with a specified particle size. For example, after the dried filter cake is ground and classified, silicon micropowder with D50 = 1~10μm and SiO2 purity ≥99% can be obtained.

[0033] In summary, this invention achieves efficient decoupling and targeted enrichment of Si, Ti, and C-containing composite solid waste by sequentially processing chlorinated waste brine quenching slag through multiple steps, including drying and ball milling, magnetic separation for impurity removal, oxidative roasting for decarburization, and acid leaching separation. Based on this, high-purity silicon micropowder is prepared by drying, grinding, and airflow classification of the silicon-rich components, and the titanium-rich components are converted into TiO2 through hydrolysis and calcination. This not only significantly improves the comprehensive recovery rate and added value of silicon and titanium resources but also effectively reduces solid waste emissions and environmental pollution. It overcomes the problems of existing technologies that only focus on single-element recovery or insufficient silicon resource utilization, achieving high-value and clean utilization of waste resources.

[0034] The present invention will be further explained below with reference to specific embodiments and comparative examples.

[0035] Example 1 The composition of the quenched slag from the molten salt chloride waste water used in this embodiment is shown in Table 1, and the others are other insoluble substances.

[0036] Table 1. Composition of molten salt chlorination slag (%)

[0037] (1) Raw material pretreatment: The water-quenched slag is dried, crushed and ball-milled to ≤200 mesh to obtain pretreated material A.

[0038] (2) Magnetic separation: The pretreated material A is subjected to wet strong magnetic separation under a magnetic field strength of 12000 Gs, and the iron removal rate is ≥95% to obtain non-magnetic mixture B.

[0039] (3) Oxidative decarburization: Non-magnetic mixture B is oxidized and roasted at 650℃ for 2 hours, and the carbon removal rate is ≥98%, resulting in decarburized solid C.

[0040] (4) Acid leaching: 4.1 First step: Acid leaching: A mixed acid solution of hydrochloric acid and sulfuric acid in a volume ratio of 3:1 is used. The total H₂ content of this mixed acid is... + The concentration was 4 mol / L, and the solid-liquid ratio was 1:5 g / L. The solution was leached at 85℃ for 3 h, and the residue was obtained after filtration. 4.2 Second step: Acid leaching: A mixed acid mixture of hydrochloric acid, sulfuric acid, and hydrofluoric acid in a volume ratio of 4:1.5:0.1 is used. The total H₂ content of this mixed acid is...+ The concentration was 2 mol / L, and the solution was leached at 85℃ for 2.5 h at a solid-liquid ratio of 1:5 g / L. The solution was then filtered and washed until neutral to obtain a silica-rich filter cake D and a titanium-rich filtrate E. The titanium-rich filtrate E was used as a raw material for Ti recovery.

[0041] (5) Preparation of silicon micro powder: The silicon-rich filter cake D was dried, ultra-finely ground and air-classified to obtain high-purity silicon micro powder with D50=3.6 μm and SiO2 purity of 99.3%.

[0042] Example 2 This embodiment uses the same batch of raw materials as Embodiment 1, the difference being that some process parameters have been adjusted.

[0043] (1) Raw material pretreatment: The water-quenched slag is dried, crushed and ball-milled to ≤200 mesh to obtain pretreated material A.

[0044] (2) Magnetic separation: The pretreated material A is subjected to wet strong magnetic separation under a magnetic field strength of 15000 Gs, and the iron removal rate is ≥96%, resulting in non-magnetic mixture B.

[0045] (3) Oxidative decarburization: Non-magnetic mixture B is oxidized and roasted at 450℃ for 2.5 hours, and the carbon removal rate is ≥96%, resulting in decarburized solid C.

[0046] (4) Acid leaching: 4.1 First step: Acid leaching: A mixed acid solution of hydrochloric acid and sulfuric acid in a volume ratio of 2:1 is used. The total H₂ content of this mixed acid is... + The concentration was 3 mol / L, and the solid-liquid ratio was 1:3 g / L. The solution was leached at 75℃ for 2 h, and the residue was obtained after filtration. 4.2 Second step: Acid leaching: A mixed acid mixture of hydrochloric acid, sulfuric acid, and hydrofluoric acid in a volume ratio of 3:2:0.2 is used. The total H₂ content of this mixed acid is... + The concentration was 4 mol / L, and the solution was leached at 75℃ for 3.0 h at a solid-liquid ratio of 1:3 g / L. The solution was then filtered and washed until neutral to obtain a silica-rich filter cake D and a titanium-rich filtrate E. The titanium-rich filtrate E was used as a raw material for Ti recovery.

[0047] (5) Preparation of silicon micro powder: The silicon-rich filter cake D was dried, ultra-finely ground and air-classified to obtain high-purity silicon micro powder with D50=6.1 μm and SiO2 purity of 99.2%.

[0048] Example 3 This embodiment illustrates the recovery of TiO2, using the same batch of raw materials as in Example 1.

[0049] (1) Raw material pretreatment: The water-quenched slag is dried, crushed and ball-milled to ≤200 mesh to obtain pretreated material A.

[0050] (2) Magnetic separation: The pretreated material A is subjected to wet strong magnetic separation under a magnetic field strength of 15000 Gs, and the iron removal rate is ≥96%, resulting in non-magnetic mixture B.

[0051] (3) Oxidative decarburization: Non-magnetic mixture B is oxidized and roasted at 550℃ for 2.5 hours, and the carbon removal rate is ≥96%, resulting in decarburized solid C.

[0052] (4) Acid leaching: 4.1 First step acid leaching: A mixed acid with a volume ratio of hydrochloric acid to sulfuric acid of 2:1 and a total H+ concentration of 3 mol / L is used. The mixture is leached at 75℃ for 2 h with a solid-liquid ratio of 1:3 g / L. The residue is obtained after filtration. 4.2 Second step: Acid leaching: A mixed acid mixture of hydrochloric acid, sulfuric acid, and hydrofluoric acid in a volume ratio of 3:2:0.2 is used. The total H₂ content of this mixed acid is... + The concentration was 4 mol / L, and the solution was leached at 75℃ for 3.0 h at a solid-liquid ratio of 1:3 g / L. The solution was then filtered and washed until neutral to obtain silica-rich filter cake D and titanium-rich filtrate E.

[0053] (5) Preparation of silicon micro powder: The silicon-rich filter cake D was dried, ultra-finely ground and air-classified to obtain high-purity silicon micro powder with D50=5.6 μm and SiO2 purity of 99.1%.

[0054] (6) Recovery of Ti from Titanium-Rich Filtrate E: Heat titanium-rich filtrate E to 95°C, add boric acid as a hydrolysis agent, adjust the final pH value to 3.0, hydrolyze for 3 h, filter to obtain metatitanic acid filter cake, calcine at 700°C for 3 h to obtain TiO2 with a purity of 95.2%. The waste acid after hydrolysis is returned to (4) acid leaching process.

[0055] In summary, this invention uses quenched slag from molten salt chloride wastewater as raw material. Through pretreatment, magnetic separation, oxidative decarburization, two-step acid leaching, graded preparation of silicon micropowder, and heating with a synergistic hydrolysis agent to recover TiO2, it achieves efficient separation and high-value utilization of silicon and titanium components. This method is simple, easy to operate, and low-cost, with a total component resource utilization rate of ≥90% and no waste discharge, demonstrating significant economic and environmental benefits.

[0056] The above are exemplary embodiments disclosed in this invention. However, it should be noted that various changes and modifications can be made without departing from the scope of the embodiments of this invention as defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular number.

[0057] It should be understood that, as used herein, the singular form “a” is intended to include the plural form as well, unless the context clearly supports an exception. It should also be understood that, as used herein, “and / or” refers to any and all possible combinations of one or more of the associated listed items.

[0058] The embodiment numbers disclosed in the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0059] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of different aspects of the invention exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine, characterized in that, include: S1, the quenching slag from molten salt chloride wastewater is dried and ball-milled to obtain pretreated material; S2, the pretreated material is subjected to magnetic separation to obtain a non-magnetic mixture; S3, the non-magnetic mixture is oxidized and roasted to obtain decarburized solids; S4, the decarbonized solids are acid-leached, filtered and washed to obtain a silica-rich filter cake and a titanium-rich filtrate; S5. The silica-rich filter cake is dried, ground, and air-separated to obtain silica powder. The titanium-rich filtrate is added to a hydrolyzing agent and heated to carry out a hydrolysis reaction. After filtration, a metatitanic acid filter cake is obtained and then calcined to dehydrate it to obtain titanium dioxide.

2. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 1, characterized in that, In step S1, the quenching slag from molten salt chlorination wastewater is ball-milled to a mesh size of less than or equal to 200. By mass percentage, the composition of the quenching slag from molten salt chlorination wastewater includes: 20-40% SiO2, 10-20% TiO2, 10-20% C, and ≤1% Cl, with Fe+Al+Ca+Mg ≤20% as the balance being water and unavoidable impurities.

3. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 1, characterized in that, In step S2, the magnetic separation includes wet high-intensity magnetic separation with a magnetic field strength of 8000~15000Gs.

4. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 1, characterized in that, In step S3, the oxidative calcination temperature is 450~650℃ and the time is 0.5~3h.

5. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 1, characterized in that, In step S4, acid leaching includes a first acid leaching step and a second acid leaching step. In the first acid leaching step, the decarbonized solid is leached with a first mixed acid including hydrochloric acid and sulfuric acid, and then filtered to obtain filter residue. In the second acid leaching step, the filter residue is leached with a second mixed acid including hydrochloric acid, sulfuric acid and hydrofluoric acid, and then filtered and washed until the pH value is 6.0~8.0 to obtain a silica-rich filter cake and a titanium-rich filtrate.

6. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 5, characterized in that, In step S4, the volume ratio of hydrochloric acid to sulfuric acid in the first mixed acid is (2~3):1, the total hydrogen ion concentration in the first mixed acid is 3~5 mol / L, the solid-liquid ratio of the first mixed acid is 1:(3~5) g / L, the leaching temperature of the first acid leaching step is 70~85℃, and the leaching time is 2~3h.

7. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 5, characterized in that, In step S4, the volume ratio of hydrochloric acid, sulfuric acid and hydrofluoric acid in the second mixed acid is (3~5):(1~2):(0.05~0.2), the total hydrogen ion concentration in the second mixed acid is 1~4 mol / L, the solid-liquid ratio of the second mixed acid is 1:(3~8) g / L, the leaching temperature of the second acid leaching step is 60~95℃, and the leaching time is 1~4h.

8. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 1, characterized in that, In step S5, the particle size of the silicon micro powder is D50 = 1~10μm, and the purity of SiO2 in the silicon micro powder is greater than or equal to 99%.

9. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 1, characterized in that, In step S5, the hydrolysing agent includes one or more of boric acid, ammonium sulfate, ammonia and urea. The pH value of the hydrolysis reaction is 2.0~4.0, the hydrolysis temperature is 80~100℃, and the hydrolysis time is 2~4h.

10. The method for preparing high-purity silicon micropowder and titanium dioxide based on quenched slag from chlorinated waste brine according to claim 9, characterized in that, In step S5, the calcination temperature is 500~850℃, the calcination time is 2~5h, and the purity of titanium dioxide is greater than or equal to 90%.

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