A method for purifying titanium dioxide and a method for recovering its byproducts.

Abstract

This invention provides a method for purifying titanium dioxide and recovering its byproducts, relating to the field of titanium dioxide technology. The preparation method includes: crushing crude raw materials, mixing with concentrated sulfuric acid, acidolysis, dilution with water, and filtration to obtain an acid-hydrolyzed filtrate and a filter cake; subjecting the acid-hydrolyzed filtrate to rotary sieving and magnetic adsorption to obtain a physically purified filtrate; adjusting the pH of the filtrate, heating, adding phosphoric acid solution, filtering to remove precipitates, adding ammonia water, filtering to remove precipitates again, and then crystallizing to obtain titanium oxysulfate crystals. This titanium dioxide purification method, through acidolysis, multi-stage physical purification, and deep chemical purification, yields titanium dioxide with high purity, significantly reduces heavy metal ion content, reduces wastewater discharge and waste residue generation, effectively reduces overall energy consumption, and is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide technology, specifically to a method for purifying titanium dioxide and a method for recovering its byproducts. Background Technology

[0002] Titanium dioxide (TiO2) is an important white pigment, and its purity directly determines the product performance. Traditional sulfuric acid process for producing titanium dioxide has problems such as long process, incomplete impurity removal, and low utilization rate of by-products; physical sieving alone can only remove large particulate impurities and cannot remove ionic metal pollutants; chemical methods consume a lot of reagents, discharge a lot of wastewater, and put significant pressure on environmental protection.

[0003] Current technologies for producing titanium dioxide primarily focus on single-product output, failing to fully exploit the value of byproducts and thus struggling to meet the industry's demands for high-quality, low-energy consumption. Ferrous sulfate, a byproduct of titanium dioxide production, has a high content of insoluble solids and metallic impurities, requiring purification before reuse. However, current research on the purification of titanium dioxide and the recovery of its byproducts has not been extensive.

[0004] Therefore, providing a method for purifying titanium dioxide and a method for recovering its byproducts is an urgent problem to be solved. Summary of the Invention

[0005] Specifically addressing the shortcomings of existing technologies, this paper provides a method for purifying titanium dioxide and recovering its byproducts, comprising the following steps: crushing coarse raw materials, mixing with concentrated sulfuric acid, acidolysis, dilution with water, and filtration to obtain an acid-hydrolyzed filtrate and a filter cake; subjecting the acid-hydrolyzed filtrate to rotary sieving and magnetic adsorption to obtain a physically purified filtrate; adjusting the pH of the filtrate, heating, adding phosphoric acid solution, filtering to remove precipitates, adding ammonia water, filtering to remove precipitates again, and then crystallizing to obtain titanium oxysulfate crystals; this titanium dioxide purification method, through acidolysis, multi-stage physical purification, and deep chemical purification, yields titanium dioxide with high purity, significantly reduces heavy metal ion content, reduces wastewater discharge and waste residue generation, effectively reduces overall energy consumption, and is suitable for large-scale industrial production.

[0006] The objective of this invention is achieved through the following technical solution: In a first aspect, the present invention provides a method for purifying titanium dioxide, the purification method comprising the following steps: S1. The coarse raw material is crushed, mixed with concentrated sulfuric acid, acidified, diluted with water, and filtered to obtain the acidified filtrate and filter cake. S2. The acid-hydrolyzed filtrate is subjected to rotary sieving and magnetic adsorption to obtain a physically purified filtrate. S3. Adjust the pH of the filtrate after physical purification to 1.0-3.0, heat it, add 50%-80% phosphoric acid solution, filter to remove the precipitate, add ammonia water, filter to remove the precipitate, and then crystallize to obtain titanium oxysulfate crystals and the crystallized waste liquid. S4. The titanium oxysulfate crystals are hydrolyzed, filtered, and calcined to produce titanium dioxide.

[0007] In some specific embodiments of the present invention, in step S1, the particle size of the coarse raw material is 30-100 micrometers, and the mass ratio of the coarse raw material to the concentrated sulfuric acid is 1:2. The acid hydrolysis is performed at a temperature of 170–190°C for 1.5–2.5 hours.

[0008] In some specific embodiments of the present invention, in step S1, the product of acidolysis is a mixture of titanium oxysulfate and ferrous sulfate.

[0009] In some specific embodiments of the present invention, in step S3, the temperature of the heating is 60-85°C, and the amount of phosphoric acid solution added is 1%-8% of the mass of the filtrate after physical impurity removal.

[0010] In some specific embodiments of the present invention, in step S3, the crystallization method is to evaporate and concentrate the solution after adding ammonia water and filtering to remove the precipitate, cool it down, and adjust the pH to 1.0-2.0 to obtain titanium oxysulfate crystals; the crystallization can be repeated multiple times.

[0011] Secondly, the present invention provides a method for recovering the byproduct ferrous sulfate, wherein the substances that can generate the byproduct ferrous sulfate in the recovery method are the filter cake after acid hydrolysis in step S1 of the first aspect and the iron filings magnetically adsorbed in step S2.

[0012] In some specific embodiments of the present invention, the recovery method involves subjecting the substance that can produce the byproduct ferrous sulfate to phosphoric acid purification, ammoniation precipitation, multiple crystallizations, and calcination to obtain the byproduct ferrous sulfate crystals.

[0013] Thirdly, the present invention provides a method for recovering dilute sulfuric acid as a byproduct, wherein the substance that can generate dilute sulfuric acid as a byproduct in the recovery method is the waste liquid after crystallization in step S3 of the first aspect. The method for recovering the byproduct dilute sulfuric acid involves concentrating and filtering the substance that can produce the byproduct dilute sulfuric acid to obtain the byproduct dilute sulfuric acid.

[0014] Fourthly, the present invention provides the use of dilute sulfuric acid obtained by the method for recovering dilute sulfuric acid byproduct described in the third aspect for use in the acidolysis step S1.

[0015] Fifthly, the present invention provides the use of titanium dioxide obtained by the purification method of titanium dioxide described in the first aspect in coatings, plastics, and papermaking.

[0016] The beneficial effects achieved by this invention are as follows: 1. The titanium dioxide purification method provided by this invention, through acid hydrolysis, multi-stage physical impurity removal, and deep chemical purification, yields titanium dioxide with high purity, significantly reduced heavy metal ion content, whiteness exceeding 95%, uniform crystal particles, concentrated particle size distribution, hiding power higher than 400 square centimeters / gram, strong stability, and resistance to aging, deterioration, and discoloration, as well as enhanced catalytic activity. The titanium dioxide purification process employs a closed-loop system and modular production process, improving process flexibility and making it suitable for large-scale industrial production. 2. In the process of purifying titanium dioxide, the byproduct ferrous sulfate produced by this invention can be used as a flocculant, colorant, and fertilizer raw material. Furthermore, the waste acid generated during the purification process can be recycled in the acidolysis step with a recovery rate of up to 90%, reducing wastewater discharge and waste residue generation, effectively reducing overall energy consumption, lowering production costs, realizing the full utilization of titanium ore raw materials, and enhancing the economic value of byproducts. Attached Figure Description

[0017] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a flowchart of a method for purifying titanium dioxide and recovering its byproducts. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments are not intended to limit the present invention, but only to illustrate the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are generally performed under conventional conditions. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0020] Example A method for purifying titanium dioxide, the flowchart of which is shown below. Figure 1 As shown, the specific steps include: 1) Acid hydrolysis pretreatment. The crude raw materials (titanium ore, titanium slag) are ultra-finely pulverized to a particle size of 30-100 micrometers. They are then mixed with concentrated sulfuric acid at a mass ratio of 1:2. Acid hydrolysis is performed at 180℃ for 2 hours to obtain the acid hydrolysis product, mainly a mixed solution of titanium oxysulfate and ferrous sulfate. This solution is then diluted with water, stirred, and preliminarily filtered. The filtrate is then used for further processing.

[0021] 2) Multi-stage physical impurity removal. The filtrate is sequentially introduced into subsequent physical impurity removal devices, where it is crushed, adsorbed, dissolved, filtered, and magnetically separated. Among them, a rotary vibrating screen filters out large insoluble particles, and a drum-type magnetic separator removes magnetic impurities such as iron filings and iron-containing ores.

[0022] 3) Deep Chemical Purification. Add calcium hydroxide or sodium hydroxide to adjust the pH of the filtrate to 1.0-3.0, raise the temperature to 60-85℃, add a 50%-80% (w / w) phosphoric acid solution (1%-8% of the mass of the filtrate after physical purification), stir, and filter to remove precipitates, primarily removing impurity cations such as iron and aluminum ions. Add ammonia water to primarily remove impurity cations such as copper and magnesium ions. Perform multiple crystallizations to obtain high-purity titanium oxysulfate crystals. The crystallization method involves evaporating and concentrating the solution after ammonia purification, adjusting the temperature to 10-35℃, and adjusting the pH to 1.0-2.0 to obtain high-purity titanium oxysulfate crystals. The temperature is 60-85℃, and the amount of phosphoric acid solution added is 1%-8% of the mass of the filtrate after physical purification.

[0023] 4) Preparation of high-purity titanium dioxide. Titanium oxysulfate crystals are processed through multiple steps such as hydrolysis, filtration, and calcination to produce high-purity titanium dioxide.

[0024] 5) Preparation and wastewater recovery of ferrous sulfate byproduct. Iron-containing compounds obtained during pickling and magnetic adsorption processes are treated with phosphoric acid for impurity removal, ammoniation precipitation, multiple crystallizations, and calcination to obtain high-purity ferrous sulfate crystals. The dilute sulfuric acid generated during production is concentrated, filtered for impurities, and recovered for reuse in the acidolysis pretreatment process, achieving acid recycling.

[0025] The obtained titanium dioxide was tested and found to have a purity of over 99%, with impurities reduced by over 90%, and no color deviation. Its whiteness reached over 95%, with uniform crystal particles, concentrated particle size distribution, and good dispersibility. Its hiding power was higher than 400 square centimeters / gram. It exhibited strong stability, was not prone to aging, deterioration, or discoloration, had enhanced catalytic activity, and its heavy metal content met food or cosmetic standards, making it suitable for high-end, high-value applications.

[0026] The above specific embodiments further illustrate the purpose, technical solution and beneficial effects of this application. It should be understood that the above are only specific embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solution of this application should be included within the scope of protection of this application.

Claims

1. A method for purifying titanium dioxide, characterized in that, The purification method includes the following steps: S1. The coarse raw material is crushed, mixed with concentrated sulfuric acid, acidified, diluted with water, and filtered to obtain the acidified filtrate and filter cake. S2. The acid-hydrolyzed filtrate is subjected to rotary sieving and magnetic adsorption to obtain a physically purified filtrate. S3. Adjust the pH of the filtrate after physical purification to 1.0-3.0, heat it, add 50%-80% phosphoric acid solution, filter to remove the precipitate, add ammonia water, filter to remove the precipitate, and then crystallize to obtain titanium oxysulfate crystals and the crystallized waste liquid. S4. The titanium oxysulfate crystals are hydrolyzed, filtered, and calcined to produce titanium dioxide.

2. The purification method according to claim 1, characterized in that, In step S1, the particle size of the crude raw material is 30-100 micrometers, and the mass ratio of the crude raw material to the concentrated sulfuric acid is 1:

2. The acid hydrolysis is performed at a temperature of 170–190°C for 1.5–2.5 hours.

3. The purification method according to claim 1, characterized in that, In step S1, the product of acid hydrolysis is a mixture of titanium oxysulfate and ferrous sulfate.

4. The purification method according to claim 1 or 3, characterized in that, In step S3, the heating temperature is 60-85℃, and the amount of phosphoric acid solution added is 1%-8% of the mass of the filtrate after physical impurity removal.

5. The purification method according to claim 4, characterized in that, In step S3, the crystallization method is to evaporate and concentrate the solution after adding ammonia and filtering to remove the precipitate, cool it down, and adjust the pH to 1.0-2.0 to obtain titanium oxysulfate crystals; the crystallization can be repeated multiple times.

6. A method for recovering the byproduct ferrous sulfate, characterized in that, The substances that can produce ferrous sulfate as a byproduct in the recovery method are the filter cake after acid hydrolysis in step S1 of any one of claims 1 to 5 and the iron filings magnetically adsorbed in step S2.

7. The method for recovering the byproduct ferrous sulfate according to claim 6, characterized in that, The recovery method involves subjecting the substance that can produce the byproduct ferrous sulfate to phosphoric acid purification, ammoniation precipitation, multiple crystallizations, and calcination to obtain the byproduct ferrous sulfate crystals.

8. A method for recovering dilute sulfuric acid as a byproduct, characterized in that, The substance that can produce dilute sulfuric acid as a byproduct in the recovery method is the waste liquid after crystallization in step S3 of any one of claims 1 to 5; The method for recovering the byproduct dilute sulfuric acid involves concentrating and filtering the substance that can produce the byproduct dilute sulfuric acid to obtain the byproduct dilute sulfuric acid.

9. The use of the dilute sulfuric acid obtained by the method for recovering the dilute sulfuric acid byproduct as described in claim 8 for use in the acidolysis step S1.

10. The use of titanium dioxide obtained by the purification method of any one of claims 1 to 5 in coatings, plastics, and papermaking.

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