A method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue

Abstract

This invention provides a method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue, comprising the following steps: a hydrolysis step: mixing titanium-containing waste residue with water to hydrolyze titanium tetrachloride in the waste residue; a reduction step: adding a reducing agent to the hydrolyzed solution to reduce ferric iron in the solution to ferrous iron; a pH adjustment step: adjusting the pH value of the solution to obtain crude titanium dioxide precipitate; and a washing step: washing the crude titanium dioxide to produce the titanium dioxide product. This invention achieves the resource utilization of titanium in titanium-containing waste residue, with fewer production steps, and effectively improves the purity of titanium dioxide through reduction and washing processes.

Description

Technical Field

[0001] This invention relates to the field of solid waste treatment, specifically to a method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue. Background Technology

[0002] Regarding the treatment of titanium-containing waste residue from petrochemical catalysts, CN103769406A discloses a method for treating titanium-containing waste residue from polyolefin catalysts. This method involves directly mixing and reacting quicklime slurry with the titanium-containing waste residue to generate a slurry, which is then allowed to solidify and prepare cement clinker. This achieves the reduction and harmless disposal of the titanium-containing waste residue. However, the titanium element is not utilized at a high value, resulting in resource waste. CN118371518A discloses a method for resource-based disposal of titanium-containing waste residue, using a urea-ammonium chloride mixture to co-hydrolyze the titanium-containing waste residue, recovering titanium dioxide, and producing high-value by-product urea ammonium nitrogen fertilizer. However, the titanium dioxide production process is lengthy and costly, hindering mass production. Furthermore, using urea and ammonium chloride as additives in the reaction generates toxic and harmful gases that pollute the environment, posing a significant challenge to environmental governance and producing large amounts of by-product ammonium salts.

[0003] Given the above issues, how to effectively utilize titanium while reducing production steps when treating titanium-containing waste is an urgent problem to be solved. Summary of the Invention

[0004] The technical objective of this invention is to address the shortcomings of the prior art by providing a method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue, thereby realizing the resource utilization of titanium in titanium-containing waste residue, reducing the number of production steps, and effectively improving the purity of titanium dioxide through reduction and washing processes.

[0005] The technical solution adopted by this invention to solve its technical problem is: a method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue, comprising the following steps:

[0006] Hydrolysis process: Titanium-containing waste residue is mixed with water to hydrolyze titanium tetrachloride in the titanium-containing waste residue;

[0007] Reduction process: A reducing agent is added to the hydrolyzed solution to reduce the ferric iron in the solution to ferrous iron;

[0008] pH adjustment process: Adjusting the pH value of the solution to obtain crude titanium dioxide precipitate;

[0009] Washing process: Wash the crude titanium dioxide to produce titanium dioxide products.

[0010] Furthermore, the titanium-containing waste residue is titanium-containing waste residue from petrochemical catalysts, wherein the titanium content is 15wt%-25wt% and the iron content is 0.1wt%-0.2wt%.

[0011] Furthermore, in the hydrolysis process, the mass-to-volume ratio of titanium-containing waste residue to water is 1g:(5-8)ml; the hydrolysis temperature is 50℃-60℃.

[0012] Furthermore, the hydrolysis process also includes post-hydrolysis filtration, followed by settling of the filtrate, separation to remove oil, and obtaining an oil-free hydrolysate.

[0013] Furthermore, the reducing agent in the reduction process is sodium metabisulfite, which is added at a mass ratio of 1:(80-100) to the titanium-containing waste residue.

[0014] Furthermore, in the reduction process, before adding the reducing agent to the solution, the pH of the solution is adjusted to 1-1.5.

[0015] Furthermore, the reverse pH adjustment process includes: adding an alkaline reagent to the solution after the reduction process, adjusting the pH value of the solution to 2-4, and filtering after the reaction to obtain crude titanium dioxide wet residue.

[0016] Furthermore, the washing process includes an acid washing process, specifically: mixing and washing crude titanium dioxide with dilute hydrochloric acid of pH=2-3 at a temperature of 50℃-60℃.

[0017] Furthermore, the washing process also includes a water washing process, specifically: the wet residue filtered after acid washing is mixed and washed with sodium hypochlorite and water, wherein the amount of sodium hypochlorite added is 0.2%-0.4% of the mass of titanium-containing waste residue, and the water is added according to the ratio of sodium hypochlorite:water = (0.5-1)g:1000ml.

[0018] Furthermore, the filtered washing liquid from the washing process can be recycled as the hydrolysate from the hydrolysis process.

[0019] Furthermore, the method also includes a drying process, in which the product after the washing process is dried at a temperature of 60-80°C for 6-8 hours.

[0020] Furthermore, the method also includes evaporating and crystallizing the filtrate from the pH adjustment process. The water vapor generated during the evaporation and crystallization process can be condensed and used to prepare the pickling solution in the pickling process, or to wash the filter residue.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention utilizes the hydrolysis reaction of titanium tetrachloride to dissolve titanium in titanium-containing waste residue in water, reducing ferric ions in the solution to ferrous ions. Then, by adjusting the pH value, all titanium dioxide is precipitated. After washing, titanium dioxide product is obtained. This invention optimizes the process of preparing titanium dioxide from titanium-containing waste residue and reduces production steps.

[0023] This invention reduces harmful gas emissions through direct hydrolysis with water, achieving clean, green, and environmentally friendly production. This invention uses the reduction of ferric ions to ferrous ions to prevent iron from precipitating in subsequent processes, thereby improving the purity of titanium dioxide. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] like Figure 1 As shown, a method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue includes the following steps:

[0027] Hydrolysis process: Titanium-containing waste residue is mixed with water, the mixture is heated to 50℃-60℃, stirred for 1 hour and then filtered. After filtration, the filtrate is poured into a separating funnel and left to stand for 1 hour to separate the oil and liquid.

[0028] Reduction process: Add alkali to the filtrate until the pH is 1-1.5, then add sodium metabisulfite to the hydrolyzed solution, stir the reaction for 0.5-1 hour, and filter to obtain the reduced solution;

[0029] pH adjustment process: Slowly add liquid alkali to the reduced solution to adjust the pH of the solution to 2-4. After reacting for 1 hour, filter to obtain wet residue and filtrate.

[0030] Acid washing process: Prepare a dilute hydrochloric acid solution with a pH of 2-3, heat it to 50℃-60℃, add wet residue and stir and wash it. After stirring for 1 hour, filter it. Add pure water to rinse the filter residue during filtration.

[0031] Washing process: After washing, the wet residue is stirred and reacted with water and sodium hypochlorite solution for 1 hour, and then filtered to obtain titanium dioxide wet residue;

[0032] Drying process: The wet titanium dioxide residue is dehydrated and dried at a temperature of 60-80℃ for 6-8 hours, and then packaged and shipped.

[0033] The titanium-containing waste residue is a titanium-containing waste residue from petrochemical catalysts, wherein the titanium content is 15wt%-25wt% and the iron content is 0.1wt%-0.2wt%.

[0034] In the hydrolysis process, the mass-volume ratio of titanium-containing waste residue to water is 1g:(5-8)ml.

[0035] The sodium metabisulfite is added at a mass ratio of 1:(80-100) to the titanium-containing waste residue.

[0036] In the pickling process, the dilute hydrochloric acid is added at a ratio of titanium-containing waste residue: dilute hydrochloric acid = 1g: (2-4)ml.

[0037] In the water washing process, the amount of sodium hypochlorite added is 0.2%-0.4% of the mass of titanium-containing waste residue, and the water is added according to the ratio of sodium hypochlorite:water = (0.5-1)g:1000ml, and the sodium hypochlorite is calculated according to the sodium hypochlorite content contained in the sodium hypochlorite solution.

[0038] The filtered acid-stirring and water-stirring washing solutions from the pickling and water-washing processes can be recycled as hydrolysate in the hydrolysis process.

[0039] The method further includes evaporating and crystallizing the filtrate from the pH adjustment process. The water vapor generated during the evaporation and crystallization process can be condensed and used to prepare the pickling solution in the pickling process or to wash the filter residue.

[0040] In the embodiments of the present invention, the concentration of sodium hypochlorite solution in the water washing process is 15wt%; and the concentration of liquid alkali in the pH adjustment process is 30wt%.

[0041] For specific implementation parameters, please refer to the respective embodiments. In each embodiment, titanium-containing waste residue from a certain factory was used to conduct experiments to prepare titanium dioxide. The main element content (wt%) of the titanium-containing waste residue is shown in Table 1.

[0042] Table 1

[0043] Ti (%) Fe (%) Al（%） Cr（%） Cu (%) K（%） Na (%) Mg (%) Mn (%) 20.31 0.15 4.42 0.0023 0.1927 0.59 14.81 0.93 0.0019

[0044] Example 1

[0045] A method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue includes the following steps:

[0046] 100g of titanium-containing waste residue from a certain factory was used to prepare titanium dioxide. The elemental content (wt%) of the titanium-containing waste residue is shown in Table 1.

[0047] Step 1: Take 500ml of water and put it into a 1000ml beaker. Slowly add 100g of waste residue. Heat the solution to 60℃ and stir for 1 hour. Then filter the solution. After filtration, pour the filtrate into a separatory funnel and let it stand for 1 hour to separate the oil and liquid.

[0048] Step 2: Place 500ml of the separated filtrate in a beaker and stir. Add sodium hydroxide solid to the filtrate until the pH reaches 1.0. Then add 1g of sodium metabisulfite solid and continue stirring for 1 hour. Filter the solution to obtain the reduced solution.

[0049] Step 3: Put 500ml of the reduced solution into a beaker and start stirring. Slowly add 600g of liquid alkali and adjust the pH to 2.0. After reacting for 1 hour, filter to obtain 438.2g of wet residue and 0.6L of filtrate (filtrate 1).

[0050] Step 4: Prepare 400ml of hydrochloric acid solution with pH value 2-3, heat to 50℃, add wet residue and stir and wash, after stirring for 1 hour, filter, add 300ml of pure water to rinse, and obtain 655ml of filtrate (filtrate 2).

[0051] Step 5: Add sodium hypochlorite solution (containing 0.25g sodium hypochlorite) and 400ml water to the washed wet residue, stir and react for 1 hour, and filter to obtain 236.46g of titanium dioxide wet residue and 550ml of filtrate (filtrate 3).

[0052] Step 6: Dehydrate and dry the wet residue at 60℃ for 8 hours to obtain 40.34g of dry residue.

[0053] The filtrate data analysis in Example 1 is shown in Table 2:

[0054] Table 2

[0055] Volume (ml) Ti(g / l) pH value Filtrate 1 600 0.1 2 Filtrate 2 655 1.3 2 Filtrate 3 555 3.4 3

[0056] The elemental content (wt%) of the titanium dioxide product in Example 1 is shown in Table 3:

[0057] Table 3

[0058] dry weight Moisture Ti Fe Al Ca Cr Cu K Na Mg Mn Zn Ni Si g % % % % % % % % % % % % % % 40.34 82.95 41.7 0.038 0.895 0.05 0.0005 0.01 0.007 0.47 0.037 0.001 0.0005 0.0006 0.15

[0059] Example 2

[0060] A method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue includes the following steps:

[0061] 800g of titanium-containing waste residue from a certain factory was used to prepare titanium dioxide. The main element content (wt%) of the titanium-containing waste residue is shown in Table 1.

[0062] Step 1: Take 800g of titanium-containing waste residue into 4L of pure water, heat to 60℃, stir for 1 hour and then filter. After filtration, pour the filtrate into a separatory funnel and let it stand for 1 hour to separate the oil and liquid.

[0063] Step 2: Place 4L of the separated filtrate in a beaker and stir. Add sodium hydroxide solid to the filtrate until the pH reaches 1.0. Then add 8g of sodium metabisulfite solid and continue stirring for 0.5h.

[0064] Step 3: Add liquid alkali to pH 2.0, react for 1 hour and then filter to obtain 1940 ml of filtrate (filtrate 4) and 3046.76 g of wet residue.

[0065] Step 4: Add 2L of dilute hydrochloric acid with pH=2-3 to the wet residue, heat and stir at 60℃ for 1 hour, then filter, wash with 2L of water to obtain 3.54L of filtrate (filtrate 5) and 2051.53g of wet residue.

[0066] Step 5: Pour the wet residue into 2L of water, turn on the stirrer, add sodium hypochlorite solution (containing 2g of sodium hypochlorite), react at room temperature for 1 hour, filter, and obtain 2334.71g of wet residue and 2.4L of filtrate (filtrate 6);

[0067] Step 6: Dehydrate and dry the wet residue at 60℃ for 8 hours to obtain 321.96g of dry residue.

[0068] The filtrate data analysis in Example 2 is shown in Table 4:

[0069] Table 4

[0070] Experiment Name Volume (ml) Ti(g / l) pH value Filtrate 4 1940 0.16 3 Filtrate 5 3540 0.23 3 Filtrate 6 2400 0.32 3

[0071] The elemental content (wt%) of the titanium dioxide product in Example 2 is shown in Table 5:

[0072] Table 5

[0073] dry weight Moisture Ti Fe Al Ca Cr Cu K Na Mg Mn Zn Ni Si g % % % % % % % % % % % % % % 321.96 86.21 45.44 0.01 0.159 0.068 0.0006 0.01 0.028 1.28 0.83 0.0003 0.0005 0.0008 0.17

[0074] The above technical solutions illustrate the technical concept of the present invention, but should not be construed as limiting the scope of protection of the present invention. Any modifications or alterations made to the above technical solutions based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue, characterized in that: Includes the following steps: Hydrolysis process: Titanium-containing waste residue is mixed with water to hydrolyze titanium tetrachloride in the titanium-containing waste residue; Reduction process: A reducing agent is added to the hydrolyzed solution to reduce the ferric iron in the solution to ferrous iron; pH adjustment process: Adjusting the pH value of the solution to obtain crude titanium dioxide precipitate; Washing process: Wash the crude titanium dioxide to produce titanium dioxide products.

2. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: The mass-to-volume ratio of titanium-containing waste residue to water in the hydrolysis process is 1g:(5-8)ml; the hydrolysis temperature is 50℃-60℃.

3. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: The hydrolysis process also includes post-hydrolysis filtration, followed by settling of the filtrate, separation of the liquid to remove oil, and obtaining an oil-free hydrolysate.

4. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: Before adding the reducing agent to the solution in the reduction process, the pH of the solution is adjusted to 1-1.

5.

5. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: The reducing agent in the reduction process is sodium metabisulfite, which is added at a mass ratio of 1:(80-100) to the titanium-containing waste residue.

6. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: The reverse pH adjustment process includes: adding an alkaline reagent to the solution after the reduction process, adjusting the pH value of the solution to 2-4, and filtering after the reaction to obtain crude titanium dioxide wet residue.

7. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: The washing process includes acid washing and water washing. The acid washing process specifically involves mixing and washing crude titanium dioxide with dilute hydrochloric acid at pH 2-3. The water washing process specifically involves mixing and washing the wet residue filtered after acid washing with sodium hypochlorite and water.

8. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 6, characterized in that: The pickling temperature in the pickling process is 50℃-60℃, the amount of sodium hypochlorite added in the water washing process is 0.2%-0.4% of the mass of titanium-containing waste residue, and the water is added according to the ratio of sodium hypochlorite:water = (0.5-1)g:1000ml.

9. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: The method also includes a drying process, in which the product after the washing process is dried at a temperature of 60-80℃ for 6-8 hours.

10. The method for preparing titanium dioxide by hydrolysis of titanium-containing waste residue according to claim 1, characterized in that: The filtered washing liquid in the washing process can be recycled as the hydrolysate in the hydrolysis process; the method also includes evaporating and crystallizing the filtrate in the reverse pH adjustment process, and the water vapor generated during the evaporation and crystallization process can be used to prepare the pickling solution in the pickling process or to wash the filter residue.

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