Method for promoting crystallization growth of by-product white gypsum from titanium dioxide waste acid

Abstract

The application relates to the technical field of recycling of waste by-products in the sulfuric acid method titanium dioxide industry, in particular to a method for promoting the crystallization growth of white gypsum by-products of waste acid of titanium dioxide; the method for promoting the crystallization growth of white gypsum by-products of waste acid of titanium dioxide comprises the following steps: mixing an alkaline neutralizing agent and a crystallization promoter to obtain an alkaline slurry containing the crystallization promoter; and adding the alkaline slurry containing the crystallization promoter into waste acid of titanium dioxide to perform reaction and filtration, so as to obtain white gypsum crystals; the application discloses a method for promoting the crystallization growth of white gypsum by-products of waste acid of titanium dioxide, wherein the crystallization promoter is added in the process of neutralization of the waste acid of titanium dioxide, so that coarse, three-dimensional and rhombic gypsum with low water content is obtained.

Description

Technical Field

[0001] This application relates to the technical field of recycling waste resources in the sulfuric acid process titanium dioxide industry, and in particular to a method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid. Background Technology

[0002] Currently, there are three main methods for treating the waste acid generated during the sulfuric acid process of titanium dioxide production: concentration and recovery, neutralization, and comprehensive utilization. Most of these methods involve neutralization with lime or salt mud, resulting in white gypsum crystals under acidic conditions. However, the separated gypsum particles are small, needle-like, and often have a free water content exceeding 35%, exhibiting poor dehydration performance. High-moisture gypsum is highly unfavorable for loading and transportation and cannot replace natural gypsum for resource utilization. Furthermore, excessively fine particles and high moisture content make it difficult to control the amount of water added after calcination, leading to problems such as particle segregation, poor rheological properties, and excessively high product density, which do not meet the requirements for building gypsum.

[0003] Conventional titanium dioxide waste acid neutralization process seriously affects the quality of gypsum. Current technologies have only conducted extensive research on parameters such as reaction temperature, reaction time, solution pH, and stirring speed, and cannot prepare white gypsum crystals with low water content.

[0004] Therefore, how to treat the waste acid generated during the sulfuric acid process of titanium dioxide production and prepare white gypsum crystals with low water content has become an urgent problem to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid. In this application, a crystallization promoter is added during the neutralization process of titanium dioxide waste acid, thereby obtaining coarse, three-dimensional, rhomboid gypsum crystals with low water content, thus improving the washing and filtering effect of the gypsum crystals.

[0006] In a first aspect, this application provides a method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, using the following technical solution: A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, includes the following steps: An alkaline neutralizer and a crystallization accelerator are mixed to obtain an alkaline slurry containing a crystallization accelerator. An alkaline slurry containing a crystallization promoter is added to titanium dioxide waste acid for reaction, and then filtered to obtain white gypsum crystals.

[0007] By adopting the above technical solutions, this application effectively improves the morphology and particle size of gypsum crystals, enhances crystal quality, and increases the application value of gypsum crystals by optimizing the formulation of the crystallization promoter and the process for promoting crystal growth.

[0008] Preferably, the crystallization promoter comprises the following components by mass percentage: 5-10% crystallization agent, 15-25% adsorbent surfactant, 1-5% sulfonated melamine-formaldehyde resin, 8-15% organic solvent, and the balance being water.

[0009] Preferably, the crystallization agent is citric acid.

[0010] Preferably, the adsorbent surfactant is polyethylene glycol.

[0011] Preferably, the organic solvent is ethanol.

[0012] By adopting the above technical solution, this application uses citric acid as a crystallization agent, polyethylene glycol as an adsorbent surfactant, and sulfonated melamine-formaldehyde resin (SMF) as a crystallization promoter to obtain coarse, low-moisture white gypsum crystals. Citric acid, as the crystallization agent, can regulate the morphology of white gypsum crystals because its functional groups can restrict the crystal growth space, thus affecting the crystal morphology. For example, carboxyl groups or organic acid anions are adsorbed on the Z-axis crystal plane (i.e., the 111 crystal plane) of calcium sulfate crystals, interacting with the Ca on the crystal plane. 2+ The active sites of the crystal bind, reducing its surface energy and inhibiting its growth along the Z-axis, thus decreasing its aspect ratio. The adsorbent surfactant polyethylene glycol is used to create a synergistic effect, promoting uniform growth of gypsum crystals along the X, Y, and Z axes, thereby reducing the probability of needle-like and plate-like crystal formation. Furthermore, the organic solvent ethanol improves the crystallization environment, enhances the stability and flowability of the crystallization promoter, and increases crystallization efficiency.

[0013] The resulting by-product gypsum crystals can be used in building gypsum, primarily in cement. When gypsum crystals are applied to cement, a complex (SMF-Ca) is formed between the polymer sulfonated melamine-formaldehyde resin (SMF) and metallic calcium ions. 2+ It can further optimize the performance of cement and improve its compressive and flexural strength; the gypsum crystals in cement can regulate the setting time of cement, prevent it from solidifying too quickly, and improve its compressive and flexural strength.

[0014] In this application, citric acid, polyethylene glycol, and polymer sulfonated melamine-formaldehyde resin (SMF) are used as crystallization promoters. Through their synergistic effect, they promote crystallization, thereby obtaining coarse white gypsum crystals with low water content.

[0015] Preferably, the mass ratio of the alkaline neutralizing agent, the crystallization promoter, and the titanium dioxide waste acid is 1:(0.03-0.06):(5-5.5).

[0016] Preferably, the alkaline neutralizing agent is salt mud slurry.

[0017] Preferably, the titanium dioxide waste acid is pretreated by the following steps: filtering the titanium dioxide waste acid to obtain pretreated titanium dioxide waste acid.

[0018] By adopting the above technical solution, this application removes insoluble impurities through filtration, thereby obtaining white gypsum crystals with higher purity.

[0019] Preferably, when adding the alkaline slurry containing the crystallization promoter to the titanium dioxide waste acid for reaction, the alkaline slurry containing the crystallization promoter is added to the titanium dioxide waste acid in multiple portions.

[0020] By adopting the above technical solution, this application adds alkaline slurry containing crystallization promoter to titanium dioxide waste acid in multiple batches for reaction. This is mainly because when added in multiple batches, the gypsum generated by the reaction of calcium carbonate in the first batch of alkaline neutralizing agent salt mud slurry with sulfuric acid in titanium dioxide waste acid can serve as seed crystals. When alkaline neutralizing agent salt mud slurry is added again, the newly generated gypsum by the reaction of calcium carbonate in the alkaline neutralizing agent with sulfuric acid continues to nucleate and grow on the surface of the seed crystals.

[0021] Preferably, when the alkaline slurry containing the crystallization promoter is added to the titanium dioxide waste acid for reaction, the reaction temperature of the slurry solution is 45-55℃; for example, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃ or 55℃.

[0022] Preferably, when the alkaline slurry containing the crystallization promoter is added to the titanium dioxide waste acid for reaction, the reaction time of the slurry solution is 3-5 hours; for example, 3 hours, 4 hours or 5 hours.

[0023] By adopting the above technical solution, this application controls the reaction temperature and reaction time of the slurry solution, thereby obtaining white gypsum crystals with relatively regular morphology and low water content.

[0024] Preferably, when adding the alkaline slurry containing the crystallization promoter to the titanium dioxide waste acid for reaction, the pH of the slurry at the reaction endpoint is controlled to be 1.5-2.

[0025] By adopting the above technical solution, in a reaction system with a low pH value, H + Can react with SO4 2- Combine to form HSO4 - Increase the amount of free SO4 in the solution 2- A higher concentration of OH will accelerate the growth rate at the top of the crystal and correspondingly increase the crystal's aspect ratio; conversely, a higher pH concentration will have the opposite effect. - With Ca 2+ Calcium hydroxide is generated, which hinders the longitudinal growth of crystals; therefore, the pH of the slurry at the reaction endpoint is controlled to be acidic at 1.5-2.

[0026] In summary, this application includes at least one of the following beneficial technical effects: This application discloses a method for promoting the crystal growth of white gypsum, a byproduct of titanium dioxide waste acid. This application improves the preparation process by adding a crystallization promoter. The crystallization is promoted through the synergistic effect between citric acid, polyethylene glycol, and polymer sulfonated melamine-formaldehyde resin, thereby obtaining coarse, three-dimensional, rhomboid, low-moisture gypsum. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the crystal shape of the white gypsum prepared in Example 1; Figure 2 This is a schematic diagram of the crystal shape of the white gypsum prepared in Comparative Example 1. Detailed Implementation

[0028] The technical solutions of this application are further illustrated by specific embodiments below. These specific embodiments do not represent a limitation on the scope of protection of this application. Any non-essential modifications and adjustments made by others based on the concept of this application still fall within the scope of protection of this application.

[0029] All raw materials involved in this application are commercially available products, among which, Polymer sulfonated melamine-formaldehyde resin (SMF), manufacturer: Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., model: 9003-08-1.

[0030] Polyethylene glycol was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0031] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0032] A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, comprises the following steps: (1) The titanium dioxide waste acid is filtered to remove insoluble impurities and pretreated titanium dioxide waste acid is obtained. (2) Add water to the alkaline neutralizer and slurry it. Then, under stirring conditions, add crystallization promoter and mix to obtain an alkaline slurry containing crystallization promoter. (3) Add the pretreated titanium dioxide waste acid to the reaction vessel, and add the alkaline slurry containing crystallization promoter to the pretreated titanium dioxide waste acid in multiple batches for reaction, and control the pH of the slurry at the end of the reaction to be 1.5-2. (4) After the gypsum obtained by the neutralization reaction is filtered, it is washed with a certain amount of deionized water. The washing endpoint is when the filter cake is filtered until there is no filtrate within 30 seconds, and coarse, three-dimensional, rhomboid white gypsum crystals with low water adhesion are obtained. (5) Observe the crystal form of white gypsum crystals under a microscope and test the content of attached water.

[0033] Preferably, the mass ratio of the alkaline neutralizing agent, the crystallization promoter, and the titanium dioxide waste acid is 1:(0.03-0.06):(5-5.5).

[0034] Preferably, the alkaline neutralizing agent is salt mud slurry.

[0035] Preferably, in step (3), an alkaline slurry containing a crystallization promoter is added to titanium dioxide waste acid for reaction, the reaction temperature of the slurry solution is 45-55℃, and the reaction time is 3-5 hours.

[0036] Preferably, the crystallization promoter comprises the following components by mass percentage: 5-10% citric acid as a crystallization agent, 15-25% polyethylene glycol as an adsorbent surfactant, 1-5% sulfonated melamine-formaldehyde resin (SMF) as a polymer, 8-15% ethanol as an organic solvent, and the balance being water.

[0037] Example 1:

[0038] A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, includes the following steps: (1) The titanium dioxide waste acid is filtered to remove insoluble impurities, and the filtered titanium dioxide waste acid is obtained. (2) Add water to the salt mud slurry and beat it to obtain 1000mL of salt mud slurry (the mass fraction of calcium carbonate in the salt mud slurry is 28%). Then, under stirring conditions, add 16.8g of crystallization promoter and stir evenly to obtain salt mud slurry containing crystallization promoter. (3) Add 1540g of filtered titanium dioxide waste acid (the mass fraction of sulfuric acid in the titanium dioxide waste acid is 20%) to the reaction vessel. (4) First, heat the salt mud slurry containing crystallization promoter to 50°C. Then, add the heated salt mud slurry containing crystallization promoter in four equal volumes to the filtered titanium dioxide waste acid. During the reaction, control the reaction temperature of the slurry solution to 50°C and the reaction time to 4 hours. Control the pH of the slurry at the reaction endpoint to 1.8. After the reaction, filter and separate the white gypsum crystals. Wash with deionized water three times and filter until there is no filtrate within 30 seconds to obtain the white gypsum crystal sample.

[0039] The crystallization accelerator comprises the following components by mass percentage: 8% citric acid, 20% polyethylene glycol, 3% sulfonated melamine-formaldehyde resin, 11% ethanol, and water to make up to 100%.

[0040] The preparation method of the crystallization accelerator is as follows: citric acid, polyethylene glycol, sulfonated melamine-formaldehyde resin, ethanol, and water are mixed and stirred evenly to prepare the crystallization accelerator.

[0041] Example 2:

[0042] The difference from Example 1 is that the raw material components of the crystallization accelerator are different.

[0043] In this embodiment, the crystallization promoter comprises the following components by mass percentage: 5% citric acid, 25% polyethylene glycol, 1% sulfonated melamine-formaldehyde resin, 15% ethanol, and water is added to make up to 100%.

[0044] Example 3:

[0045] The difference from Example 1 is that the raw material components of the crystallization accelerator are different.

[0046] In this embodiment, the crystallization promoter comprises the following components by mass percentage: 10% citric acid, 15% polyethylene glycol, 5% sulfonated melamine-formaldehyde resin, 8% ethanol, and water is added to make up to 100%.

[0047] Example 4:

[0048] The difference from Example 1 is that the amount of crystallization promoter added is different.

[0049] In this embodiment, the amount of crystallization promoter added is 8.4g.

[0050] Example 5:

[0051] The difference from Example 1 is that the amount of crystallization promoter added is different.

[0052] In this embodiment, the amount of crystallization promoter added is 11.2g.

[0053] Example 6:

[0054] The difference from Example 1 is that the amount of crystallization promoter added is different.

[0055] In this embodiment, the amount of crystallization promoter added is 14.0g.

[0056] Example 7:

[0057] The difference from Example 1 is that in step (3), the salt mud slurry containing crystallization promoter is added to the titanium dioxide waste acid in two equal volumes.

[0058] Example 8:

[0059] The difference from Example 1 is that in step (3), the salt mud slurry containing crystallization promoter is added to the titanium dioxide waste acid in three equal volumes.

[0060] Example 9:

[0061] The difference from Example 1 is that in step (3), the salt mud slurry containing crystallization promoter is added to the titanium dioxide waste acid in five equal volumes.

[0062] Example 10:

[0063] A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, includes the following steps: (1) The titanium dioxide waste acid is filtered to remove insoluble impurities, and the filtered titanium dioxide waste acid is obtained. (2) Add water to the salt mud slurry and beat it to obtain 1000mL of salt mud slurry (the mass fraction of calcium carbonate in the salt mud slurry is 28%). Then, under stirring conditions, add 8.4g of crystallization promoter and stir evenly to obtain salt mud slurry containing crystallization promoter. (3) Add 1400g of filtered titanium dioxide waste acid (the mass fraction of sulfuric acid in the titanium dioxide waste acid is 20%) to the reaction vessel. (4) First, heat the salt mud slurry containing crystallization promoter to 45°C. Then, add the heated salt mud slurry containing crystallization promoter in equal volumes in 4 portions to the filtered titanium dioxide waste acid. During the reaction, control the reaction temperature of the slurry solution to 45°C and the reaction time to 3 hours. Control the pH of the slurry at the end of the reaction to 2. After the reaction, filter and separate the white gypsum crystals. Wash with deionized water 3 times and filter until there is no filtrate within 30 seconds to obtain the white gypsum crystal sample.

[0064] The crystallization accelerator comprises the following components by mass percentage: 8% citric acid, 20% polyethylene glycol, 3% sulfonated melamine-formaldehyde resin, 11% ethanol, and water to make up to 100%.

[0065] The preparation method of the crystallization accelerator is as follows: citric acid, polyethylene glycol, sulfonated melamine-formaldehyde resin, ethanol, and water are mixed and stirred evenly to prepare the crystallization accelerator.

[0066] Example 11:

[0067] A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, includes the following steps: (1) The titanium dioxide waste acid is filtered to remove insoluble impurities, and the filtered titanium dioxide waste acid is obtained. (2) Add water to the salt mud slurry and beat it to obtain 1000mL of salt mud slurry (the mass fraction of calcium carbonate in the salt mud slurry is 28%). Then, under stirring conditions, add 16.8g of crystallization promoter and stir evenly to obtain salt mud slurry containing crystallization promoter. (3) Add 1484g of filtered titanium dioxide waste acid (the mass fraction of sulfuric acid in the titanium dioxide waste acid is 20%) to the reaction vessel. (4) First, heat the salt mud slurry containing crystallization promoter to 55°C. Then, add the heated salt mud slurry containing crystallization promoter in four equal volumes to the filtered titanium dioxide waste acid. During the reaction, control the reaction temperature of the slurry solution to 55°C and the reaction time to 5 hours. Control the pH of the slurry at the reaction endpoint to 1.5. After the reaction, filter and separate the white gypsum crystals. Wash with deionized water three times and filter until there is no filtrate within 30 seconds to obtain the white gypsum crystal sample.

[0068] The crystallization accelerator comprises the following components by mass percentage: 8% citric acid, 20% polyethylene glycol, 3% sulfonated melamine-formaldehyde resin, 11% ethanol, and water to make up to 100%.

[0069] The preparation method of the crystallization accelerator is as follows: citric acid, polyethylene glycol, sulfonated melamine-formaldehyde resin, ethanol, and water are mixed and stirred evenly to prepare the crystallization accelerator.

[0070] Comparative Example 1:

[0071] A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, includes the following steps: (1) The titanium dioxide waste acid is filtered to remove insoluble impurities, and the filtered titanium dioxide waste acid is obtained. (2) Add water to the salt mud slurry and beat it to obtain 1000 mL of salt mud slurry (the mass fraction of calcium carbonate in the salt mud slurry is 28%). (3) Add 1540g of filtered titanium dioxide waste acid (the mass fraction of sulfuric acid in the titanium dioxide waste acid is 20%) to the reaction vessel. (4) First, heat the salt mud slurry to 50°C, and then add the heated salt mud slurry in equal volumes in 4 portions to the filtered titanium dioxide waste acid. During the reaction, control the reaction temperature of the slurry solution to 50°C and the reaction time to 4 hours. Control the pH of the slurry at the end of the reaction to 1.8. After the reaction, filter and separate the white gypsum crystals, wash them 3 times with deionized water, and filter until there is no filtrate within 30 seconds to obtain the white gypsum crystal sample.

[0072] Comparative Example 2:

[0073] The difference from Example 1 is that the amount of crystallization promoter added is different.

[0074] In this comparative example, the amount of crystallization accelerator added was 5.6g.

[0075] Comparative Example 3:

[0076] The difference from Example 1 is that the amount of crystallization promoter added is different.

[0077] In this comparative example, the amount of crystallization accelerator added was 19.6g.

[0078] Comparative Example 4:

[0079] A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, includes the following steps: (1) The titanium dioxide waste acid is filtered to remove insoluble impurities, and the filtered titanium dioxide waste acid is obtained. (2) Add water to the salt mud slurry and beat it to obtain 1000mL of salt mud slurry (the mass fraction of calcium carbonate in the salt mud slurry is 28%). Then, under stirring conditions, add 16.8g of crystallization promoter and stir evenly to obtain salt mud slurry containing crystallization promoter. (3) Add 1540g of filtered titanium dioxide waste acid (the mass fraction of sulfuric acid in the titanium dioxide waste acid is 20%) to the reaction vessel. (4) First, heat the salt mud slurry containing crystallization promoter to 50°C, and then add all the heated salt mud slurry containing crystallization promoter to the filtered titanium dioxide waste acid. During the reaction, control the reaction temperature of the slurry solution to 50°C, the reaction time to 4 hours, and control the pH of the slurry at the reaction endpoint to 1.8. After the reaction, filter and separate the white gypsum crystals, wash them 3 times with deionized water, and filter until there is no filtrate within 30 seconds to obtain the white gypsum crystal sample.

[0080] The crystallization accelerator comprises the following components by mass percentage: 8% citric acid, 20% polyethylene glycol, 3% sulfonated melamine-formaldehyde resin, 11% ethanol, and water to make up to 100%.

[0081] The preparation method of the crystallization accelerator is as follows: citric acid, polyethylene glycol, sulfonated melamine-formaldehyde resin, ethanol, and water are mixed and stirred evenly to prepare the crystallization accelerator.

[0082] Comparative Example 5:

[0083] A method for promoting the crystal growth of gypsum, a byproduct of titanium dioxide waste acid, includes the following steps: (1) Add water to the salt mud slurry and beat it to obtain 1000mL of salt mud slurry (the mass fraction of calcium carbonate in the salt mud slurry is 28%). Then, under stirring conditions, add 16.8g of crystallization promoter and stir evenly to obtain salt mud slurry containing crystallization promoter. (2) Add 1540g of titanium dioxide waste acid (the mass fraction of sulfuric acid in the titanium dioxide waste acid is 20%) to the reaction vessel. (3) First, heat the salt mud slurry containing crystallization promoter to 50°C. Then, add the heated salt mud slurry containing crystallization promoter to titanium dioxide waste acid in four equal volumes. During the reaction, control the reaction temperature of the slurry solution to 50°C and the reaction time to 4 hours. Control the pH of the slurry at the end of the reaction to 1.8. After the reaction, filter and separate the white gypsum crystals. Wash with deionized water three times and filter until there is no filtrate within 30 seconds to obtain the white gypsum crystal sample.

[0084] The crystallization accelerator comprises the following components by mass percentage: 8% citric acid, 20% polyethylene glycol, 3% sulfonated melamine-formaldehyde resin, 11% ethanol, and water to make up to 100%.

[0085] The preparation method of the crystallization accelerator is as follows: citric acid, polyethylene glycol, sulfonated melamine-formaldehyde resin, ethanol, and water are mixed and stirred evenly to prepare the crystallization accelerator.

[0086] Performance testing:

[0087] The attached water content, crystal shape, and particle size of the white gypsum crystals prepared in the above embodiments and comparative examples were tested, as follows: Adhered water content: The adhered water content was detected using a gypsum phase composition analyzer; White gypsum crystal shape: Observation of white gypsum crystal form under a microscope; Gypsum particle size analysis: Particle size distribution was tested using a laser particle size analyzer to obtain the average particle size. The larger the particle size, the better the gypsum pressure filtration and dewatering performance. Table 1 Performance Test Results Example 1 8.5 56.4 Large, three-dimensional, rhomboid Example 2 12.2 41.6 Large, three-dimensional, rhomboid Example 3 10.9 45.8 Large, three-dimensional, rhomboid Example 4 10.2 45.1 Large, three-dimensional, rhomboid Example 5 9.6 52.7 Large, three-dimensional, rhomboid Example 6 8.8 54.5 Large, three-dimensional, rhomboid Example 7 13.3 38.2 Large, three-dimensional, rhomboid Example 8 10.6 46.5 Large, three-dimensional, rhomboid Example 9 10.1 47.3 Large, three-dimensional, rhomboid Example 10 9.9 51.2 Large, three-dimensional, rhomboid Example 11 8.7 55.4 Large, three-dimensional, rhomboid Comparative Example 1 23.3 19.5 flakes Comparative Example 2 15.1 28.2 A mixture of flakes and rhombuses Comparative Example 3 14.4 31.4 thin plate-shaped rhombus Comparative Example 4 14.9 30.6 thin plate-shaped rhombus Comparative Example 5 17.2 24.6 A mixture of flakes and rhombuses Based on the test results of Examples 1-11, it can be seen that the white gypsum crystals prepared in Examples 1-11 have good pressure filtration and dehydration performance, indicating that this application effectively improves the pressure filtration and dehydration performance of white gypsum crystals by adding a crystallization promoter during the neutralization process of titanium dioxide waste acid to obtain white gypsum crystals with low water content. From the crystal morphology observation, the white gypsum crystals prepared in Examples 1-11 have larger and more three-dimensional crystals. Figure 1 This demonstrates that the method for promoting the crystal growth of white gypsum, a byproduct of titanium dioxide waste acid, has significant advantages in improving crystal formation. The method described in this application can yield large, three-dimensional, rhomboid white gypsum crystals with low water content.

[0088] Based on the test results of Example 1 and Comparative Example 1, it can be seen that the filtration and dehydration performance of the white gypsum crystals prepared in Example 1 is better than that of Comparative Example 1. This indicates that the addition of a crystallization promoter during the neutralization process of titanium dioxide waste acid in this application effectively improves the filtration and dehydration performance of the white gypsum crystals, thereby obtaining coarse, three-dimensional, rhomboid white gypsum crystals with low water content.

[0089] Based on the test results of Examples 1, 4-6, Comparative Examples 2 and 3, it can be seen that the amount of crystallization accelerator added has a certain influence on the pressure filtration and dehydration performance of gypsum crystallization. Furthermore, when the mass ratio of alkaline neutralizer to crystallization accelerator is 1:(0.03-0.06), the prepared gypsum crystals exhibit the best pressure filtration and dehydration performance.

[0090] Based on the test results of Examples 1, 7-9, and Comparative Example 4, it can be seen that the white gypsum crystals prepared in Example 1 exhibit the best pressure filtration and dehydration performance. This indicates that during the neutralization reaction, adding equal volumes of salt mud slurry containing crystallization promoters to the titanium dioxide waste acid in multiple portions results in better overall pressure filtration and dehydration performance of the white gypsum crystals. This is mainly because when the salt mud slurry containing crystallization promoters is added to the titanium dioxide waste acid in multiple portions, the white gypsum generated by the reaction of calcium carbonate in the first added alkaline neutralizing agent salt mud slurry with sulfuric acid in the titanium dioxide waste acid can serve as seed crystals. When the alkaline neutralizing agent salt mud slurry is added later, the newly generated white gypsum from the reaction of calcium carbonate in the alkaline neutralizing agent with sulfuric acid continues to nucleate and grow on the surface of the seed crystals. Therefore, adding equal volumes of alkaline slurry containing crystallization promoters to the titanium dioxide waste acid in multiple portions can produce white gypsum crystals with larger particles.

[0091] Based on the test results of Example 1 and Comparative Example 5, it can be seen that the filtration and dehydration performance of the white gypsum crystals prepared in Example 1 is better than that of Comparative Example 5. This shows that pretreatment of titanium dioxide waste acid and filtration of titanium dioxide waste acid to remove insoluble impurities result in better overall filtration and dehydration performance of the prepared gypsum.

Claims

1. A method for promoting the crystalline growth of by-product white gypsum from titanium white waste acid, characterized by: Includes the following steps: An alkaline neutralizer and a crystallization accelerator are mixed to obtain an alkaline slurry containing a crystallization accelerator. An alkaline slurry containing a crystallization promoter is added to titanium dioxide waste acid for reaction, and then filtered to obtain white gypsum crystals. The crystallization promoter comprises the following components by mass percentage: 5-10% crystallization agent, 15-25% adsorbent surfactant, 1-5% sulfonated melamine-formaldehyde resin, 8-15% organic solvent, and the balance being water.

2. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 1, is characterized in that: The crystallization agent is citric acid.

3. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 1, is characterized in that: The adsorbent surfactant is polyethylene glycol; the organic solvent is ethanol.

4. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 1, is characterized in that: The mass ratio of the alkaline neutralizer, crystallization promoter, and titanium dioxide waste acid is 1:(0.03-0.06):(5-5.5).

5. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 4, is characterized in that: The alkaline neutralizing agent is salt mud slurry.

6. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 1, is characterized in that: The pretreatment of titanium dioxide waste acid is carried out by the following steps: filtering the titanium dioxide waste acid to obtain pretreated titanium dioxide waste acid.

7. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 1, is characterized in that: When adding alkaline slurry containing crystallization promoter to titanium dioxide waste acid for reaction, the alkaline slurry containing crystallization promoter is added to titanium dioxide waste acid in multiple batches.

8. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 1, is characterized in that: When an alkaline slurry containing a crystallization promoter is added to titanium dioxide waste acid for reaction, the reaction temperature of the slurry solution is 45-55℃ and the reaction time is 3-5 hours.

9. The method for promoting the crystallization and growth of gypsum, a byproduct of titanium dioxide waste acid, according to claim 1, is characterized in that: When adding alkaline slurry containing crystallization promoter to titanium dioxide waste acid for reaction, the pH of the slurry at the reaction endpoint should be controlled to be 1.5-2.

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