A method of hydrolysis filtration aid

Abstract

The application discloses a hydrolysis material filtration aid method, comprising the following steps: S1, uniformly dispersing fly filter into the hydrolysis material and heating to obtain a mixture of the fly filter and the hydrolysis material; S2, adding a flocculating agent into the mixture of the fly filter and the hydrolysis material obtained in S1 and uniformly stirring to obtain a second mixture; S3, filtering the second mixture in S2 to obtain a filter cake, and washing the filter cake with water to obtain a filter cake with a standard iron content; wherein the mass fractions of the hydrolysis material, the fly filter and the flocculating agent are 100 parts, 0.01-1 parts and 0.001-0.01 parts respectively. The application is beneficial to realize rapid filtration, effectively control the TiO2 particle filtration phenomenon, improve the water washing yield and ensure that the ferrous ion in the hydrolysis material meets the standard.

Description

Technical Field

[0001] This invention relates to a filtration aid method, and more particularly to a filtration aid method for hydrolyzed materials. Background Technology

[0002] After concentration, the total titanium concentration of the titanium solution is increased to approximately 195-200 g / L. It then proceeds to the hydrolysis process. The purpose of hydrolysis is to hydrolyze TiO2SO4 under heating to generate hydrated titanium dioxide, i.e., metatitanic acid (H2TiO3). The concentrated titanium solution is heated to 95°C, and the prepared hydrolyzed seed crystals are added. After stirring evenly, the material is placed in a hydrolysis tank, and the temperature is further increased to boiling. The boiling state is maintained until the titanium solution turns bluish-gray. Heating is stopped for 30 minutes, and the temperature is further increased to a second boil. A gentle boil is maintained for 3 hours, at which point the hydrolysis is complete, yielding hydrated titanium dioxide with a large amount of mother liquor adsorbed on its surface.

[0003] The mother liquor contains a large amount of ferrous sulfate and sulfates of metals such as magnesium, aluminum, chromium, manganese, copper, and lead. The presence of these impurities severely affects the optical properties, pigment performance, and application performance of the product; therefore, it is essential to remove these impurities from the mother liquor. The water washing process utilizes the insolubility of hydrated titanium dioxide and the solubility of impurity ions to remove these ions, thereby purifying the hydrated titanium dioxide.

[0004] However, the TiO2 particles in the hydrolyzed material are very small, and their huge surface free energy causes them to aggregate, resulting in a large average particle size distribution. Although the aggregates are large, their volume is easily compressed, forming a dense filter cake. Impurities such as iron ions are tightly encapsulated and cannot diffuse into the water, resulting in poor washing performance.

[0005] Patent CN1040303468, "A Method for Preparing High-Whiteness Rutile Titanium Dioxide," discloses a method for washing hydrolyzed materials. The method involves adding cellulose after hydrolysis, which aids in washing, but does not address the issue of washing away fine hydrolyzed particles. In this patent, the hydrolyzed metatitanic acid particles are uneven in size, containing small particles. During filtration, these small particles clog the pores of the filter cloth, affecting the filtration performance of the hydrolyzed material; they also penetrate the filtrate, impacting the yield. This patent does not provide solutions for the clogging of the filter cloth by small particles or for their penetration into the filtrate.

[0006] Patent CN110143712A, "A Pretreatment Method for Leachate from Hazardous Waste Landfills," discloses a pretreatment method for leachate from hazardous waste landfills, comprising the following steps: S1. Collecting leachate, filtering under pressure to obtain coarse filtrate for later use, removing the filter cake, drying and crushing it to obtain filter residue particles for later use; S2. Adding activated carbon particles, iron filings, and sulfuric acid to the coarse filtrate obtained in S1, followed by stirring, with hydrogen peroxide added during the stirring process; S3. Adding polyaluminum ferric sulfate to the mixture obtained after stirring in S2, allowing it to stand for a period of time, collecting the supernatant, collecting the centrifuged liquid for later use, drying and crushing the solid matter obtained from centrifugation and the filter cake obtained from filtration, and mixing the crushed solid matter with the filter residue particles obtained in S1 to obtain a filter residue mixture for later use; S4. Introducing air into the centrifuged liquid obtained in S3 for air flotation to remove sludge; S5. Introducing the liquid obtained in S4 into an evaporation system for heating and evaporation, collecting the evaporated gas, condensing it, and recovering it for later use. With this invention, the leachate treatment eliminates the wall-clinging phenomenon in the evaporation system, extending the service life of the evaporation system. This patent incorporates filtrate into a plate and frame filter press. The function of filtrate is to adsorb the filter residue and retain the solids. After plate and frame filtration, the filtrate and the solids are discarded together.

[0007] Patent CN103638744B, entitled "A Method for Improving the Filtration Performance of Acidic Fly Ash Slurry," discloses a method for improving the filtration performance of acidic fly ash slurry. This patent employs the addition of filter aids, flocculants, or surfactants, or mixtures of two or more, during the filtration process of acidic fly ash slurry to enhance the filtration performance and achieve effective separation of the fly ash slurry. In this patent, cellulose is added for plate and frame filtration, adsorbing the filter residue and retaining the solids. After plate and frame filtration, the filter aid is discarded along with the solids. Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a method for filtration of hydrolyzed materials that addresses the shortcomings of existing technologies, thereby facilitating rapid filtration, effectively controlling the filtration phenomenon of TiO2 particles, improving water washing yield, and ensuring that the ferrous ion content in the hydrolyzed material meets the standards.

[0009] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for filtration of hydrolyzed materials, comprising the following steps:

[0010] S1. Disperse the filtrate evenly in the hydrolysate and heat it to obtain a mixture of filtrate and hydrolysate.

[0011] S2. Add flocculant to the mixture of filtrate and hydrolyzed material obtained in S1 and stir evenly to obtain mixture two;

[0012] S3. Filter the mixture from S2 to obtain filter cake. Wash the filter cake with water to obtain filter cake with the required iron content.

[0013] The mass fractions of hydrolysate, filtrate, and flocculant are 100 parts, 0.01-1 parts, and 0.001-0.01 parts, respectively.

[0014] When filtrate is added to the hydrolyzed material, the TiO2 particles in the hydrolyzed material mix with the filtrate, forming an irregular network on the filter membrane surface. The filtrate fully utilizes its bridging function, improving the filter cake structure and gradually thickening the internal structure during TiO2 filtration. This crisscrossing, irregular three-dimensional network provides excellent dispersion and more filtration channels for the TiO2 particles, effectively controlling TiO2 particle permeation. The filtrate also has slippery properties, making the filter cake easy to remove and significantly improving work efficiency.

[0015] If too little of the filter element is added, it will not have any effect on filtration; if too much is added, it will be wasteful and will affect the filtration effect and the quality of the final product.

[0016] Adding flocculants helps to agglomerate fine particles into larger particles, which then migrate to the three-dimensional structure of the filter media, preventing fine particles from clogging the filter cloth pores and passing through the filter. Without flocculants, fine particles are prone to clogging the filter cloth pores or passing through the filter. Adding too little flocculant has little effect, while adding too much increases the viscosity of the hydrolysate, hindering its filtration performance.

[0017] In a preferred embodiment of the present invention, the heating temperature in S1 is 110°C-115°C.

[0018] This temperature range is more conducive to the formation of a larger network by felicin, and a smaller amount of felicin can achieve better results.

[0019] In a preferred embodiment of the present invention, in S1, filtrate is added before the end of titanium liquid hydrolysis, so that filtrate can be uniformly dispersed in the hydrolysate after the end of titanium liquid hydrolysis.

[0020] The hydrolysate is constantly stirred and boiling during the hydrolysis process, and it is also constantly in a flowing state. After adding the filtrate, the filtrate is continuously mixed with the hydrolysate by means of the flow of the hydrolysate, so that it can be evenly dispersed in the hydrolysate.

[0021] The hydrolysis process of the hydrolyzed material involves the hydrolysis of TiOSO4 to generate metatitanic acid H2TiO3, also known as hydrated titanium dioxide.

[0022] In a preferred embodiment of the present invention, in S1, filtrate is added 20-40 minutes before the end of titanium liquid hydrolysis.

[0023] Adding filtrate before the end of titanium hydrolysis allows for more uniform mixing of the hydrolysate and filtrate due to the boiling state of the hydrolysate, significantly saving production time. If filtrate is added after hydrolysis, it requires a long stirring time to ensure even mixing.

[0024] In a preferred embodiment of the present invention, the ash content of the filtrate in S1 after calcination is less than 0.01 parts.

[0025] In this invention, the amount of filtrate added is 0.1-1%, and the solid TiO2 needs to be processed and calcined. The ash content of the filtrate is strictly controlled, requiring it to be less than 0.01%. If too much filtrate is added, the ash content of the filtrate after calcination will affect the quality of the final product.

[0026] In a preferred embodiment of the present invention, the specific method in S3 includes the following steps: filtering the mixture in S2;

[0027] Once the thickness of the filter cake obtained from filtering the mixture in S2 reaches the standard, the filter cake is washed with water. The washing is stopped when the concentration of ferrous ions in the washing filtrate reaches the standard.

[0028] After washing, remove the filter cake and add deionized water to make a paste.

[0029] In a preferred embodiment of the present invention, the method for detecting that the iron ion concentration in the water washing filtrate meets the standard is as follows: after washing for a period of time, take the water washing filtrate, add 8-12% potassium ferricyanide by mass, and if the color is light green, it indicates that the ferrous ion concentration meets the standard.

[0030] In a preferred embodiment of the present invention, the reaction temperature of S2 is 50-65°C.

[0031] The hydrolyzed material is pumped into a cooling tank, and once the material temperature drops to 50-65℃, a pre-prepared flocculant with a concentration of 100-200ppm is added.

[0032] In this invention, the flocculation effect is not obvious when the flocculant concentration is higher than 200 ppm.

[0033] In a preferred embodiment of the present invention, the flocculant in S2 is anionic polyacrylamide with a molecular weight of 12 million or more.

[0034] The hydrolyzed TiO2 particles are extremely fine, with the smallest being only a few tenths of a micrometer. In this invention, anionic polyacrylamide is used as the flocculant, with a fractional mass exceeding 12 million, which can more quickly agglomerate the fine particles into larger particles.

[0035] The specific steps of this invention include:

[0036] 1. Half an hour before the end of hydrolysis, add 0.01-1% filtrate (calculated as TiO2);

[0037] 2. Continue until hydrolysis is complete, ensuring that the filtrate is evenly dispersed in the hydrolysate;

[0038] 3. Pump the hydrolyzed material into the cooling tank, add 0.001-0.01% flocculant (pre-prepared concentration of 100-200ppm) and stir. Then pump the hydrolyzed material into the leaf filter suction tank and use a vacuum leaf filter to suction the leaf filters.

[0039] 4. Once the filter cake thickness reaches the standard, transfer the blades to the washing box.

[0040] 5. After washing with water for a period of time, take a small amount of filtrate from the vacuum tube and drop two drops onto the dropping plate. Use two drops of 10% potassium ferricyanide for qualitative testing of ferrous iron. If the color is a very light green, it indicates that the ferrous iron has been basically removed.

[0041] 6. After washing, remove the filter cake, add deionized water and mix evenly. Take a sample of the slurry to test its iron content.

[0042] This invention improves the filtration performance of hydrolyzed material by adding filtrate and flocculants, accelerates the filtration efficiency of hydrolyzed material, and quickly removes iron impurities.

[0043] The filtration of hydrolyzed material is called the first wash, and its purpose is to remove a large amount of iron impurities. The iron content of the hydrolyzed material after the first wash should be controlled below 500 ppm, because the hydrolyzed material will undergo a second wash after the first wash to further remove iron, until the iron content is less than 30 ppm.

[0044] The differences between this application and patent publication number CN110143712A are as follows:

[0045] 1. The mechanisms of action of the filtrate are different. Patent CN110143712A describes adding filtrate to a plate and frame filter press. The filtrate's function is to adsorb the filter cake and retain the solids. After plate and frame filtration, the filtrate and solids are discarded together. This invention focuses on removing iron impurities from solid TiO2. TiO2 particles are bridged by the filtrate to form a loose filter cake. The filtrate increases the filtration channels in the filter cake, facilitating the rapid removal of iron impurities.

[0046] 2. Different amounts of filtrate added. Patent CN110143712A specifies a filtrate addition of 7% of the TiO2 mass. In this invention, the filtrate addition is 0.1-1% of the TiO2 mass. The solid TiO2 needs to be calcined, requiring the filtrate ash content to be less than 0.01%. If too much filtrate is added, the ash content of the calcined filtrate will affect the quality of the final product.

[0047] 3. The addition temperature of the filter aid is different. The patent with publication number CN110143712A states that the filter aid is added at room temperature. In this invention, the filter aid is added at a temperature above 110℃, and the boiling and heat preservation temperature of the hydrolysate is 110-115℃. Adding it at this temperature results in more meshes formed by the filter aid, and a smaller amount of filter aid can achieve better results.

[0048] The differences between this application and patent publication number CN103638744B are as follows:

[0049] 1. The flocculants are different. The polyacrylamide used in the patent with publication number CN103638744B is cationic with a molecular weight of 500,000 to 5 million, while the polyacrylamide of this invention is anionic with a molecular weight of more than 12 million.

[0050] 2. The initial concentration of flocculant is different. The initial concentration of polyacrylamide in patent CN103638744B is 0.5-3g / L, which is equivalent to 500-3000ppm. The initial concentration of polyacrylamide in this invention is 100-200ppm.

[0051] The hydrolyzed TiO2 particles are extremely fine, with the smallest being only a few tenths of a micrometer. In this invention, anionic polyacrylamide is used as the flocculant, with a fractional concentration exceeding 12 million, which can more quickly agglomerate the fine particles into larger particles. Furthermore, the flocculation effect is not significant when the concentration of this flocculant exceeds 200 ppm.

[0052] 3. Different Filter Aids. The filter aid used in patent CN103638744B can be lime, ash, sawdust, cellulose, etc. This invention uses filtrate as the filter aid. The filter aid similar to that in patent CN103638744B is cellulose, specifically ordinary cellulose. The filtrate used in this invention is modified cellulose. This invention has strict requirements for the ash content control of filtrate, requiring the ash content after calcination to be less than 0.01%.

[0053] 4. Different mechanisms of action for filter aids. Patent CN103638744B: Cellulose is added during plate and frame filtration to adsorb the filter cake, retaining the solids. After plate and frame filtration, the filter aid is discarded along with the solids. This invention focuses on removing iron impurities from solid TiO2. The filter aid causes the hydrolyzed material to form a loose filter cake, increasing the filter cake filtration channels and facilitating rapid iron removal.

[0054] 5. Different filter aid addition temperatures. Patent CN103638744B specifies adding the filter aid at room temperature. The filter aid in this invention, Felfiltrate, is added during the hydrolysis and boiling process. The boiling temperature of the hydrolysate is 110-115℃, and the TiO2 particles in the hydrolysate are nano- and micron-sized, with a particle size of 0.5-1.8 microns. Adding Felfiltrate at this temperature results in better performance.

[0055] 6. In patent CN103638744B, the filter aid and flocculant do not interact. In this invention, the filter aid and flocculant interact. Adding a small amount of flocculant causes the fine particles of the hydrolyzed material to agglomerate, while the flocculant loosens the filter cake, reduces its viscosity, and improves filtration. Because the hydrolyzed material contains fine particles, adding only flocculant would cause these fine particles to penetrate or clog the filter cloth. Adding only flocculant, due to the high acidity of the hydrolyzed material (acidity exceeding 20%), would cause the fine particles to agglomerate under strong acidity, but it would increase the viscosity of the hydrolyzed material, resulting in a denser filter cake with fewer channels for filtering impurities and iron.

[0056] Compared with the prior art, the beneficial effects of the present invention are as follows: The present invention adds flocculant, and the hydrolyzed TiO2 particles rely on the adsorption and bridging effect of their high molecular long chains to flocculate the particles into agglomerates, preventing fine particles from clogging the filter cloth, thereby forming a filter cake with good permeability, which is conducive to rapid water filtration and improving water washing yield.

[0057] Felfilled filter media possesses high strength, toughness, and fibrous properties. When added to the hydrolyzed material, the mixture of titanium dioxide particles and ferrite forms an irregular network on the filter membrane surface during filtration. Felfilled filter media effectively acts as a bridging agent. With an appropriate amount of ferriteed filter media, an irregular three-dimensional network is formed within the gradually thickening filter cake during TiO2 filtration. This not only improves the structure of the hydrolyzed material filter cake but also increases the number of filtration channels, ensuring good dispersion and more filtration channels for TiO2 particles. It also effectively controls TiO2 particle permeation. The slippery nature of ferriteed filter media also contributes to good filter cake peeling performance, making the filter cake easy to remove and greatly improving work efficiency.

[0058] On the one hand, the flocculant of this invention agglomerates fine particles into large particles. The large particles have better filtration performance than the fine particles. The filter cake is formed in a short time. Moreover, under the action of the flocculant, the filter cake is looser, and iron impurity ions diffuse into the water quickly, resulting in rapid iron removal.

[0059] This invention facilitates rapid filtration, effectively controls the filtration phenomenon of TiO2 particles, improves water washing yield, and ensures that the ferrous ion content in the hydrolysate meets the standard. Attached Figure Description

[0060] Figure 1 Photograph of the filtrate after filtration of the hydrolyzed material;

[0061] (a) is a photograph of the filtrate after filtration of the hydrolyzed material in Example 1; (b) is a photograph of the filtrate after filtration of the hydrolyzed material in Comparative Example 1; the left (a) image shows the filtrate in the filtration bottle is brown, which is the color of the waste acid, and the right (b) image shows the filtrate in the filtration bottle is milky white, which is because the waste acid contains TiO2 that has passed through the filter.

[0062] Figure 2 Photograph of the filtrate after washing the filter cake;

[0063] (a) is a photograph of the filter cake washing filtrate in Example 1; (b) is a photograph of the filter cake washing filtrate in Comparative Example 1; the left (a) image shows the filter cake being washed with water without passing through the filter, and the right (b) image shows the filter cake being washed with water after passing through the filter.

[0064] Figure 3 This is a three-dimensional network diagram formed in the filter cake of Embodiment 1 of the present invention. Detailed Implementation

[0065] Example

[0066] Half an hour before the end of the hydrolysis and heat preservation, add 0.03% flocculant (by mass ratio of TiO2) to the hydrolysis tank; continue hydrolysis until completion, pump the hydrolysate into the cooling tank, and after the hydrolysate cools to 60℃, add 0.001% flocculant according to the mass ratio of solid TiO2 in the hydrolysate. Then pump the material into the filter cake suction tank, and suction the filter cake until the cake thickness reaches 5cm. The suction time is 53 minutes. Transfer the filter cake to the washing box and wash for 3 hours. Take the filtrate onto a drip plate, add 2 drops of 10% potassium ferricyanide, and the solution will turn light green. Remove the filter cake, slurry it, and take a sample to test the iron content, which is 285ppm.

[0067] The flocculant used in the examples and comparative examples was anionic polyacrylamide with a molecular weight of 10-12 million. The initial concentration was 100-200 ppm.

[0068] Example

[0069] Half an hour before the end of the hydrolysis and heat preservation, add 0.7% flocculant (based on the mass ratio of TiO2) to the hydrolysis tank; continue hydrolysis until completion, pump the hydrolysate into the cooling tank, and after the hydrolysate cools to 55℃, add 0.003% flocculant according to the mass ratio of solid TiO2 in the hydrolysate. Then pump the material into the filter cake suction tank, and suction the filter cake until the cake thickness reaches 5cm. The suction time is 48 minutes. Transfer the filter cake to the water washing box and wash for 3 hours. Take the filtrate onto a drip plate, add 2 drops of 10% potassium ferricyanide, and the solution will turn light green. Remove the filter cake, slurry it, and take a sample to test the iron content, which is 235ppm.

[0070] Example

[0071] Half an hour before the end of the hydrolysis and heat preservation, add 0.6% flocculant (based on the mass ratio of TiO2) to the hydrolysis tank; continue hydrolysis until completion, pump the hydrolysate into the cooling tank, and after the hydrolysate cools to 50℃, add 0.002% flocculant (based on the mass ratio of solid TiO2), then pump the material into the floc suction tank, suction the filter cake until the cake thickness reaches 5cm, and the suction time is 50 minutes. Transfer the filter cake to the water washing box, and wash for 3 hours. Take the filtrate onto a drip plate, add 2 drops of 10% potassium ferricyanide, and the mixture will turn light green. Remove the filter cake, slurry it, and take a sample to test the iron content, which is 270ppm. Example

[0072] Half an hour before the end of the hydrolysis and heat preservation, add 1.0% flocculant (based on the mass ratio of TiO2) to the hydrolysis tank; continue hydrolysis until completion, pump the hydrolysate into the cooling tank, and after the hydrolysate cools to 65℃, add 0.005% flocculant (based on the mass ratio of solid TiO2). Pump the material into the leaf filter suction tank, and use a leaf filter to suction the filter until the leaf thickness reaches 5cm. The suction time is 52 minutes. Transfer the filter to the water washing box, and wash for 3 hours. Take the filtrate onto a drip plate and add 2 drops of 10% potassium ferricyanide (light green). Remove the filter cake, slurry it, and take a sample to test the iron content, which is 260ppm.

[0073] Example

[0074] Half an hour before the end of the hydrolysis and heat preservation, add 0.5% filtrate (based on the mass ratio of TiO2) to the hydrolysis tank; continue hydrolysis until completion, pump the hydrolysate into the cooling tank, and after the hydrolysate cools to 65℃, add 0.002% flocculant (based on the mass ratio of solid TiO2). Pump the material into the leaf filter tray, and use a leaf filter to suction the filter until the leaf thickness reaches 5cm. The suction time is 55 minutes. Transfer the filter to the washing box and wash for 3 hours. Take the filtrate onto a drip plate and add 2 drops of 10% potassium ferricyanide for a light green color. Remove the filter cake, slurry it, and take a sample to test the iron content, which is 280ppm. Compared with no filter aid or flocculant, the filtration time is reduced by 46.1%. Compared with filtrate alone, the filtration time is reduced by 31.7%. Compared with flocculant alone, the filtration time is reduced by 51.2%.

[0075] Comparative Example 1

[0076] After hydrolysis, the hydrolysate is pumped into a cooling tank and cooled to 55°C. Then, it is pumped into a filter cake suction tank and suctioned to form a 5cm thick filter cake over a specified time of 80 minutes. The filter cake is then transferred to a washing tank and washed for 3 hours. The filtrate is collected on a drip plate, and two drops of 10% potassium ferricyanide are added, resulting in a deep blue color. A small sample of the filter cake is taken and tested; the iron content is 830 ppm. After further washing for 2 hours, the iron content of the filter cake is 500 ppm.

[0077] Comparative Example 2

[0078] The difference between Comparative Example 2 and Example 5 is that no flocculant was added.

[0079] Comparative Example 3

[0080] The difference between Comparative Example 3 and Example 5 is that no filtrates was added. The experimental results of Example 5 and Comparative Examples 1-3 are shown in Table 1:

[0081] Table 1. Comparison of experimental results between Example 5 and Comparative Examples 1-3

[0082]

[0083] The filtration time is the time required to form a filter cake of a specified thickness plus the water washing time when the iron content of the filter cake is below 500 ppm.

[0084] TiO2 lost in the filtrate; a high TiO2 content indicates that more fine TiO2 particles have passed through the filtrate, resulting in greater TiO2 loss.

[0085] Adding filtrate to the hydrolyzed material: Fel filtrate primarily serves to bridge the filter cake, creating an irregular three-dimensional network. This results in a looser filter cake, increasing filtration channels and accelerating the removal of impurity ions and iron in a shorter time. However, extremely fine particles can penetrate the filter cloth, leading to some TiO2 loss or clogging of the filter cloth pores. After a period of use, the filter cloth needs to be soaked in HF acid to dissolve the TiO2 clogging the pores. Removing these fine particles would severely impact the filtration speed of the hydrolyzed material.

[0086] Adding flocculants alone to hydrolyzed material: The flocculant aggregates the fine particles of the hydrolyzed material into larger particles, preventing the loss of TiO2. However, without the addition of filter aids, the resulting filter cake is denser, takes longer to form (up to 90 minutes), and is more compact, making it difficult for impurity ions to diffuse into the water. This results in a longer time to achieve the required iron content in the washed water. Therefore, flocculants cannot be added alone to the hydrolyzed material. While this solves the problem of fine particles passing through the filter, it increases the viscosity of the material, affecting its filtration performance.

[0087] Adding filtrate and flocculant to hydrolyzed material: On the one hand, flocculant agglomerates fine particles into large particles. Large particles have better filtration performance than fine particles. The filter cake formation time is short. Moreover, under the action of filtrate, the filter cake is looser, and iron impurity ions diffuse into the water quickly, resulting in rapid iron removal.

[0088] The function of filtrate: Without filtrate, the hydrolyzed material takes a long time to form a filter cake, resulting in a longer adsorption time and a denser filter cake. Iron ions and other impurities are tightly trapped, hindering the smooth flow of the washing channels and making it difficult for them to diffuse into the water. This leads to a longer washing time, and as the washing time increases, the Fe in the filter cake... 2+ Oxidized to Fe 3+The filter cake surface is distinctly brown, and this brown color is due to Fe. 3+ The generated insoluble Fe(OH)3 also resulted in a high iron content in the slurry after water washing.

[0089] When hydrolyzed material is mixed with filtrate, the filtrate fully exerts its bridging effect, forming an irregular three-dimensional network. The resulting filter cake is loose, increasing the filtration channels and ensuring that TiO2 particles have good dispersion and more filtration channels. Due to the slippery nature of filtrate, the filter cake has good peeling performance and is easy to remove.

[0090] The function of flocculants is to agglomerate fine particles into larger particles and migrate them onto the three-dimensional structure of the filter cloth. This prevents fine particles from clogging the gaps in the filter cloth and from passing through the filter.

[0091] Fel-filtrate is an organic flocculent fibrous material obtained from plants through chemical processing.

[0092] The flocculant flocculates fine particles and migrates them onto the three-dimensional structure of felicin. The flocculant and felicin work synergistically.

[0093] The main benefits of using filtrate to improve the filtration performance of hydrolyzed materials and to prevent fine particles from clogging the filter cloth and causing TiO2 to pass through the filter are: good filtration performance of hydrolyzed materials is reflected in short loading and washing times and low iron content in the water.

Claims

1. A method for filtering hydrolyzed materials, characterized in that, Includes the following steps: S1. Disperse the filtrate evenly in the hydrolysate and heat it to obtain a mixture of filtrate and hydrolysate. S2. Add flocculant to the mixture of filtrate and hydrolyzed material obtained in S1 and stir evenly to obtain mixture two; S3. Filter the mixture from S2 to obtain filter cake. Wash the filter cake with water to obtain filter cake with the required iron content. The mass fractions of hydrolyzed material, filtrate, and flocculant are 100 parts, 0.01-1 parts, and 0.001-0.01 parts, respectively. In S1, add Felicin 20-40 minutes before the end of titanium liquid hydrolysis, and heat at 110℃-115℃. The hydrolysis process of the hydrolysate is that TiOSO4 is hydrolyzed to generate metatitanic acid H2TiO3; The reaction temperature of S2 is 50-65℃.

2. The method for filtration of hydrolyzed materials according to claim 1, characterized in that, In S1, before the titanium liquid hydrolysis is completed, filtrate is added. After the titanium liquid hydrolysis is completed, filtrate can be evenly dispersed in the hydrolysate.

3. The method for filtration of hydrolyzed materials according to claim 1, characterized in that, The ash content of S1 filtrate after calcination is less than 0.01 parts.

4. The method for filtration of hydrolyzed materials according to any one of claims 1-3, characterized in that, The specific method in S3 includes the following steps: filtering the mixture in S2; Once the thickness of the filter cake obtained from filtering the mixture in S2 reaches the standard, the filter cake is washed with water. The washing is stopped when the concentration of ferrous ions in the washing filtrate reaches the standard. After washing, remove the filter cake and add deionized water to make a paste.

5. The method for filtration of hydrolyzed materials according to claim 4, characterized in that, The method for testing whether the iron ion concentration in the washing filtrate meets the standard is as follows: After washing with water for a period of time, take the washing filtrate and add 8-12% potassium ferricyanide by mass. If the color is light green, it indicates that the ferrous ion concentration meets the standard.

6. The method for filtration of hydrolyzed materials according to any one of claims 1-3, characterized in that, The flocculant in S2 is anionic polyacrylamide with a molecular weight of over 12 million.

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