A decolorizing agent for sulfuric acid production

Abstract

This application relates to the technical field of decolorizing agents, and specifically discloses a decolorizing agent for sulfuric acid production. A decolorizing agent for sulfuric acid production comprises the following raw materials in parts by weight: 15-30 parts of enhanced magnetic mesoporous carbon; 5-15 parts of nano-silica; 8-20 parts of polyvinylidene fluoride; 1-5 parts of aluminum sulfate; 1-5 parts of ferrous sulfate; 1-3 parts of triphenyl phosphite; 3-7 parts of dispersant; the enhanced magnetic mesoporous carbon is obtained by modifying magnetic mesoporous carbon with dopamine. The decolorizing agent of this application has a good decolorizing effect through the synergistic effect of nano-silica, polyvinylidene fluoride, aluminum sulfate, ferrous sulfate, triphenyl phosphite and dispersant with the enhanced magnetic mesoporous carbon, and also has a stable decolorizing effect under high temperature conditions.

Description

Technical Field

[0001] This application relates to the technical field of decolorizing agents, and more specifically, to a decolorizing agent for sulfuric acid production. Background Art

[0002] In modern industrial production, sulfuric acid is a basic chemical raw material and is widely used in many fields such as fertilizers, metallurgy, and petrochemical industry. During the production process of sulfuric acid, due to the complexity of raw materials and the characteristics of the production process, the prepared sulfuric acid often contains various impurities. Among them, pigment impurities will affect the appearance and quality of sulfuric acid. Therefore, it is necessary to use a decolorizing agent to remove pigments, improve the purity and quality of sulfuric acid, and meet the strict requirements of different industrial applications for the quality of sulfuric acid. Therefore, the decolorizing agent plays an indispensable role in sulfuric acid production and is directly related to the market competitiveness of sulfuric acid products.

[0003] Currently, in the industrial production process of sulfuric acid, activated carbon-based decolorizing agents are mainly used to remove impurity pigments in sulfuric acid. Its main components include high-quality carbon-containing raw materials such as coconut shells and coal, which are the basis for forming the rich pore structure of activated carbon. During the preparation process, activators such as phosphoric acid and zinc chloride are usually added. The activators can promote the decomposition and recombination of raw materials at high temperatures, further expand the pore structure of activated carbon, and increase its specific surface area. The working principle of activated carbon-based decolorizing agents is based on physical adsorption and partial chemical adsorption. From the perspective of physical adsorption, activated carbon has a highly developed pore structure, and pigment molecules are adsorbed on the pore surface of activated carbon through van der Waals forces, which can effectively intercept and fix pigments. In terms of chemical adsorption, there are some oxygen-containing functional groups on the surface of activated carbon, such as carboxyl groups and hydroxyl groups. These functional groups can react with pigment molecules to form chemical bonds, thereby enhancing the adsorption effect on pigments and achieving the purpose of decolorizing sulfuric acid.

[0004] However, this existing decolorizing agent has obvious defects. During the production process of sulfuric acid, the reaction temperature will fluctuate due to factors such as process stages and equipment operating conditions. Under high-temperature conditions, high temperature will affect the adsorption equilibrium of activated carbon. The adsorption of pigments by activated carbon is a process jointly affected by physical adsorption and chemical adsorption, and the adsorption process is often accompanied by heat changes. According to the adsorption theory, when the temperature rises, the physical adsorption process will shift towards desorption, that is, pigment molecules originally adsorbed on the surface of activated carbon will have more opportunities to break away from the surface of activated carbon, resulting in a decrease in the adsorption amount of activated carbon for pigments and thus reducing the decolorizing effect. The problem of unstable decolorizing performance caused by temperature changes restricts the continuity of sulfuric acid production and the stability of product quality. Summary of the Invention

[0005] In order to enhance the decolorizing stability of the decolorizing agent under high-temperature conditions, this application provides a decolorizing agent for sulfuric acid production.

[0006] A decolorizing agent for sulfuric acid production provided by this application adopts the following technical solution:

[0007] A decolorizing agent for sulfuric acid production, comprising raw materials in the following parts by weight:

[0008] 15 - 30 parts of enhanced magnetic mesoporous carbon;

[0009] 5 - 15 parts of nano - silica;

[0010] 8 - 20 parts of polyvinylidene fluoride;

[0011] 1 - 5 parts of aluminum sulfate;

[0012] 1 - 5 parts of ferrous sulfate;

[0013] 1 - 3 parts of triphenyl phosphite;

[0014] 3 - 7 parts of dispersant;

[0015] The enhanced magnetic mesoporous carbon is obtained by modifying magnetic mesoporous carbon with dopamine.

[0016] By adopting the above - mentioned technical solution, the enhanced magnetic mesoporous carbon is the core component, which is obtained by modifying magnetic mesoporous carbon with dopamine. The enhanced magnetic mesoporous carbon has magnetism and a rich mesoporous structure. The magnetism facilitates the rapid separation and recovery using an external magnetic field after decolorization, avoiding the destruction of its structure and the decline of its performance caused by long - term residence in a high - temperature sulfuric acid system. The mesoporous structure provides a large specific surface area, which can provide a large number of adsorption sites for pigment molecules at normal temperature and has good adsorption and decolorization ability. Under high - temperature conditions, the modification of dopamine plays a key role. Dopamine contains a catechol structure and has strong chemical activity. At high temperature, it can have special interactions such as hydrogen - bond interaction and π - π stacking with pigment molecules, enhancing the adsorption stability of pigments, making the adsorbed pigment molecules not easily desorb at high temperature and maintaining a high decolorization performance.

[0017] Nano - silica, polyvinylidene fluoride, aluminum sulfate, ferrous sulfate, triphenyl phosphite and dispersant act synergistically with the enhanced magnetic mesoporous carbon. Nano - silica can enhance the overall stability; polyvinylidene fluoride, as a fluorine - containing high - temperature - resistant polymer, improves the stability of the decolorizing agent in a high - temperature environment; aluminum sulfate and ferrous sulfate may participate in certain chemical reactions to assist decolorization; triphenyl phosphite, as a heat stabilizer, protects the structure and performance of the decolorizing agent; the dispersant helps each component to be evenly dispersed and play a full role, jointly ensuring the stable decolorization effect of the decolorizing agent at high temperature.

[0018] Optionally, the enhanced magnetic mesoporous carbon is prepared by the following method:

[0019] A. Disperse mesoporous carbon in deionized water, then add magnetic micropowder to the deionized water, and then perform ultrasonic stirring for 10 - 30 min to obtain a dispersion. Heat the dispersion to 60 - 80 °C under nitrogen protection, then dropwise add sodium silicate solution. After the addition is completed, stir and react at 60 - 80 °C for 1 - 3 h, and then obtain magnetic mesoporous carbon through filtration, washing, and drying.

[0020] B. Mix dopamine hydrochloride with a buffer solution and stir to dissolve to obtain a dopamine solution. Add magnetic mesoporous carbon to the dopamine solution and stir for 10 - 15 min. Then add β - alanine solution and continue to stir for 10 - 15 min. Then react at 20 - 25 °C for 20 - 24 h. After the reaction is completed, use a magnetic field to separate the modified magnetic mesoporous carbon, and then obtain enhanced magnetic mesoporous carbon after washing and drying.

[0021] By adopting the above technical solution, mesoporous carbon, as the basic carrier, has a rich mesoporous structure, provides a large specific surface area, and provides a large number of sites for subsequent loading of magnetic components and ultimately for the adsorption of pigment molecules. Its own physical structure characteristics enable it to have a certain adsorption capacity at normal temperature, laying a foundation for the adsorption performance of enhanced magnetic mesoporous carbon. Load magnetic micropowder on mesoporous carbon under alkaline conditions to endow mesoporous carbon with magnetism, so as to facilitate subsequent separation and recovery using an external magnetic field and avoid the adverse effects caused by staying in a high - temperature sulfuric acid system for a long time. During the preparation process, the silicate ions generated by the hydrolysis of sodium silicate can adsorb on the surfaces of magnetite micropowder and mesoporous carbon, increasing the charge density on the particle surface. According to the principle of electrostatic repulsion, particles with the same charge will repel each other, effectively preventing the aggregation of magnetite micropowder and mesoporous carbon particles and enabling them to maintain a good dispersion state in the reaction system. This helps to improve the loading uniformity of magnetite on the surface of mesoporous carbon, and further enhances the consistency of the overall performance of magnetic mesoporous carbon. Moreover, since silicic acid is unstable, it will further polymerize to form silicon dioxide (SiO2). Under the reaction conditions, these silicon dioxides will deposit on the surfaces of magnetite micropowder and mesoporous carbon, gradually forming a continuous and dense silicon dioxide coating layer. This coating layer tightly fixes the magnetite micropowder on the surface of mesoporous carbon, not only enhancing the binding force between magnetite and mesoporous carbon, but also constructing a stable magnetic mesoporous carbon structure to prevent magnetite from falling off the surface of mesoporous carbon during subsequent processing or use. In addition, the silicon dioxide coating layer can act as a physical barrier to separate magnetite from corrosive substances such as sulfuric acid in the outside world. Silicon dioxide has stable chemical properties and is not easy to react with sulfuric acid, effectively protecting magnetic mesoporous carbon and enabling it to maintain magnetism and structural integrity during use.

[0022] In a buffer solution environment, dopamine undergoes a self-polymerization reaction to form a modification layer on the surface of magnetic mesoporous carbon. Dopamine contains a catechol structure and has strong chemical activity. At high temperatures, it can form special interactions such as hydrogen bonding and π-π stacking with pigment molecules, enhancing the adsorption stability of pigments, making the adsorbed pigment molecules less likely to desorb at high temperatures, and maintaining a high decolorization performance.

[0023] β-alanine contains an amino group and a carboxyl group and is amphoteric. During the process of dopamine-modifying magnetic mesoporous carbon, its amino group can form a hydrogen bond with the catechol structure in dopamine molecules, and at the same time, the carboxyl group can also form hydrogen bonds or electrostatic interactions with some groups on the surface of magnetic mesoporous carbon or the already polymerized dopamine molecules. This multiple interaction enhances the binding force between dopamine molecules and between dopamine and magnetic mesoporous carbon, making the dopamine modification layer more stable during formation, less likely to fall off or undergo structural changes. In addition, β-alanine may also affect the rate and degree of dopamine polymerization. By interacting with dopamine molecules, it regulates the polymerization process of dopamine, enabling it to form a denser and more stable modification layer on the surface of magnetic mesoporous carbon, thereby enhancing the adsorption stability of pigments and further improving the decolorization performance of magnetic mesoporous carbon at high temperatures.

[0024] Optionally, the magnetic micropowder in step A is preferably magnetite micropowder.

[0025] Optionally, the mass ratio of mesoporous carbon, deionized water, and magnetic micropowder in step A is 5:10:(1 - 3).

[0026] By adopting the above technical solution, mesoporous carbon serves as a carrier, and its dosage determines the adsorption basis and structural framework of the final product; deionized water plays the role of a dispersing and reaction medium. An appropriate amount of deionized water can evenly disperse mesoporous carbon and magnetic micropowder, ensuring full progress of the reaction. The proportion of magnetic micropowder directly affects the loading amount of magnetic substances. If the proportion is too low, the magnetism of magnetic mesoporous carbon is insufficient, which is not conducive to subsequent separation; if the proportion is too high, it may cause agglomeration of magnetic substances, affecting the adsorption performance. This mass ratio ensures uniform loading of magnetic components, laying a good foundation for subsequent dopamine modification and the final decolorization performance.

[0027] Optionally, the addition amount of the sodium silicate solution in step A is 15% - 25% of the magnetic micropowder; the concentration of the sodium silicate solution is 2 - 2.5 mol / L.

[0028] By adopting the above technical solution, sodium silicate solution is crucial in the preparation of magnetic mesoporous carbon. The appropriate addition amount and concentration of sodium silicate solution are the key to ensuring the uniform dispersion of magnetite fine powder in the dispersion liquid. If the addition amount is too large or the concentration is too high, side reactions may occur, affecting the loading effect of magnetic substances and the structure of mesoporous carbon. The above solution accurately defines this parameter to ensure the uniform loading of magnetic fine powder on mesoporous carbon, improve the quality of magnetic mesoporous carbon, and further ensure the performance of enhanced magnetic mesoporous carbon.

[0029] Optionally, the purity of dopamine hydrochloride in step B is greater than 99.7%.

[0030] By adopting the above technical solution, high-purity dopamine hydrochloride is the key factor to ensure the smooth progress of the modification reaction. During the modification of magnetic mesoporous carbon with dopamine, the presence of impurities may interfere with the self-polymerization reaction of dopamine, affecting the formation and quality of the modification layer. High purity ensures that dopamine molecules can fully react with magnetic mesoporous carbon in the alkaline environment provided by the buffer solution to form a stable and effective modification layer. Only pure dopamine hydrochloride can ensure the special interaction between its catechol structure and pigment molecules at high temperature, enhance the adsorption stability of pigments, thereby improving the decolorization performance of enhanced magnetic mesoporous carbon at high temperature and solving the problem of unstable performance of existing decolorizing agents at high temperature.

[0031] Optionally, the buffer solution in step B is any one of Tris-HCl buffer solution and phosphate buffer solution.

[0032] By adopting the above technical solution, these two buffer solutions play an important role in maintaining the stability of pH value during the dopamine modification process. The self-polymerization reaction of dopamine needs to be carried out in a specific alkaline environment. Tris-HCl buffer solution and phosphate buffer solution can effectively stabilize the pH value of the reaction system. The stable pH value ensures the chemical activity of dopamine molecules, enabling them to polymerize smoothly on the surface of magnetic mesoporous carbon. If the pH value is unstable, it may lead to abnormal dopamine polymerization reaction and unable to form a uniform and effective modification layer. The appropriate selection of buffer solution ensures the smooth progress of the dopamine modification reaction, providing the necessary conditions for enhanced magnetic mesoporous carbon to obtain good high-temperature adsorption performance.

[0033] Optionally, the mass ratio of dopamine hydrochloride to the buffer solution in step B is 1:(3 - 5).

[0034] Optionally, the mass ratio of magnetic mesoporous carbon to dopamine solution in step B is (0.5 - 0.8):1.

[0035] Optionally, the mass concentration of β-alanine solution in step B is 10% - 15%, and the addition amount of β-alanine solution is 10% - 20% of the mass of dopamine solution.

[0036] By adopting the above technical solution, the β-alanine solution plays a role in enhancing the stability of the modification layer during the dopamine modification process. The appropriate mass concentration and addition amount ensure that β-alanine can effectively interact with dopamine molecules and the surface of magnetic mesoporous carbon. The amino group and carboxyl group of β-alanine can form hydrogen bonds or electrostatic interactions with dopamine molecules, enhancing the binding force between dopamine molecules and between dopamine and magnetic mesoporous carbon. If the concentration or addition amount is inappropriate, it may not be able to effectively enhance the stability of the modification layer and may even interfere with the polymerization reaction of dopamine. The parameters defined in the above solution ensure that β-alanine plays its best role and improves the performance of enhanced magnetic mesoporous carbon at high temperatures.

[0037] In summary, the present application has the following beneficial effects:

[0038] 1. The decolorizing agent of the present application takes enhanced magnetic mesoporous carbon as the core, and is paired with nano-silica, polyvinylidene fluoride, aluminum sulfate, ferrous sulfate, triphenyl phosphite and a dispersant. The enhanced magnetic mesoporous carbon is convenient for separation and recovery due to its magnetism, avoiding damage to its structure and performance at high temperatures. The mesoporous structure provides a large number of adsorption sites, and the dopamine modification enhances the adsorption stability of pigments at high temperatures; nano-silica enhances the overall stability, polyvinylidene fluoride improves the high-temperature stability, aluminum sulfate and ferrous sulfate assist in decolorization, triphenyl phosphite protects the structure and performance, and the dispersant promotes the uniform dispersion of each component. Due to this synergistic combination of raw materials, a stable decolorizing effect under high-temperature conditions is obtained, solving the problem that the decolorizing performance of existing activated-carbon-based decolorizing agents is unstable due to temperature changes, and ensuring the continuity of sulfuric acid production and the stability of product quality.

[0039] 2. During the preparation of the enhanced magnetic mesoporous carbon in the present application, mesoporous carbon is used as the carrier to uniformly load the magnetic components on the mesoporous carbon. During the preparation process, sodium silicate can effectively prevent the agglomeration of magnetite fine powder and mesoporous carbon particles, keeping them in a good dispersion state in the reaction system. Moreover, the silica formed by the hydrolysis and polymerization of sodium silicate will deposit on the surfaces of the magnetite fine powder and mesoporous carbon, gradually forming a continuous and dense silica coating layer. This coating layer tightly fixes the magnetite fine powder on the surface of the mesoporous carbon, not only enhancing the binding force between magnetite and mesoporous carbon, but also constructing a stable magnetic mesoporous carbon structure to prevent magnetite from falling off the surface of the mesoporous carbon during subsequent processing or use.

[0040] 3. When dopamine is used to modify and strengthen magnetic mesoporous carbon in this application, β-alanine is added. The β-alanine molecule contains an amino group and a carboxyl group and is amphoteric. During the modification process, its amino group forms a hydrogen bond with the catechol structure in the dopamine molecule, and the carboxyl group has a hydrogen bond or electrostatic interaction with the surface groups of magnetic mesoporous carbon or the polymerized dopamine molecules. Due to these multiple interactions, the binding force between dopamine molecules and between dopamine and magnetic mesoporous carbon is enhanced, making the dopamine modification layer more stable and not easily falling off or undergoing structural changes. In addition, β-alanine also regulates the rate and degree of dopamine polymerization, promoting the formation of a denser modification layer on the surface of magnetic mesoporous carbon, thus significantly enhancing the adsorption stability of pigments and further improving the decolorization performance of the strengthened magnetic mesoporous carbon at high temperatures, effectively solving the problem of poor performance of existing decolorizing agents in high-temperature environments. Detailed implementation mode

[0041] The following further elaborates on this application in conjunction with examples.

[0042] Preparation example of strengthened magnetic mesoporous carbon

[0043] In this preparation example, mesoporous carbon powder with a specific surface area of 1000 m² / g and an average pore diameter of 30 nm is used, and the fineness of the ferric oxide micropowder is 5000 mesh.

[0044] Preparation example 1

[0045] The strengthened magnetic mesoporous carbon is prepared by the following method:

[0046] A. Disperse 5 kg of mesoporous carbon in 10 kg of deionized water, then add 1 kg of ferric oxide micropowder to the deionized water, and then perform ultrasonic stirring for 10 min to obtain a dispersion. The ultrasonic frequency is 300 Hz. Heat the dispersion to 60 °C under nitrogen protection, then dropwise add 0.15 kg of sodium silicate solution with a concentration of 2 mol / L. After the dropping is completed, stir and react at 60 °C for 1 h, then filter, and take the solid phase and wash it repeatedly with deionized water until the pH value of the washing solution is 7. Dry the washed solid phase in a vacuum drying oven at 60 °C for 12 hours to obtain magnetic mesoporous carbon;

[0047] B. Mix 1 kg of dopamine hydrochloride with 3 kg of Tris-HCl buffer solution and stir to dissolve to obtain a dopamine solution. Take 2 kg of magnetic mesoporous carbon and add it to the dopamine solution, stir for 10 min, then add 0.4 kg of β-alanine solution with a mass concentration of 10% and continue to stir for 10 min, and then react at 20 °C for 20 h. After the reaction is completed, use a magnetic field to separate the modified magnetic mesoporous carbon, and wash the modified magnetic mesoporous carbon repeatedly with deionized water until the pH value of the washing solution is 7, and then dry it in a vacuum drying oven at 50 °C for 8 hours to obtain the strengthened magnetic mesoporous carbon.

[0048] Preparation Example 2

[0049] The enhanced magnetic mesoporous carbon is prepared by the following method:

[0050] A. Disperse 5 kg of mesoporous carbon in 10 kg of deionized water. Then add 2 kg of iron tetroxide fine powder to the deionized water, and then perform ultrasonic stirring for 20 min to obtain a dispersion liquid. The ultrasonic frequency is 300 Hz. Heat the dispersion liquid to 70 °C under nitrogen protection, and then dropwise add 0.40 kg of sodium silicate solution with a concentration of 2.2 mol / L. After the dropping is completed, stir and react at 70 °C for 2 h, then perform filtration. Take the solid phase and wash it repeatedly with deionized water until the pH value of the washing liquid is 7. Dry the washed solid phase in a vacuum drying oven at 60 °C for 12 hours to obtain magnetic mesoporous carbon;

[0051] B. Mix 1 kg of dopamine hydrochloride with 4 kg of phosphate buffer solution and stir to dissolve to obtain a dopamine solution. Take 3.5 kg of magnetic mesoporous carbon and add it to the dopamine solution, stir for 12 min, then add 0.75 kg of β-alanine solution with a mass concentration of 12% and continue to stir for 12 min, and then react at 22 °C for 22 h. After the reaction is completed, use a magnetic field to separate the modified magnetic mesoporous carbon, and wash the modified magnetic mesoporous carbon repeatedly with deionized water until the pH value of the washing liquid is 7, and then dry it in a vacuum drying oven at 50 °C for 8 hours to obtain the enhanced magnetic mesoporous carbon.

[0052] Preparation Example 3

[0053] The enhanced magnetic mesoporous carbon is prepared by the following method:

[0054] A. Disperse 5 kg of mesoporous carbon in 10 kg of deionized water. Then add 3 kg of iron tetroxide fine powder to the deionized water, and then perform ultrasonic stirring for 30 min to obtain a dispersion liquid. The ultrasonic frequency is 300 Hz. Heat the dispersion liquid to 80 °C under nitrogen protection, and then dropwise add 0.75 kg of sodium silicate solution with a concentration of 2.5 mol / L. After the dropping is completed, stir and react at 80 °C for 3 h, then perform filtration. Take the solid phase and wash it repeatedly with deionized water until the pH value of the washing liquid is 7. Dry the washed solid phase in a vacuum drying oven at 60 °C for 12 hours to obtain magnetic mesoporous carbon;

[0055] B. Mix 1 kg of dopamine hydrochloride with 5 kg of phosphate buffer solution and stir to dissolve to obtain a dopamine solution. Take 4 kg of magnetic mesoporous carbon and add it to the dopamine solution, stir for 15 min, then add 1.2 kg of a 15% β-alanine solution and continue to stir for 15 min. Then react at 25 °C for 24 h. After the reaction, use a magnetic field to separate the modified magnetic mesoporous carbon, and repeatedly wash the modified magnetic mesoporous carbon with deionized water until the pH value of the washing solution is 7. Then dry it in a vacuum drying oven at 50 °C for 8 hours to obtain enhanced magnetic mesoporous carbon.

[0056] Preparation Example 4

[0057] Enhanced magnetic mesoporous carbon, different from Preparation Example 1 in that in step B, an equal amount of deionized water is used to replace the Tris-HCl buffer solution.

[0058] Preparation Example 5

[0059] Enhanced magnetic mesoporous carbon, different from Preparation Example 1 in that in step B, an equal amount of deionized water is used to replace the β-alanine solution.

[0060] Preparation Example 6

[0061] Enhanced magnetic mesoporous carbon, different from Preparation Example 1 in that in step B, the mass concentration of the β-alanine solution is 25%.

[0062] Preparation Example 7

[0063] Enhanced magnetic carbon material, different from Preparation Example 1 in that in this preparation example, an equal amount of activated carbon is used to participate in the preparation reaction instead of mesoporous carbon.

[0064] Example

[0065] Example 1

[0066] A decolorizing agent for sulfuric acid production, the raw material components and dosages of which are shown in Table 1. Among them, the enhanced magnetic mesoporous carbon is the enhanced magnetic mesoporous carbon prepared in Preparation Example 1; the average particle size of the nano-silica is 20 nm; the molecular weight of the polyvinylidene fluoride is 50000 g / mol; the dispersant is polyethylene glycol.

[0067] A decolorizing agent for sulfuric acid production is prepared by the following method:

[0068] S1. Mix nano-silica, aluminum sulfate, ferrous sulfate and a dispersant, and stir for 30 min to obtain a dispersion;

[0069] S2. Add polyvinylidene fluoride and triphenyl phosphite to the dispersion, stir at 60 °C for 2 h, then add the enhanced magnetic mesoporous carbon, and continue to stir for 1 h to obtain the decolorizing agent.

[0070] Example 2

[0071] A decolorizing agent for sulfuric acid production, the raw material components and dosages of which are shown in Table 1. Among them, the enhanced magnetic mesoporous carbon is the enhanced magnetic mesoporous carbon prepared in Preparation Example 2; the average particle size of the nano-silica is 20 nm; the molecular weight of the polyvinylidene fluoride is 50,000 g / mol; the dispersant is polyethylene glycol.

[0072] A decolorizing agent for sulfuric acid production is prepared by the following method:

[0073] S1. Mix nano-silica, aluminum sulfate, ferrous sulfate and the dispersant, and stir for 40 min to obtain a dispersion;

[0074] S2. Add polyvinylidene fluoride and triphenyl phosphite to the dispersion, stir at 62 °C for 2 h, then add the enhanced magnetic mesoporous carbon, and continue to stir for 1 h to obtain the decolorizing agent.

[0075] Example 3

[0076] A decolorizing agent for sulfuric acid production, the raw material components and dosages of which are shown in Table 1. Among them, the enhanced magnetic mesoporous carbon is the enhanced magnetic mesoporous carbon prepared in Preparation Example 3; the average particle size of the nano-silica is 20 nm; the molecular weight of the polyvinylidene fluoride is 50,000 g / mol; the dispersant is polyethylene glycol.

[0077] A decolorizing agent for sulfuric acid production is prepared by the following method:

[0078] S1. Mix nano-silica, aluminum sulfate, ferrous sulfate and the dispersant, and stir for 45 min to obtain a dispersion;

[0079] S2. Add polyvinylidene fluoride and triphenyl phosphite to the dispersion, stir at 65 °C for 2 h, then add the enhanced magnetic mesoporous carbon, and continue to stir for 1 h to obtain the decolorizing agent.

[0080] Table 1 Raw material components and dosages (kg) of the decolorizing agent in Examples 1 - 3

[0081]

[0082] Example 4

[0083] A decolorizing agent for sulfuric acid production, which is different from Example 1 in that the enhanced magnetic mesoporous carbon prepared in Preparation Example 4 is selected in this example.

[0084] Example 5

[0085] A decolorizing agent for sulfuric acid production, which is different from Example 1 in that the enhanced magnetic mesoporous carbon prepared in Preparation Example 5 is selected in this example.

[0086] Example 6

[0087] A decolorizing agent for sulfuric acid production, which is different from that in Example 1 in that the enhanced magnetic mesoporous carbon prepared in Preparation Example 6 is selected in this example.

[0088] Comparative Example

[0089] Comparative Example 1

[0090] A decolorizing agent for sulfuric acid, the raw materials of which include 5.8 kg of hydrogen peroxide, 2.4 kg of absolute ethanol and 1.8 kg of activated carbon, and the mass concentration of hydrogen peroxide is 27.5%. When preparing the decolorizing agent, hydrogen peroxide, absolute ethanol and activated carbon are mixed and stirred for 20 minutes to obtain it.

[0091] Comparative Example 2

[0092] A decolorizing agent for sulfuric acid production, which is different from that in Example 1 in that the enhanced magnetic mesoporous carbon prepared in Preparation Example 7 is selected in this comparative example.

[0093] Comparative Example 3

[0094] A decolorizing agent for sulfuric acid production, which is different from that in Example 1 in that polyvinylidene fluoride is not added in this comparative example.

[0095] Performance Detection Test

[0096] Test Materials: The decolorizing agents prepared in Examples 1-6 and Comparative Examples 1-3; industrial sulfuric acid with a mass concentration of 98%.

[0097] Test Equipment: Constant temperature water bath, magnetic stirrer, spectrophotometer, electronic balance (accuracy 0.01 g), stoppered colorimetric tube (100 mL), volumetric flask (1000 mL, 500 mL).

[0098] Test Method: Weigh 0.5 g of the decolorizing agents in Examples 1-6 and Comparative Examples 1-3 respectively, accurate to 0.01 g. Put the stoppered colorimetric tube containing 100 mL of sulfuric acid sample into the constant temperature water bath, adjust the temperature to 20 °C, 50 °C, 80 °C respectively, and keep the temperature constant for 15 minutes. After reaching the set temperature, quickly add the weighed decolorizing agent into the sulfuric acid sample, immediately turn on the magnetic stirrer, and stir at a speed of 200 r / min for 30 minutes. After the stirring is completed, let the sulfuric acid sample stand and precipitate for 30 minutes to fully separate the decolorizing agent from the sulfuric acid. Take the supernatant and measure its absorbance with a spectrophotometer at a wavelength of 500 nm. At the same time, take the same sulfuric acid sample without adding the decolorizing agent and measure its absorbance according to the same method as a blank control. Then calculate the decolorization rate, decolorization rate (%) = (blank control absorbance - sample absorbance) / blank control absorbance × 100%. The test results are shown in Table 2.

[0099] Table 2 Test Results

[0100]

[0101] Combined with Examples 1 - 3 and Table 2, it can be seen that the decolorizing agents in Examples 1 - 3 maintain a high decolorization rate at different temperatures with relatively small fluctuations. At 20°C, the decolorization rate reaches about 95%. At 50°C, it remains around 94%. At 80°C, it can also be maintained at about 93%. This benefits from its scientific and reasonable raw material formula and the preparation process of enhanced magnetic mesoporous carbon. With enhanced magnetic mesoporous carbon as the core, components such as nano-silica and polyvinylidene fluoride act synergistically. The magnetism of enhanced magnetic mesoporous carbon facilitates separation and recovery, avoiding damage to its structure and performance at high temperatures. The mesoporous structure provides a large number of adsorption sites, and dopamine modification enhances the adsorption stability of pigments at high temperatures; nano-silica enhances the overall stability, and polyvinylidene fluoride improves the high-temperature stability. When preparing enhanced magnetic mesoporous carbon, the magnetic components are evenly loaded through sodium silicate solution, laying a good foundation for subsequent dopamine modification and the final decolorization performance.

[0102] Compared with Example 1, the decolorization rate of Examples 4 - 6 decreases, and the decrease is more obvious at high temperatures. In Example 4, an equal amount of deionized water is used to replace the Tris-HCl buffer solution, resulting in an unstable pH environment for the dopamine polymerization reaction, unable to form a uniform and effective modification layer, reducing the adsorption stability of pigments at high temperatures. The decolorization rate drops to 76.2% at 80°C. In Example 5, an equal amount of deionized water is used to replace the β-alanine solution, making the stability of the dopamine modification layer insufficient and reducing the adsorption stability of pigments at high temperatures. The decolorization rate is 78.9% at 80°C. In Example 6, the mass concentration of the β-alanine solution is 25%, deviating from the optimal range, affecting its interaction with dopamine and magnetic mesoporous carbon, resulting in the compactness and stability of the modification layer being affected. The decolorization rate is 85.2% at 80°C.

[0103] In Comparative Example 1, traditional hydrogen peroxide, anhydrous ethanol, and activated carbon are used as the decolorizing agent. The decolorization rate is only 75.2% at 20°C. As the temperature rises to 80°C, the decolorization rate drops significantly to 48.6%. This is because a large number of pigment molecules physically adsorbed by activated carbon desorb at high temperatures, and chemical adsorption is also affected, unable to effectively maintain the decolorization effect, fully demonstrating the significant advantage of the technology of this application in solving the problem of unstable decolorization at high temperatures.

[0104] In Comparative Example 2, activated carbon is used to replace mesoporous carbon to prepare enhanced magnetic mesoporous carbon. The pore structure and surface properties of activated carbon are different from those of mesoporous carbon, which is not conducive to the uniform loading of magnetic substances and the modification of dopamine, resulting in a lower decolorization rate at each temperature compared to Examples 1 - 3, and a significant decrease at high temperatures. The decolorization rate is 51.5% at 80°C, further proving that mesoporous carbon plays a key role in improving the performance of the decolorizing agent in this application.

[0105] In Comparative Example 3, polyvinylidene fluoride was not added. As a fluorine-containing high-temperature resistant polymer, polyvinylidene fluoride is crucial for improving the stability of the decolorizing agent in high-temperature environments. The decolorization rate of this comparative example decreased significantly compared to Example 1 at 80 °C, dropping to 65.1%, indicating that polyvinylidene fluoride is indispensable for maintaining the decolorization performance at high temperatures and can effectively resist the damage of high temperatures to the structure and performance of the decolorizing agent.

[0106] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A decolorizing agent for sulfuric acid production, characterized in that, It includes raw materials in the following parts by weight: 15 - 30 parts of reinforced magnetic mesoporous carbon; 5 - 15 parts of nano-silica; 8 - 20 parts of polyvinylidene fluoride; 1 - 5 parts of aluminum sulfate; 1 - 5 parts of ferrous sulfate; 1 - 3 parts of triphenyl phosphite; 3 - 7 parts of dispersant; The reinforced magnetic mesoporous carbon is prepared by the following method: A. Disperse the mesoporous carbon in deionized water, then add magnetic micropowder to the deionized water, and then carry out ultrasonic stirring for 10 - 30 min to obtain a dispersion liquid. Heat the dispersion liquid to 60 - 80 °C under nitrogen protection, then dropwise add sodium silicate solution. After the addition is completed, stir and react at 60 - 80 °C for 1 - 3 h, and then obtain magnetic mesoporous carbon through filtration, washing and drying; B. Mix dopamine hydrochloride with a buffer solution and stir to dissolve to obtain a dopamine solution. Add the magnetic mesoporous carbon to the dopamine solution, stir for 10 - 15 min, then add β-alanine solution and continue to stir for 10 - 15 min, and then react at 20 - 25 °C for 20 - 24 h. After the reaction is completed, use a magnetic field to separate the modified magnetic mesoporous carbon, and then obtain the reinforced magnetic mesoporous carbon after washing and drying.

2. The decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step A, the magnetic micropowder is magnetite micropowder.

3. A decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step A, the mass ratio of mesoporous carbon, deionized water and magnetic micropowder is 5:10:(1 - 3).

4. A decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step A, the addition amount of sodium silicate solution is 15% - 25% of the magnetic micropowder; the concentration of the sodium silicate solution is 2 - 2.5 mol / L.

5. A decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step B, the purity of dopamine hydrochloride is greater than 99.7%.

6. A decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step B, the buffer solution is any one of Tris-HCl buffer solution and phosphate buffer solution.

7. A decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step B, the mass ratio of dopamine hydrochloride to the buffer solution is 1:(3 - 5).

8. A decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step B, the mass ratio of magnetic mesoporous carbon to the dopamine solution is (0.5 - 0.8):

1.

9. A decolorizing agent for sulfuric acid production according to claim 1, characterized in that: In step B, the mass concentration of β-alanine solution is 10% - 15%, and the addition amount of β-alanine solution is 10% - 20% of the mass of the dopamine solution.

Images