Processing method for preparing anhydrous sodium sulphate based on denitration of high-salt brine
By treating high-salt brine with modified activated carbon, filter aids, and scale inhibitors, the problems of high impurity residue and low evaporation efficiency in the preparation of sodium sulfate from high-salt brine were solved, and high-purity sodium sulfate was prepared efficiently.
Patent Information
- Application Number
- CN202511497336.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-20
- Publication Date
- 2026-01-13
AI Technical Summary
In the process of preparing sodium sulfate from high-salt brine, there are problems such as calcium and magnesium ion scaling reducing evaporation and concentration efficiency, high impurity residue rate, and membrane fouling.
High-salinity brine was treated using modified activated carbon, filter aid, and scale inhibitor. Modified activated carbon was used to increase its specific surface area and hydrophobicity. Filter aid was used to remove solid impurities. Scale inhibitor chelated trace amounts of calcium and magnesium ions. Modified anion exchange resin was used for selective adsorption and denitrification. Combined with evaporation and concentration, sodium sulfate was obtained.
It improves the service life of activated carbon and resin, reduces the residual rate of impurities, enhances the evaporation and concentration efficiency, and improves the purity and production efficiency of sodium sulfate.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium sulfate preparation technology, specifically a processing method for preparing sodium sulfate based on denitrification of high-salt brine. Background Technology
[0002] Sodium sulfate, also known as anhydrous sodium sulfate, has a bitter taste and appears as colorless, transparent granular crystals. When exposed to air, it readily absorbs moisture to form sodium sulfate decahydrate (also known as Glauber's salt). Sodium sulfate is a common inorganic chemical raw material widely used in organic synthesis and fuel production. With the increasing demand for sodium sulfate from various related industries, its production is also steadily growing. High-salinity brines such as salt lakes, seawater, and saline wastewater are preferred materials for preparing sodium sulfate due to their high sodium sulfate content. However, high-salinity brines also contain inorganic salt ions (such as K+). + Ca 2+ Mg 2+ Cl - Impurities include calcium and magnesium ions, silica, and organic matter. Currently, the preparation of sodium sulfate from high-salt brine faces problems such as calcium and magnesium ion scaling reducing evaporation and concentration efficiency, high impurity residue rates, and membrane fouling. Therefore, developing a novel processing method for preparing sodium sulfate from high-salt brine is of great significance. Summary of the Invention
[0003] The purpose of this invention is to provide a processing method for preparing sodium sulfate based on denitrification of high-salt brine, so as to solve the problems mentioned in the prior art.
[0004] To achieve the above objectives, the present invention provides the following technical solution: A processing method for preparing sodium sulfate based on denitrification of high-salt brine includes the following steps: S1: Add a filter aid to the high-salinity brine, stir and filter, add sodium carbonate and magnesium chloride, adjust the pH to 11-11.2, stir and filter, adjust the pH of the filtrate to 7-7.2, filter with modified activated carbon to obtain crude high-salinity brine; S2: Add scale inhibitor to the crude high-salt brine and use modified anion exchange resin for adsorption and denitrification. Collect the filtrate to obtain low-nitrate brine. S3: The low-nitrate brine is evaporated and concentrated until the sodium sulfate concentration reaches 80-100 g / L. Then, it is pre-cooled and cooled in a gradient, and then vacuum dried to obtain sodium sulfate.
[0005] Further, in step S1, the mass ratio of high-salt brine to filter aid is 100:(1-2); the filter aid is one or more of magnesium hydroxide, diatomaceous earth, fly ash, and expanded perlite.
[0006] Further, in step S1, the modified activated carbon is prepared as follows: the activated carbon is soaked in water, taken out and dried, placed in a superhydrophobic modification solution, soaked at 40-50℃ for 1-2 hours, rotary evaporated at 80-100℃ for 1-2 hours, and dried at 200-300℃ for 8-12 hours to obtain the modified activated carbon. In the preparation process of the modified activated carbon, the mass ratio of activated carbon to superhydrophobic modification liquid is 1:(5-7).
[0007] Further, the preparation method of the activated carbon is as follows: straw powder is mixed and ground with ferric chloride, heated to 500-700℃ at a rate of 5-10℃ / h for 1-2h, cooled to room temperature, soaked in deionized water for 1-2h, filtered, soaked in hydrochloric acid for 8-12h, washed, dried and ground to obtain activated carbon. In the process of preparing activated carbon, the mass ratio of straw powder to ferric chloride is (1-3):(1-2).
[0008] Furthermore, the preparation method of the superhydrophobic modified liquid is as follows: butyl acetate is added to ammonia water, magnetically stirred, and then silica is added, followed by propyltrimethoxysilane and hexadecyltrimethoxysilane. The mixture is heated and stirred in a water bath at 40-50°C for 36-48 hours to obtain the hydrophobic modified liquid. In the preparation of the superhydrophobic modified liquid, the mass ratio of butyl acetate, ammonia, silica, propyltrimethoxysilane and hexadecyltrimethoxysilane is 100:(6-8)(15-20):(3-5):(8-12).
[0009] Furthermore, in step S2, the mass ratio of the high-salt brine crude solution to the scale inhibitor is 100:(0.005-0.01).
[0010] Further, in step S2, the preparation method of the scale inhibitor is as follows: epoxy succinic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid are added to deionized water and stirred until well mixed. Isopropanol and ammonium persulfate are added in sequence, and the mixture is heated to 50-70°C. Then sodium bisulfite and hydrogen peroxide are added, and the mixture is reacted at 50-70°C for 3-5 hours. The mixture is then cooled to room temperature to obtain the scale inhibitor. In the preparation process of the scale inhibitor, the mass ratio of epoxy succinic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, isopropanol, ammonium persulfate, sodium bisulfite and hydrogen peroxide is (15-20):(6-8):(10-15):(25-30):(0.8-1.2):(0.4-0.6):(1-2).
[0011] Further, in step S2, the preparation method of the modified anion exchange resin is as follows: the anion exchange resin is purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain a dry anion exchange resin. The dry anion exchange resin is placed in acetonitrile solution and soaked for 1-2 hours. Potassium iodide, n-octane bromide and benzyl bromide are added, and the mixture is slowly stirred and heated for 36-48 hours. The resin is purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain the modified anion exchange resin. In the preparation process of the modified anion exchange resin, the mass ratio of anion exchange resin, acetonitrile, potassium iodide, n-octane bromide and benzyl bromide is (5-10):(250-300):(0.1-0.3):(1-1.5):(0.3-0.5).
[0012] Compared with the prior art, the beneficial effects of the present invention are: This invention introduces modified activated carbon for pretreatment of high-salinity brine. Activated carbon is prepared using ferric chloride as an activator to promote micropore formation, and the carbon layer is etched to form mesopores, increasing the specific surface area of the activated carbon and enhancing its adsorption capacity for organic matter and residual suspended particles. Simultaneously, this invention modifies the activated carbon with silica-grafted silane coupling agents. On one hand, silica is chemically anchored to the activated carbon through the silane coupling agent, increasing the surface roughness of the activated carbon and improving its resistance to chemical corrosion. On the other hand, propyltrimethoxysilane forms a hydrophobic base layer on the activated carbon surface, while the long-chain hydrophobic alkyl groups on hexadecyltrimethoxysilane reduce the surface energy of the hydrophobic base layer, forming a stronger hydrophobic barrier, improving the hydrophobicity and long-term stability of the activated carbon, thereby enhancing its adsorption capacity for organic matter and residual suspended particles and extending its service life. Furthermore, pretreatment of high-salinity brine with activated carbon mitigates organic matter contamination of the resin, extending the resin's service life.
[0013] This invention also introduces filter aids such as diatomaceous earth and fly ash to pretreat high-salinity brine, removing solid impurities, preventing clogging of activated carbon and resin, and extending their service life. In an alkaline environment with a pH of 11, sodium carbonate and magnesium chloride can efficiently remove calcium and magnesium ions and silica from high-salinity brine, reducing contamination of activated carbon and resin and extending their service life.
[0014] In this invention, adding a scale inhibitor to the crude high-salinity brine can chelate residual trace amounts of calcium and magnesium ions, inhibiting the formation of calcium and magnesium crystals and reducing their clogging of the resin. Simultaneously, the sulfonic acid groups can improve the salt resistance of the scale inhibitor, thereby enhancing its stability in the high-salinity brine. This invention introduces a modified D311 resin for the selective adsorption of nitrate ions in the crude high-salinity brine. On one hand, the hydrophobic long-chain alkyl group of n-octane bromide and the hydrophobic benzyl bromide ring enhance the resin's hydrophobicity, thereby increasing the resin's selective adsorption of nitrate ions with lower hydration energy. On the other hand, since the resin needs to exchange two active sites to adsorb sulfate ions, the introduction of long-chain alkyl groups and benzyl bromide into the resin increases the distance between the two active sites, thus inhibiting the resin's exchange of sulfate ions. The resin only needs one active site to adsorb nitrate ions, thus achieving selective adsorption of nitrate ions. Furthermore, n-octane bromide and benzyl bromide form a hydrophobic barrier on the resin, reducing water molecule permeability, inhibiting resin swelling, and extending the resin's service life. Detailed Implementation
[0015] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0016] In the following examples, the CAS number of butyl acetate is 123-86-4; the CAS number of propyltrimethoxysilane is 1067-25-0; the CAS number of hexadecyltrimethoxysilane is 16415-12-6; the CAS number of epoxysuccinic acid is 16533-72-5; the CAS number of itaconic acid is 368-21-8; the CAS number of 2-acrylamido-2-methylpropanesulfonic acid is 15214-89-8; the CAS number of bromooctane is 111-83-1; the CAS number of benzyl bromide is 100-39-0; and the anion exchange resin is D311 resin.
[0017] Example 1: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S1: Mix and grind 100 parts of straw powder and 100 parts of ferric chloride, heat to 500℃ at a rate of 5℃ / h for 1h carbonization, cool to room temperature, soak in deionized water for 1h, filter, soak in 5% hydrochloric acid for 8h, wash, dry and grind to obtain activated carbon. S2: Add 100 parts of butyl acetate to 6 parts of ammonia water, stir magnetically, then add 15 parts of silica, 3 parts of propyltrimethoxysilane and 8 parts of hexadecyltrimethoxysilane, heat and stir in a water bath at 40°C for 36 hours to obtain a hydrophobic modified solution. S3: Soak 100 parts of activated carbon in water, take it out and dry it, put it in 50 parts of superhydrophobic modification solution, soak it at 40℃ for 1 hour, rotary evaporate it at 80℃ for 1 hour, and dry it at 200℃ for 8 hours to obtain modified activated carbon. S4: Add 1 part diatomaceous earth to 100 parts of high-salt brine, stir and filter, add sodium carbonate and magnesium chloride, adjust the pH to 11, stir and filter, add hydrochloric acid to the filtrate to adjust the pH to 7, filter with modified activated carbon to obtain crude high-salt brine. S5: 15 parts of epoxy succinic acid, 6 parts of itaconic acid and 10 parts of 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until well mixed. Then, 25 parts of isopropanol and 0.8 parts of ammonium persulfate were added sequentially, and the mixture was heated to 50°C. Then, 0.4 parts of sodium bisulfite and 1 part of hydrogen peroxide were added, and the mixture was reacted at 50°C for 3 hours. The mixture was then cooled to room temperature to obtain the scale inhibitor. S6: D311 resin was purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain dry D311 resin. 5 parts of dry D311 resin were placed in 250 parts of acetonitrile solution and soaked for 1 hour. 0.1 parts of potassium iodide, 1 part of bromooctane and 0.3 parts of benzyl bromide were added, and the mixture was slowly stirred and heated at 50°C for 36 hours. After purification by hydrochloric acid and sodium hydroxide solution, the resin was washed and dried to obtain modified D311 resin. S7: Add 0.005 parts of scale inhibitor to 100 parts of high-salt brine crude liquid, and use modified D311 resin for adsorption and denitrification. Collect the filtrate to obtain low-nitrate brine. S8: The low-nitrate brine is evaporated and concentrated. After the sodium sulfate concentration rises to 80 g / L, it is pre-cooled at 20°C and gradually cooled to 5°C. Then, it is vacuum dried at 90°C to obtain sodium sulfate.
[0018] Example 2: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S1: Mix and grind 200 parts of straw powder with 150 parts of ferric chloride, heat to 600℃ at a rate of 8℃ / h for carbonization for 1.5h, cool to room temperature, soak in deionized water for 1.5h, filter, soak in 5% hydrochloric acid for 10h, wash, dry and grind to obtain activated carbon; S2: Add 100 parts of butyl acetate to 7 parts of ammonia water, stir magnetically, then add 18 parts of silica, 4 parts of propyltrimethoxysilane and 10 parts of hexadecyltrimethoxysilane, heat and stir in a water bath at 45°C for 42 hours to obtain a hydrophobic modified solution. S3: Soak 100 parts of activated carbon in water, take it out and dry it, put it in 60 parts of superhydrophobic modification solution, soak it at 45℃ for 1.5h, rotary evaporate it at 90℃ for 1.5h, and dry it at 250℃ for 10h to obtain modified activated carbon. S4: Add 1.5 parts of diatomaceous earth to 100 parts of high-salt brine, stir and filter, add sodium carbonate and magnesium chloride, adjust the pH to 11, stir and filter, add hydrochloric acid to the filtrate to adjust the pH to 7, filter with modified activated carbon to obtain crude high-salt brine. S5: 15 parts of epoxy succinic acid, 6 parts of itaconic acid and 10 parts of 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until well mixed. Then, 25 parts of isopropanol and 0.8 parts of ammonium persulfate were added sequentially, and the mixture was heated to 50°C. Then, 0.4 parts of sodium bisulfite and 1 part of hydrogen peroxide were added, and the mixture was reacted at 50°C for 3 hours. The mixture was then cooled to room temperature to obtain the scale inhibitor. S6: D311 resin was purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain dry D311 resin. 5 parts of dry D311 resin were placed in 250 parts of acetonitrile solution and soaked for 1 hour. 0.1 parts of potassium iodide, 1 part of bromooctane and 0.3 parts of benzyl bromide were added, and the mixture was slowly stirred and heated at 50°C for 36 hours. After purification by hydrochloric acid and sodium hydroxide solution, the resin was washed and dried to obtain modified D311 resin. S7: Add 0.005 parts of scale inhibitor to 100 parts of high-salt brine crude liquid, and use modified D311 resin for adsorption and denitrification. Collect the filtrate to obtain low-nitrate brine. S8: The low-nitrate brine is evaporated and concentrated. After the sodium sulfate concentration rises to 80 g / L, it is pre-cooled at 20°C and gradually cooled to 5°C. Then, it is vacuum dried at 90°C to obtain sodium sulfate.
[0019] Example 3: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S1: Mix and grind 300 parts of straw powder with 200 parts of ferric chloride, heat to 700℃ at a rate of 10℃ / h for 2h carbonization, cool to room temperature, soak in deionized water for 2h, filter, soak in 5% hydrochloric acid for 12h, wash, dry and grind to obtain activated carbon. S2: Add 100 parts of butyl acetate to 8 parts of ammonia water, stir magnetically, then add 20 parts of silica, 4 parts of propyltrimethoxysilane and 12 parts of hexadecyltrimethoxysilane, heat and stir in a water bath at 50°C for 48 hours to obtain a hydrophobic modified solution. S3: Soak 100 parts of activated carbon in water, take it out and dry it, put it in 70 parts of superhydrophobic modification solution, soak it at 40℃ for 1 hour, rotary evaporate it at 80℃ for 1 hour, and dry it at 200℃ for 8 hours to obtain modified activated carbon. S4: Add 2 parts diatomaceous earth to 100 parts of high-salt brine, stir and filter, add sodium carbonate and magnesium chloride, adjust the pH to 11, stir and filter, add hydrochloric acid to the filtrate to adjust the pH to 7, filter with modified activated carbon to obtain crude high-salt brine. S5: 15 parts of epoxy succinic acid, 6 parts of itaconic acid and 10 parts of 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until well mixed. Then, 25 parts of isopropanol and 0.8 parts of ammonium persulfate were added sequentially, and the mixture was heated to 50°C. Then, 0.4 parts of sodium bisulfite and 1 part of hydrogen peroxide were added, and the mixture was reacted at 50°C for 3 hours. The mixture was then cooled to room temperature to obtain the scale inhibitor. S6: D311 resin was purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain dry D311 resin. 5 parts of dry D311 resin were placed in 250 parts of acetonitrile solution and soaked for 1 hour. 0.1 parts of potassium iodide, 1 part of bromooctane and 0.3 parts of benzyl bromide were added, and the mixture was slowly stirred and heated at 50°C for 36 hours. After purification by hydrochloric acid and sodium hydroxide solution, the resin was washed and dried to obtain modified D311 resin. S7: Add 0.005 parts of scale inhibitor to 100 parts of high-salt brine crude liquid, and use modified D311 resin for adsorption and denitrification. Collect the filtrate to obtain low-nitrate brine. S8: The low-nitrate brine is evaporated and concentrated. After the sodium sulfate concentration rises to 80 g / L, it is pre-cooled at 20°C and gradually cooled to 5°C. Then, it is vacuum dried at 90°C to obtain sodium sulfate.
[0020] Example 4: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S1: Mix and grind 300 parts of straw powder with 200 parts of ferric chloride, heat to 700℃ at a rate of 10℃ / h for carbonization for 2h, cool to room temperature, soak in deionized water for 2h, filter, soak in 5% hydrochloric acid for 12h, wash, dry and grind to obtain activated carbon. S2: Add 100 parts of butyl acetate to 8 parts of ammonia water, stir magnetically, then add 20 parts of silica, 4 parts of propyltrimethoxysilane and 12 parts of hexadecyltrimethoxysilane, heat and stir in a water bath at 50°C for 48 hours to obtain a hydrophobic modified solution. S3: Soak 100 parts of activated carbon in water, take it out and dry it, put it in 70 parts of superhydrophobic modification solution, soak it at 40℃ for 1 hour, rotary evaporate it at 80℃ for 1 hour, and dry it at 200℃ for 8 hours to obtain modified activated carbon. S4: Add 2 parts diatomaceous earth to 100 parts of high-salt brine, stir and filter, add sodium carbonate and magnesium chloride, adjust the pH to 11, stir and filter, add hydrochloric acid to the filtrate to adjust the pH to 7, filter with modified activated carbon to obtain crude high-salt brine. S5: 18 parts of epoxy succinic acid, 7 parts of itaconic acid and 12 parts of 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until well mixed. Then, 28 parts of isopropanol and 1 part of ammonium persulfate were added in sequence, and the mixture was heated to 60°C. Then, 0.5 parts of sodium bisulfite and 1.5 parts of hydrogen peroxide were added, and the mixture was reacted at 60°C for 4 hours. After cooling to room temperature, the scale inhibitor was obtained. S6: D311 resin was purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain dried D311 resin. Eight parts of dried D311 resin were placed in 280 parts of acetonitrile solution and soaked for 1.5 h. Then, 0.2 parts of potassium iodide, 1.2 parts of bromooctane and 0.4 parts of benzyl bromide were added, and the mixture was stirred slowly and heated at 50 °C for 42 h. After purification by hydrochloric acid and sodium hydroxide solution, the resin was washed and dried to obtain modified D311 resin. S7: Add 0.0075 parts of scale inhibitor to 100 parts of high-salt brine crude liquid, and use modified D311 resin for adsorption and denitrification. Collect the filtrate to obtain low-nitrate brine. S8: The low-nitrate brine is evaporated and concentrated. After the sodium sulfate concentration rises to 90 g / L, it is pre-cooled at 20°C and gradually cooled to 5°C. Then, it is vacuum dried at 90°C to obtain sodium sulfate.
[0021] Example 5: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S1: Mix and grind 300 parts of straw powder with 200 parts of ferric chloride, heat to 700℃ at a rate of 10℃ / h for 2h carbonization, cool to room temperature, soak in deionized water for 2h, filter, soak in 5% hydrochloric acid for 12h, wash, dry and grind to obtain activated carbon. S2: Add 100 parts of butyl acetate to 8 parts of ammonia water, stir magnetically, then add 20 parts of silica, 4 parts of propyltrimethoxysilane and 12 parts of hexadecyltrimethoxysilane, heat and stir in a water bath at 50°C for 48 hours to obtain a hydrophobic modified solution. S3: Soak 100 parts of activated carbon in water, take it out and dry it, put it in 70 parts of superhydrophobic modification solution, soak it at 40℃ for 1 hour, rotary evaporate it at 80℃ for 1 hour, and dry it at 200℃ for 8 hours to obtain modified activated carbon. S4: Add 2 parts diatomaceous earth to 100 parts of high-salt brine, stir and filter, add sodium carbonate and magnesium chloride, adjust the pH to 11, stir and filter, add hydrochloric acid to the filtrate to adjust the pH to 7, filter with modified activated carbon to obtain crude high-salt brine. S5: 20 parts of epoxy succinic acid, 8 parts of itaconic acid and 15 parts of 2-acrylamido-2-methylpropanesulfonic acid were added to deionized water and stirred until well mixed. Then, 30 parts of isopropanol and 1.2 parts of ammonium persulfate were added sequentially, and the mixture was heated to 70°C. Then, 0.6 parts of sodium bisulfite and 2 parts of hydrogen peroxide were added, and the mixture was reacted at 70°C for 5 hours. The mixture was then cooled to room temperature to obtain the scale inhibitor. S6: D311 resin was purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain dry D311 resin. 10 parts of dry D311 resin were placed in 300 parts of acetonitrile solution and soaked for 2 hours. 0.3 parts of potassium iodide, 1.5 parts of bromooctane and 0.5 parts of benzyl bromide were added, and the mixture was stirred slowly and heated at 50°C for 48 hours. After purification by hydrochloric acid and sodium hydroxide solution, the resin was washed and dried to obtain modified D311 resin. S7: Add 0.01 parts of scale inhibitor to 100 parts of high-salt brine crude liquid, and use modified D311 resin for adsorption and denitrification. Collect the filtrate to obtain low-nitrate brine. S8: The low-nitrate brine is evaporated and concentrated until the sodium sulfate concentration reaches 100 g / L. It is then pre-cooled at 20°C and gradually cooled to 5°C. Finally, it is vacuum dried at 90°C to obtain sodium sulfate.
[0022] Comparative Example 1: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S1: 300 parts of straw powder are mixed and ground, heated to 700℃ at a rate of 10℃ / h for 2h carbonization, cooled to room temperature, soaked in deionized water for 2h, filtered, soaked in 5% hydrochloric acid for 12h, washed, dried and ground to obtain activated carbon. S2: Add 100 parts of butyl acetate to 8 parts of ammonia water, stir magnetically, then add 20 parts of silica and 4 parts of propyltrimethoxysilane. Heat and stir in a water bath at 50°C for 48 hours to obtain a hydrophobic modified solution. The remaining steps are the same as in Example 5.
[0023] Comparative Example 2: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S4: Add sodium carbonate and magnesium chloride to 100 parts of high-salt brine, adjust the pH value to 11, stir and filter, add hydrochloric acid to the filtrate to adjust the pH to 7, filter with modified activated carbon to obtain crude high-salt brine. The remaining steps are the same as in Example 5.
[0024] Comparative Example 3: A processing method for preparing sodium sulfate based on denitrification of high-salt brine: S5: 20 parts of epoxy succinic acid, 8 parts of itaconic acid and 15 parts of acrylamide are added to deionized water and stirred until well mixed. Then, 30 parts of isopropanol and 1.2 parts of ammonium persulfate are added sequentially, heated to 70°C, and then 0.6 parts of sodium bisulfite and 2 parts of hydrogen peroxide are added. The mixture is reacted at 70°C for 5 hours and then cooled to room temperature to obtain a scale inhibitor. S6: D311 resin was purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain dry D311 resin. 10 parts of dry D311 resin were placed in 300 parts of acetonitrile solution and soaked for 2 hours. 0.3 parts of potassium iodide and 0.5 parts of benzyl bromide were added, and the mixture was stirred slowly and heated at 50°C for 48 hours. After purification by hydrochloric acid and sodium hydroxide solution, the resin was washed and dried to obtain modified D311 resin. The remaining steps are the same as in Example 5.
[0025] Testing: Take the sodium sulfate samples prepared in the examples and comparative examples, and test the contents of sodium sulfate, calcium magnesium and water insoluble matter according to GB / T 6009-2014 standard.
[0026] Table 1. Data on relevant indicators of sodium sulfate
[0027] Conclusion: By adjusting the proportions of the components in the filter aid, modified activated carbon, scale inhibitor, and modified D311 resin, the purity of sodium sulfate prepared from high-salt brine was improved.
[0028] In Comparative Example 1, ferric chloride was not used to etch the carbon layer during the activated carbon preparation process, which reduced the specific surface area of the activated carbon and thus its adsorption capacity. During the modification of the activated carbon, no long-chain silane coupling agent was introduced, which reduced the hydrophobicity and increased the water absorption of the activated carbon. This not only reduced the activated carbon's resistance to chemical corrosion in high-salt brine but also decreased its adsorption capacity, ultimately leading to an increase in the impurity content of the prepared sodium sulfate.
[0029] In Comparative Example 2, no filter aid was added to the high-salt brine, which reduced the removal rate of suspended colloids, increased the risk of activated carbon and resin clogging, reduced the adsorption capacity of activated carbon and resin, thereby reducing the purity of sodium sulfate, shortening the service life of activated carbon and resin, and increasing production costs.
[0030] The scale inhibitor copolymer in Comparative Example 3 lacks sulfonic acid groups, which reduces the hydrophilicity and ability to dissociate sparingly soluble salts. This increases the likelihood of gelation in high-salt brine, which not only clogs the resin and shortens its lifespan but also affects the freeze-crystallization of low-nitrate brine, reducing the purity of sodium sulfate. Furthermore, using only benzyl bromide for hydrophobic modification, lacking the hydrophobic long chain of n-octane bromide, not only reduces the resin's hydrophobicity, increasing the risk of resin swelling and shortening its lifespan, but also reduces the resin's selective adsorption of nitrate ions, thereby lowering the purity of sodium sulfate.
[0031] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A processing method for preparing sodium sulfate based on denitrification of high-salt brine, characterized in that: Includes the following steps: S1: Add a filter aid to the high-salinity brine, stir and filter, add sodium carbonate and magnesium chloride, adjust the pH to 11-11.2, stir and filter, adjust the pH of the filtrate to 7-7.2, filter with modified activated carbon to obtain crude high-salinity brine; S2: Add scale inhibitor to the crude high-salt brine and use modified anion exchange resin for adsorption and denitrification. Collect the filtrate to obtain low-nitrate brine. S3: The low-nitrate brine is evaporated and concentrated until the sodium sulfate concentration reaches 80-100 g / L. Then, it is pre-cooled and cooled in a gradient, and then vacuum dried to obtain sodium sulfate.
2. The processing method for preparing sodium sulfate based on denitrification of high-salt brine according to claim 1, characterized in that: In step S1, the mass ratio of high-salt brine to filter aid is 100:(1-2); the filter aid is one or more of magnesium hydroxide, diatomaceous earth, fly ash, and expanded perlite.
3. The processing method for preparing sodium sulfate based on denitrification of high-salt brine according to claim 1, characterized in that: In step S1, the modified activated carbon is prepared as follows: the activated carbon is soaked in water, taken out and dried, placed in a superhydrophobic modification solution, soaked at 40-50℃ for 1-2 hours, rotary evaporated at 80-100℃ for 1-2 hours, and dried at 200-300℃ for 8-12 hours to obtain the modified activated carbon. In the preparation process of the modified activated carbon, the mass ratio of activated carbon to superhydrophobic modification liquid is 1:(5-7).
4. The processing method for preparing sodium sulfate based on denitrification of high-salt brine according to claim 3, characterized in that: The method for preparing the activated carbon is as follows: straw powder is mixed and ground with ferric chloride, heated to 500-700℃ at a rate of 5-10℃ / h for 1-2h, cooled to room temperature, soaked in deionized water for 1-2h, filtered, soaked in hydrochloric acid for 8-12h, washed, dried and ground to obtain activated carbon. In the process of preparing activated carbon, the mass ratio of straw powder to ferric chloride is (1-3):(1-2).
5. The processing method for preparing sodium sulfate based on denitrification of high-salt brine according to claim 3, characterized in that: The preparation method of the superhydrophobic modified liquid is as follows: butyl acetate is added to ammonia water, magnetically stirred, and then silica is added. Propyltrimethoxysilane and hexadecyltrimethoxysilane are added, and the mixture is heated and stirred in a water bath at 40-50℃ for 36-48 hours to obtain the hydrophobic modified liquid. In the preparation of the superhydrophobic modified liquid, the mass ratio of butyl acetate, ammonia, silica, propyltrimethoxysilane and hexadecyltrimethoxysilane is 100:(6-8)(15-20):(3-5):(8-12).
6. The processing method for preparing sodium sulfate based on denitrification of high-salt brine according to claim 1, characterized in that: In step S2, the mass ratio of the high-salt brine crude solution to the scale inhibitor is 100:(0.005-0.01).
7. The processing method for preparing sodium sulfate based on denitrification of high-salt brine according to claim 1, characterized in that: In step S2, the preparation method of the scale inhibitor is as follows: epoxy succinic acid, itaconic acid and 2-acrylamido-2-methylpropanesulfonic acid are added to deionized water and stirred until well mixed. Isopropanol and ammonium persulfate are added in sequence, and the mixture is heated to 50-70°C. Then sodium bisulfite and hydrogen peroxide are added, and the mixture is reacted at 50-70°C for 3-5 hours. The mixture is then cooled to room temperature to obtain the scale inhibitor. In the preparation process of the scale inhibitor, the mass ratio of epoxy succinic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, isopropanol, ammonium persulfate, sodium bisulfite and hydrogen peroxide is (15-20):(6-8):(10-15):(25-30):(0.8-1.2):(0.4-0.6):(1-2).
8. The processing method for preparing sodium sulfate based on denitrification of high-salt brine according to claim 1, characterized in that: In step S2, the modified anion exchange resin is prepared as follows: the anion exchange resin is purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain a dry anion exchange resin. The dry anion exchange resin is placed in acetonitrile solution and soaked for 1-2 hours. Potassium iodide, n-octane bromide and benzyl bromide are added, and the mixture is slowly stirred and heated for 36-48 hours. The resin is then purified by hydrochloric acid and sodium hydroxide solution, washed and dried to obtain the modified anion exchange resin. In the preparation process of the modified anion exchange resin, the mass ratio of anion exchange resin, acetonitrile, potassium iodide, n-octane bromide and benzyl bromide is (5-10):(250-300):(0.1-0.3):(1-1.5):(0.3-0.5).