Preparation method of ion exchange resin for efficiently removing nitrate, obtained product and application

Abstract

The invention belongs to the field of ion exchange resin preparation, and particularly relates to a preparation method of ion exchange resin for efficiently removing nitrate, an obtained product and application. The resin matrix provided by the invention is mainly synthesized by taking styrene (St) and divinylbenzene (DVB) as main monomers through free radical polymerization reaction. The crosslinking degree and the pore structure of the resin can be adjusted by accurately controlling polymerization conditions, so that the ion exchange performance of the resin is optimized, and the pore structure is optimized and the surface characteristics are modified by further introducing specific functional groups (such as amino groups and sulfonic acid groups). The adsorption capacity of the resin on nitrate can be effectively improved, stable performance is kept under various water quality conditions, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the field of ion exchange resin preparation, and specifically relates to a preparation method of an ion exchange resin for efficiently removing nitrates, and the obtained product and application. Background Art

[0002] In order to remove nitrate from water, researchers have proposed a variety of water treatment technologies in recent years, among which ion exchange is a common and efficient technology. Ion exchange resins are widely used to remove nitrate, chloride ions, fluoride ions, etc. from water, but the existing technology has some shortcomings.

[0003] Traditional cation exchange resins, such as polystyrene / divinylphenyl resins, usually exchange ions by exchanging cations (such as sodium ions) in water with dissolved salts (such as nitrates) in water. However, the exchange performance of these resins is poorly selective for nitrates and is easily affected by other anions, resulting in low nitrate removal efficiency.

[0004] Anion exchange resins are good at removing nitrates because they can directly exchange anions in water. For example, the use of amine resins, quaternary ammonium resins, etc. can improve the selectivity for nitrates. However, the cost of these resins is relatively high, and under different water quality conditions, the adsorption capacity is easily reduced due to surface modification of the resin or changes in the pore structure.

[0005] In the prior art, there are other methods for removing nitrates, such as reverse osmosis, nano-adsorbent materials, etc., but these methods are expensive, and the regeneration of reverse osmosis membranes is poor, and they are easily blocked by pollutants, which limits their application in large-scale water treatment. Existing patents involve anion exchange resins and modified resins for water treatment, but their selectivity and stability are poor, and the removal effect of nitrates is limited. At the same time, the selectivity for nitrates is limited, and the modification process is relatively complicated, which increases the production cost. Therefore, the development of an ion exchange resin with high selectivity, high adsorption capacity and strong adaptability for removing nitrates has become a problem to be solved. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides a method for preparing an ion exchange resin for efficiently removing nitrate.

[0007] The present invention further provides an ion exchange resin for efficiently removing nitrates prepared by the above preparation method.

[0008] The invention also provides application of the ion exchange resin in removing nitrate.

[0009] The technical solution provided by the present invention improves the selectivity and exchange capacity of ion exchange resin for nitrate by optimizing its structure. The specific technical solution involves the synthesis of resin, the introduction of functional groups, the adjustment of pore structure and other aspects.

[0010] The technical solution adopted by the present invention to achieve the above-mentioned purpose is: The present invention provides a method for preparing an ion exchange resin for efficiently removing nitrate, comprising the following steps: (1) Using styrene and divinylbenzene as monomers, adding the monomers and initiator into a solvent to carry out a free radical polymerization reaction to obtain a resin matrix; (2) soaking the resin matrix in a chloroethylamine solution to obtain an amino-modified resin matrix after reaction; (3) continuing to immerse the amino modified resin matrix in a trimethylammonium chloride solution to obtain a quaternary ammonium modified resin matrix after reaction; (4) immersing the quaternary ammonium modified resin matrix in a chlorosulfonic acid solution to obtain a sulfonic acid modified resin matrix after reaction; (5) soaking the sulfonic acid modified resin matrix in chloroacetic acid to obtain a modified resin matrix after reaction; (6) The modified resin matrix is ​​sieved and then heat-treated, washed and dried to a constant weight to obtain an ion exchange resin.

[0011] Furthermore, in step (1), the raw material percentage composition of the resin matrix is: styrene (St) 85%, divinylbenzene (DVB) 14% and initiator 1%; the initiator is potassium persulfate (KPS) or azobisisobutyronitrile (AIBN); the solvent is composed of toluene and benzene in a volume ratio of 1:1; the volume ratio of styrene to solvent is 12-13:15.

[0012] Furthermore, in step (1), the free radical polymerization reaction is carried out at a temperature of 70-80° C. for 6-8 hours.

[0013] Furthermore, in step (2), the mass concentration of the chloroethylamine solution is 2-5%; the solvent of the chlorosulfonic acid solution is chloroform, with a mass fraction of 20%; and the reaction is carried out at a temperature of 75° C. for 4 hours.

[0014] Furthermore, in step (3), the concentration of the trimethylammonium chloride solution is 3-8%; and the reaction is carried out at a temperature of 80° C. for 5 hours.

[0015] Furthermore, in step (4), the reaction is carried out at a temperature of 60-70° C. for 2 h.

[0016] Furthermore, in step (5), the reaction is carried out at a temperature of 50-60° C. for 2 h.

[0017] Furthermore, in step (6), the sieved particle size is 300-800 μm; and the heat treatment is drying at 120° C. for 6 hours.

[0018] The invention also provides an ion exchange resin prepared by the preparation method.

[0019] The invention also provides application of the ion exchange resin in removing nitrate from sewage.

[0020] The present invention provides an ion exchange resin with high selectivity, high exchange capacity and strong adaptability for nitrate. By introducing specific functional groups (such as amino groups, sulfonic acid groups, etc.), optimizing pore structure and modifying surface characteristics, the present invention can effectively improve the resin's adsorption capacity for nitrate, maintain stable performance under various water quality conditions, and reduce production costs.

[0021] The resin matrix provided by the present invention is mainly composed of styrene (St) and divinylbenzene (DVB) as main monomers and is synthesized by free radical polymerization. By accurately controlling the polymerization conditions, the crosslinking degree and pore structure of the resin can be adjusted, thereby optimizing the ion exchange performance of the resin. The polymerization reaction will form a crosslinked polystyrene structure, and the degree of crosslinking directly affects the mechanical strength and ion exchange performance of the resin.

[0022] The beneficial effects of the present invention are: (1) High selectivity: The resin's selectivity for nitrate is significantly better than existing technologies and can effectively remove nitrate from water while reducing the impact of other anions.

[0023] (2) Higher ion exchange capacity: Compared with existing resins, the resin of the present invention has a higher ion exchange capacity, so that it can still maintain a high removal efficiency after long-term use.

[0024] (3) Strong adaptability: The resin can adapt to different water conditions, including water with different pH values ​​and ionic strengths, and its performance is relatively stable.

[0025] (4) Low cost: The production process is simple, the required raw materials are relatively cheap, and the production cost of the resin is significantly lower than that of existing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a comparison chart of the adsorption capacity of ion exchange resins; Figure 2 Schematic diagram of the preparation process. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is further explained and illustrated by means of specific embodiments below.

[0028] Unless otherwise specified, the raw materials used in the present invention are all commercially available; among them, chlorosulfonic acid was purchased from Shanghai Aladdin Reagent Co., Ltd.

[0029] The schematic flow diagram of the ion exchange resin prepared by the present invention is as follows Figure 2 shown.

[0030] Example 1 1. Synthesis of resin matrix Raw material ratio: Styrene (St): 85% Divinylbenzene (DVB): 14% Initiator: Azobisisobutyronitrile (AIBN) 1% Polymerization conditions: Temperature: 70-80°C Time: 6-8 hours Solvent: Toluene and benzene (1:1 volume ratio) The specific preparation process is as follows: 425g of styrene, 70g of divinylbenzene and 5g of initiator are added into a mixed solvent consisting of 247.5mL of toluene and 247.5mL of benzene, and a free radical polymerization reaction is carried out at 70°C for 8h to obtain a resin matrix.

[0031] (II) Functional modification of resin 1. Amination modification: Amino groups (-NH2) were introduced by immersing the polymerized resin in a solution of ethylamine (the solution must completely cover the resin to ensure that the resin particles are evenly in contact with the reactants and to avoid insufficient local reaction); the reaction temperature was controlled at 75°C, the reaction time was 4 hours, and the concentration of ethylamine used was 5%.

[0032] Reaction formula: Resin-Cl + ethyl chloride → Resin-NH2 + HCl 2. Quaternization modification: In order to further improve the resin's adsorption capacity for nitrates, the resin needs to be quaternized. The resin is soaked in a trimethylammonium chloride solution to introduce a quaternary ammonium group (-NR3⁺). The reaction temperature is controlled at 80°C, the reaction time is 5 hours, and the concentration of trimethylammonium chloride used is 6%.

[0033] Reaction formula: Resin-NH2+trimethylammonium chloride→Resin-NR3++HCl 3. Introduction of sulfonic acid groups: The sulfonic acid group (-SO3H) can significantly increase the resin's affinity for nitrates. The reaction was carried out using chlorosulfonic acid at 60-70°C for 2 hours.

[0034] Reaction formula: Resin-H + chlorosulfonic acid → Resin-SO3H + HCl 4. Introduction of carboxyl groups: The carboxyl group (-COOH) can further enhance the resin's ability to adsorb nitrates, especially under neutral and weakly alkaline conditions. Chloroacetic acid is used to react with the resin at a temperature of 50-60°C for 2 hours.

[0035] Reaction formula: Resin-H + chloroacetic acid → Resin-COOH + HCl 5. Optimization of resin pore structure (1) Cross-linking degree adjustment: By adjusting the content of divinylbenzene (DVB), the crosslinking degree of the resin can be controlled. The degree of crosslinking directly affects the porosity and mechanical strength of the resin. When the degree of crosslinking is high, the mechanical strength of the resin is enhanced, but the pores are small and the ion exchange capacity is low; when the degree of crosslinking is low, the pores of the resin are large, the exchange capacity is high, but the mechanical strength is poor. The present invention maximizes its pore structure and enhances its adsorption capacity while ensuring the mechanical strength of the resin by adjusting the proportion of divinylbenzene (10%-20%). Specific results are shown in Table 1.

[0036] Table 1 (2) Aperture control: The pore size of the resin is controlled between 2-10 nm, which has the best effect on the adsorption of nitrate ions. In order to obtain this pore size structure, the ratio of solvent to monomer can be adjusted during the polymerization process, or the pore size of the resin can be adjusted using solvent extraction technology during post-treatment.

[0037] 6. Screening and post-processing of resin The modified resin particles are sieved through a 300-800 μm screen to obtain a uniform particle size distribution. This particle size range is suitable for water treatment processes, providing good exchange kinetics and reducing pressure drop.

[0038] 7. Heat treatment: The modified resin particles were heat treated at 120°C for 6 hours to enhance the mechanical strength and chemical stability of the resin. This process can further remove unreacted residues and ensure the long-term stability of the resin.

[0039] 8. Washing and drying: After the resin is heat treated, it needs to be repeatedly washed with deionized water to remove unreacted chemicals on the surface. After washing, the resin is dried to constant weight to ensure its good adsorption performance.

[0040] Effect Example 1 (1) Experimental conditions: Initial nitrate concentration: 20 mg / L pH range: 5-9 Resin dosage: 2 g / L Contact time: 0-120 minutes (dynamic adsorption) Temperature: 25°C (normal temperature).

[0041] (2) Experimental process: Prepare artificial wastewater containing nitrate (add coexisting ions such as Cl⁻, SO4²⁻ to simulate actual sewage).

[0042] A fixed amount of resin was mixed with the solution at different initial concentrations and stirred using a thermostatic oscillator.

[0043] Samples were taken, filtered, and nitrate concentrations were determined using ion chromatography. The adsorption and removal rates were calculated.

[0044] The resin was regenerated with 1.2 mol / L NaCl solution and reused 10 times, and the changes in nitrate removal efficiency were recorded.

[0045] The experimental results are shown in Table 2.

[0046] Table 2 Effect Example 2 According to the same method as in Example 1, control groups were set up: control group 1 was an unmodified resin matrix; control group 2 was an amination-modified resin matrix; control group 3 was an amination-+quaternization-modified resin matrix; control group 4 was an amination-+quaternization-+sulfonation-modified resin matrix; the specific results are shown in Figure 1 and Table 3.

[0047] Table 3

Claims

1. A method for preparing an ion exchange resin for efficiently removing nitrates, characterized in that: The following steps are involved: (1) Using styrene and divinylbenzene as monomers, adding the monomers and initiator into a solvent to carry out a free radical polymerization reaction to obtain a resin matrix; (2) soaking the resin matrix in a chloroethylamine solution to obtain an amino-modified resin matrix after reaction; (3) continuing to immerse the amino modified resin matrix in a trimethylammonium chloride solution to obtain a quaternary ammonium modified resin matrix after reaction; (4) immersing the quaternary ammonium modified resin matrix in a chlorosulfonic acid solution to obtain a sulfonic acid modified resin matrix after reaction; (5) soaking the sulfonic acid modified resin matrix in chloroacetic acid to obtain a modified resin matrix after reaction; (6) The modified resin matrix is ​​sieved and then heat-treated, washed and dried to a constant weight to obtain an ion exchange resin.

2. The preparation method according to claim 1, characterized in that: In step (1), the raw material percentage composition of the resin matrix is: styrene (St) 85%, divinylbenzene (DVB) 14% and initiator 1%; the initiator is potassium persulfate (KPS) or azobisisobutyronitrile (AIBN); the solvent is composed of toluene and benzene in a volume ratio of 1:1; the volume ratio of styrene to solvent is 12-13:

15.

3. The preparation method according to claim 1 or 2, characterized in that: In step (1), the free radical polymerization reaction is carried out at a temperature of 70-80° C. for 6-8 hours.

4. The preparation method according to any one of claims 1 to 3, characterized in that In step (2), the mass concentration of the chloroethylamine solution is 2-5%; the solvent of the chlorosulfonic acid solution is chloroform, with a mass fraction of 20%; and the reaction is carried out at a temperature of 75° C. for 4 hours.

5. The preparation method according to claim 1 or 4, characterized in that: In step (3), the concentration of the trimethylammonium chloride solution is 3-8%; and the reaction is carried out at 80° C. for 5 hours.

6. The preparation method according to claim 1 or 5, characterized in that: In step (4), the reaction is carried out at a temperature of 60-70° C. for 2 h.

7. The preparation method according to any one of claims 1 or 6, characterized in that: In step (5), the reaction is carried out at a temperature of 50-60° C. for 2 h.

8. The preparation method according to any one of claims 1 to 7, characterized in that: In step (6), the sieved particle size is 300-800 μm; and the heat treatment is drying at 120° C. for 6 hours.

9. An ion exchange resin prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the ion exchange resin according to claim 9 in removing nitrate from sewage.

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