An anion exchange resin based on ethylene carbonate-N,N-dimethylformamide solution system, and a preparation method and application thereof

Abstract

The application provides an anion exchange resin based on an ethylene carbonate-N,N-dimethylformamide solution system and a preparation method and application thereof, and belongs to the technical field of water treatment adsorption materials. The preparation method comprises the following steps: adding chloromethyl polystyrene crosslinked microspheres into a mixed solution of ethylene carbonate and N,N-dimethylformamide, swelling to obtain a resin mixed solution; adding triethylamine into the resin mixed solution to perform an amination reaction, filtering off an amination mother liquor, mixing the microspheres with dilute hydrochloric acid, and filtering to obtain an anion exchange resin. The method of the application uses a green solvent EC as a core solvent, improves reaction conditions and resin performance, and improves environmental friendliness, and can replace traditional organic solvents in the resin synthesis process; the preparation process is simple, the reaction conditions are mild, the chloromethyl polystyrene microspheres with low price are used as raw materials, and the anion exchange resin with high adsorption performance can be prepared at a lower temperature and in a shorter amination time.

Description

Technical Field

[0001] This invention relates to the field of water treatment adsorption materials technology, and in particular to an anion exchange resin based on a ethylene carbonate-N,N-dimethylformamide solution system, its preparation method, and its application. Background Technology

[0002] Nitrogen pollution in water bodies is a major problem facing the water treatment industry. Excessive nitrogen discharge into water bodies leads to eutrophication, such as the proliferation of algae, oxygen depletion, and the production of toxic substances; it also poses a carcinogenic risk to human drinking water safety. Wastewater treatment plants are the main sites for treating polluted water, and the secondary effluent, after meeting wastewater discharge standards, ultimately flows into rivers and lakes. However, the quality of currently discharged effluent differs significantly from that of surface water, contributing to eutrophication. Improving the denitrification efficiency of wastewater treatment plants and reducing the total nitrogen (TN) content in the effluent will inevitably reduce the TN content entering rivers (Chemosphere, 2022, 291: 132728), thereby effectively alleviating eutrophication. Adsorption methods can bind pollutants in water to the surface or pores of adsorbents, offering advantages such as low cost, high efficiency, and wide applicability compared to other treatment methods. Resin is an adsorbent with excellent pore area and high stability. Due to its strong adsorption capacity and good regeneration ability, it is a commonly used adsorbent to effectively reduce the total nitrogen content in wastewater by adsorbing nitrate nitrogen.

[0003] The principle of anion exchange resin in removing nitrate nitrogen from water is NO3. - Cl on the anion exchange resin - or HCO3 -Nitrate nitrogen is removed through exchange. Currently, styrene or acrylic-based strong-base anion exchange resins are most commonly used for adsorbing nitrate nitrogen from water. Norhayati et al. (Materials Today: Proceedings, 2019, 17: 679-685) used the chlorostyrene-based resin Amberlite IRA958 to remove nitrate nitrogen from water, achieving a nitrate nitrogen removal rate of 87% at a contact time of 3 hours and an initial nitrate concentration of 20 mg / L. Thakshila Nadeeshani Dharmapriya et al. (Polymers, 2022, 14(7): 1442) prepared hydrogel-based anion exchange resins using 2-aminoethyl methacrylate hydrochloride (AMHC) and methacryloyloxyethyltrimethylammonium chloride (MTAC) as solutions to synthesize the resins. The resins were modified with different amines and finally tested to determine their ability to adsorb nitrates and nitrites from water. In the batch experiments, the maximum adsorption capacities of PEGDA-MTAC and PEDGA-AMHC type resins were 13.51 mg nitrate nitrogen / g and 13.1 mg nitrate nitrogen / g, respectively. Hai Ou Song et al. (Chinese Chemical Letters, 2012, 23(5): 603-606) synthesized anion exchange resins by copolymerization of divinylbenzene, methyl acrylate, benzoyl peroxide, and benzene as reaction solutions. The resins were then amination with triethylamine, and their selective removal performance of nitrates in a mixed solution of sulfate and nitrates was investigated. The adsorption kinetics of the NDP-5 resin conformed to pseudo-first-order and pseudo-second-order kinetic models. In summary, anion exchange resins often use traditional organic solvents such as toluene and N-methylpyrrolidone (NMP). However, these solvents have disadvantages such as high volatility, high toxicity, and high environmental risk, which are not conducive to green environmental protection requirements.

[0004] Ethylene carbonate (EC) is a polar aprotic solvent synthesized from ethylene oxide and carbon dioxide. It is characterized by low volatility, low toxicity, clean and renewable sources, aligning with green chemistry principles. Using EC as the core solvent in amination resin reactions can significantly reduce potential hazards to operators and the environment while ensuring reaction efficiency and resin performance.

[0005] Therefore, there is an urgent need to provide a method for preparing an amination resin based on a mixed solution system of EC and DMF, which improves amination efficiency and has excellent adsorption performance and structural stability. Summary of the Invention

[0006] The purpose of this invention is to provide an anion exchange resin based on a ethylene carbonate-N,N-dimethylformamide solution system, its preparation method, and its application, in order to solve the problems of poor solvent environmental friendliness and insufficient resin adsorption performance in the prior art.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing anion exchange resin based on a ethylene carbonate-N,N-dimethylformamide solution system, comprising the following steps:

[0009] 1) Chloromethyl polystyrene cross-linked microspheres were added to a mixed solution and swollen to obtain a resin mixture; the mixed solution consisted of ethylene carbonate and N,N-dimethylformamide.

[0010] 2) Triethylamine was added to the resin mixture to carry out the amination reaction, and the amination mother liquor was filtered off. The microspheres were mixed with dilute hydrochloric acid and filtered to obtain anion exchange resin.

[0011] Preferably, the volume ratio of ethylene carbonate and N,N-dimethylformamide in step 1) is 2~2.6:1.

[0012] Preferably, the chloromethyl polystyrene cross-linked microspheres are sequentially rinsed and dried before being added to the mixed solution. The rinsing reagent is anhydrous ethanol, the rinsing temperature is 80~100℃, and the rinsing time is 2~4h. The drying temperature is 40~50℃, and the drying time is 8~15h.

[0013] Preferably, the swelling time is 0.25~1h.

[0014] Preferably, the volume-to-mass ratio of the triethylamine to the resin mixture is 1-2 mL: 1 g.

[0015] Preferably, the amination reaction is carried out at a temperature of 50-70°C for 7.5-10 hours.

[0016] Preferably, the mixing temperature is 55~65℃ and the mixing time is 1~2h.

[0017] The present invention also provides an anion exchange resin prepared by the method for preparing the anion exchange resin based on the ethylene carbonate-N,N-dimethylformamide solution system.

[0018] The present invention also provides the application of the anion exchange resin based on the ethylene carbonate-N,N-dimethylformamide solution system in the removal of nitrate nitrogen from wastewater.

[0019] The beneficial effects of this invention are:

[0020] 1) This invention utilizes ethylene carbonate (EC) as the main solution and a small amount of N,N-dimethylformamide as the auxiliary solution to synthesize an anion exchange resin through amination. The method of this invention uses the green solvent EC as the core solvent, which not only improves the reaction conditions and resin performance, but also enhances environmental friendliness and can replace traditional organic solvents in the resin synthesis process.

[0021] 2) The preparation process of the present invention is simple, the reaction conditions are mild, and the efficiency is high. Using inexpensive chloromethyl polystyrene microspheres as raw materials, anion exchange resins with high adsorption performance can be prepared at lower temperatures and shorter amination times.

[0022] 3) The anion exchange resin prepared by this invention exhibits excellent nitrate nitrogen adsorption performance in water treatment. The entire synthesis process is not only simple to operate but also involves mild reaction conditions, requires a small amount of amination reagent, and exhibits strong adsorption performance. The resin of this invention achieves a static saturated adsorption capacity of 15.46 mg / g for nitrate nitrogen in wastewater, effectively meeting the total nitrogen treatment needs under complex water quality conditions such as industrial wastewater and municipal tailwater, and thus offering significant economic benefits. Attached Figure Description

[0023] Figure 1 The image shows a SEM image of the anion exchange resin prepared in Example 1. Detailed Implementation

[0024] This invention provides a method for preparing anion exchange resin based on a ethylene carbonate-N,N-dimethylformamide solution system, comprising the following steps:

[0025] 1) Chloromethyl polystyrene cross-linked microspheres were added to the mixed solution and swollen to obtain a resin mixture; the mixed solution consisted of ethylene carbonate (EC) and N,N-dimethylformamide (DMF).

[0026] 2) Triethylamine was added to the resin mixture to carry out the amination reaction, and the amination mother liquor was filtered off. The microspheres were mixed with dilute hydrochloric acid and filtered to obtain anion exchange resin.

[0027] In this invention, the volume ratio of ethylene carbonate and N,N-dimethylformamide in step 1) is preferably 2~2.6:1, more preferably 2.1~2.5:1, and even more preferably 2.3:1.

[0028] In this invention, the chloromethyl polystyrene crosslinked microspheres are preferably rinsed and dried sequentially before being added to the mixed solution. The rinsing reagent is preferably anhydrous ethanol, the rinsing temperature is preferably 80~100℃, more preferably 85~95℃, and even more preferably 90℃, and the rinsing time is preferably 2~4h, more preferably 2.5~3.5h, and even more preferably 3h. The drying temperature is preferably 40~50℃, more preferably 42~48℃, and even more preferably 45~46℃, and the drying time is preferably 8~15h, more preferably 10~13h, and even more preferably 11~12h.

[0029] In this invention, the chloromethyl polystyrene crosslinked microspheres are preferably rinsed in a Soxhlet extractor to remove impurities.

[0030] In this invention, the swelling time is preferably 0.25~1h, and more preferably 0.5~0.75h.

[0031] In this invention, the volume-to-mass ratio of the triethylamine to the resin mixture is preferably 1-2 mL:1 g, more preferably 1.2-1.8 mL:1 g, and even more preferably 1.5-1.6 mL:1 g.

[0032] In this invention, the temperature of the amination reaction is preferably 50~70℃, more preferably 55~65℃, and even more preferably 55~60℃, and the time of the amination reaction is preferably 7.5~10h, and even more preferably 8~9h.

[0033] In this invention, the volume of hydrochloric acid is preferably the same as the volume of the resin mixture; the concentration of hydrochloric acid is preferably 0.8~1.2 mol / L, and more preferably 1 mol / L.

[0034] In this invention, the mixing temperature is preferably 55~65℃, more preferably 58~62℃, and even more preferably 60℃, and the mixing time is preferably 1~2h, and even more preferably 1.5h.

[0035] In this invention, the microspheres are mixed with dilute hydrochloric acid, filtered, and preferably washed and dried sequentially to obtain anion exchange resin; the washing reagents are water, anhydrous ethanol, and water in sequence; the drying temperature is preferably 40~50℃, and more preferably 45℃.

[0036] The present invention also provides an anion exchange resin prepared by the method for preparing the anion exchange resin based on the ethylene carbonate-N,N-dimethylformamide solution system.

[0037] The present invention also provides the application of the anion exchange resin based on the ethylene carbonate-N,N-dimethylformamide solution system in the removal of nitrate nitrogen from wastewater.

[0038] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0039] In the examples and comparative examples, the initial indicators of the wastewater are shown in Table 1.

[0040] Table 1 Initial index test results of wastewater

[0041]

[0042] Example 1

[0043] Chloromethyl polystyrene cross-linked microspheres were washed with anhydrous ethanol at 90°C for 3 h in a Soxhlet extractor, and then dried at 45°C for 10 h. The dried chloromethyl polystyrene cross-linked microspheres were added to a mixed solution of ethylene carbonate and N,N-dimethylformamide (volume ratio of ethylene carbonate to N,N-dimethylformamide was 2.3:1), and swollen at room temperature for 0.5 h to obtain a resin mixture.

[0044] Triethylamine (volume-to-mass ratio of triethylamine to resin mixture is 1.5 mL: 1 g) was added to the resin mixture. After amination reaction at 60 °C for 8 h, the amination mother liquor was filtered off and the microspheres were rinsed with a large amount of deionized water. The rinsed microspheres were placed in a round-bottom bottle, and an equal volume of 1 mol / L dilute hydrochloric acid was added. The mixture was mixed and stored at 60 °C for 1.5 h. The anion exchange resin was obtained by filtration and then rinsed sequentially with deionized water, anhydrous ethanol, and deionized water until the effluent was neutral. The resin was then dried at 45 °C for later use.

[0045] The anion exchange resin prepared in this embodiment was used to adsorb nitrate nitrogen in wastewater at room temperature using a static adsorption method. A certain amount of resin was weighed into a beaker, and wastewater was added. The resin dosage in the wastewater was 13 g / L. Adsorption was performed at 300 rpm for 30 min. The total nitrogen index of the supernatant was measured. The total nitrogen value (TN) of the effluent was 22.6 mg / L. Compared with the initial TN value of 220 mg / L, the TN degradation rate reached 89.73%, and the resin adsorption capacity was 15.18 mg / g.

[0046] Example 2

[0047] The difference between this embodiment and Example 1 is that the volume-to-mass ratio of triethylamine to resin mixture is 1 mL: 1 g, while all other conditions are the same as in Example 1.

[0048] In this embodiment, the TN degradation rate was 88.6%, and the resin adsorption capacity was 15.00 mg / g.

[0049] Example 3

[0050] The difference between this embodiment and Example 1 is that the volume-to-mass ratio of triethylamine to resin mixture is 2 mL: 1 g, while all other conditions are the same as in Example 1.

[0051] In this embodiment, the TN degradation rate is 90%, and the resin adsorption capacity is 15.23 mg / g.

[0052] Example 4

[0053] The difference between this embodiment and Example 1 is that the amination reaction temperature is 50°C, while all other conditions are the same as in Example 1.

[0054] In this embodiment, the TN degradation rate was 89.7%, and the resin adsorption capacity was 15.18 mg / g.

[0055] Example 5

[0056] The difference between this embodiment and Example 1 is that the amination reaction temperature is 55°C, while all other conditions are the same as in Example 1.

[0057] In this embodiment, the TN degradation rate was 91.4%, and the resin adsorption capacity was 15.46 mg / g.

[0058] Example 6

[0059] The difference between this embodiment and Example 1 is that the amination reaction temperature is 70°C, while all other conditions are the same as in Example 1.

[0060] In this embodiment, the TN degradation rate was 88.6%, and the resin adsorption capacity was 15.00 mg / g.

[0061] Example 7

[0062] The difference between this embodiment and Example 1 is that the amination reaction temperature is 55°C and the reaction time is 9 hours, while all other conditions are the same as in Example 1.

[0063] In this embodiment, the TN degradation rate was 90.5%, and the resin adsorption capacity was 15.31 mg / g.

[0064] Comparative Example 1

[0065] The difference between this comparative example and Example 1 is that the volume ratio of ethylene carbonate to N,N-dimethylformamide is 1:1, while all other conditions are the same as in Example 1.

[0066] The TN degradation rate in this comparative example was 81.5%, and the resin adsorption capacity was 13.8 mg / g.

[0067] Comparative Example 2

[0068] The difference between this comparative example and Example 1 is that the volume ratio of ethylene carbonate to N,N-dimethylformamide is 1:1.5, while all other conditions are the same as in Example 1.

[0069] The TN degradation rate in this comparative example was 84.8%, and the resin adsorption capacity was 14.35 mg / g.

[0070] Comparative Example 3

[0071] The difference between this comparative example and Example 1 is that the volume ratio of ethylene carbonate to N,N-dimethylformamide is 1:2.3, while all other conditions are the same as in Example 1.

[0072] The TN degradation rate in this comparative example was 80.45%, and the resin adsorption capacity was 13.62 mg / g.

[0073] Comparative Example 4

[0074] The difference between this comparative example and Example 1 is that the volume ratio of ethylene carbonate to N,N-dimethylformamide is 1.5:1, while all other conditions are the same as in Example 1.

[0075] The TN degradation rate in this comparative example was 85.9%, and the resin adsorption capacity was 14.54 mg / g.

[0076] Comparative Example 5

[0077] The difference between this comparative example and Example 1 is that the amination agent is ethylenediamine, the volume ratio of ethylene carbonate to N,N-dimethylformamide is 1:1, and all other conditions are the same as in Example 1.

[0078] The TN degradation rate in this comparative example was 30.2%, and the resin adsorption capacity was 5.12 mg / g.

[0079] Comparative Example 6

[0080] The difference between this comparative example and Example 1 is that the amination agent is diethylenetriamine, the volume ratio of ethylene carbonate to N,N-dimethylformamide is 1:1, and all other conditions are the same as in Example 1.

[0081] The TN degradation rate in this comparative example was 28.1%, and the resin adsorption capacity was 4.75 mg / g.

[0082] Comparative Example 7

[0083] The difference between this comparative example and Example 1 is that the amination reaction temperature is 40°C, while all other conditions are the same as in Example 1.

[0084] The TN degradation rate in this comparative example was 85.4%, and the resin adsorption capacity was 14.44 mg / g.

[0085] Comparative Example 8

[0086] The difference between this comparative example and Example 1 is that the amination reaction temperature is 55°C and the reaction time is 4 hours, while all other conditions are the same as in Example 1.

[0087] The TN degradation rate in this comparative example was 78.3%, and the resin adsorption capacity was 13.25 mg / g.

[0088] Comparative Example 9

[0089] The difference between this comparative example and Example 1 is that the amination reaction temperature is 55°C and the reaction time is 5 hours, while all other conditions are the same as in Example 1.

[0090] The TN degradation rate in this comparative example was 78.6%, and the resin adsorption capacity was 13.31 mg / g.

[0091] Comparative Example 10

[0092] The difference between this comparative example and Example 1 is that the amination reaction temperature is 55°C and the reaction time is 6 hours, while all other conditions are the same as in Example 1.

[0093] The TN degradation rate in this comparative example was 78.8%, and the resin adsorption capacity was 13.34 mg / g.

[0094] Comparative Example 11

[0095] The difference between this comparative example and Example 1 is that the amination reaction temperature is 55°C and the reaction time is 7 hours, while all other conditions are the same as in Example 1.

[0096] The TN degradation rate in this comparative example was 85.5%, and the resin adsorption capacity was 14.35 mg / g.

[0097] The scanning electron microscope (SEM) image of the anion exchange resin prepared in Example 1 is shown below. Figure 1 As shown. By Figure 1 It is evident that the resin surface exhibits a distinct porous structure with uniform pore distribution and good connectivity, indicating the formation of a well-developed microporous network during synthesis or curing. At lower magnifications, numerous irregular pores with a wide pore size distribution are visible on the material surface, with some areas showing interconnected pores or collapsed structures, indicating phase separation or gas escape during the molding process, resulting in larger pores within the matrix. Overall, this resin material possesses both macroporous and mesoporous structures, demonstrating sufficient cross-linking reactions during polymerization or curing, and a stable and uniform microstructure. The formation of this hierarchical porous structure not only improves the specific surface area of ​​the material but also provides a structural basis for subsequent functional modification and enhanced adsorption performance.

[0098] The method of this invention uses triethylamine (EC) as the main solvent and N,N-dimethylformamide (DMF) as the auxiliary solvent to form a mixed solution. Triethylamine is used as the amination reagent. By optimizing the ratio of EC to DMF, the amount of triethylamine, and the reaction conditions, the efficient amination modification of the resin is achieved. Compared with traditional solvent systems that only use DMF, using EC as the core green solvent not only improves the reaction process and resin performance, but also enhances the environmental friendliness of the method.

[0099] The method for preparing anion exchange resin according to this invention is simple to operate, operates under mild conditions, and is environmentally friendly. The prepared anion exchange resin has a strong adsorption capacity for nitrate nitrogen in the effluent of wastewater treatment plants. At a dosage of 13 g / L, it can reduce the initial total nitrogen from 220 mg / L to 19 mg / L, demonstrating excellent total nitrogen removal capacity, high adsorption capacity and stability. It is suitable for the treatment of total nitrogen in industrial wastewater and domestic sewage and has broad prospects in water treatment.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for producing an anion exchange resin based on an ethylene carbonate-N,N-dimethylformamide solution system, characterized by, The method comprises the following steps: 1) adding chloromethyl polystyrene crosslinked microspheres into a mixed solution to swell, to obtain a resin mixed solution; the mixed solution is ethylene carbonate and N,N-dimethylformamide; 2) adding triethylamine into the resin mixed solution to perform an amination reaction, filtering off the amination mother liquor, mixing the microspheres with dilute hydrochloric acid, and filtering to obtain an anion exchange resin; In step 1), the volume ratio of the ethylene carbonate and N,N-dimethylformamide is 2-2.6:1; and the swelling time is 0.25-1 h; The amination reaction temperature is 50-70 ℃, the amination reaction time is 8-10 h, and the volume / mass ratio of the triethylamine to the resin mixed solution is 1-2 mL:1 g.

2. The method for producing an anion exchange resin based on an ethylene carbonate-N,N-dimethylformamide solution system according to claim 1, characterized by, After the chloromethyl polystyrene crosslinked microspheres are sequentially washed and dried, the chloromethyl polystyrene crosslinked microspheres are added into the mixed solution; the washing reagent is anhydrous ethanol, the washing temperature is 80-100 ℃, the washing time is 2-4 h, the drying temperature is 40-50 ℃, and the drying time is 8-15 h.

3. The method for producing an anion exchange resin based on an ethylene carbonate-N,N-dimethylformamide solution system according to claim 2, characterized by, The mixing temperature is 55-65 ℃, and the mixing time is 1-2 h.

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