A water treatment agent for wastewater containing microplastics and a preparation method thereof

Abstract

The invention relates to the technical field of sewage treatment, and discloses a water treatment agent for sewage containing microplastics and a preparation method thereof. The invention obtains a water treatment agent for sewage containing microplastics by adding quaternary ammonium salt-modified chitosan-modified carbon nanotubes, carboxybetaine cellulose-modified polyacrylamide, and polyaluminium chloride into a reactor for stirring. Carbon nanotubes can provide abundant adsorption sites to adsorb microplastic particles in water; quaternary ammonium modification enhances the charge neutralization, bonding bridging, and net-catching and sweeping effects of chitosan; after the quaternary ammonium salt-modified chitosan and carbon nanotubes are composited, the dispersibility of carbon nanotubes is increased, and the removal effect of microplastics is enhanced; long-chain groups are grafted on the surface of cellulose to increase its hydrophobicity and improve the surface activity of cellulose; polyacrylamide molecular chains contain both anionic and cationic groups, which will be subject to the interaction of positive and negative charges in water, and a cross-linked network is formed within and between molecular chains, thereby improving the removal effect of microplastics.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a water treatment agent for sewage containing microplastics and a preparation method thereof. Background Art

[0002] Microplastics usually refer to plastic particles with a diameter of less than 5mm. Microplastics have a wide range of sources and strong mobility. Industrial wastewater discharge and surface runoff are the main sources of microplastics in the water environment. Microplastics are not easy to degrade, can exist and accumulate for a long time, and will be enriched and transmitted along the food chain, eventually causing harm to humans. Microplastics have a large specific surface area. Aged and broken microplastics have rich functional groups. They have an enrichment effect on heavy metals, organic pollutants, pathogens, etc. during the migration and transformation process, thus forming complex pollution. Therefore, the pollution control of microplastics in water bodies is imminent. The removal effect of microplastics by commonly used microplastic treatment technologies needs to be improved. In the literature "Research on the Removal of Microplastics in Water Bodies by Polyferric Sulfate and Polyaluminium Chloride", polyferric sulfate and polyaluminium chloride were used as flocculants, and the flocculation method was used to flocculate microplastics in water bodies. The study found that the removal efficiency of microplastics by polyferric sulfate was above 85%, and the removal efficiency of microplastics by polyaluminium chloride was above 95%. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the shortcomings of the prior art, the present invention provides a water treatment agent for wastewater containing microplastics and a preparation method thereof, so as to achieve efficient removal of microplastics in wastewater.

[0005] (II) Technical solution

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical scheme: a water treatment agent containing microplastic wastewater, comprising the following components by weight: 15-20 parts by weight of quaternary ammonium salt-modified chitosan-modified carbon nanotubes, 12-18 parts by weight of carboxybetaine cellulose-modified polyacrylamide, and 4-8 parts by weight of polyaluminium chloride.

[0007] Preferably, the method for preparing the quaternary ammonium salt-modified chitosan-modified carbon nanotubes comprises the following steps:

[0008] (1) Add 5-8 g of chitosan to a 1%-1.5% mass fraction glacial acetic acid solution, stir to dissolve, pass nitrogen to purge for 10-15 min to exclude air, add 0.05-0.09 g of initiator, pretreat for 6-10 min, then drop 18-22 g of (3-acrylamidopropyl)trimethylammonium chloride, the drop time is controlled at 20-25 min, react at 60-68 ° C for 4-6 h, cool to room temperature after the reaction, centrifuge, wash and dry to obtain quaternary ammonium salt modified chitosan;

[0009] (2) Add chlorinated multi-walled carbon nanotubes into N,N-dimethylformamide solvent, ultrasonically disperse for 1-3 hours, then add 16-20 g of quaternary ammonium salt modified chitosan, ultrasonically disperse for 40-50 minutes, introduce nitrogen protection, react at 95-100°C for 20-24 hours. After the reaction is completed, filter, wash with deionized water until neutral, and vacuum dry to obtain quaternary ammonium salt modified chitosan modified carbon nanotubes.

[0010] Preferably, the initiator in step (1) is potassium persulfate.

[0011] Preferably, the preparation method of the chlorinated multi-walled carbon nanotubes in step (2) is as follows: 15-18 g of carboxylated multi-walled carbon nanotubes and 30-40 g of thionyl chloride are added to a reactor, stirred and mixed, heated to 68-72° C., refluxed for 12-16 h, rotary evaporated to remove unreacted thionyl chloride, washed with N,N-dimethylformamide solvent, centrifuged, and vacuum dried to obtain chlorinated multi-walled carbon nanotubes.

[0012] Preferably, the method for preparing the carboxybetaine cellulose modified polyacrylamide comprises the following steps:

[0013] S1. Add 16-24 g of sodium hydroxide solution, 4-8 g of cellulose, and 18-24 g of 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to a toluene solvent, stir and mix, introduce nitrogen protection, heat to 130-140 ° C, react at 600-800 rpm for 10-12 h, after the reaction is completed, centrifuge, wash with deionized water, add hydrochloric acid to neutralize, and vacuum dry to obtain alkenyl-containing cellulose;

[0014] S2. Add alkenyl cellulose, 11-bromodencanoic acid, and potassium iodide catalyst to anhydrous ethanol solvent, introduce nitrogen protection, react at 34-38° C. for 20-24 hours, filter, wash, and dry to obtain carboxy betaine cellulose;

[0015] S3. Add 13-17g of acrylamide, 6-9g of carboxybetaine cellulose, and 3-5g of sodium dodecyl sulfate emulsifier to the sodium chloride solution, stir to dissolve, pass nitrogen to deoxygenate for 20-30min, add 0.07-0.09g of azo initiator, heat to 42-50°C, react for 17-20h, and after the reaction is completed, immerse in acetone for 8-10h to remove unreacted monomers, and vacuum dry to obtain carboxybetaine cellulose modified polyacrylamide.

[0016] Preferably, the mass fraction of the sodium hydroxide solution in S1 is 83%-87%.

[0017] Preferably, the mass ratio of alkenyl cellulose, 11-bromodecaneic acid and potassium iodide in S2 is 1:1.1-1.3:0.06-0.09.

[0018] Preferably, the mass fraction of the sodium chloride solution in S3 is 4%-4.8%, and the azo initiator is azobisisobutylimidazoline hydrochloride.

[0019] Preferably, the preparation method of the microplastic wastewater treatment agent is: adding quaternary ammonium salt-modified chitosan-modified carbon nanotubes, carboxy betaine cellulose-modified polyacrylamide, and polyaluminum chloride into a reactor, stirring at 1200-1500 rpm for 12-20 minutes to obtain the microplastic wastewater treatment agent.

[0020] 3. Beneficial technical effects

[0021] The present invention obtains a microplastic-containing sewage water treatment agent by adding quaternary ammonium salt-modified chitosan-modified carbon nanotubes, carboxyl betaine cellulose-modified polyacrylamide and polyaluminium chloride into a reactor for stirring.

[0022] Amino groups in chitosan and alkenyl groups in (3-acrylamidopropyl)trimethylammonium chloride undergo graft polymerization reaction to obtain quaternary ammonium salt-modified chitosan, carboxylated multi-walled carbon nanotubes undergo acyl chloride reaction with thionyl chloride, and then react with hydroxyl groups in quaternary ammonium salt-modified chitosan to obtain quaternary ammonium salt-modified chitosan-modified carbon nanotubes. Hydroxyl groups in cellulose undergo etherification reaction with chlorine in 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to obtain alkenyl-containing cellulose, tertiary amines in alkenyl-containing cellulose undergo quaternization reaction with 11-bromonounde acid to obtain carboxybetaine cellulose, and carboxybetaine cellulose and acrylamide are polymerized in aqueous solution to obtain carboxybetaine cellulose-modified polyacrylamide.

[0023] Carbon nanotubes have an extremely high specific surface area and can provide abundant adsorption sites to adsorb microplastic particles in water. Chitosan, as a natural organic polymer flocculant, can neutralize the negative charge on the surface of microplastics through its positive charge, reduce the surface charge density of microplastics, and thus promote the aggregation and sedimentation of microplastics. Quaternary ammonium modification increases the positive charge density of chitosan, enhances the charge neutralization, bonding bridging and net-catching and sweeping effects of chitosan, and gives it good flocculation properties, thereby enhancing the removal effect of microplastics. The particle size of quaternary ammonium salt-modified chitosan with long molecular chains and multi-walled carbon nanotubes becomes larger after being composited, and it can It settles quickly and increases the dispersibility of carbon nanotubes, further enhancing the removal effect of microplastics. The cellulose molecules dispersed in water can form bridges with microplastic particles through the cross-linking effect between their molecular chains, causing the microplastic particles to aggregate and settle. By grafting long-chain groups on the cellulose surface to increase its hydrophobicity, the surface activity of cellulose is improved. By introducing a carboxybetaine structure into polyacrylamide, the polyacrylamide molecular chain contains both anionic and cationic groups, which will be affected by the electrostatic interaction of positive and negative charges in water, resulting in the mutual association within and between the molecular chains to form a cross-linked network, thereby improving the removal effect of microplastics. DETAILED DESCRIPTION

[0024] Example 1

[0025] (1) Add 5 g of chitosan to a 1% glacial acetic acid solution, stir to dissolve, pass nitrogen gas for 10 min to exclude air, add 0.05 g of potassium persulfate initiator, pretreat for 6 min, then drop 18 g of (3-acrylamidopropyl)trimethylammonium chloride into it, the dropping time is controlled within 20 min, react at 60 ° C for 4 h, after the reaction is completed, cool to room temperature, centrifuge, wash and dry to obtain quaternary ammonium salt modified chitosan;

[0026] (2) Add 15 g of carboxylated multi-walled carbon nanotubes and 30 g of thionyl chloride into the reactor, stir and mix, heat to 68 ° C, reflux for 12 h, remove unreacted thionyl chloride by rotary evaporation, wash with N, N-dimethylformamide solvent, centrifuge and vacuum dry to obtain chlorinated multi-walled carbon nanotubes;

[0027] (3) Add chlorinated multi-walled carbon nanotubes to N,N-dimethylformamide solvent, ultrasonically disperse for 1 hour, then add 16 g of quaternary ammonium salt-modified chitosan, ultrasonically disperse for 40 minutes, pass nitrogen protection, react at 95°C for 20 hours, filter after the reaction, wash with deionized water until neutral, and vacuum dry to obtain quaternary ammonium salt-modified chitosan-modified carbon nanotubes;

[0028] (4) Add 16 g of 83% sodium hydroxide solution, 4 g of cellulose, and 18 g of 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to a toluene solvent, stir and mix, introduce nitrogen protection, heat to 130° C., react at 600 rpm for 10 h, and after the reaction is completed, centrifuge, wash with deionized water, add hydrochloric acid to neutralize, and vacuum dry to obtain alkenyl-containing cellulose;

[0029] (5) Adding alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide catalyst to anhydrous ethanol solvent, wherein the mass ratio of alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide is 1:1.1:0.06, introducing nitrogen protection, reacting at 34° C. for 20 hours, filtering, washing, and drying after the reaction is completed to obtain carboxy betaine cellulose;

[0030] (6) Add 13 g of acrylamide, 6 g of carboxybetaine cellulose, and 3 g of sodium dodecyl sulfate emulsifier to a 4% sodium chloride solution, stir and dissolve, introduce nitrogen to deoxygenate for 20 min, add 0.07 g of azobisisobutylimidazoline hydrochloride initiator, heat to 42 °C, react for 17 h, and after the reaction is completed, immerse in acetone for 8 h to remove unreacted monomers, and vacuum dry to obtain carboxybetaine cellulose modified polyacrylamide;

[0031] (7) 15 parts by weight of quaternary ammonium salt-modified chitosan-modified carbon nanotubes, 12 parts by weight of carboxy betaine cellulose-modified polyacrylamide, and 4 parts by weight of polyaluminium chloride were added into a reactor and stirred at 1200 rpm for 12 min to obtain a wastewater treatment agent containing microplastics.

[0032] Example 2

[0033] (1) Add 8 g of chitosan to a 1.5% mass fraction glacial acetic acid solution, stir to dissolve, pass nitrogen gas for 15 min to exclude air, add 0.09 g of potassium persulfate initiator, pretreat for 10 min, then drop 22 g of (3-acrylamidopropyl)trimethylammonium chloride into it, the dropping time is controlled within 25 min, react at 68 ° C for 6 h, after the reaction is completed, cool to room temperature, centrifuge, wash and dry to obtain quaternary ammonium salt modified chitosan;

[0034] (2) Add 18 g of carboxylated multi-walled carbon nanotubes and 40 g of thionyl chloride into the reactor, stir and mix, heat to 72 ° C, reflux for 16 h, remove unreacted thionyl chloride by rotary evaporation, wash with N, N-dimethylformamide solvent, centrifuge and vacuum dry to obtain chlorinated multi-walled carbon nanotubes;

[0035] (3) Adding chlorinated multi-walled carbon nanotubes to N,N-dimethylformamide solvent, ultrasonically dispersing for 3 hours, then adding 20 g of quaternary ammonium salt-modified chitosan, ultrasonically dispersing for 50 minutes, passing nitrogen protection, reacting at 100°C for 24 hours, filtering after the reaction, washing with deionized water until neutral, and vacuum drying to obtain quaternary ammonium salt-modified chitosan-modified carbon nanotubes;

[0036] (4) Add 24 g of 87% sodium hydroxide solution, 8 g of cellulose, and 24 g of 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to a toluene solvent, stir and mix, introduce nitrogen protection, heat to 140° C., react at 800 rpm for 12 h, and after the reaction is completed, centrifuge, wash with deionized water, add hydrochloric acid to neutralize, and vacuum dry to obtain alkenyl-containing cellulose;

[0037] (5) Adding alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide catalyst to anhydrous ethanol solvent, wherein the mass ratio of alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide is 1:1.3:0.09, introducing nitrogen protection, reacting at 38°C for 24 hours, filtering, washing, and drying after the reaction to obtain carboxy betaine cellulose;

[0038] (6) Add 17 g of acrylamide, 9 g of carboxybetaine cellulose, and 5 g of sodium dodecyl sulfate emulsifier to a sodium chloride solution with a mass fraction of 4.8%, stir to dissolve, pass nitrogen to deoxygenate for 30 min, add 0.09 g of azobisisobutylimidazoline hydrochloride initiator, heat to 50 ° C, react for 20 h, and after the reaction is completed, immerse in acetone for 10 h to remove unreacted monomers, and vacuum dry to obtain carboxybetaine cellulose modified polyacrylamide;

[0039] (7) 20 parts by weight of quaternary ammonium salt-modified chitosan-modified carbon nanotubes, 18 parts by weight of carboxy betaine cellulose-modified polyacrylamide, and 8 parts by weight of polyaluminium chloride were added into a reactor and stirred at 1500 rpm for 20 min to obtain a wastewater treatment agent containing microplastics.

[0040] Example 3

[0041] (1) Add 6.5 g of chitosan to a 1.2% mass fraction glacial acetic acid solution, stir to dissolve, pass nitrogen gas for 12 min to exclude air, add 0.07 g of potassium persulfate initiator, pretreat for 8 min, then drop 20 g of (3-acrylamidopropyl)trimethylammonium chloride into it, the dropping time is controlled within 22 min, react at 64 ° C for 5 h, after the reaction is completed, cool to room temperature, centrifuge, wash and dry to obtain quaternary ammonium salt modified chitosan;

[0042] (2) Add 16.5 g of carboxylated multi-walled carbon nanotubes and 35 g of thionyl chloride into the reactor, stir and mix, heat to 70°C, reflux for 14 h, remove unreacted thionyl chloride by rotary evaporation, wash with N,N-dimethylformamide solvent, centrifuge, and vacuum dry to obtain chlorinated multi-walled carbon nanotubes;

[0043] (3) Add chlorinated multi-walled carbon nanotubes to N,N-dimethylformamide solvent, ultrasonically disperse for 2 hours, then add 18 g of quaternary ammonium salt-modified chitosan, ultrasonically disperse for 45 minutes, pass nitrogen protection, react at 98°C for 22 hours, filter, wash with deionized water until neutral, and vacuum dry to obtain quaternary ammonium salt-modified chitosan-modified carbon nanotubes;

[0044] (4) Add 20 g of 85% sodium hydroxide solution, 6 g of cellulose, and 21 g of 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to a toluene solvent, stir and mix, introduce nitrogen protection, heat to 135° C., react at 700 rpm for 11 h, and after the reaction is completed, centrifuge, wash with deionized water, add hydrochloric acid to neutralize, and vacuum dry to obtain alkenyl-containing cellulose;

[0045] (5) Adding alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide catalyst to anhydrous ethanol solvent, wherein the mass ratio of alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide is 1:1.2:0.08, introducing nitrogen protection, reacting at 36°C for 22 hours, filtering, washing, and drying after the reaction is completed to obtain carboxy betaine cellulose;

[0046] (6) Add 15 g of acrylamide, 7.5 g of carboxybetaine cellulose, and 4 g of sodium dodecyl sulfate emulsifier to a sodium chloride solution with a mass fraction of 4.4%, stir to dissolve, pass nitrogen to deoxygenate for 25 min, add 0.08 g of azobisisobutylimidazoline hydrochloride initiator, heat to 46 ° C, react for 18 h, and after the reaction is completed, immerse in acetone for 9 h to remove unreacted monomers, and vacuum dry to obtain carboxybetaine cellulose modified polyacrylamide;

[0047] (7) 18 parts by weight of quaternary ammonium salt-modified chitosan-modified carbon nanotubes, 15 parts by weight of carboxy betaine cellulose-modified polyacrylamide, and 6 parts by weight of polyaluminium chloride were added into a reactor and stirred at 1350 rpm for 16 min to obtain a wastewater treatment agent containing microplastics.

[0048] Example 4

[0049] (1) Add 5 g of chitosan to a 1% glacial acetic acid solution, stir to dissolve, pass nitrogen gas for 10 min to exclude air, add 0.05 g of potassium persulfate initiator, pretreat for 6 min, then drop 18 g of (3-acrylamidopropyl)trimethylammonium chloride into it, the dropping time is controlled within 20 min, react at 60 ° C for 4 h, after the reaction is completed, cool to room temperature, centrifuge, wash and dry to obtain quaternary ammonium salt modified chitosan;

[0050] (2) Add 15 g of carboxylated multi-walled carbon nanotubes and 30 g of thionyl chloride into the reactor, stir and mix, heat to 68 ° C, reflux for 12 h, remove unreacted thionyl chloride by rotary evaporation, wash with N, N-dimethylformamide solvent, centrifuge and vacuum dry to obtain chlorinated multi-walled carbon nanotubes;

[0051] (3) Add chlorinated multi-walled carbon nanotubes to N,N-dimethylformamide solvent, ultrasonically disperse for 1 hour, then add 16 g of quaternary ammonium salt-modified chitosan, ultrasonically disperse for 40 minutes, pass nitrogen protection, react at 95°C for 20 hours, filter after the reaction, wash with deionized water until neutral, and vacuum dry to obtain quaternary ammonium salt-modified chitosan-modified carbon nanotubes;

[0052] (4) Add 24 g of 87% sodium hydroxide solution, 8 g of cellulose, and 24 g of 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to a toluene solvent, stir and mix, introduce nitrogen protection, heat to 140° C., react at 800 rpm for 12 h, and after the reaction is completed, centrifuge, wash with deionized water, add hydrochloric acid to neutralize, and vacuum dry to obtain alkenyl-containing cellulose;

[0053] (5) Adding alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide catalyst to anhydrous ethanol solvent, wherein the mass ratio of alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide is 1:1.3:0.09, introducing nitrogen protection, reacting at 38°C for 24 hours, filtering, washing, and drying after the reaction to obtain carboxy betaine cellulose;

[0054] (6) Add 15 g of acrylamide, 7.5 g of carboxybetaine cellulose, and 4 g of sodium dodecyl sulfate emulsifier to a sodium chloride solution with a mass fraction of 4.4%, stir to dissolve, pass nitrogen to deoxygenate for 25 min, add 0.08 g of azobisisobutylimidazoline hydrochloride initiator, heat to 46 ° C, react for 18 h, and after the reaction is completed, immerse in acetone for 9 h to remove unreacted monomers, and vacuum dry to obtain carboxybetaine cellulose modified polyacrylamide;

[0055] (7) 18 parts by weight of quaternary ammonium salt-modified chitosan-modified carbon nanotubes, 15 parts by weight of carboxy betaine cellulose-modified polyacrylamide, and 6 parts by weight of polyaluminium chloride were added into a reactor and stirred at 1350 rpm for 16 min to obtain a wastewater treatment agent containing microplastics.

[0056] Example 5

[0057] (1) Add 8 g of chitosan to a 1.5% mass fraction glacial acetic acid solution, stir to dissolve, pass nitrogen gas for 15 min to exclude air, add 0.09 g of potassium persulfate initiator, pretreat for 10 min, then drop 22 g of (3-acrylamidopropyl)trimethylammonium chloride into it, the dropping time is controlled within 25 min, react at 68 ° C for 6 h, after the reaction is completed, cool to room temperature, centrifuge, wash and dry to obtain quaternary ammonium salt modified chitosan;

[0058] (2) Add 18 g of carboxylated multi-walled carbon nanotubes and 40 g of thionyl chloride into the reactor, stir and mix, heat to 72 ° C, reflux for 16 h, remove unreacted thionyl chloride by rotary evaporation, wash with N, N-dimethylformamide solvent, centrifuge and vacuum dry to obtain chlorinated multi-walled carbon nanotubes;

[0059] (3) Adding chlorinated multi-walled carbon nanotubes to N,N-dimethylformamide solvent, ultrasonically dispersing for 3 hours, then adding 20 g of quaternary ammonium salt-modified chitosan, ultrasonically dispersing for 50 minutes, passing nitrogen protection, reacting at 100°C for 24 hours, filtering after the reaction, washing with deionized water until neutral, and vacuum drying to obtain quaternary ammonium salt-modified chitosan-modified carbon nanotubes;

[0060] (4) Add 20 g of 85% sodium hydroxide solution, 6 g of cellulose, and 21 g of 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to a toluene solvent, stir and mix, introduce nitrogen protection, heat to 135° C., react at 700 rpm for 11 h, and after the reaction is completed, centrifuge, wash with deionized water, add hydrochloric acid to neutralize, and vacuum dry to obtain alkenyl-containing cellulose;

[0061] (5) Adding alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide catalyst to anhydrous ethanol solvent, wherein the mass ratio of alkenyl cellulose, 11-bromodecaneic acid, and potassium iodide is 1:1.2:0.08, introducing nitrogen protection, reacting at 36°C for 22 hours, filtering, washing, and drying after the reaction is completed to obtain carboxy betaine cellulose;

[0062] (6) Add 13 g of acrylamide, 6 g of carboxybetaine cellulose, and 3 g of sodium dodecyl sulfate emulsifier to a 4% sodium chloride solution, stir and dissolve, introduce nitrogen to deoxygenate for 20 min, add 0.07 g of azobisisobutylimidazoline hydrochloride initiator, heat to 42 °C, react for 17 h, and after the reaction is completed, immerse in acetone for 8 h to remove unreacted monomers, and vacuum dry to obtain carboxybetaine cellulose modified polyacrylamide;

[0063] (7) 15 parts by weight of quaternary ammonium salt-modified chitosan-modified carbon nanotubes, 12 parts by weight of carboxy betaine cellulose-modified polyacrylamide, and 4 parts by weight of polyaluminium chloride were added into a reactor and stirred at 1200 rpm for 12 min to obtain a wastewater treatment agent containing microplastics.

[0064] Comparative Example 1

[0065] Compared with Example 1, the difference in this comparative example is that no quaternary ammonium salt is added to modify the chitosan-modified carbon nanotubes.

[0066] Comparative Example 2

[0067] Compared with Example 1, this comparative example is different in that carboxy betaine cellulose modified polyacrylamide is not added.

[0068] Weigh 50 mg of polystyrene, polyethylene, polypropylene, and polyvinyl chloride microplastics, dilute with deionized water to 50 mg / L, pH 6.5, add 0.05 g of wastewater treatment agent containing microplastics and 100 mL of microplastic solution into a centrifuge tube, stir at 250 rpm at 25 ° C for 8 h, let it settle for 1 h, and measure the residual microplastic concentration in the supernatant by spectrophotometer to calculate the microplastic removal rate. The test results are shown in Table 1.

[0069] Table 1: Microplastic removal rate.

[0070] project Microplastic removal rate (%) Example 1 99.2 Example 2 99.4 Example 3 98.6 Example 4 99.1 Example 5 98.7 Comparative Example 1 86.5 Comparative Example 2 83.4

[0071] It can be seen from Table 1 that Examples 1-5 of the present invention have better removal effects on microplastics than Comparative Examples 1-2, and the removal rates are all above 98%.

[0072] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A water treatment agent for wastewater containing microplastics, characterized in that: The invention comprises the following components by weight: 15-20 parts by weight of quaternary ammonium salt-modified chitosan-modified carbon nanotubes, 12-18 parts by weight of carboxybetaine cellulose-modified polyacrylamide, and 4-8 parts by weight of polyaluminium chloride; The method for preparing quaternary ammonium salt-modified chitosan-modified carbon nanotubes comprises the following steps: (1) Add 5-8 g of chitosan to a 1%-1.5% mass fraction glacial acetic acid solution, stir to dissolve, pass nitrogen to purge for 10-15 min to exclude air, add 0.05-0.09 g of initiator, pretreat for 6-10 min, then drop 18-22 g of (3-acrylamidopropyl)trimethylammonium chloride, the drop time is controlled at 20-25 min, react at 60-68 ° C for 4-6 h, cool to room temperature after the reaction, centrifuge, wash and dry to obtain quaternary ammonium salt modified chitosan; (2) Adding acyl chloride multi-walled carbon nanotubes to N,N-dimethylformamide solvent, ultrasonically dispersing for 1-3 hours, then adding 16-20 g of quaternary ammonium salt modified chitosan, ultrasonically dispersing for 40-50 minutes, passing nitrogen protection, reacting at 95-100°C for 20-24 hours, filtering after the reaction, washing with deionized water until neutral, and vacuum drying to obtain quaternary ammonium salt modified chitosan modified carbon nanotubes; The preparation method of the carboxybetaine cellulose modified polyacrylamide comprises the following steps: S1. Add 16-24 g of sodium hydroxide solution, 4-8 g of cellulose, and 18-24 g of 2-chloro-N-phenyl-N-prop-2-enyl-acetamide to a toluene solvent, stir and mix, introduce nitrogen protection, heat to 130-140 ° C, react at 600-800 rpm for 10-12 h, after the reaction is completed, centrifuge, wash with deionized water, add hydrochloric acid to neutralize, and vacuum dry to obtain alkenyl-containing cellulose; S2. Add alkenyl cellulose, 11-bromodencanoic acid, and potassium iodide catalyst to anhydrous ethanol solvent, introduce nitrogen protection, react at 34-38° C. for 20-24 hours, filter, wash, and dry to obtain carboxy betaine cellulose; S3. Add 13-17g of acrylamide, 6-9g of carboxybetaine cellulose, and 3-5g of sodium dodecyl sulfate emulsifier to the sodium chloride solution, stir to dissolve, pass nitrogen to deoxygenate for 20-30min, add 0.07-0.09g of azo initiator, heat to 42-50°C, react for 17-20h, and after the reaction is completed, immerse in acetone for 8-10h to remove unreacted monomers, and vacuum dry to obtain carboxybetaine cellulose modified polyacrylamide.

2. The microplastic wastewater treatment agent according to claim 1, characterized in that: The initiator in step (1) is potassium persulfate.

3. The microplastics-containing wastewater treatment agent according to claim 1, characterized in that: The preparation method of the chlorinated multi-walled carbon nanotubes in step (2) is as follows: 15-18 g of carboxylated multi-walled carbon nanotubes and 30-40 g of thionyl chloride are added to a reactor, stirred and mixed, heated to 68-72° C., refluxed for 12-16 h, and unreacted thionyl chloride was removed by rotary evaporation, washed with N,N-dimethylformamide solvent, centrifuged, and vacuum dried to obtain chlorinated multi-walled carbon nanotubes.

4. The microplastic wastewater treatment agent according to claim 1, characterized in that: The mass fraction of the sodium hydroxide solution in S1 is 83%-87%.

5. The microplastic wastewater treatment agent according to claim 1, characterized in that: The mass ratio of alkenyl cellulose, 11-bromodecaneic acid and potassium iodide in S2 is 1:1.1-1.3:0.06-0.

09.

6. The microplastic wastewater treatment agent according to claim 1, characterized in that: The mass fraction of the sodium chloride solution in S3 is 4%-4.8%, and the azo initiator is azobisisobutylimidazoline hydrochloride.

7. A method for preparing a water treatment agent for wastewater containing microplastics according to any one of claims 1 to 6, characterized in that: The preparation method of the microplastic wastewater treatment agent is as follows: adding quaternary ammonium salt-modified chitosan-modified carbon nanotubes, carboxyl betaine cellulose-modified polyacrylamide, and polyaluminum chloride into a reactor, stirring at 1200-1500 rpm for 12-20 minutes, and obtaining the microplastic wastewater treatment agent.