A composite material for wastewater treatment and its preparation method

Abstract

This invention discloses a composite material for wastewater treatment and its preparation method, relating to the field of wastewater treatment technology. It is obtained by loading an acrylic-chitosan copolymer onto the surface of polyethyleneimine-modified attapulgite. In the preparation process, the acrylic-chitosan copolymer is first acyl-chlorinated, and then crosslinked with methacrylic acid and acrylamide. The polyethyleneimine-modified attapulgite is obtained by crosslinking attapulgite, polyethyleneimine, and glutaraldehyde. The composite material for wastewater treatment of this invention exhibits good flocculation effects on both acidic and alkaline wastewater, effectively adsorbing heavy metal impurities and pollutants in the wastewater. Furthermore, its microporous structure is not easily clogged, exhibiting structural stability and maintaining excellent adsorption performance over a long period.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a composite material for wastewater treatment and its preparation method. Background Technology

[0002] Wastewater treatment methods include physical, chemical, and biological methods. Physical methods primarily rely on physical adsorption to remove substances floating or suspended in water, without affecting the chemical properties of the wastewater. Chemical methods remove or transform harmful substances in water through chemical reactions, while biological methods mainly remove pollutants through microbial degradation and biofilm filtration. Among these three methods, physical methods are widely used in the wastewater treatment industry due to their simplicity, low cost, and high safety. However, existing physical adsorption methods mainly utilize adsorbents such as activated carbon and molecular sieves. Although these resources are abundant and inexpensive, their wastewater treatment efficiency needs further improvement. Conventional wastewater treatment agents have the following problems: First, they are sensitive to the pH value of the wastewater, suitable only for acidic, alkaline, or neutral wastewater. They may even require pretreatment with acid or alkali to adjust the pH to neutral; otherwise, the wastewater treatment agent will become ineffective. Second, as adsorption proceeds, the microporous structure of the adsorbent is easily blocked, causing microporous aggregation and adhesion, affecting the adsorption effect, and even leading to adsorbent failure.

[0003] Therefore, there is an urgent need to develop a highly efficient wastewater treatment agent that can be used to treat both acidic and alkaline wastewater, and whose microporous structure is not easily clogged and can maintain excellent adsorption performance over a long period of time. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a composite material for wastewater treatment and its preparation method, which can be used to treat both acidic and alkaline wastewater, and whose microporous structure is not easily clogged, thus maintaining excellent adsorption performance over a long period of time.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A composite material for wastewater treatment is obtained by loading an acrylic chitosan copolymer onto the surface of polyethyleneimine-modified attapulgite; the acrylic chitosan copolymer is prepared by first acyl chloride chitosan, and then crosslinking the acyl chloride chitosan with methacrylic acid and acrylamide; the polyethyleneimine-modified attapulgite is obtained by crosslinking attapulgite, polyethyleneimine and glutaraldehyde.

[0007] This invention also includes a method for preparing a composite material for wastewater treatment, comprising the following steps:

[0008] ① Preparation of polyethyleneimine-modified attapulgite: Add attapulgite to a first hydrochloric acid aqueous solution and stir at 20~30℃ for 2~4 hours. Add polyethyleneimine and glutaraldehyde aqueous solution while stirring and stir for 2~4 hours. Add sodium borohydride and stir for 0.5~1 hours. Filter and dry the solid to obtain polyethyleneimine-modified attapulgite.

[0009] The mass ratio of attapulgite, first hydrochloric acid aqueous solution, polyethyleneimine, glutaraldehyde aqueous solution and sodium borohydride is 10:400~500:1~3:1~3:2~3;

[0010] ② Preparation of acrylic chitosan copolymer: Chitosan and triethylamine are added to N,N-dimethylformamide. Acryloyl chloride is added at 5~15℃ with stirring. After the addition is complete, the mixture is stirred at 20~40℃ for 4~8 hours. The mixture is then poured into first methanol and stirred for 5~15 minutes. After filtration, the filter cake is washed with second methanol, dried, and added to deionized water. Methacrylic acid, acrylamide, and an initiator are added to the mixture. The mixture is stirred for 4~8 hours. After filtration, washing with water, and drying of the filter cake, the acrylic chitosan copolymer is obtained.

[0011] The mass ratio of chitosan, triethylamine, N,N-dimethylformamide, acryloyl chloride, first methanol, deionized water, methacrylic acid, acrylamide, and initiator is 10:1~3:100~300:1~3:1000~3000:500~1000:3~5:1~3:0.15~0.5;

[0012] ③ Preparation of composite material for wastewater treatment: Add the polyethyleneimine-modified attapulgite clay obtained in step ① to the second hydrochloric acid aqueous solution, stir at 10~25℃ for 2~4 hours, add the acrylic chitosan copolymer obtained in step ②, stir for 3~7 hours, filter, wash with water, and dry to obtain the composite material for wastewater treatment.

[0013] The mass ratio of the polyethyleneimine-modified attapulgite clay obtained in step ①, the second hydrochloric acid aqueous solution, and the acrylic chitosan copolymer obtained in step ② is 2~5:20~30:1.

[0014] Preferably, the initiator is potassium persulfate or ammonium persulfate.

[0015] Preferably, the chitosan has a molecular weight of 50,000 to 100,000 and a degree of deacetylation greater than 95%.

[0016] Preferably, the pH of the first hydrochloric acid aqueous solution is 4-6; and the pH of the second hydrochloric acid aqueous solution is 3-5.

[0017] Preferably, the concentration of the glutaraldehyde aqueous solution is 25-50%.

[0018] Preferably, in step ①, the mass ratio of attapulgite, first hydrochloric acid aqueous solution, polyethyleneimine, glutaraldehyde aqueous solution and sodium borohydride is 10:450:2:2:2.5.

[0019] Preferably, in step ②, the mass ratio of chitosan, triethylamine, N,N-dimethylformamide, acryloyl chloride, first methanol, deionized water, methacrylic acid, acrylamide and initiator is 10:2:200:2:2000:800:4:2:0.4.

[0020] Preferably, in step ③, the mass ratio of the polyethyleneimine-modified attapulgite clay obtained in step ①, the second hydrochloric acid aqueous solution, and the acrylic chitosan copolymer obtained in step ② is 4:25:1.

[0021] Preferably, the molecular weight of the polyethyleneimine is 10,000 to 30,000.

[0022] The present invention has the following advantages over the prior art:

[0023] The composite material for wastewater treatment of the present invention has good flocculation effect on both acidic and alkaline wastewater, can effectively adsorb heavy metal impurities and pollutants in wastewater, and its microporous structure is not easily blocked, has a stable structure, and can maintain excellent adsorption effect for a long time.

[0024] The wastewater treatment composite material of the present invention comprises the following steps: First, acryloyl chloride-modified chitosan is further copolymerized with methacrylic acid and acrylamide to prepare an acrylic-chitosan copolymer. This copolymer contains both basic amino groups and acidic carboxyl groups, giving it adaptability to both acidic and alkaline environments, allowing the composite material to be used for treating both acidic and alkaline wastewater. Second, polyethyleneimine is crosslinked with glutaraldehyde and then combined with attapulgite, resulting in a highly crosslinked polymer structure on the attapulgite surface. This ensures a high porosity structure when combined with the acrylic-chitosan copolymer. The composite material contains abundant amino and carboxyl groups, and a hyperbranched polyethyleneimine structure, enabling it to adsorb various metal ions with high adsorption efficiency. Finally, the composite material of the present invention loads the acrylic-chitosan copolymer onto the surface of polyethyleneimine-modified attapulgite, forming a complex crosslinked network structure. The hyperbranched polyethyleneimine structure effectively protects the microporous structure of the attapulgite, preventing adsorbed macromolecular particles from entering the micropores. Therefore, the micropores are not easily blocked, resulting in a stable structure and maintaining excellent adsorption performance over a long period. Detailed Implementation

[0025] The purpose of this invention is to provide a composite material for wastewater treatment and its preparation method. The invention will be further described below with reference to specific embodiments.

[0026] Example 1: A method for preparing a composite material for wastewater treatment, comprising the following steps:

[0027] ① Preparation of polyethyleneimine-modified attapulgite: 1 kg of attapulgite was added to 40 kg of hydrochloric acid aqueous solution with pH 6, and stirred at 20°C for 4 hours. While stirring, 0.1 kg of polyethyleneimine and 0.1 kg of glutaraldehyde aqueous solution were added, and the mixture was stirred for 2 hours. Then, 0.2 kg of sodium borohydride was added, and the mixture was stirred for 0.5 hours. The mixture was filtered, and the solid was dried to obtain polyethyleneimine-modified attapulgite. The molecular weight of the polyethyleneimine was 10,000; the concentration of the glutaraldehyde aqueous solution was 25%.

[0028] ② Preparation of acrylic-chitosan copolymer: 1 kg chitosan and 0.1 kg triethylamine were added to 10 kg N,N-dimethylformamide. 0.1 kg acryloyl chloride was added at 5 °C with stirring. After the addition was complete, the mixture was stirred at 20 °C for 8 hours. The mixture was then poured into 100 kg methanol and stirred for 5 minutes. After filtration, the filter cake was washed with 5 kg methanol, dried, and added to 50 kg deionized water. 0.3 kg methacrylic acid, 0.1 kg acrylamide, and 0.015 kg potassium persulfate were added to the mixture. The mixture was stirred for 4 hours, filtered, washed with water, and the filter cake was dried to obtain the acrylic-chitosan copolymer.

[0029] The chitosan has a molecular weight of 50,000 and a degree of deacetylation greater than 95%.

[0030] ③ Preparation of composite material for wastewater treatment: Add 1 kg of polyethyleneimine-modified attapulgite clay obtained in step ① to 10 kg of hydrochloric acid aqueous solution with pH 5, stir at 10℃ for 2 hours, add 0.5 kg of acrylic chitosan copolymer obtained in step ②, stir for 3 hours, filter, wash with water, and dry to obtain composite material for wastewater treatment.

[0031] Example 2: A method for preparing a composite material for wastewater treatment, comprising the following steps:

[0032] ① Preparation of polyethyleneimine-modified attapulgite: 1 kg of attapulgite was added to 50 kg of hydrochloric acid aqueous solution with pH 4, and stirred at 30°C for 2 hours. While stirring, 0.3 kg of polyethyleneimine and 0.3 kg of glutaraldehyde aqueous solution were added, and the mixture was stirred for 4 hours. Then, 0.3 kg of sodium borohydride was added, and the mixture was stirred for 1 hour. The mixture was filtered, and the solid was dried to obtain polyethyleneimine-modified attapulgite. The molecular weight of the polyethyleneimine was 30,000; the concentration of the glutaraldehyde aqueous solution was 50%.

[0033] ② Preparation of acrylic-chitosan copolymer: 1 kg chitosan and 0.3 kg triethylamine were added to 30 kg N,N-dimethylformamide. 0.3 kg acryloyl chloride was added at 15 °C with stirring. After the addition was complete, the mixture was stirred at 40 °C for 4 hours. The mixture was then poured into 300 kg methanol and stirred for 15 minutes. After filtration, the filter cake was washed with 5 kg methanol, dried, and added to 100 kg deionized water. 0.5 kg methacrylic acid, 0.3 kg acrylamide, and 0.05 kg ammonium persulfate were added to the mixture. The mixture was stirred for 8 hours. After filtration, washing with water, and drying of the filter cake, the acrylic-chitosan copolymer was obtained.

[0034] The chitosan has a molecular weight of 100,000 and a degree of deacetylation greater than 95%.

[0035] ③ Preparation of composite material for wastewater treatment: Add 1 kg of polyethyleneimine-modified attapulgite clay obtained in step ① to 6 kg of hydrochloric acid aqueous solution with pH 3, stir at 25℃ for 2 hours, add 0.2 kg of acrylic chitosan copolymer obtained in step ②, stir for 7 hours, filter, wash with water, and dry to obtain composite material for wastewater treatment.

[0036] Example 3: A method for preparing a composite material for wastewater treatment, comprising the following steps:

[0037] ① Preparation of polyethyleneimine-modified attapulgite: 1 kg of attapulgite was added to 42 kg of hydrochloric acid aqueous solution with pH 5.5 and stirred at 22°C for 2.5 hours. While stirring, 0.15 kg of polyethyleneimine and 0.12 kg of glutaraldehyde aqueous solution were added and stirred for another 2.5 hours. Then, 0.22 kg of sodium borohydride was added and stirred for 40 minutes. The mixture was filtered, and the solid was dried to obtain polyethyleneimine-modified attapulgite. The molecular weight of the polyethyleneimine was 25,000; the concentration of the glutaraldehyde aqueous solution was 30%.

[0038] ② Preparation of acrylic-chitosan copolymer: 1 kg chitosan and 0.12 kg triethylamine were added to 14 kg N,N-dimethylformamide. 0.14 kg acryloyl chloride was added at 8 °C with stirring. After the addition was complete, the mixture was stirred at 22 °C for 5 hours. The mixture was then poured into 150 kg methanol and stirred for 6 minutes. After filtration, the filter cake was washed with 8 kg methanol, dried, and added to 60 kg deionized water. 0.35 kg methacrylic acid, 0.14 kg acrylamide, and 0.02 kg ammonium persulfate were added to the mixture. The mixture was stirred for 5 hours, filtered, washed with water, and the filter cake was dried to obtain the acrylic-chitosan copolymer.

[0039] The chitosan has a molecular weight of 60,000 and a degree of deacetylation greater than 95%.

[0040] ③ Preparation of composite material for wastewater treatment: Add 0.9 kg of polyethyleneimine-modified attapulgite clay obtained in step ① to 6.6 kg of hydrochloric acid aqueous solution with pH 4.5, stir at 15℃ for 2.5 hours, add 0.3 kg of acrylic chitosan copolymer obtained in step ②, stir for 4 hours, filter, wash with water, and dry to obtain composite material for wastewater treatment.

[0041] Example 4: A method for preparing a composite material for wastewater treatment, comprising the following steps:

[0042] ① Preparation of polyethyleneimine-modified attapulgite: 1 kg of attapulgite was added to 44 kg of hydrochloric acid aqueous solution with pH 4.5 and stirred at 25°C for 3 hours. While stirring, 0.18 kg of polyethyleneimine and 0.12 kg of glutaraldehyde aqueous solution were added and stirred for another 3 hours. Then, 0.24 kg of sodium borohydride was added and stirred for 45 minutes. The mixture was filtered, and the solid was dried to obtain polyethyleneimine-modified attapulgite. The molecular weight of the polyethyleneimine was 15,000; the concentration of the glutaraldehyde aqueous solution was 40%.

[0043] ② Preparation of acrylic-chitosan copolymer: 1 kg chitosan and 0.24 kg triethylamine were added to 28 kg N,N-dimethylformamide. 0.26 kg acryloyl chloride was added at 8 °C with stirring. After the addition was complete, the mixture was stirred at 25 °C for 6 hours. The mixture was then poured into 200 kg methanol and stirred for 12 minutes. After filtration, the filter cake was washed with 10 kg methanol, dried, and added to 70 kg deionized water. 0.36 kg methacrylic acid, 0.22 kg acrylamide, and 0.04 kg potassium persulfate were added to the mixture. The mixture was stirred for 6 hours, filtered, washed with water, and the filter cake was dried to obtain the acrylic-chitosan copolymer.

[0044] The chitosan has a molecular weight of 80,000 and a degree of deacetylation greater than 95%.

[0045] ③ Preparation of composite material for wastewater treatment: 1 kg of polyethyleneimine-modified attapulgite clay obtained in step ① was added to 6.25 kg of hydrochloric acid aqueous solution with pH 3.5, stirred at 15℃ for 3.5 hours, 0.25 kg of acrylic chitosan copolymer obtained in step ② was added, stirred for 5 hours, filtered, washed with water, and dried to obtain composite material for wastewater treatment.

[0046] Example 5: A method for preparing a composite material for wastewater treatment, comprising the following steps:

[0047] ① Preparation of polyethyleneimine-modified attapulgite: 1 kg of attapulgite was added to 45 kg of hydrochloric acid aqueous solution with pH 4.5 and stirred at 25°C for 2.5 hours. While stirring, 0.2 kg of polyethyleneimine and 0.2 kg of glutaraldehyde aqueous solution were added and stirred for 3.5 hours. Then, 0.25 kg of sodium borohydride was added and stirred for 45 minutes. The mixture was filtered, and the solid was dried to obtain polyethyleneimine-modified attapulgite. The molecular weight of the polyethyleneimine was 20,000; the concentration of the glutaraldehyde aqueous solution was 30%.

[0048] ② Preparation of acrylic chitosan copolymer: 1 kg chitosan and 0.2 kg triethylamine were added to 20 kg N,N-dimethylformamide. 0.2 kg acryloyl chloride was added at 10 °C with stirring. After the addition was complete, the mixture was stirred at 30 °C for 5 hours. The mixture was then poured into 200 kg methanol and stirred for 10 minutes. After filtration, the filter cake was washed with 5 kg methanol, dried, and added to 80 kg deionized water. 0.4 kg methacrylic acid, 0.2 kg acrylamide, and 0.04 kg potassium persulfate were added to the mixture. The mixture was stirred for 6 hours. After filtration, washing with water, and drying of the filter cake, the acrylic chitosan copolymer was obtained.

[0049] The chitosan has a molecular weight of 70,000 and a degree of deacetylation greater than 95%.

[0050] ③ Preparation of composite material for wastewater treatment: 1 kg of polyethyleneimine-modified attapulgite clay obtained in step ① was added to 6.25 kg of hydrochloric acid aqueous solution with pH 4.5, stirred at 18℃ for 3 hours, 0.4 kg of acrylic chitosan copolymer obtained in step ② was added, stirred for 5 hours, filtered, washed with water, and dried to obtain composite material for wastewater treatment.

[0051] Example 6: A method for preparing a composite material for wastewater treatment, comprising the following steps:

[0052] ① Preparation of polyethyleneimine-modified attapulgite: 1 kg of attapulgite was added to 45 kg of hydrochloric acid aqueous solution with pH 5, and stirred at 24°C for 3 hours. While stirring, 0.2 kg of polyethyleneimine and 0.2 kg of glutaraldehyde aqueous solution were added, and the mixture was stirred for another 3 hours. Then, 0.25 kg of sodium borohydride was added, and the mixture was stirred for 50 minutes. The mixture was filtered, and the solid was dried to obtain polyethyleneimine-modified attapulgite. The molecular weight of the polyethyleneimine was 20,000; the concentration of the glutaraldehyde aqueous solution was 40%.

[0053] ② Preparation of acrylic chitosan copolymer: 1 kg chitosan and 0.2 kg triethylamine were added to 20 kg N,N-dimethylformamide. 0.2 kg acryloyl chloride was added at 8 °C with stirring. After the addition was complete, the mixture was stirred at 25 °C for 6 hours. The mixture was then poured into 200 kg methanol and stirred for 10 minutes. After filtration, the filter cake was washed with 5 kg methanol, dried, and added to 80 kg deionized water. 0.4 kg methacrylic acid, 0.2 kg acrylamide, and 0.04 kg ammonium persulfate were added to the mixture. The mixture was stirred for 5 hours, filtered, washed with water, and the filter cake was dried to obtain the acrylic chitosan copolymer.

[0054] The chitosan has a molecular weight of 60,000 and a degree of deacetylation greater than 95%.

[0055] ③ Preparation of composite material for wastewater treatment: 1 kg of polyethyleneimine-modified attapulgite clay obtained in step ① was added to 6.25 kg of hydrochloric acid aqueous solution with pH 4, stirred at 15℃ for 3 hours, 0.25 kg of acrylic chitosan copolymer obtained in step ② was added, stirred for 5 hours, filtered, washed with water, and dried to obtain composite material for wastewater treatment.

[0056] The composite material for wastewater treatment of the present invention can be used for wastewater treatment in high-concentration, difficult-to-degrade organic industrial parks such as pharmaceutical, leather, papermaking, pesticide, and chemical industries with a pH value of 2 to 10.

[0057] Wastewater with a pH of 3.1 was collected from a paper manufacturing industrial park. The wastewater treatment composite materials obtained in Examples 1-6 were used for direct wastewater treatment. The wastewater treatment composite materials obtained in Examples 1-6 were added to the collected wastewater at a concentration of 18 g / L. The mixture was stirred and adsorbed for 20 minutes, then filtered to obtain the treated wastewater. The concentrations of COD, BOD5, SS, TN, and TP before and after wastewater treatment were measured. The results are shown in Table 1.

[0058] Table 1. Test data before and after wastewater treatment

[0059]

[0060] As can be seen from the results in Table 1, when the amount of the composite material for wastewater treatment of the present invention is 18 g / L, it can effectively treat pollutants in wastewater, and the treatment effect on COD and BOD5 is particularly significant.

[0061] The pH of the above-mentioned wastewater was adjusted using a 2 mol / L HCl aqueous solution or a 2 mol / L NaOH aqueous solution, with the pH values ​​successively adjusted to 1.5, 2.0, 2.5, 3.5, 4.5, 5.5, and 6.5. No other pretreatment was performed. Then, the wastewater treatment composite material obtained in Example 6 was added sequentially, with an addition amount of 18 g / L for each addition. The mixture was stirred and adsorbed for 20 minutes, then filtered to obtain the treated wastewater. The concentrations of COD, BOD5, SS, TN, and TP before and after wastewater treatment were measured, and the results are shown in Table 2.

[0062] Table 2. Test data of wastewater before and after pH change.

[0063]

[0064] As shown in Table 2, the wastewater treatment composite material of the present invention can effectively treat wastewater when the pH value is ≥2. Furthermore, the treatment efficiency gradually increases as the pH value of the wastewater approaches neutral, and the TN and TP indices tend to balance out, no longer increasing with increasing pH value. This is because the present invention uses acryloyl chloride-modified chitosan, which is further copolymerized with methacrylic acid and acrylamide to prepare an acrylic-chitosan copolymer. This copolymer contains both basic amino groups and acidic carboxyl groups, giving it adaptability to both acidic and alkaline environments. Therefore, the composite material can be used to treat both acidic and alkaline wastewater.

[0065] Wastewater containing heavy metals (pH=4.6) from the industrial production process of a pharmaceutical factory was collected. The wastewater treatment composite materials obtained in Examples 1-6 were used for wastewater treatment. The composite materials were added to the collected wastewater at a concentration of 12 g / L, stirred and adsorbed for 25 minutes, and then filtered to obtain the treated wastewater. The Cd concentrations before and after wastewater treatment were compared. 2+ Pb 2+ Ni 2+ Hg 2+ The content of [agent] was detected by atomic absorption spectrophotometry, and the results are shown in Table 3.

[0066] Table 3. Heavy metal detection results before and after wastewater treatment

[0067]

[0068] As shown in Table 3, the composite material for wastewater treatment of the present invention can effectively remove heavy metal ions from wastewater. This is because the composite material contains abundant amino and carboxyl groups and a hyperbranched structure of polyethyleneimine, which can adsorb a variety of metal ions with high adsorption efficiency. Furthermore, the composite material of the present invention loads an acrylic-chitosan copolymer onto the surface of polyethyleneimine-modified attapulgite, forming a complex cross-linked network structure. The hyperbranched structure of polyethyleneimine effectively protects the microporous structure of the attapulgite, preventing adsorbed large molecular particles from entering the micropores. Therefore, the micropores are not easily blocked, the structure is stable, and it can maintain excellent adsorption performance over a long period.

Claims

1. A composite material for wastewater treatment, characterized in that: The material is obtained by loading an acrylic chitosan copolymer onto the surface of polyethyleneimine-modified attapulgite; the acrylic chitosan copolymer is prepared by first acyl chloride chitosan, and then crosslinking the acyl chloride chitosan with methacrylic acid and acrylamide; the polyethyleneimine-modified attapulgite is obtained by crosslinking attapulgite, polyethyleneimine and glutaraldehyde. The above-mentioned composite material for wastewater treatment is prepared according to the following steps: ① Preparation of polyethyleneimine-modified attapulgite: Add attapulgite to a first hydrochloric acid aqueous solution and stir at 20~30℃ for 2~4 hours. Add polyethyleneimine and glutaraldehyde aqueous solution while stirring and stir for 2~4 hours. Add sodium borohydride and stir for 0.5~1 hours. Filter and dry the solid to obtain polyethyleneimine-modified attapulgite. The mass ratio of attapulgite, first hydrochloric acid aqueous solution, polyethyleneimine, glutaraldehyde aqueous solution and sodium borohydride is 10:400~500:1~3:1~3:2~3; ② Preparation of acrylic chitosan copolymer: Chitosan and triethylamine are added to N,N-dimethylformamide. Acryloyl chloride is added at 5~15℃ with stirring. After the addition is complete, the mixture is stirred at 20~40℃ for 4~8 hours. The mixture is then poured into first methanol and stirred for 5~15 minutes. After filtration, the filter cake is washed with second methanol, dried, and added to deionized water. Methacrylic acid, acrylamide, and an initiator are added to the mixture. The mixture is stirred for 4~8 hours. After filtration, washing with water, and drying of the filter cake, the acrylic chitosan copolymer is obtained. The mass ratio of chitosan, triethylamine, N,N-dimethylformamide, acryloyl chloride, first methanol, deionized water, methacrylic acid, acrylamide, and initiator is 10:1~3:100~300:1~3:1000~3000:500~1000:3~5:1~3:0.15~0.5; ③ Preparation of composite material for wastewater treatment: Add the polyethyleneimine-modified attapulgite clay obtained in step ① to the second hydrochloric acid aqueous solution, stir at 10~25℃ for 2~4 hours, add the acrylic chitosan copolymer obtained in step ②, stir for 3~7 hours, filter, wash with water, and dry to obtain the composite material for wastewater treatment. The mass ratio of the polyethyleneimine-modified attapulgite clay obtained in step ①, the second hydrochloric acid aqueous solution, and the acrylic chitosan copolymer obtained in step ② is 2~5:20~30:

1.

2. The composite material for wastewater treatment according to claim 1, characterized in that: The initiator is potassium persulfate or ammonium persulfate.

3. The composite material for wastewater treatment according to claim 1, characterized in that: The chitosan has a molecular weight of 50,000 to 100,000 and a degree of deacetylation greater than 95%.

4. The composite material for wastewater treatment according to claim 1, characterized in that: The pH of the first hydrochloric acid aqueous solution is 4-6; the pH of the second hydrochloric acid aqueous solution is 3-5.

5. The composite material for wastewater treatment according to claim 1, characterized in that: The concentration of the glutaraldehyde aqueous solution is 25-50%.

6. The composite material for wastewater treatment according to claim 1, characterized in that: In step ①, the mass ratio of attapulgite, first hydrochloric acid aqueous solution, polyethyleneimine, glutaraldehyde aqueous solution and sodium borohydride is 10:450:2:2:2.

5.

7. The composite material for wastewater treatment according to claim 1, characterized in that: In step ②, the mass ratio of chitosan, triethylamine, N,N-dimethylformamide, acryloyl chloride, first methanol, deionized water, methacrylic acid, acrylamide and initiator is 10:2:200:2:2000:800:4:2:0.

4.

8. The composite material for wastewater treatment according to claim 1, characterized in that: In step ③, the mass ratio of the polyethyleneimine-modified attapulgite clay obtained in step ①, the second hydrochloric acid aqueous solution, and the acrylic chitosan copolymer obtained in step ② is 4:25:

1.

9. The composite material for wastewater treatment according to claim 1, characterized in that: The molecular weight of the polyethyleneimine is 10,000 to 30,000.

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