A sewage treatment flocculant and a preparation method thereof

Abstract

The application discloses a kind of sewage treatment flocculants, its preparation method is as follows: (1) the modification treatment is carried out to chitosan, obtains primary modified product;(2) further processing is carried out to the primary modified product, obtains secondary modified product;(3) obtains chitosan modified product;(4) obtains magnetite modified product by treating nano magnetite powder;(5) the chitosan modified product and magnetite modified product are combined, and the sewage treatment flocculants are obtained.The flocculants prepared by the method have good adsorption removal effect on heavy metals in sewage, and the treatment operation process is simple, the required removal time is short, the sewage heavy metal purification efficiency is high, and has higher application value.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, and in particular to a wastewater treatment flocculant and its preparation method. Background Technology

[0002] Flocculation is currently the most commonly used wastewater treatment method. Traditional flocculants include inorganic and organic flocculants. Inorganic flocculants include polyaluminum salts and polyferric salts, while organic flocculants include synthetic flocculants such as polyacrylamide and natural flocculants such as chitosan. Chitosan is a polymeric polysaccharide obtained from chitin through deacetylation. It is a natural result of the removal of some acetyl groups during the synthesis of chitin and is the only alkaline polysaccharide among natural polysaccharides, belonging to the category of natural organic polymeric flocculants. Chitosan possesses strong decomposition capabilities in various organic chemical reactions because it can contain a variety of active groups within a small molecule, making it widely applicable in many fields such as food, agriculture, textiles, and wastewater treatment. In addition, chitosan has excellent flocculation properties, including efficient charge neutralization and bridging effects. Summary of the Invention

[0003] Therefore, the present invention provides a wastewater treatment flocculant, the preparation method of which is as follows:

[0004] (1) Prepare a composite solution of chitosan, glycine and acetic acid. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine and acetic acid. After the addition is completed, stir the solution for 10-20 min. Then adjust the pH of the solution to 5.5 with dilute hydrochloric acid. Keep the solution at 35±2℃ in a water bath for more than 10 h. During the heat preservation process, reflux the solution. Then add sodium hydroxide solution dropwise to the solution while stirring at 35±2℃. After the addition is completed, stir the mixture for 20-30 min to form a precipitate. Separate the solid and liquid phases. Wash the solid phase with deionized water more than 3 times and dry it at 80℃ for more than 1 h to obtain the first modified product.

[0005] (2) Prepare an ethanol solution of epichlorohydrin. Keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath. During the stirring process, disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension. After the addition is completed, continue to keep the suspension at 35±2℃ and stir for more than 16 hours. Then, under stirring, add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the suspension. After the addition is completed, heat the suspension to 60±3℃ in a water bath. After reaching the temperature, keep it at the temperature and stir for 4-5 hours. Then, cool it to room temperature and separate the solid and liquid. Wash the solid phase three times each with ethanol and deionized water, and dry it at 80℃ for more than 30 minutes to obtain the secondary modified product.

[0006] (3) Disperse the secondary modified product in deionized water to form an aqueous suspension, add 3-chloro-1,2-propanediol to the aqueous suspension, stir the aqueous suspension for 10-20 min after the addition is completed, add hydrochloric acid to the aqueous suspension while stirring, stir for 3-4 h after the addition is completed, then separate the solid and liquid phases, wash the solid phase with deionized water more than 3 times, and dry at 80°C for more than 30 min to obtain the chitosan modified product;

[0007] (4) Disperse nano-Fe3O4 powder in toluene to form a toluene suspension. Stir the toluene suspension and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring. After the addition is completed, heat and boil the suspension for more than 15 hours. During the heating process, reflux is carried out. Then, the heating is stopped and the suspension is cooled to room temperature. The solid and liquid are separated. The solid phase is washed with ethanol more than 3 times and dried at 80°C for more than 3 hours. The dried solid phase is dispersed again in N,N-dimethylformamide to form a secondary suspension. Stir the secondary suspension and add succinic anhydride to the secondary suspension while stirring. After the addition is completed, stir the suspension for more than 15 hours. Then, the solid and liquid are separated. The solid phase is washed with ethanol more than 3 times and dried at 80°C for more than 3 hours to obtain the modified Fe3O4 product.

[0008] (5) Disperse the chitosan modified product in deionized water to form a suspension, stir the suspension, add the iron oxide modified product to the suspension while stirring, after the addition is completed, place the suspension in an ultrasonic environment and stir ultrasonically for more than 20 minutes, then separate the solid and liquid, and dry the solid phase at 50°C for more than 6 hours to obtain the wastewater treatment flocculant.

[0009] Further, in step (1), the concentration of chitosan in the composite solution of chitosan, glycine, and acetic acid is 0.9–1 g / 100 mL, the concentration of glycine is 1–2 g / 100 mL, the mass percentage of acetic acid is 1.6%–2%, and the solvent is water; the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the composite solution of chitosan, glycine, and acetic acid is 1.8–2.0 g: 0.9–1.3 g: 200 mL.

[0010] Further, in step (1), the concentration of the solute in the dilute hydrochloric acid is 0.1-0.2 mol / L; the concentration of sodium hydroxide in the sodium hydroxide solution is 0.8-1.4 mol / L, and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:1.

[0011] Further, in step (2), the volume percentage of epichlorohydrin in the ethanol solution of epichlorohydrin is 5% to 6%; the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; the mass ratio of the added N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 2 to 4:1:10.

[0012] Further, in step (3), the solid-liquid mass ratio of the secondary modified product dispersed in deionized water to form an aqueous suspension is 1:100; the ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 6-8g: 2-3mL: 1g; the mass percentage of solute in the hydrochloric acid is 40%.

[0013] Further, in step (4), the solid-liquid mass ratio of the nano-iron oxide powder dispersed in toluene is solid / liquid = 1:300; the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of the nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 16-20:1.

[0014] Further, in step (4), the solid-liquid mass ratio of the solid phase dispersed in N,N-dimethylformamide is solid / liquid = 1:300; the mass ratio of the added succinic anhydride to the mass of the solid phase in the secondary suspension is succinic anhydride: solid = 2~3:1.

[0015] Further, in step (5), the mass ratio of the chitosan modified product dispersed in deionized water is chitosan modified product: deionized water = 1:100; the mass ratio of the iron oxide modified product added to the suspension to the mass ratio of the chitosan modified product is iron oxide modified product: chitosan modified product = 0.6~1.2:1.

[0016] Furthermore, the ultrasonic power is 200-300W and the ultrasonic frequency is 20-30kHz.

[0017] The technical principle of this invention is as follows: First, a macromolecular active group structure is introduced on the surface of chitosan to improve the adsorption and complexation effect of the flocculant on large particulate pollutants and heavy metal ions in wastewater; at the same time, chitosan and nano-ferric oxide are modified respectively, which on the one hand improves the binding strength of chitosan and ferric oxide particles, and on the other hand, the combination of the two provides more coordination functional groups on the overall surface of the flocculant, thus exhibiting a stronger adsorption and complexation effect on particles and ions in wastewater.

[0018] The beneficial effects of the present invention are as follows: the flocculant prepared by the method of the present invention has a good adsorption and removal effect on heavy metals in wastewater, and the treatment operation is simple, the required removal time is short, the wastewater heavy metal purification efficiency is high, and it has high application value. Detailed Implementation

[0019] The present invention will be further described below with reference to the embodiments.

[0020] Example 1

[0021] A wastewater treatment flocculant, the preparation method of which is as follows:

[0022] (1) Prepare a composite solution of chitosan, glycine, and acetic acid, wherein the concentration of chitosan is 0.9 g / 100 mL, the concentration of glycine is 1 g / 100 mL, the mass percentage of acetic acid is 1.6%, and the solvent is water; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine, and acetic acid, wherein the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the composite solution of chitosan, glycine, and acetic acid is 1.8:1. g: 0.9g: 200mL; after the addition is complete, stir the solution at 60r / min for 10min, then adjust the pH of the solution to 5.5 with dilute hydrochloric acid, wherein the concentration of the solute in the dilute hydrochloric acid is 0.1mol / L; keep the solution in a water bath at 35±2℃ for 10h, and reflux during the holding process; then add sodium hydroxide solution dropwise to the solution at 35±2℃ with stirring at 60r / min, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 1mol / L and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:1; after the addition is complete, stir the mixture at 60r / min for 20min to form a precipitate, separate the solid and liquid, wash the solid phase three times with deionized water, and dry at 80℃ for 1h to obtain the first modified product;

[0023] (2) Prepare an ethanol solution of epichlorohydrin, wherein the volume percentage of epichlorohydrin in the ethanol solution is 5%, and the solvent is ethanol; keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath, and disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension during stirring at 60r / min, wherein the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; after the addition is completed, continue to keep the suspension at 35±2℃ and stir for 16h, and then add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N to the suspension while stirring. The mass ratio of N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 2:1:10. After the addition is completed, the suspension is heated to 60±3℃ in a water bath, kept at 60r / min and stirred for 4h, then cooled to room temperature, and the solid and liquid are separated. The solid phase is washed 3 times each with ethanol and deionized water, and dried at 80℃ for 30min to obtain the secondary modified product.

[0024] (3) The secondary modified product is dispersed in deionized water to form an aqueous suspension. The solid-liquid mass ratio of the secondary modified product in the aqueous suspension is 1:100. 3-chloro-1,2-propanediol is added to the aqueous suspension. After the addition is completed, the aqueous suspension is stirred at 60 r / min for 10 min. Then, hydrochloric acid is added to the aqueous suspension while stirring. The ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 6 g: 2 mL: 1 g. The mass percentage of solute in the hydrochloric acid is 40%. After the addition is completed, stirring is continued at 60 r / min for 3 h. Then, solid and liquid are separated. The solid phase is washed three times with deionized water and dried at 80 °C for 30 min to obtain the chitosan modified product.

[0025] (4) Disperse nano-iron oxide powder in toluene to form a toluene suspension, wherein the solid-liquid mass ratio of the nano-iron oxide powder in toluene is solid / liquid = 1:300; stir the toluene suspension at 60 r / min, and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring, wherein the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 16:1; after the addition is completed, heat and boil the suspension for 15 h, reflux during the heating process, then stop heating and air cool to room temperature, and separate the solid and liquid components. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours. The dried solid phase was then dispersed again in N,N-dimethylformamide to form a secondary suspension. The solid-liquid mass ratio of the solid phase in N,N-dimethylformamide was 1:300. The secondary suspension was stirred at 60 r / min. During the stirring process, succinic anhydride was added to the secondary suspension. The mass ratio of the added succinic anhydride to the solid phase in the secondary suspension was 2:1. After the addition was completed, the suspension was stirred at 60 r / min for 15 hours. Then, the solid and liquid phases were separated. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours to obtain the modified iron(III) oxide product.

[0026] (5) The chitosan-modified product is dispersed in deionized water to form a suspension, wherein the mass ratio of the chitosan-modified product to the deionized water is 1:100; the suspension is stirred at 60 r / min, and the ferric oxide-modified product is added to the suspension while stirring, wherein the mass ratio of the ferric oxide-modified product to the chitosan-modified product is 0.6:1; after the addition is completed, the suspension is ultrasonically stirred for 20 min in an ultrasonic environment, wherein the ultrasonic power is 200 W and the ultrasonic frequency is 20 kHz; then the solid and liquid phases are separated, and the solid phase is dried at 50°C for 6 h to obtain the wastewater treatment flocculant.

[0027] Example 2

[0028] A wastewater treatment flocculant, the preparation method of which is as follows:

[0029] (1) Prepare a composite solution of chitosan, glycine, and acetic acid, wherein the concentration of chitosan is 0.9 g / 100 mL, the concentration of glycine is 1 g / 100 mL, the mass percentage of acetic acid is 1.8%, and the solvent is water; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine, and acetic acid, wherein the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the composite solution of chitosan, glycine, and acetic acid is 1.9 g / 100 mL. g: 1.1g: 200mL; after the addition is complete, stir the solution at 60r / min for 10min, then adjust the pH of the solution to 5.5 with dilute hydrochloric acid, wherein the concentration of the solute in the dilute hydrochloric acid is 0.1mol / L; keep the solution in a water bath at 35±2℃ for 10h, and reflux during the holding process; then add sodium hydroxide solution dropwise to the solution at 35±2℃ with stirring at 60r / min, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 1mol / L and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:1; after the addition is complete, stir the mixture at 60r / min for 20min to form a precipitate, separate the solid and liquid, wash the solid phase three times with deionized water, and dry at 80℃ for 1h to obtain the first modified product;

[0030] (2) Prepare an ethanol solution of epichlorohydrin, wherein the volume percentage of epichlorohydrin in the ethanol solution is 5%, and the solvent is ethanol; keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath, and disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension during stirring at 60r / min, wherein the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; after the addition is completed, continue to keep the suspension at 35±2℃ and stir for 16h, and then add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N to the suspension while stirring. The mass ratio of N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 3:1:10. After the addition is completed, the suspension is heated to 60±3℃ in a water bath, and then stirred at 60r / min for 4h. After that, it is cooled to room temperature, and the solid and liquid are separated. The solid phase is washed three times each with ethanol and deionized water, and then dried at 80℃ for 30min to obtain the secondary modified product.

[0031] (3) The secondary modified product is dispersed in deionized water to form an aqueous suspension. The solid-liquid mass ratio of the secondary modified product in the aqueous suspension is 1:100. 3-chloro-1,2-propanediol is added to the aqueous suspension. After the addition is completed, the aqueous suspension is stirred at 60 r / min for 10 min. Then, hydrochloric acid is added to the aqueous suspension while stirring. The ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 7 g: 2 mL: 1 g. The mass percentage of solute in the hydrochloric acid is 40%. After the addition is completed, the stirring is continued at 60 r / min for 3 h. Then, the solid and liquid are separated. The solid phase is washed three times with deionized water and dried at 80 °C for 30 min to obtain the chitosan modified product.

[0032] (4) Disperse nano-iron oxide powder in toluene to form a toluene suspension, wherein the solid-liquid mass ratio of the nano-iron oxide powder in toluene is solid / liquid = 1:300; stir the toluene suspension at 60 r / min, and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring, wherein the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 18:1; after the addition is completed, heat and boil the suspension for 15 h, reflux during the heating process, then stop heating and air cool to room temperature, and separate the solid and liquid components. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours. The dried solid phase was then dispersed again in N,N-dimethylformamide to form a secondary suspension. The solid-liquid mass ratio of the solid phase in N,N-dimethylformamide was 1:300. The secondary suspension was stirred at 60 r / min. During the stirring process, succinic anhydride was added to the secondary suspension. The mass ratio of the added succinic anhydride to the solid phase in the secondary suspension was 2:1. After the addition was completed, the suspension was stirred at 60 r / min for 15 hours. Then, the solid and liquid phases were separated. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours to obtain the modified iron(III) oxide product.

[0033] (5) The chitosan-modified product is dispersed in deionized water to form a suspension, wherein the mass ratio of the chitosan-modified product to the deionized water is 1:100; the suspension is stirred at 60 r / min, and the ferric oxide-modified product is added to the suspension while stirring, wherein the mass ratio of the ferric oxide-modified product to the chitosan-modified product is 0.8:1; after the addition is completed, the suspension is ultrasonically stirred for 20 min in an ultrasonic environment, wherein the ultrasonic power is 200 W and the ultrasonic frequency is 20 kHz; then the solid and liquid phases are separated, and the solid phase is dried at 50 °C for 6 h to obtain the wastewater treatment flocculant.

[0034] Example 3

[0035] A wastewater treatment flocculant, the preparation method of which is as follows:

[0036] (1) Prepare a composite solution of chitosan, glycine, and acetic acid, wherein the concentration of chitosan is 1 g / 100 mL, the concentration of glycine is 2 g / 100 mL, the mass percentage of acetic acid is 1.8%, and the solvent is water; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine, and acetic acid, wherein the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride to the mass of the composite solution of chitosan, glycine, and acetic acid is 1.9 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride : N-hydroxy-succinimide : composite solution of chitosan, glycine, and acetic acid = 1.9 g. 1.1g:200mL; After addition, stir the solution at 60r / min for 10min, then adjust the pH of the solution to 5.5 with dilute hydrochloric acid, wherein the concentration of the solute in the dilute hydrochloric acid is 0.1mol / L; keep the solution in a water bath at 35±2℃ for 10h, and reflux during the holding process; then add sodium hydroxide solution dropwise to the solution at 35±2℃ with stirring at 60r / min, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 1mol / L and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:1; after addition, stir the mixture at 60r / min for 20min to form a precipitate, separate the solid and liquid, wash the solid phase three times with deionized water, and dry at 80℃ for 1h to obtain the first modified product;

[0037] (2) Prepare an ethanol solution of epichlorohydrin, wherein the volume percentage of epichlorohydrin in the ethanol solution is 5%, and the solvent is ethanol; keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath, and disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension during stirring at 60r / min, wherein the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; after the addition is completed, continue to keep the suspension at 35±2℃ and stir for 16h, and then add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N to the suspension while stirring. The mass ratio of N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 3:1:10. After the addition is completed, the suspension is heated to 60±3℃ in a water bath, and then stirred at 60r / min for 4h. After that, it is cooled to room temperature, and the solid and liquid are separated. The solid phase is washed three times each with ethanol and deionized water, and then dried at 80℃ for 30min to obtain the secondary modified product.

[0038] (3) The secondary modified product is dispersed in deionized water to form an aqueous suspension. The solid-liquid mass ratio of the secondary modified product in the aqueous suspension is 1:100. 3-chloro-1,2-propanediol is added to the aqueous suspension. After the addition is completed, the aqueous suspension is stirred at 60 r / min for 10 min. Then, hydrochloric acid is added to the aqueous suspension while stirring. The ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 7 g: 3 mL: 1 g. The mass percentage of solute in the hydrochloric acid is 40%. After the addition is completed, the stirring is continued at 60 r / min for 3 h. Then, the solid and liquid are separated. The solid phase is washed three times with deionized water and dried at 80 °C for 30 min to obtain the chitosan modified product.

[0039] (4) Disperse nano-iron oxide powder in toluene to form a toluene suspension, wherein the solid-liquid mass ratio of the nano-iron oxide powder in toluene is solid / liquid = 1:300; stir the toluene suspension at 60 r / min, and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring, wherein the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 18:1; after the addition is completed, heat and boil the suspension for 15 h, reflux during the heating process, then stop heating and air cool to room temperature, and separate the solid and liquid components. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours. The dried solid phase was then dispersed again in N,N-dimethylformamide to form a secondary suspension. The solid-liquid mass ratio of the solid phase in N,N-dimethylformamide was 1:300. The secondary suspension was stirred at 60 r / min. During the stirring process, succinic anhydride was added to the secondary suspension. The mass ratio of the added succinic anhydride to the solid phase in the secondary suspension was 3:1. After the addition was completed, the suspension was stirred at 60 r / min for 15 hours. Then, the solid and liquid phases were separated. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours to obtain the modified iron(III) oxide product.

[0040] (5) The chitosan-modified product is dispersed in deionized water to form a suspension, wherein the mass ratio of the chitosan-modified product to the deionized water is 1:100; the suspension is stirred at 60 r / min, and the ferric oxide-modified product is added to the suspension while stirring, wherein the mass ratio of the ferric oxide-modified product to the chitosan-modified product is 1:1; after the addition is completed, the suspension is ultrasonically stirred for 20 min in an ultrasonic environment, wherein the ultrasonic power is 200 W and the ultrasonic frequency is 20 kHz; then the solid and liquid phases are separated, and the solid phase is dried at 50 °C for 6 h to obtain the wastewater treatment flocculant.

[0041] Example 4

[0042] A wastewater treatment flocculant, the preparation method of which is as follows:

[0043] (1) Prepare a composite solution of chitosan, glycine, and acetic acid, wherein the concentration of chitosan is 1 g / 100 mL, the concentration of glycine is 2 g / 100 mL, the mass percentage of acetic acid is 2%, and the solvent is water; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine, and acetic acid, wherein the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the composite solution of chitosan, glycine, and acetic acid is 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride : N-hydroxy-succinimide : composite solution of chitosan, glycine, and acetic acid = 2.0 g: 1.3g: 200mL; after addition, stir the solution at 60r / min for 10min, then adjust the pH of the solution to 5.5 with dilute hydrochloric acid, the concentration of solute in the dilute hydrochloric acid being 0.1mol / L; keep the solution in a water bath at 35±2℃ for 10h, condensing and refluxing during the holding process; then add sodium hydroxide solution dropwise to the solution at 35±2℃ with stirring at 60r / min, the concentration of sodium hydroxide in the sodium hydroxide solution being 1mol / L, the solvent being water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine, and acetic acid is 1:1; after addition, stir the mixture at 60r / min for 20min to form a precipitate, separate the solid and liquid phases, wash the solid phase three times with deionized water, and dry it at 80℃ for 1h to obtain the first modified product;

[0044] (2) Prepare an ethanol solution of epichlorohydrin, wherein the volume percentage of epichlorohydrin in the ethanol solution is 5%, and the solvent is ethanol; keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath, and disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension during stirring at 60r / min, wherein the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; after the addition is completed, continue to keep the suspension at 35±2℃ and stir for 16h, and then add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N to the suspension while stirring. The mass ratio of N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 4:1:10. After the addition is completed, the suspension is heated to 60±3℃ in a water bath, kept at 60r / min and stirred for 4h, then cooled to room temperature, and the solid and liquid are separated. The solid phase is washed 3 times each with ethanol and deionized water, and dried at 80℃ for 30min to obtain the secondary modified product.

[0045] (3) The secondary modified product is dispersed in deionized water to form an aqueous suspension. The solid-liquid mass ratio of the secondary modified product in the aqueous suspension is 1:100. 3-chloro-1,2-propanediol is added to the aqueous suspension. After the addition is completed, the aqueous suspension is stirred at 60 r / min for 10 min. Then, hydrochloric acid is added to the aqueous suspension while stirring. The ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 8 g: 3 mL: 1 g. The mass percentage of solute in the hydrochloric acid is 40%. After the addition is completed, the stirring is continued at 60 r / min for 3 h. Then, the solid and liquid are separated. The solid phase is washed three times with deionized water and dried at 80 °C for 30 min to obtain the chitosan modified product.

[0046] (4) Disperse nano-iron oxide powder in toluene to form a toluene suspension, wherein the solid-liquid mass ratio of the nano-iron oxide powder in toluene is solid / liquid = 1:300; stir the toluene suspension at 60 r / min, and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring, wherein the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 20:1; after the addition is completed, heat and boil the suspension for 15 h, reflux during the heating process, then stop heating and air cool to room temperature, and separate the solid and liquid components. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours. The dried solid phase was then dispersed again in N,N-dimethylformamide to form a secondary suspension. The solid-liquid mass ratio of the solid phase in N,N-dimethylformamide was 1:300. The secondary suspension was stirred at 60 r / min. During the stirring process, succinic anhydride was added to the secondary suspension. The mass ratio of the added succinic anhydride to the solid phase in the secondary suspension was 3:1. After the addition was completed, the suspension was stirred at 60 r / min for 15 hours. Then, the solid and liquid phases were separated. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours to obtain the modified iron(III) oxide product.

[0047] (5) The chitosan-modified product is dispersed in deionized water to form a suspension, wherein the mass ratio of the chitosan-modified product to the deionized water is 1:100; the suspension is stirred at 60 r / min, and the ferric oxide-modified product is added to the suspension while stirring, wherein the mass ratio of the ferric oxide-modified product to the chitosan-modified product is 1.2:1; after the addition is completed, the suspension is ultrasonically stirred for 20 min in an ultrasonic environment, wherein the ultrasonic power is 200 W and the ultrasonic frequency is 20 kHz; then the solid and liquid phases are separated, and the solid phase is dried at 50°C for 6 h to obtain the wastewater treatment flocculant.

[0048] Comparative Example 1

[0049] As a contrasting flocculant, its preparation method is as follows:

[0050] (1) Prepare a composite solution of chitosan, glycine, and acetic acid, wherein the concentration of chitosan is 0.9 g / 100 mL, the concentration of glycine is 1 g / 100 mL, the mass percentage of acetic acid is 1.8%, and the solvent is water; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine, and acetic acid, wherein the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the composite solution of chitosan, glycine, and acetic acid is 1.9 g / 100 mL. g: 1.1g: 200mL; after the addition is complete, stir the solution at 60r / min for 10min, then adjust the pH of the solution to 5.5 with dilute hydrochloric acid, wherein the concentration of the solute in the dilute hydrochloric acid is 0.1mol / L; keep the solution in a water bath at 35±2℃ for 10h, and reflux during the holding process; then add sodium hydroxide solution dropwise to the solution at 35±2℃ with stirring at 60r / min, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 1mol / L and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:1; after the addition is complete, stir the mixture at 60r / min for 20min to form a precipitate, separate the solid and liquid, wash the solid phase three times with deionized water, and dry at 80℃ for 1h to obtain the first modified product;

[0051] (2) Prepare an ethanol solution of epichlorohydrin, wherein the volume percentage of epichlorohydrin in the ethanol solution is 5% and the solvent is ethanol; keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath and stir at 60r / min to disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension, wherein the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; after the addition is completed, continue to keep the suspension at 35±2℃ and stir for 16h, then raise the temperature of the suspension in a water bath to 60±3℃, keep it at 60r / min and stir for 4h, then air cool to room temperature, separate the solid and liquid, wash the solid phase three times each with ethanol and deionized water, and dry at 80℃ for 30min to obtain the secondary modified product of this comparative example.

[0052] (3) The secondary modified product is dispersed in deionized water to form an aqueous suspension. The solid-liquid mass ratio of the secondary modified product in the aqueous suspension is 1:100. 3-chloro-1,2-propanediol is added to the aqueous suspension. After the addition is completed, the aqueous suspension is stirred at 60 r / min for 10 min. Then, hydrochloric acid is added to the aqueous suspension while stirring. The ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 7 g: 2 mL: 1 g. The mass percentage of solute in the hydrochloric acid is 40%. After the addition is completed, the stirring is continued at 60 r / min for 3 h. Then, the solid and liquid are separated. The solid phase is washed three times with deionized water and dried at 80 °C for 30 min to obtain the chitosan modified product.

[0053] (4) Disperse nano-iron oxide powder in toluene to form a toluene suspension, wherein the solid-liquid mass ratio of the nano-iron oxide powder in toluene is solid / liquid = 1:300; stir the toluene suspension at 60 r / min, and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring, wherein the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 18:1; after the addition is completed, heat and boil the suspension for 15 h, reflux during the heating process, then stop heating and air cool to room temperature, and separate the solid and liquid components. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours. The dried solid phase was then dispersed again in N,N-dimethylformamide to form a secondary suspension. The solid-liquid mass ratio of the solid phase in N,N-dimethylformamide was 1:300. The secondary suspension was stirred at 60 r / min. During the stirring process, succinic anhydride was added to the secondary suspension. The mass ratio of the added succinic anhydride to the solid phase in the secondary suspension was 2:1. After the addition was completed, the suspension was stirred at 60 r / min for 15 hours. Then, the solid and liquid phases were separated. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours to obtain the modified iron(III) oxide product.

[0054] (5) The chitosan-modified product is dispersed in deionized water to form a suspension, wherein the mass ratio of the chitosan-modified product to the deionized water is 1:100; the suspension is stirred at 60 r / min, and the ferric oxide-modified product is added to the suspension while stirring, wherein the mass ratio of the ferric oxide-modified product to the chitosan-modified product is 0.8:1; after the addition is completed, the suspension is ultrasonically stirred for 20 min in an ultrasonic environment, wherein the ultrasonic power is 200 W and the ultrasonic frequency is 20 kHz; then the solid and liquid phases are separated, and the solid phase is dried at 50°C for 6 h to obtain the flocculant described in this comparative example.

[0055] Comparative Example 2

[0056] As a contrasting flocculant, its preparation method is as follows:

[0057] (1) Prepare a composite solution of chitosan, glycine, and acetic acid, wherein the concentration of chitosan is 0.9 g / 100 mL, the concentration of glycine is 1 g / 100 mL, the mass percentage of acetic acid is 1.8%, and the solvent is water; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine, and acetic acid, wherein the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the composite solution of chitosan, glycine, and acetic acid is 1.9 g / 100 mL. g: 1.1g: 200mL; after the addition is complete, stir the solution at 60r / min for 10min, then adjust the pH of the solution to 5.5 with dilute hydrochloric acid, wherein the concentration of the solute in the dilute hydrochloric acid is 0.1mol / L; keep the solution in a water bath at 35±2℃ for 10h, and reflux during the holding process; then add sodium hydroxide solution dropwise to the solution at 35±2℃ with stirring at 60r / min, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 1mol / L and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:1; after the addition is complete, stir the mixture at 60r / min for 20min to form a precipitate, separate the solid and liquid, wash the solid phase three times with deionized water, and dry at 80℃ for 1h to obtain the first modified product;

[0058] (2) Prepare an ethanol solution of epichlorohydrin, wherein the volume percentage of epichlorohydrin in the ethanol solution is 5%, and the solvent is ethanol; keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath, and disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension during stirring at 60r / min, wherein the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; after the addition is completed, continue to keep the suspension at 35±2℃ and stir for 16h, and then add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylureahexafluoro to the suspension while stirring. The mass ratio of the added N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 3:1:10. After the addition is completed, the suspension is heated to 60±3℃ in a water bath, and then stirred at 60r / min for 4h. After that, it is cooled to room temperature, and the solid and liquid are separated. The solid phase is washed three times each with ethanol and deionized water, and then dried at 80℃ for 30min to obtain the secondary modified product, which is used as the chitosan modified product of this comparative example.

[0059] (3) Disperse nano-iron oxide powder in toluene to form a toluene suspension, wherein the solid-liquid mass ratio of the nano-iron oxide powder in toluene is solid / liquid = 1:300; stir the toluene suspension at 60 r / min, and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring, wherein the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 18:1; after the addition is completed, heat and boil the suspension for 15 h, reflux during the heating process, then stop heating and air cool to room temperature, and separate the solid and liquid components. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours. The dried solid phase was then dispersed again in N,N-dimethylformamide to form a secondary suspension. The solid-liquid mass ratio of the solid phase in N,N-dimethylformamide was 1:300. The secondary suspension was stirred at 60 r / min. During the stirring process, succinic anhydride was added to the secondary suspension. The mass ratio of the added succinic anhydride to the solid phase in the secondary suspension was 2:1. After the addition was completed, the suspension was stirred at 60 r / min for 15 hours. Then, the solid and liquid phases were separated. The solid phase was washed three times with ethanol and dried at 80°C for 3 hours to obtain the modified iron(III) oxide product.

[0060] (4) The chitosan-modified product is dispersed in deionized water to form a suspension. The mass ratio of the chitosan-modified product to the deionized water is 1:100. The suspension is stirred at 60 r / min. While stirring, the ferric oxide-modified product is added to the suspension. The mass ratio of the ferric oxide-modified product to the chitosan-modified product is 0.8:1. After the addition is completed, the suspension is ultrasonically stirred for 20 min in an ultrasonic environment. The ultrasonic power is 200 W and the ultrasonic frequency is 20 kHz. Then, the solid and liquid phases are separated, and the solid phase is dried at 50°C for 6 h to obtain the flocculant described in this comparative example.

[0061] Comparative Example 3

[0062] As a contrasting flocculant, its preparation method is as follows:

[0063] (1) Prepare a composite solution of chitosan, glycine, and acetic acid, wherein the concentration of chitosan is 0.9 g / 100 mL, the concentration of glycine is 1 g / 100 mL, the mass percentage of acetic acid is 1.8%, and the solvent is water; add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine, and acetic acid, wherein the mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the composite solution of chitosan, glycine, and acetic acid is 1.9 g / 100 mL. g: 1.1g: 200mL; after the addition is complete, stir the solution at 60r / min for 10min, then adjust the pH of the solution to 5.5 with dilute hydrochloric acid, wherein the concentration of the solute in the dilute hydrochloric acid is 0.1mol / L; keep the solution in a water bath at 35±2℃ for 10h, and reflux during the holding process; then add sodium hydroxide solution dropwise to the solution at 35±2℃ with stirring at 60r / min, wherein the concentration of sodium hydroxide in the sodium hydroxide solution is 1mol / L and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:1; after the addition is complete, stir the mixture at 60r / min for 20min to form a precipitate, separate the solid and liquid, wash the solid phase three times with deionized water, and dry at 80℃ for 1h to obtain the first modified product;

[0064] (2) Prepare an ethanol solution of epichlorohydrin, wherein the volume percentage of epichlorohydrin in the ethanol solution is 5%, and the solvent is ethanol; keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath, and disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension during stirring at 60r / min, wherein the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; after the addition is completed, continue to keep the suspension at 35±2℃ and stir for 16h, and then add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N to the suspension while stirring. The mass ratio of N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 3:1:10. After the addition is completed, the suspension is heated to 60±3℃ in a water bath, and then stirred at 60r / min for 4h. After that, it is cooled to room temperature, and the solid and liquid are separated. The solid phase is washed three times each with ethanol and deionized water, and then dried at 80℃ for 30min to obtain the secondary modified product.

[0065] (3) The secondary modified product is dispersed in deionized water to form an aqueous suspension. The solid-liquid mass ratio of the secondary modified product in the aqueous suspension is 1:100. 3-chloro-1,2-propanediol is added to the aqueous suspension. After the addition is completed, the aqueous suspension is stirred at 60 r / min for 10 min. Then, hydrochloric acid is added to the aqueous suspension while stirring. The ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 7 g: 2 mL: 1 g. The mass percentage of solute in the hydrochloric acid is 40%. After the addition is completed, the stirring is continued at 60 r / min for 3 h. Then, the solid and liquid are separated. The solid phase is washed three times with deionized water and dried at 80 °C for 30 min to obtain the chitosan modified product.

[0066] (4) The chitosan-modified product is dispersed in deionized water to form a suspension. The mass ratio of the chitosan-modified product to the deionized water is 1:100. The suspension is stirred at 60 r / min. While stirring, nano-iron oxide powder (the same batch of nano-iron oxide powder used in each embodiment, but without the above modification treatment) is added to the suspension. The mass ratio of the nano-iron oxide powder to the chitosan-modified product is 0.8:1. After the addition is completed, the suspension is ultrasonically stirred for 20 min in an ultrasonic environment. The ultrasonic power is 200 W and the ultrasonic frequency is 20 kHz. Then, the solid and liquid are separated, and the solid phase is dried at 50°C for 6 h to obtain the flocculant described in this comparative example.

[0067] Example 5

[0068] The flocculants prepared by the methods described in the above embodiments and comparative examples were tested for their effect on Pb in wastewater. 2+ Ion removal rate: A simulated wastewater solution with a lead ion concentration of 25 mg / L was prepared. The pH of the simulated wastewater solution was adjusted to 5.5 using 5% hydrochloric acid or 5% sodium hydroxide solution. Then, flocculant was added to the simulated wastewater solution at a ratio of flocculant / simulated wastewater solution = 300 mg / L. After adding the flocculant, the solution was stirred at 60 r / min for 10 min, and then allowed to stand for 30 min. The supernatant was then taken from 2 cm below the liquid surface using a pipette, and the remaining Pb in the solution was measured. 2+ Calculate the removal rate based on the ion content. Removal rate = (Pb) / (Pb) 2+ Initial ion concentration - Pb after treatment 2+ (ion concentration) / Pb 2+ The removal rates of each group of flocculants were calculated as follows: initial ion concentration × 100%. Table 1 shows the results.

[0069] Table 1

[0070]

[0071]

[0072] As shown in Table 1, the flocculant prepared by the method of the present invention has a good adsorption and removal effect on heavy metals in wastewater. The removal rate of divalent lead ions in water can reach more than 95%. Moreover, the treatment operation is simple, the required removal time is short, and the wastewater heavy metal purification efficiency is high, which has high application value.

[0073] The technical solutions provided by the present invention have been described in detail above. For those skilled in the art, there will be changes in specific implementation methods and application scope based on the ideas of the embodiments of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A wastewater treatment flocculant, characterized in that, The preparation method is as follows: (1) Prepare a composite solution of chitosan, glycine and acetic acid. Add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the composite solution of chitosan, glycine and acetic acid. After the addition is completed, stir the solution for 10-20 min. Then adjust the pH of the solution to 5.5 with dilute hydrochloric acid. Keep the solution at 35±2℃ in a water bath for more than 10 h. During the heat preservation process, reflux the solution. Then add sodium hydroxide solution dropwise to the solution while stirring at 35±2℃. After the addition is completed, stir the mixture for 20-30 min to form a precipitate. Separate the solid and liquid phases. Wash the solid phase with deionized water more than 3 times and dry it at 80℃ for more than 1 h to obtain the first modified product. (2) Prepare an ethanol solution of epichlorohydrin. Keep the ethanol solution of epichlorohydrin at a constant temperature of 35±2℃ in a water bath. During the stirring process, disperse the primary modified product in the ethanol solution of epichlorohydrin to form a suspension. After the addition is completed, continue to stir the suspension at 35±2℃ for more than 16 hours. Then, under stirring, add N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the suspension. After the addition is completed, heat the suspension to 60±3℃ in a water bath. After reaching the temperature, keep it at the temperature and stir for 4-5 hours. Then, cool it to room temperature. Separate the solid and liquid phases. Wash the solid phase three times each with ethanol and deionized water. Dry it at 80℃ for more than 30 minutes to obtain the secondary modified product. (3) The secondary modified product is dispersed in deionized water to form an aqueous suspension, and the solid-liquid mass ratio of the secondary modified product in the aqueous suspension is 1:100; 3-chloro-1,2-propanediol is added to the aqueous suspension, and the aqueous suspension is stirred for 10-20 min after the addition is completed. Then, hydrochloric acid is added to the aqueous suspension while stirring. The ratio of the amount of 3-chloro-1,2-propanediol and hydrochloric acid added to the amount of secondary modified product in the aqueous suspension is 3-chloro-1,2-propanediol: hydrochloric acid: secondary modified product = 6-8 g: 2-3 mL: 1 g; the mass percentage of solute in the hydrochloric acid is 40%; after the addition is completed, the mixture is stirred for 3-4 h, and then the solid and liquid phases are separated. The solid phase is washed with deionized water more than 3 times and dried at 80°C for more than 30 min to obtain the chitosan modified product. (4) Disperse nano-Fe3O4 powder in toluene to form a toluene suspension. Stir the toluene suspension and add 3-aminopropyltriethoxysilane to the toluene suspension while stirring. After the addition is completed, heat and boil the suspension for more than 15 hours. During the heating process, reflux is carried out. Then, the heating is stopped and the suspension is cooled to room temperature. The solid and liquid are separated. The solid phase is washed with ethanol more than 3 times and dried at 80°C for more than 3 hours. The dried solid phase is dispersed again in N,N-dimethylformamide to form a secondary suspension. Stir the secondary suspension and add succinic anhydride to the secondary suspension while stirring. After the addition is completed, stir the suspension for more than 15 hours. Then, the solid and liquid are separated. The solid phase is washed with ethanol more than 3 times and dried at 80°C for more than 3 hours to obtain the modified Fe3O4 product. (5) The chitosan modified product is dispersed in deionized water to form a suspension. The suspension is stirred, and the iron oxide modified product is added to the suspension while stirring. After the addition is completed, the suspension is placed in an ultrasonic environment and ultrasonically stirred for more than 20 minutes. Then, the solid and liquid are separated, and the solid phase is dried at 50°C for more than 6 hours to obtain the wastewater treatment flocculant.

2. The wastewater treatment flocculant according to claim 1, characterized in that, In step (1), the chitosan, glycine, and acetic acid composite solution contains chitosan at a concentration of 0.9–1 g / 100 mL, glycine at a concentration of 1–2 g / 100 mL, and acetic acid at a mass percentage of 1.6%–2%, with water as the solvent. The mass ratio of the added 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxy-succinimide to the mass of the chitosan, glycine, and acetic acid composite solution is 1.8–2.0 g: 0.9–1.3 g: 200 mL.

3. The wastewater treatment flocculant according to claim 1, characterized in that, In step (1), the concentration of the solute in the dilute hydrochloric acid is 0.1-0.2 mol / L; the concentration of sodium hydroxide in the sodium hydroxide solution is 0.8-1.4 mol / L, and the solvent is water; the volume ratio of the added sodium hydroxide solution to the volume of the composite solution of chitosan, glycine and acetic acid is 1:

1.

4. The wastewater treatment flocculant according to claim 1, characterized in that, In step (2), the volume percentage of epichlorohydrin in the ethanol solution of epichlorohydrin is 5% to 6%; the solid-liquid mass ratio of the primary modified product dispersed in the ethanol solution of epichlorohydrin is solid / liquid = 1:100; the mass ratio of the added N,N-dimethyl-1,3-propanediamine and 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate to the mass ratio of the primary modified product in the suspension is N,N-dimethyl-1,3-propanediamine: 2-(7-azobenzotriazole)-N,N,N',N'-tetramethylurea hexafluorophosphate: primary modified product = 2 to 4:1:

10.

5. The wastewater treatment flocculant according to claim 1, characterized in that, In step (4), the solid-liquid mass ratio of the nano-iron oxide powder dispersed in toluene is solid / liquid = 1:300; the mass ratio of the added 3-aminopropyltriethoxysilane to the mass of the nano-iron oxide powder in the toluene suspension is 3-aminopropyltriethoxysilane: nano-iron oxide powder = 16-20:

1.

6. The wastewater treatment flocculant according to claim 1, characterized in that, In step (4), the solid-liquid mass ratio of the solid phase dispersed in N,N-dimethylformamide is solid / liquid = 1:300; the mass ratio of the added succinic anhydride to the mass of the solid phase in the secondary suspension is succinic anhydride: solid = 2-3:

1.

7. The wastewater treatment flocculant according to claim 1, characterized in that, In step (5), the mass ratio of the chitosan modified product dispersed in deionized water is chitosan modified product: deionized water = 1:100; the mass ratio of the iron oxide modified product added to the suspension to the chitosan modified product is iron oxide modified product: chitosan modified product = 0.6~1.2:

1.

8. The wastewater treatment flocculant according to claim 1, characterized in that, The ultrasonic power is 200-300W and the ultrasonic frequency is 20-30kHz.

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