Degradable polymeric flocculant and application thereof

Abstract

The invention discloses a degradable polymeric flocculant and application thereof.The preparation method specifically comprises the following steps that sulfonated starch is dissolved in deionized water, chitosan composite powder is added, the mixture is heated and stirred until the chitosan composite powder is dissolved, acrylamide is added after ultrasonic dispersion, then N, N '-methylene bisacrylamide and potassium persulfate are added, the mixture is stirred until a gel state is formed, and the degradable polymeric flocculant is obtained; cutting the gel into small blocks, soaking the small blocks in distilled water for washing, and drying, crushing and sieving the washed gel to obtain the degradable polymeric flocculant. According to the preparation method, the flocculation capacity and the degradation capacity are improved by compounding synthesized organic polymer and natural polymer materials, the antibacterial capacity and the degradation performance are improved by compounding silver oxide, titanium oxide and graphene oxide, and the composite material is good in flocculation and sedimentation capacity, excellent in degradation performance and good in antibacterial capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and specifically relates to a degradable polymer flocculant and application thereof. Background Art

[0002] With the continuous development of industrialization, water resource problems are becoming more and more serious. Industrial sewage and domestic sewage have become the main sources of water pollution. Polluted water sources need to be treated and then recycled. At present, the most widely used and lowest-cost method is the flocculation method using flocculants. Flocculants include synthetic organic polymer flocculants and natural organic polymer flocculants. Synthetic organic polymer flocculants have high production costs and there are a certain amount of residual monomers, which inevitably bring toxicity to the environment. In addition, synthetic organic polymer flocculants are difficult to degrade and will bring further pollution to the environment. Natural organic polymer flocculants include derivatives of starch, chitosan, cellulose polysaccharides and proteins, as well as modified products of plant gums. They are widely used because of their low cost, high performance, no secondary pollution and renewable recycling. However, natural polymer flocculants are unstable and have poor sedimentation performance.

[0003] A Chinese invention patent application with publication number CN103183780A discloses a method for preparing a cellulose-based wastewater flocculant, in which the cellulose-based wastewater flocculant is prepared by grafting polymerization of cellulose and acrylamide, and pulp fiber is used as the basic molecular skeleton to partially replace the original polymer material, thereby reducing the dependence of traditional polymer wastewater flocculants on petroleum resources and improving the biodegradability of the flocculant; however, when treating domestic sewage with excessive eutrophication and high bacterial content, bacterial metabolites and large molecular organic eutrophic substances may consume a large amount of flocculant, and the flocculation performance of the polymer flocculant will be significantly reduced.

[0004] The Chinese invention patent application with publication number CN118271522A discloses an antibacterial flocculant and its preparation method and application, which is to prepare an antibacterial flocculant with a local high charge concentration by graft copolymerization of a carbon source, an alkali solution, an etherifying agent, an initiator and a grafting monomer; however, the flocculant in this scheme is formed by the polymerization of organic matter, which is difficult to degrade in the environment and is not conducive to the ecological environment.

[0005] Therefore, there is a need for a high molecular weight flocculant with antibacterial ability, which has good flocculation performance, degradability and antibacterial ability. Summary of the invention

[0006] The purpose of the present invention is to solve the problem of how to improve the degradability and antibacterial properties of a flocculant, and to provide a degradable polymer flocculant and its application.

[0007] The present invention improves flocculation ability and degradability by compounding synthetic organic polymers and natural polymer materials, and compounding silver oxide, titanium oxide and graphene oxide to improve antibacterial ability and degradation performance. It has good flocculation and sedimentation ability, excellent degradability and good antibacterial ability.

[0008] The purpose of the present invention can be achieved by the following technical scheme: A degradable polymer flocculant, the preparation method of the degradable polymer flocculant comprises the following steps:

[0009] Step 1: ultrasonically disperse the graphene composite powder in deionized water to prepare a graphene composite powder dispersion, mix 1-1.5wt% of the graphene composite powder dispersion and 1-1.5wt% of the chitosan acetic acid aqueous solution in equal volumes in a reactor, heat to 85-95°C and react for 5-6h, add 70wt% ethylamine solution of half the volume of the chitosan acetic acid aqueous solution after cooling, stir and react for 20-24h, collect the precipitate by centrifugation, wash the precipitate, and freeze-dry to obtain the chitosan composite powder.

[0010] Step 2: Dissolve sulfonated starch in deionized water in a reaction kettle, add chitosan composite powder, heat to 60-70°C, stir until dissolved, ultrasonically disperse for 30-40 minutes, then add acrylamide, stir to dissolve, add N,N'-methylenebisacrylamide and potassium persulfate, stir until a gel is formed, cut the gel into small pieces and immerse in distilled water for washing, dry the washed gel at 60-70°C for 20-24 hours, crush and pass through a 200-mesh sieve to obtain a degradable polymer flocculant.

[0011] Furthermore, in step 2, the dosage ratio of sulfonated starch, deionized water, chitosan composite powder, acrylamide, N,N'-methylenebisacrylamide and potassium persulfate is 10-15g: 100-150mL: 3-6g: 30-50g: 0.4-0.5g: 0.8-1g.

[0012] Furthermore, in step 1, the chitosan acetic acid aqueous solution is prepared by dissolving chitosan in a 0.1 M acetic acid aqueous solution.

[0013] Furthermore, the graphene composite powder in step 1 is prepared by the following steps:

[0014] In a reaction kettle, zinc nitrate hexahydrate and 2-aminoterephthalic acid are dissolved in DMF and deionized water, Ti / graphene nanosheets are added, ultrasonic dispersion is carried out for 30-40 minutes, the temperature is raised to 90-100° C. under stirring conditions, the reaction is carried out for 20-24 hours, the precipitate is collected by centrifugation after cooling, the precipitate is washed and vacuum dried for 10-12 hours to obtain Ti / Zn composite graphene nanosheets, the Ti / Zn composite graphene nanosheets are placed in a muffle furnace, the temperature is raised to 500-550° C. at a rate of 5° C. / min under an argon atmosphere, the reaction is carried out for 4-5 hours, and a graphene composite powder is obtained.

[0015] Further, the usage ratio of zinc nitrate hexahydrate, 2-aminoterephthalic acid, DMF, deionized water and Ti / graphene nanosheets is 8-10 g: 3-4 g: 200-300 mL: 200-300 mL: 2-4 g.

[0016] Further, Ti / graphene nanosheets are prepared by the following steps:

[0017] In a reaction kettle, 2-aminoterephthalic acid and tetrabutyl titanate are dissolved in a mixed solvent of DMF and methanol, and then graphene oxide nanosheets are added, and ultrasonic dispersion is performed for 30-40 minutes. The temperature is raised to 140-150° C. under stirring conditions and the reaction is performed for 40-48 hours. After cooling, the precipitate is collected by centrifugation, and the precipitate is washed and vacuum dried to obtain Ti / graphene nanosheets.

[0018] Furthermore, the usage ratio of 2-aminoterephthalic acid, tetrabutyl titanate, DMF, methanol and graphene oxide nanosheets is 5-6 g: 3-4 mL: 150-200 mL: 20-30 mL: 2-4 g.

[0019] Furthermore, in step 1, the sulfonated starch is prepared by the following steps:

[0020] Mix aminosulfonic acid and urea in a reaction kettle, stir and heat to 75-85°C for reaction for 60-80 minutes, add starch, heat to 90-95°C for reaction for 5-6 hours, cool and filter to collect precipitates, wash and dry the precipitates to obtain sulfonated starch.

[0021] Furthermore, the usage ratio of aminosulfonic acid, urea and starch is 100-120g:120-150g:15-20g.

[0022] The starch is any one of potato starch, corn starch and tapioca starch.

[0023] The invention discloses an application of a degradable polymer flocculant in the treatment of bacteria-containing sewage.

[0024] Beneficial effects of the present invention:

[0025] (1) The biodegradable polymer flocculant prepared in the present invention is prepared by compounding synthetic organic polymers and natural polymer materials to improve flocculation ability and degradability. The antibacterial ability and degradation performance of the synthetic organic polymer are improved by compounding silver oxide, titanium oxide and graphene oxide. The prepared biodegradable polymer flocculant has good flocculation and sedimentation ability, excellent degradability and good antibacterial ability.

[0026] (2) The present invention also synthesizes Ti-MOF and Zn-MOF whose ligands contain amino groups, and utilizes amino groups to form strong covalent bonds with graphene oxide nanosheets, so that Ti-MOF and Zn-MOF are successively grafted on the surface of graphene oxide nanosheets. Under high-temperature carbonization, Ti-MOF and Zn-MOF are oxidized into nano-scale titanium oxide and zinc oxide at high temperature. Under the carbonization of ligands in the original Ti-MOF and Zn-MOF, titanium oxide and zinc oxide are firmly bound to the surface of graphene oxide, thereby increasing the surface area of ​​graphene oxide. In addition, the structure formed by carbonization continues the porous structure of Ti-MOF and Zn-MOF, thereby improving the adsorption capacity of graphene oxide. Zinc oxide has antibacterial ability, so that the graphene composite powder has antibacterial properties.

[0027] (3) The present invention also compounds chitosan and graphene through an amide reaction to obtain chitosan-coated graphene composite powder. Chitosan has improved antibacterial properties, and chitosan is easily degradable and environmentally friendly. Amino groups are grafted onto the surface of chitosan through an ethylamine solution. After starch is sulfonated and modified, it is easy to combine with the chitosan composite powder containing amino groups. The bonding strength is high and the dispersion is high, which improves the adsorption capacity of the chitosan composite powder. Sulfonated starch has a strong adsorption capacity for cations in water. Sulfonated starch can also improve the water absorption capacity of the flocculant, improve the contact with the water to be treated, and improve the flocculation efficiency. In addition, the starch-based flocculant further improves the degradability of the flocculant.

[0028] (4) The present invention also uses acrylamide as a monomer to polymerize on the starch base to form a polymer flocculant polyacrylamide, thereby improving the flocculation ability of the flocculant. Free radicals are easily generated at the edges of graphene oxide in the graphene composite powder, and the free radicals also have a destructive effect on bacteria. They synergize with zinc oxide and chitosan to improve the antibacterial ability of the degradable polymer flocculant. Titanium dioxide has a degradation-promoting effect on polyacrylamide, thereby increasing the degradation rate of the difficult-to-degrade organic polymer flocculant polyacrylamide, thereby improving the degradation performance of the degradable polymer flocculant. DETAILED DESCRIPTION

[0029] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1: A degradable polymer flocculant is prepared by the following steps:

[0031] S1. Dissolve 5 g of 2-aminoterephthalic acid and 3 mL of tetrabutyl titanate in a mixed solvent of 150 mL of DMF and 20 mL of methanol in a reactor, add 2 g of graphene oxide nanosheets, and disperse them ultrasonically for 30 min. Heat to 140 °C under stirring for 40 h. Collect the precipitate by centrifugation after cooling, wash the precipitate with DMF and methanol, and dry it in vacuum at 60 °C for 10 h to obtain Ti / graphene nanosheets.

[0032] S2. In a reactor, 8 g of zinc nitrate hexahydrate and 3 g of 2-aminoterephthalic acid were dissolved in 200 mL of DMF and 200 mL of deionized water, and 2 g of Ti / graphene nanosheets were added. The mixture was ultrasonically dispersed for 30 min, and the temperature was raised to 90° C. under stirring for 20 h. After cooling, the precipitate was collected by centrifugation, and the precipitate was washed with DMF and deionized water, and vacuum dried at 60° C. for 10 h to obtain Ti / Zn composite graphene nanosheets. The Ti / Zn composite graphene nanosheets were placed in a muffle furnace and heated to 500° C. at a rate of 5° C. / min under an argon atmosphere for 4 h to obtain a graphene composite powder.

[0033] S3. In a reactor, ultrasonically disperse the graphene composite powder in deionized water to prepare a 1wt% graphene composite powder dispersion, dissolve chitosan in a 0.1M acetic acid aqueous solution to prepare a 1wt% chitosan acetic acid aqueous solution, mix the graphene composite powder dispersion and the chitosan acetic acid aqueous solution in equal volumes, heat to 85°C and react for 5h, add a 70wt% ethylamine solution which is half the volume of the chitosan acetic acid aqueous solution after cooling, stir and react for 20h, collect the precipitate by centrifugation, wash the precipitate with 0.1M acetic acid aqueous solution and deionized water, and freeze-dry to obtain the chitosan composite powder.

[0034] S4. In a reactor, 100 g of aminosulfonic acid and 120 g of urea were mixed, stirred and heated to 75° C. for reaction for 60 min, 15 g of potato starch was added, the temperature was raised to 90° C. for reaction for 5 h, and the precipitate was collected by filtration after cooling. The precipitate was washed with deionized water and dried at 40° C. for 20 h to obtain sulfonated starch.

[0035] S5. Dissolve 10 g of sulfonated starch in 100 mL of deionized water in a reactor, add 3 g of chitosan composite powder, heat to 60°C, stir until dissolved, ultrasonically disperse for 30 min, then add 30 g of acrylamide, stir until dissolved, add 0.4 g of N, N'-methylenebisacrylamide and 0.8 g of potassium persulfate to initiate polymerization, stir until a gel is formed, cut the gel into small pieces and immerse in distilled water for washing. After washing the gel, dry it at 60°C for 20 h, crush it through a 200-mesh sieve to obtain a degradable polymer flocculant.

[0036] Example 2: A degradable polymer flocculant is prepared by the following steps:

[0037] S1. In a reactor, 5.5 g of 2-aminoterephthalic acid and 3.5 mL of tetrabutyl titanate were dissolved in a mixed solvent of 175 mL of DMF and 25 mL of methanol, and 3 g of graphene oxide nanosheets were added. The mixture was ultrasonically dispersed for 35 min, and the temperature was raised to 145° C. under stirring for 44 h. After cooling, the precipitate was collected by centrifugation, washed with DMF and methanol, and dried under vacuum at 65° C. for 11 h to obtain Ti / graphene nanosheets.

[0038] S2. In a reactor, 9 g of zinc nitrate hexahydrate and 3.5 g of 2-aminoterephthalic acid were dissolved in 250 mL of DMF and 250 mL of deionized water, and 3 g of Ti / graphene nanosheets were added. The mixture was ultrasonically dispersed for 35 min, and the temperature was raised to 95° C. under stirring for 22 h. After cooling, the precipitate was collected by centrifugation, and the precipitate was washed with DMF and deionized water, and vacuum dried at 65° C. for 11 h to obtain Ti / Zn composite graphene nanosheets. The Ti / Zn composite graphene nanosheets were placed in a muffle furnace and heated to 525° C. at a rate of 5° C. / min under an argon atmosphere for 4.5 h to obtain a graphene composite powder.

[0039] S3. In a reactor, ultrasonically disperse the graphene composite powder in deionized water to prepare a 1.25wt% graphene composite powder dispersion, dissolve chitosan in a 0.1M acetic acid aqueous solution to prepare a 1.25wt% chitosan acetic acid aqueous solution, mix the graphene composite powder dispersion and the chitosan acetic acid aqueous solution in equal volumes, heat to 90°C and react for 5.5h, add a 70wt% ethylamine solution which is half the volume of the chitosan acetic acid aqueous solution after cooling, stir and react for 22h, collect the precipitate by centrifugation, wash the precipitate with 0.1M acetic acid aqueous solution and deionized water, and freeze-dry to obtain the chitosan composite powder.

[0040] S4. In a reactor, 110 g of aminosulfonic acid and 135 g of urea were mixed, stirred and heated to 80° C. for reaction for 70 min, 17.5 g of corn starch was added, the temperature was raised to 92.5° C. for reaction for 5.5 h, and the precipitate was collected by filtration after cooling. The precipitate was washed with deionized water and dried at 45° C. for 22 h to obtain sulfonated starch.

[0041] S5. Dissolve 12.5 g of sulfonated starch in 125 mL of deionized water in a reactor, add 4.5 g of chitosan composite powder, heat to 65°C, stir until dissolved, ultrasonically disperse for 35 min, then add 40 g of acrylamide, stir to dissolve, add 0.45 g of N, N'-methylenebisacrylamide and 0.9 g of potassium persulfate to initiate polymerization, stir until a gel is formed, cut the gel into small pieces and immerse in distilled water for washing. After washing the gel, dry it at 65°C for 22 h, crush it through a 200-mesh sieve to obtain a degradable polymer flocculant.

[0042] Example 3: A degradable polymer flocculant is prepared by the following steps:

[0043] S1. Dissolve 6 g of 2-aminoterephthalic acid and 4 mL of tetrabutyl titanate in a mixed solvent of 200 mL of DMF and 30 mL of methanol in a reactor, add 4 g of graphene oxide nanosheets, and disperse them ultrasonically for 40 min. Heat to 150 °C under stirring for 48 h. Collect the precipitate by centrifugation after cooling, wash the precipitate with DMF and methanol, and dry it in vacuo at 70 °C for 12 h to obtain Ti / graphene nanosheets.

[0044] S2. In a reactor, 10 g of zinc nitrate hexahydrate and 4 g of 2-aminoterephthalic acid were dissolved in 300 mL of DMF and 300 mL of deionized water, and 4 g of Ti / graphene nanosheets were added. The mixture was ultrasonically dispersed for 40 min, and the temperature was raised to 100 ° C. under stirring for 24 h. After cooling, the precipitate was collected by centrifugation, and the precipitate was washed with DMF and deionized water, and vacuum dried at 70 ° C. for 12 h to obtain Ti / Zn composite graphene nanosheets. The Ti / Zn composite graphene nanosheets were placed in a muffle furnace and heated to 550 ° C. at a rate of 5 ° C. / min under an argon atmosphere for 5 h to obtain a graphene composite powder.

[0045] By synthesizing Ti-MOF and Zn-MOF whose ligands contain amino groups, and utilizing amino groups to form strong covalent bonds with graphene oxide nanosheets, Ti-MOF and Zn-MOF are successively grafted on the surface of graphene oxide nanosheets. Under high-temperature carbonization, Ti-MOF and Zn-MOF are oxidized into nano-scale titanium oxide and zinc oxide at high temperature. Under the carbonization of ligands in the original Ti-MOF and Zn-MOF, titanium oxide and zinc oxide are firmly bound to the surface of graphene oxide, thereby increasing the surface area of ​​graphene oxide. In addition, the structure formed by carbonization continues the porous structure of Ti-MOF and Zn-MOF, thereby improving the adsorption capacity of graphene oxide. Zinc oxide has antibacterial ability, so that the graphene composite powder has certain antibacterial properties.

[0046] S3. In a reactor, ultrasonically disperse the graphene composite powder in deionized water to prepare a 1.5wt% graphene composite powder dispersion, dissolve chitosan in a 0.1M acetic acid aqueous solution to prepare a 1.5wt% chitosan acetic acid aqueous solution, mix the graphene composite powder dispersion and the chitosan acetic acid aqueous solution in equal volumes, heat to 95°C and react for 6h, add a 70wt% ethylamine solution which is half the volume of the chitosan acetic acid aqueous solution after cooling, stir and react for 24h, collect the precipitate by centrifugation, wash the precipitate with 0.1M acetic acid aqueous solution and deionized water, and freeze-dry to obtain the chitosan composite powder.

[0047] Chitosan and graphene are compounded by amide reaction to obtain chitosan-coated graphene composite powder. Chitosan has improved antibacterial properties, is easily degraded, and is environmentally friendly. Amino groups are grafted on the surface of chitosan using ethylamine solution.

[0048] S4. In a reactor, 120 g of aminosulfonic acid and 150 g of urea were mixed, stirred and heated to 85° C. for reaction for 80 min, 20 g of cassava starch was added, the temperature was raised to 95° C. for reaction for 6 h, and the precipitate was collected by filtration after cooling. The precipitate was washed with deionized water and dried at 50° C. for 24 h to obtain sulfonated starch.

[0049] After sulfonation modification, starch is easy to combine with chitosan composite powder containing amino groups, with high binding strength and high dispersion, which improves the adsorption capacity of chitosan composite powder. Sulfonated starch has a strong adsorption capacity for cations in water. Sulfonated starch can also improve the water absorption capacity of flocculants, increase contact with water to be treated, and improve flocculation efficiency. In addition, starch-based flocculants further improve the biodegradability of flocculants.

[0050] S5. Dissolve 15g of sulfonated starch in 150mL of deionized water in a reactor, add 6g of chitosan composite powder, heat to 70°C, stir until dissolved, ultrasonically disperse for 40min, then add 50g of acrylamide, stir to dissolve, add 0.5g of N,N'-methylenebisacrylamide and 1g of potassium persulfate to initiate polymerization, stir until a gel is formed, cut the gel into small pieces and immerse in distilled water for washing. After washing the gel, dry it at 70°C for 24h, crush it and pass it through a 200-mesh sieve to obtain a degradable polymer flocculant.

[0051] The polymer flocculant polyacrylamide is formed by polymerizing acrylamide as a monomer on a starch base, thereby improving the flocculation ability of the flocculant. Free radicals are easily generated at the edges of graphene oxide in the graphene composite powder, and the free radicals also have a destructive effect on bacteria. They synergize with zinc oxide and chitosan to improve the antibacterial ability of the degradable polymer flocculant. Titanium dioxide promotes the degradation of polyacrylamide, thereby increasing the degradation rate of the difficult-to-degrade organic polymer flocculant polyacrylamide, thereby improving the degradation performance of the degradable polymer flocculant.

[0052] Chitosan is a high molecular weight chitosan, 310,000-375,000 Da, with a degree of deacetylation >75%.

[0053] Comparative Example 1: The difference from Example 1 is that in S2, graphene nanosheets are used to replace Ti / graphene nanosheets to prepare a degradable polymer flocculant.

[0054] Comparative Example 2: The difference from Example 1 is that in S5, starch is used to replace sulfonated starch to prepare a degradable polymer flocculant.

[0055] Comparative Example 3: The difference from Example 1 is that in S3, no ethylamine solution is added to obtain chitosan composite powder and a degradable polymer flocculant.

[0056] The performance of the degradable polymer flocculants prepared in Examples 1 to 3 and Comparative Examples 1 to 3 was tested.

[0057] 1L of 1wt% kaolin suspension was used to simulate wastewater, stirred at 25rpm for 30min at room temperature, and allowed to stand for 30min. The turbidity of the supernatant was tested by a WGZ-200 photoelectric turbidity meter, and the turbidity removal rate was calculated.

[0058] Escherichia coli (ATCC25922) was inoculated into solid LB medium for activation culture, and then expanded into liquid medium to obtain a cell density of 1×10 8 CFU / mL of Escherichia coli suspension, add 1g of biodegradable polymer flocculant to 1L of Escherichia coli suspension, stir at 25rpm for 30min, let stand for 30min, take 1mL of flocs and disperse them in physiological saline, dilute the sample to be tested by ten-fold steps, take 0.1mL of the dilution and drop it into solid LB culture medium for activation culture, use the same method to expand the culture in liquid culture medium, calculate the number of floc colonies, and calculate the antibacterial efficiency using the number of floc colonies and the number of Escherichia coli suspension colonies. The calculation formula is as follows:

[0059] Antibacterial rate % = (1-floc colony count / 1×10 8 CFU / mL)×100%.

[0060] 300g of fresh soil was added to 1L of deionized water, stirred vigorously for 20min, and then centrifuged at 6000rpm for 15min. The supernatant was taken, and the particles and impurities in the supernatant were filtered out. 1g of degradable polymer flocculant was added to the supernatant. The supernatant was treated at a constant temperature of 37℃ and light conditions for 30 days and 90 days. The degradable polymer flocculant was taken out, dried and weighed, and the weight loss was calculated to obtain the degradation rate. The results are shown in Table 1:

[0061] Table 1: Performance test table of biodegradable polymer flocculants

[0062] As can be seen from Table 1, the degradable polymer flocculant prepared by the present invention has a higher turbidity removal rate, indicating that the flocculation performance of the present invention is good, and the antibacterial efficiency reaches more than 83%, indicating that the present invention has good antibacterial ability. The degradation rate reaches more than 50% in 30 days and more than 77% in 90 days, indicating that the degradable polymer flocculant prepared by the present invention has good degradability and is environmentally friendly.

[0063] In Comparative Example 1, since no Ti-MOF is added to form titanium oxide, the degradation promoting effect on the synthetic organic polymer polyacrylamide is poor, and thus the degradation rate is low.

[0064] In Comparative Example 2, since the starch was not sulfonated, the composite strength of the starch and chitosan composite powder was low, the flocculation effect was slightly low, and the antibacterial efficiency was also reduced. It is speculated that the sulfonic acid group also has a certain antibacterial effect on bacteria.

[0065] In Comparative Example 3, since chitosan was not aminated, the composite strength of chitosan composite powder and starch was low, the dispersion of chitosan composite powder in starch solution was low, and the antibacterial efficiency and degradation performance were both reduced.

[0066] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A degradable polymer flocculant, characterized in that: The preparation method of the degradable polymer flocculant comprises the following steps: Step 1: ultrasonically disperse the graphene composite powder in deionized water to prepare a graphene composite powder dispersion, mix 1-1.5wt% of the graphene composite powder dispersion and 1-1.5wt% of chitosan acetic acid aqueous solution in equal volumes in a reactor, heat to 85-95°C for reaction for 5-6h, add a 70wt% ethylamine solution of half the volume of the chitosan acetic acid aqueous solution after cooling, stir and react for 20-24h, collect the precipitate by centrifugation, wash the precipitate, and freeze-dry to obtain the chitosan composite powder; Step 2: Dissolve sulfonated starch in deionized water in a reaction kettle, add chitosan composite powder, heat to 60-70°C, stir until dissolved, ultrasonically disperse for 30-40 minutes, then add acrylamide, stir to dissolve, add N,N'-methylenebisacrylamide and potassium persulfate, stir until a gel is formed, cut the gel into small pieces and immerse in distilled water for washing, dry the washed gel at 60-70°C for 20-24 hours, crush and pass through a 200-mesh sieve to obtain a degradable polymer flocculant.

2. A degradable polymer flocculant according to claim 1, characterized in that: In step 2, the dosage ratio of the sulfonated starch, deionized water, chitosan composite powder, acrylamide, N,N'-methylenebisacrylamide and potassium persulfate is 10-15g: 100-150mL: 3-6g: 30-50g: 0.4-0.5g: 0.8-1g.

3. A degradable polymer flocculant according to claim 1, characterized in that: The chitosan acetic acid aqueous solution in step 1 is prepared by dissolving chitosan in a 0.1 M acetic acid aqueous solution.

4. A degradable polymer flocculant according to claim 1, characterized in that: The graphene composite powder described in step 1 is prepared by the following steps: In a reaction kettle, zinc nitrate hexahydrate and 2-aminoterephthalic acid are dissolved in DMF and deionized water, Ti / graphene nanosheets are added, ultrasonic dispersion is carried out for 30-40 minutes, the temperature is raised to 90-100° C. under stirring conditions, the reaction is carried out for 20-24 hours, the precipitate is collected by centrifugation after cooling, the precipitate is washed and vacuum dried for 10-12 hours to obtain Ti / Zn composite graphene nanosheets, the Ti / Zn composite graphene nanosheets are placed in a muffle furnace, the temperature is raised to 500-550° C. at a rate of 5° C. / min under an argon atmosphere, the reaction is carried out for 4-5 hours, and a graphene composite powder is obtained.

5. A degradable polymer flocculant according to claim 4, characterized in that: The usage ratio of the zinc nitrate hexahydrate, 2-aminoterephthalic acid, DMF, deionized water and Ti / graphene nanosheets is 8-10 g: 3-4 g: 200-300 mL: 200-300 mL: 2-4 g.

6. A degradable polymer flocculant according to claim 5, characterized in that: The Ti / graphene nanosheets are prepared by the following steps: In a reaction kettle, 2-aminoterephthalic acid and tetrabutyl titanate are dissolved in a mixed solvent of DMF and methanol, and then graphene oxide nanosheets are added, and ultrasonic dispersion is performed for 30-40 minutes. The temperature is raised to 140-150° C. under stirring conditions and the reaction is performed for 40-48 hours. After cooling, the precipitate is collected by centrifugation, and the precipitate is washed and vacuum dried to obtain Ti / graphene nanosheets.

7. A degradable polymer flocculant according to claim 6, characterized in that: The usage ratio of the 2-aminoterephthalic acid, tetrabutyl titanate, DMF, methanol and graphene oxide nanosheets is 5-6 g: 3-4 mL: 150-200 mL: 20-30 mL: 2-4 g.

8. The degradable polymer flocculant according to claim 2, characterized in that: The sulfonated starch in step 1 is prepared by the following steps: Mix aminosulfonic acid and urea in a reaction kettle, stir and heat to 75-85°C for reaction for 60-80 minutes, add starch, heat to 90-95°C for reaction for 5-6 hours, cool and filter to collect precipitates, wash and dry the precipitates to obtain sulfonated starch.

9. A degradable polymer flocculant according to claim 8, characterized in that: The usage ratio of aminosulfonic acid, urea and starch is 100-120g: 120-150g: 15-20g.

10. Use of a degradable polymer flocculant according to any one of claims 1 to 9 in the treatment of bacteria-containing wastewater.

Images