Environment-friendly polymer sludge dewatering agent and preparation method thereof

Abstract

This invention relates to the field of sludge dewatering agent preparation technology, specifically to an environmentally friendly polymeric sludge dewatering agent and its preparation method. A quaternary ammonium salt structure is introduced into the gelatinized starch molecular chain to obtain modified cationic starch. Using an emulsion copolymerization method, the modified cationic starch, methacryloyloxyethyltrimethylammonium chloride, and modifying additives are grafted and copolymerized to obtain a pretreated polymer. Then, modified fillers are introduced through covalent bonds to obtain the environmentally friendly polymeric sludge dewatering agent. The dewatering agent has both positive and negative charges on its surface. The positive charge can combine with negatively charged organic suspended matter, while the negative charge can accelerate the settling of inorganic suspended matter. The inorganic silica-alumina skeleton and metal-organic framework support the floc structure, forming large and dense flocs, thus increasing the settling velocity. Simultaneously, the long-chain alkanes on it enhance the interaction between polymer molecular chains through hydrophobic association, improving adsorption bridging and flocculation effects.

Description

Technical Field

[0001] This invention relates to the field of sludge dewatering agent preparation technology, specifically to an environmentally friendly polymer sludge dewatering agent and its preparation method. Background Technology

[0002] Environmentally friendly polymer sludge dewatering agents, as green and biodegradable water treatment agents, have been widely used in recent years in municipal sewage sludge treatment and industrial sludge dewatering in printing and dyeing, papermaking, and other industries. However, traditional dewatering agents have significant drawbacks: their dewatering efficiency is often limited, the resulting floc structure is loose, and they fail to effectively construct porous channels to facilitate water drainage, resulting in a high moisture content in the sludge cake after mechanical dewatering, increasing the difficulty and cost of subsequent transportation and disposal. By introducing specific functional groups or adjusting the molecular chain configuration, the mechanical properties of sludge are improved. The improved agents can promote the formation of larger and denser flocs from sludge particles and construct stable porous channels within the flocs, thereby effectively reducing water flow resistance and improving solid-liquid separation efficiency during high-pressure dewatering. Summary of the Invention

[0003] The purpose of this invention is to provide an environmentally friendly polymer sludge dewatering agent to overcome the shortcomings of traditional sludge dewatering agents in terms of dewatering effect.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing an environmentally friendly polymer sludge dewatering agent specifically includes the following steps:

[0006] Step S1: Mix starch, sodium hydroxide and deionized water evenly, and gelatinize at a speed of 140-160℃ and a temperature of 30-35℃ for 30-40 minutes. Then, raise the temperature to 60-65℃, stir and add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and react for 5-6 hours to obtain modified cationic starch.

[0007] Step S2: Sodium dodecyl sulfate, potassium persulfate, deionized water and modifying additives are mixed evenly. Under the conditions of 200-250 r / min and 60-70℃, modified cationic starch and methacryloyloxyethyltrimethylammonium chloride are added and reacted for 2-4 h to obtain the pretreated polymer.

[0008] Step S3: Mix the pretreated polymer, dibutyltin dilaurate, acetone and modified filler evenly, and react for 2-3 hours at a rotation speed of 160-180 r / min and a temperature of 40-50℃ to obtain an environmentally friendly polymer sludge dewatering agent.

[0009] Furthermore, the starch mentioned in step S1 is amylopectin 9037-22-3, and the ratio of starch, sodium hydroxide, deionized water and 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1g:0.2g:20mL:2g.

[0010] Furthermore, the ratio of sodium dodecyl sulfate, potassium persulfate, deionized water, modified additive, modified cationic starch, and methacryloyloxyethyltrimethylammonium chloride used in step S2 is 0.9g:0.3g:200mL:12g:18g:10g.

[0011] Furthermore, in step S3, the ratio of the pretreated polymer to the modified filler is 10-14g:2-3g, and the amount of dibutyltin dilaurate is 0.3-0.5% of the mass of the pretreated polymer.

[0012] Furthermore, the modified additive is prepared by the following steps:

[0013] Step A1: Mix hydroxyproline, tetrahydrofuran, and sodium hydride evenly, and stir for 30-50 minutes at a speed of 120-130 r / min and a temperature of 0-5℃. Add 2-bromopyridine, raise the temperature to 30-50℃, and react for 6-8 hours to obtain intermediate 1. Mix intermediate 1, epichlorohydrin, and N,N-dimethylformamide evenly, and react for 5-9 hours at a speed of 150-170 r / min and a temperature of 50-65℃. Stir and add sodium hydroxide solution, and react for 1-1.5 hours to obtain intermediate 2.

[0014] Step A2: Mix intermediate 2, aminopropyltriethoxysilane and tetrahydrofuran evenly, and react for 1-2 hours at a speed of 160-180 r / min and a temperature of 25-30℃ to obtain intermediate 3. Mix intermediate 3, tert-butyldimethylsilyl ether, imidazole and N,N-dimethylformamide evenly, and react for 2-4 hours at a speed of 140-150 r / min and a temperature of 20-25℃ to obtain intermediate 4. Mix intermediate 4, 1-hydroxybenzotriazole and dichloromethane evenly, and stir and add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide at a speed of 140-160 r / min, a temperature of 0-5℃ and a pH of 5-6, and react for 40-60 minutes. Raise the temperature to 20-30℃, stir and add oleyl alcohol and triethylamine, and react for 4-6 hours to obtain intermediate 5.

[0015] Step A3: Mix intermediate 5, tetrabutylammonium fluoride, and tetrahydrofuran evenly, and react for 2-3 hours at a speed of 130-140 r / min and a temperature of 25-30℃ to obtain intermediate 6. Mix intermediate 6, sodium chloroacetate, and N,N-dimethylformamide evenly, and react for 6-8 hours at a speed of 100-110 r / min, a temperature of 60-70℃, and a pH of 7-8 to obtain intermediate 7. Mix aluminum trichloride and deionized water evenly, and stir and add intermediate 7 and sodium hydroxide at a speed of 2000-3000 r / min and a temperature of 20-30℃, and react for 2-4 hours to obtain the modified additive.

[0016] Furthermore, the ratio of hydroxyproline, sodium hydride, and 2-bromopyridine in step A1 is 1 mmol:1.1 mmol:1 mmol, the ratio of intermediate 1, epichlorohydrin, and sodium hydroxide solution is 1 mmol:1.1-1.5 mmol:1.2 mmol, and the mass fraction of sodium hydroxide solution is 45%.

[0017] Furthermore, the amount of aminopropyltriethoxysilane used in step A2 is 2-4% of the mass of intermediate 2, the molar ratio of intermediate 3, tert-butyldimethylsilyl ether and imidazole is 1 mmol:1.2 mmol:2.5 mmol, and the molar ratio of intermediate 4, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, oleyl alcohol and triethylamine is 1.2 mmol:1.5 mmol:5-10 mL:1.5 mmol:1 mmol:3 mmol.

[0018] Furthermore, in step A3, the molar ratio of intermediate 5 to tetrabutylammonium fluoride is 1 mmol:1.1 mmol, the amount of intermediate 6 to sodium chloroacetate is 1 mmol:4.4 mol, and the ratio of aluminum trichloride, deionized water, intermediate 7 to sodium hydroxide is 10 mmol:5 mL:3-4 mmol:2 mg.

[0019] Furthermore, the modified filler is prepared by the following steps:

[0020] Step B1: Mix straw, zinc acetate, urea and deionized water evenly, soak for 10-12 hours, dry at 60-65℃, and pyrolyze at 400-450℃ for 3-5 hours to obtain nitrogen-doped biochar. Mix nitrogen-doped biochar and nitric acid evenly, and react at 60-80℃ for 2-3 hours to obtain pretreated biochar.

[0021] Step B2: Disperse the pretreated biochar in N,N-dimethylformamide, add ferric chloride hexahydrate and 2,5-dimercaptoterephthalic acid, sonicate at a frequency of 30-40 kHz for 10-15 min, place in a reaction vessel, and react at a temperature of 110-120℃ for 20-24 h to obtain modified biochar;

[0022] Step B3: Disperse the modified biochar in tetrahydrofuran, stir and add isocyanate-propyltrimethoxysilane at a speed of 200-300 r / min, a temperature of 60-80℃, and a pH of 4-5, and react for 8-10 h to obtain the modified filler.

[0023] Furthermore, in step B1, the ratio of straw, zinc acetate, urea, and deionized water is 20g:0.04mol:0.04mmol:200mL, the ratio of nitrogen-doped biochar to nitric acid is 1g:15mL, and the mass fraction of nitric acid is 65%.

[0024] Furthermore, the ratio of the amount of pretreated biochar, N,N-dimethylformamide, ferric chloride hexahydrate, and 2,5-dimercaptoterephthalic acid used in step B2 is 0.1g:50mL:4.05g:1.236g.

[0025] Furthermore, the amount of isocyanate-propyltrimethoxysilane used in step B3 is 0.5-1% of the mass of the modified biochar.

[0026] The beneficial effects of this invention are as follows: Under alkaline conditions, 3-chloro-2-hydroxypropyltrimethylammonium chloride undergoes an intramolecular cyclization reaction to generate an epoxy intermediate, which then reacts with starch, opening the epoxy ring and forming an ether bond to obtain modified cationic starch. Under the action of potassium persulfate initiator, hydrogen atoms on the cationic starch are abstracted, promoting the formation of an active center on the starch molecule and generating starch free radicals. Simultaneously, this initiates the formation of monomer free radicals from the modified additive and methacryloyloxyethyltrimethylammonium chloride, which then undergo emulsion copolymerization to obtain a pretreated polymer. The hydroxyl groups on the pretreated polymer react with the isocyanate groups on the modified filler to generate urethane groups, thus obtaining an environmentally friendly polymer sludge dewatering agent.

[0027] Modified Additives: The hydroxyl group on hydroxyproline is deionized by sodium hydride to form an oxo group. This oxo group acts as a nucleophile, attacking the bromine atom on 2-bromopyridine to obtain intermediate 1. The secondary amine on intermediate 1 undergoes a ring-opening reaction with the epoxy group on epichlorohydrin to generate a hydroxyl group. Subsequent addition of sodium hydroxide solution initiates a ring-closing reaction between the hydroxyl group and a chlorine atom, generating a new epoxy group to obtain intermediate 2. The epoxy group on intermediate 2 reacts with the amino group on aminopropyltriethoxysilane to obtain intermediate 3. In an acidic environment, the carboxylate ion on intermediate 3 is converted to a carboxyl group, which reacts with the hydroxyl group on oleyl alcohol under the action of a carboxyl activating agent to obtain intermediate 4. The tertiary amine group on intermediate 4 undergoes a substitution reaction with sodium chloroacetate to generate a quaternary ammonium salt structure to obtain intermediate 5. Aluminum trichloride dissociates in water to form aluminum ions, which further hydrolyze to form hydrated ions. The addition of sodium hydroxide promotes the formation of Al(OH)4. - Aluminum hydroxyl species are obtained. The ethoxy group on intermediate 5 hydrolyzes to form a silanol bond. Under high-speed stirring, the silanol and aluminum hydroxyl species undergo dehydration condensation to form Al-O-Si covalent bonds, thus obtaining the modified additive.

[0028] Modified filler: Zinc acetate and urea produce basic zinc carbonate. During high-temperature pyrolysis, basic zinc carbonate generates carbon dioxide, water vapor, and ammonia. Carbon dioxide and water vapor enrich the pore structure of straw biochar, while ammonia reacts with carbon atoms on the surface of the biochar's carbon framework to form structures such as pyridine nitrogen, fixing nitrogen elements within the carbon lattice to obtain nitrogen-doped biochar. Nitric acid treatment leads to oxidation of the carbon surface, introducing oxygen-containing functional groups to obtain pretreated biochar. Under high-temperature conditions, N,N-dimethylformamide decomposes to generate weakly basic dimethylamine, promoting the conversion of 2,5-dimercaptoterephthalic acid to 2,5-dimercaptoterephthalate ions. These ions, acting as organic ligands, can coordinate with iron ions provided by ferric chloride hexahydrate, forming a metal-organic framework on the surface of the pretreated biochar to obtain modified biochar. The methoxy group on isocyanate-propyltrimethoxysilane is hydrolyzed to form a silanol bond, which then undergoes dehydration condensation with Fe-OH on modified biochar to obtain the modified filler.

[0029] The modified additive contains both positive and negative charges, enabling it to more efficiently neutralize the complex positive and negative charge sites on the surface of sludge particles, thereby significantly compressing the electric double layer and disrupting colloidal stability. Simultaneously, a long-chain alkane structure and an organosilica-alumina composite structure composed of covalent bonds are introduced into the molecular chain of the modified additive. The long-chain alkanes enhance the interaction between polymer molecular chains through hydrophobic association, improving adsorption bridging and flocculation. The organosilica-alumina composite structure aggregates fine sludge particles into large flocs through the adsorption bridging of organic chains. Simultaneously, the inorganic silica-alumina framework provides a netting and rigid support, forming permeable channels during high-pressure dewatering, thus significantly improving settling velocity and dewatering efficiency, and drastically reducing the moisture content of the final sludge cake. The modified packing material is prepared by supporting nitrogen-doped biochar on a metal-organic framework. Nitrogen doping regulates the hydrophilic-hydrophobic balance of the carbon material and provides abundant active sites, thereby enhancing the adsorption and capture capacity of sludge particles and pollutants. Biochar loaded on a metal-organic framework adsorbs free water and small particles in sludge through its porous structure and large specific surface area. At the same time, it acts as a "skeleton" to support the floc structure, forming porous channels to promote water release and improve the porosity of the sludge cake. Detailed Implementation

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Example 1: A method for preparing an environmentally friendly polymer sludge dewatering agent, specifically including the following steps:

[0032] Step S1: Mix starch, sodium hydroxide and deionized water evenly, and gelatinize at 140°C and 30°C for 30 min. Then raise the temperature to 60°C, stir and add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and react for 5 h to obtain modified cationic starch.

[0033] Step S2: Sodium dodecyl sulfate, potassium persulfate, deionized water and modifying additives are mixed evenly. Under the conditions of 200 r / min and 60℃, modified cationic starch and methacryloyloxyethyltrimethylammonium chloride are added and reacted for 2 h to obtain the pretreated polymer.

[0034] Step S3: Mix the pretreated polymer, dibutyltin dilaurate, acetone and modified filler evenly, and react for 2 hours at a speed of 160 r / min and a temperature of 40℃ to obtain an environmentally friendly polymer sludge dewatering agent.

[0035] The starch mentioned in step S1 is amylopectin 9037-22-3, and the ratio of starch, sodium hydroxide, deionized water and 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1g:0.2g:20mL:2g.

[0036] The ratio of sodium dodecyl sulfate, potassium persulfate, deionized water, modified additive, modified cationic starch and methacryloyloxyethyltrimethylammonium chloride used in step S2 is 0.9g:0.3g:200mL:12g:18g:10g, and the amount of modified additive is 10g.

[0037] The ratio of the pretreated polymer to the modified filler in step S3 is 10g:2g, and the amount of dibutyltin dilaurate is 0.3% of the mass of the pretreated polymer.

[0038] The modified additive is prepared by the following steps:

[0039] Step A1: Hydroxyproline, tetrahydrofuran, and sodium hydride are mixed evenly and stirred for 30 min at 120 r / min and 0 °C. 2-Bromopyridine is added, the temperature is raised to 30 °C, and the reaction is carried out for 6 h to obtain intermediate 1. Intermediate 1, epichlorohydrin, and N,N-dimethylformamide are mixed evenly and stirred for 5 h at 150 r / min and 50 °C. Sodium hydroxide solution is added and the reaction is carried out for 1 h to obtain intermediate 2.

[0040] Step A2: Intermediate 2, aminopropyltriethoxysilane, and tetrahydrofuran are mixed evenly and reacted at 160 r / min and 25°C for 1 h to obtain intermediate 3. Intermediate 3, tert-butyldimethylsilyl ether, imidazole, and N,N-dimethylformamide are mixed evenly and reacted at 140 r / min and 20°C for 2 h to obtain intermediate 4. Intermediate 4, 1-hydroxybenzotriazole, and dichloromethane are mixed evenly and reacted at 140 r / min, 0°C, and pH 5 with stirring and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is added and reacted for 40 min. The temperature is raised to 20°C, and oleyl alcohol and triethylamine are added with stirring and reacted for 4 h to obtain intermediate 5.

[0041] Step A3: Mix intermediate 5, tetrabutylammonium fluoride and tetrahydrofuran evenly, and react for 2 hours at 130 r / min and 25°C to obtain intermediate 6. Mix intermediate 6, sodium chloroacetate and N,N-dimethylformamide evenly, and react for 6 hours at 100 r / min, 60°C and pH 7 to obtain intermediate 7. Mix aluminum trichloride and deionized water evenly, and stir and add intermediate 7 and sodium hydroxide at 2000 r / min and 20°C, and react for 2 hours to obtain the modified additive.

[0042] The ratio of hydroxyproline, sodium hydride and 2-bromopyridine used in step A1 is 1 mmol:1.1 mmol:1 mmol, the ratio of intermediate 1, epichlorohydrin and sodium hydroxide solution is 1 mmol:1.1 mmol:1.2 mmol, and the mass fraction of sodium hydroxide solution is 45%.

[0043] The amount of aminopropyltriethoxysilane used in step A2 is 2% of the mass of intermediate 2. The molar ratio of intermediate 3, tert-butyldimethylsilyl ether and imidazole is 1 mmol:1.2 mmol:2.5 mmol. The molar ratio of intermediate 4, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, oleyl alcohol and triethylamine is 1.2 mmol:1.5 mmol:5 mL:1.5 mmol:1 mmol:3 mmol.

[0044] In step A3, the molar ratio of intermediate 5 to tetrabutylammonium fluoride is 1 mmol:1.1 mmol, the amount of intermediate 6 to sodium chloroacetate is 1 mmol:4.4 mol, and the ratio of aluminum trichloride, deionized water, intermediate 7 to sodium hydroxide is 10 mmol:5 mL:3 mmol:2 mg.

[0045] The modified filler is prepared by the following steps:

[0046] Step B1: Mix straw, zinc acetate, urea and deionized water evenly, soak for 10 hours, dry at 60°C, and pyrolyze at 400°C for 3 hours to obtain nitrogen-doped biochar. Mix nitrogen-doped biochar and nitric acid evenly, and react at 60°C for 2 hours to obtain pretreated biochar.

[0047] Step B2: Disperse the pretreated biochar in N,N-dimethylformamide, add ferric chloride hexahydrate and 2,5-dimercaptoterephthalic acid, sonicate for 10 min at a frequency of 30-40 kHz, place in a reaction vessel, and react for 20 h at a temperature of 110 ℃ to obtain modified biochar.

[0048] Step B3: The modified biochar was dispersed in tetrahydrofuran, and under the conditions of 200 r / min, 60℃ and pH 4, the mixture was stirred and isocyanate-propyltrimethoxysilane was added. The reaction was carried out for 8 h to obtain the modified filler.

[0049] The ratio of straw, zinc acetate, urea and deionized water used in step B1 is 20g:0.04mol:0.04mmol:200mL, the ratio of nitrogen-doped biochar and nitric acid is 1g:15mL, and the mass fraction of nitric acid is 65%.

[0050] The ratio of the pretreated biochar, N,N-dimethylformamide, ferric chloride hexahydrate, and 2,5-dimercaptoterephthalic acid used in step B2 is 0.1 g: 50 mL: 4.05 g: 1.236 g.

[0051] The amount of isocyanate-based propyltrimethoxysilane used in step B3 is 0.5% of the mass of the modified biochar.

[0052] Example 2, a method for preparing an environmentally friendly polymer sludge dewatering agent, specifically includes the following steps:

[0053] Step S1: Mix starch, sodium hydroxide and deionized water evenly, and gelatinize at 150°C and 32°C for 35 min. Then raise the temperature to 62°C, stir and add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and react for 5 h to obtain modified cationic starch.

[0054] Step S2: Sodium dodecyl sulfate, potassium persulfate, deionized water and modifying additives are mixed evenly. Under the conditions of 230 r / min and 65℃, modified cationic starch and methacryloyloxyethyltrimethylammonium chloride are added and reacted for 3 h to obtain the pretreated polymer.

[0055] Step S3: Mix the pretreated polymer, dibutyltin dilaurate, acetone and modified filler evenly, and react for 2 hours at a speed of 170 r / min and a temperature of 45℃ to obtain an environmentally friendly polymer sludge dewatering agent.

[0056] The starch mentioned in step S1 is amylopectin 9037-22-3, and the ratio of starch, sodium hydroxide, deionized water and 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1g:0.2g:20mL:2g.

[0057] In step S2, the ratio of sodium dodecyl sulfate, potassium persulfate, deionized water, modified additive, modified cationic starch, and methacryloyloxyethyltrimethylammonium chloride is 0.9g:0.3g:200mL:12g:18g:10g, and the amount of modified additive is 11g.

[0058] The ratio of the pretreated polymer to the modified filler in step S3 is 10g:2.5g, and the amount of dibutyltin dilaurate is 0.4% of the mass of the pretreated polymer.

[0059] The modified additive is prepared by the following steps:

[0060] Step A1: Hydroxyproline, tetrahydrofuran, and sodium hydride are mixed evenly and stirred for 40 min at 125 r / min and 2 °C. 2-Bromopyridine is added, the temperature is raised to 40 °C, and the reaction is carried out for 7 h to obtain intermediate 1. Intermediate 1, epichlorohydrin, and N,N-dimethylformamide are mixed evenly and stirred for 6 h at 160 r / min and 55 °C. Sodium hydroxide solution is added and the reaction is carried out for 1 h to obtain intermediate 2.

[0061] Step A2: Intermediate 2, aminopropyltriethoxysilane, and tetrahydrofuran are mixed evenly and reacted at 170 r / min and 28°C for 1 h to obtain intermediate 3. Intermediate 3, tert-butyldimethylsilyl ether, imidazole, and N,N-dimethylformamide are mixed evenly and reacted at 145 r / min and 22°C for 3 h to obtain intermediate 4. Intermediate 4, 1-hydroxybenzotriazole, and dichloromethane are mixed evenly and stirred at 150 r / min, 2°C, and pH 5, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is added and reacted for 50 min. The temperature is raised to 25°C, stirred, and oleyl alcohol and triethylamine are added and reacted for 5 h to obtain intermediate 5.

[0062] Step A3: Intermediate 5, tetrabutylammonium fluoride, and tetrahydrofuran are mixed evenly and reacted at 135 r / min and 25°C for 2 h to obtain intermediate 6. Intermediate 6, sodium chloroacetate, and N,N-dimethylformamide are mixed evenly and reacted at 100 r / min, 65°C, and pH 7 for 7 h to obtain intermediate 7. Aluminum trichloride and deionized water are mixed evenly and stirred at 2500 r / min and 25°C, with intermediate 7 and sodium hydroxide added, and reacted for 3 h to obtain the modified additive.

[0063] The ratio of hydroxyproline, sodium hydride and 2-bromopyridine used in step A1 is 1 mmol:1.1 mmol:1 mmol, the ratio of intermediate 1, epichlorohydrin and sodium hydroxide solution is 1 mmol:1.2 mmol:1.2 mmol, and the mass fraction of sodium hydroxide solution is 45%.

[0064] The amount of aminopropyltriethoxysilane used in step A2 is 3% of the mass of intermediate 2. The molar ratio of intermediate 3, tert-butyldimethylsilyl ether and imidazole is 1 mmol:1.2 mmol:2.5 mmol. The molar ratio of intermediate 4, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, oleyl alcohol and triethylamine is 1.2 mmol:1.5 mmol:5 mL:1.5 mmol:1 mmol:3 mmol.

[0065] In step A3, the molar ratio of intermediate 5 to tetrabutylammonium fluoride is 1 mmol:1.1 mmol, the amount of intermediate 6 to sodium chloroacetate is 1 mmol:4.4 mol, and the ratio of aluminum trichloride, deionized water, intermediate 7 to sodium hydroxide is 10 mmol:5 mL:3 mmol:2 mg.

[0066] The modified filler is prepared by the following steps:

[0067] Step B1: Mix straw, zinc acetate, urea and deionized water evenly, soak for 11 hours, dry at 63°C, and pyrolyze at 425°C for 4 hours to obtain nitrogen-doped biochar. Mix nitrogen-doped biochar and nitric acid evenly and react at 70°C for 2 hours to obtain pretreated biochar.

[0068] Step B2: Disperse the pretreated biochar in N,N-dimethylformamide, add ferric chloride hexahydrate and 2,5-dimercaptoterephthalic acid, sonicate at a frequency of 35kHz for 12 minutes, place in a reaction vessel, and react at a temperature of 115℃ for 22 hours to obtain modified biochar.

[0069] Step B3: The modified biochar was dispersed in tetrahydrofuran, and under the conditions of 250 r / min, 70℃ and pH 4, the mixture was stirred and isocyanate-propyltrimethoxysilane was added. The reaction was carried out for 9 h to obtain the modified filler.

[0070] The ratio of straw, zinc acetate, urea and deionized water used in step B1 is 20g:0.04mol:0.04mmol:200mL, the ratio of nitrogen-doped biochar and nitric acid is 1g:15mL, and the mass fraction of nitric acid is 65%.

[0071] The ratio of the pretreated biochar, N,N-dimethylformamide, ferric chloride hexahydrate, and 2,5-dimercaptoterephthalic acid used in step B2 is 0.1 g: 50 mL: 4.05 g: 1.236 g.

[0072] The amount of isocyanate-based propyltrimethoxysilane used in step B3 is 0.5% of the mass of the modified biochar.

[0073] Example 3: A method for preparing an environmentally friendly polymer sludge dewatering agent, specifically including the following steps:

[0074] Step S1: Mix starch, sodium hydroxide and deionized water evenly, and gelatinize at 160°C and 35°C for 40 min. Then raise the temperature to 65°C, stir and add 3-chloro-2-hydroxypropyltrimethylammonium chloride, and react for 6 h to obtain modified cationic starch.

[0075] Step S2: Sodium dodecyl sulfate, potassium persulfate, deionized water and modifying additives are mixed evenly. Under the conditions of 250 r / min and 70℃, modified cationic starch and methacryloyloxyethyltrimethylammonium chloride are added and reacted for 4 h to obtain the pretreated polymer.

[0076] Step S3: Mix the pretreated polymer, dibutyltin dilaurate, acetone and modified filler evenly, and react for 3 hours at a speed of 180 r / min and a temperature of 50℃ to obtain an environmentally friendly polymer sludge dewatering agent.

[0077] The starch mentioned in step S1 is amylopectin 9037-22-3, and the ratio of starch, sodium hydroxide, deionized water and 3-chloro-2-hydroxypropyltrimethylammonium chloride is 1g:0.2g:20mL:2g.

[0078] The ratio of sodium dodecyl sulfate, potassium persulfate, deionized water, modified additive, modified cationic starch, and methacryloyloxyethyltrimethylammonium chloride used in step S2 is 0.9g:0.3g:200mL:12g:18g:10g, and the amount of modified additive is 12g.

[0079] The ratio of the pretreated polymer to the modified filler in step S3 is 10g:3g, and the amount of dibutyltin dilaurate is 0.5% of the mass of the pretreated polymer.

[0080] The modified additive is prepared by the following steps:

[0081] Step A1: Hydroxyproline, tetrahydrofuran, and sodium hydride are mixed evenly and stirred for 50 min at 130 r / min and 5 °C. 2-Bromopyridine is added, the temperature is raised to 50 °C, and the reaction is carried out for 8 h to obtain intermediate 1. Intermediate 1, epichlorohydrin, and N,N-dimethylformamide are mixed evenly and stirred for 9 h at 170 r / min and 65 °C. Sodium hydroxide solution is added and the reaction is carried out for 1.5 h to obtain intermediate 2.

[0082] Step A2: Intermediate 2, aminopropyltriethoxysilane and tetrahydrofuran are mixed evenly and reacted at 180 r / min and 30 °C for 2 h to obtain intermediate 3. Intermediate 3, tert-butyldimethylsilyl ether, imidazole and N,N-dimethylformamide are mixed evenly and reacted at 150 r / min and 25 °C for 4 h to obtain intermediate 4. Intermediate 4, 1-hydroxybenzotriazole and dichloromethane are mixed evenly and stirred at 160 r / min, 5 °C and pH 6, and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide is added and reacted for 60 min. The temperature is raised to 30 °C, stirred and oleyl alcohol and triethylamine are added and reacted for 6 h to obtain intermediate 5.

[0083] Step A3: Intermediate 5, tetrabutylammonium fluoride, and tetrahydrofuran are mixed evenly and reacted for 3 hours at a speed of 140 r / min and a temperature of 30°C to obtain intermediate 6. Intermediate 6, sodium chloroacetate, and N,N-dimethylformamide are mixed evenly and reacted for 8 hours at a speed of 110 r / min, a temperature of 70°C, and a pH of 8 to obtain intermediate 7. Aluminum trichloride and deionized water are mixed evenly and stirred at a speed of 3000 r / min and a temperature of 30°C. Intermediate 7 and sodium hydroxide are added and reacted for 4 hours to obtain the modified additive.

[0084] The ratio of hydroxyproline, sodium hydride and 2-bromopyridine used in step A1 is 1 mmol:1.1 mmol:1 mmol, the ratio of intermediate 1, epichlorohydrin and sodium hydroxide solution is 1 mmol:1.5 mmol:1.2 mmol, and the mass fraction of sodium hydroxide solution is 45%.

[0085] The amount of aminopropyltriethoxysilane used in step A2 is 4% of the mass of intermediate 2. The molar ratio of intermediate 3, tert-butyldimethylsilyl ether and imidazole is 1 mmol:1.2 mmol:2.5 mmol. The molar ratio of intermediate 4, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, oleyl alcohol and triethylamine is 1.2 mmol:1.5 mmol:5 mL:1.5 mmol:1 mmol:3 mmol.

[0086] In step A3, the molar ratio of intermediate 5 to tetrabutylammonium fluoride is 1 mmol:1.1 mmol, the amount of intermediate 6 to sodium chloroacetate is 1 mmol:4.4 mol, and the ratio of aluminum trichloride, deionized water, intermediate 7 to sodium hydroxide is 10 mmol:5 mL:3 mmol:2 mg.

[0087] The modified filler is prepared by the following steps:

[0088] Step B1: Mix straw, zinc acetate, urea and deionized water evenly, soak for 12 hours, dry at 65°C, and pyrolyze at 450°C for 5 hours to obtain nitrogen-doped biochar. Mix nitrogen-doped biochar and nitric acid evenly and react at 80°C for 3 hours to obtain pretreated biochar.

[0089] Step B2: Disperse the pretreated biochar in N,N-dimethylformamide, add ferric chloride hexahydrate and 2,5-dimercaptoterephthalic acid, sonicate at a frequency of 40kHz for 15min, place in a reaction vessel, and react at a temperature of 120℃ for 24h to obtain modified biochar.

[0090] Step B3: The modified biochar was dispersed in tetrahydrofuran, and under the conditions of 300 r / min, 80℃ and pH 5, the mixture was stirred and isocyanate-based propyltrimethoxysilane was added. The reaction was carried out for 10 h to obtain the modified filler.

[0091] The ratio of straw, zinc acetate, urea and deionized water used in step B1 is 20g:0.04mol:0.04mmol:200mL, the ratio of nitrogen-doped biochar and nitric acid is 1g:15mL, and the mass fraction of nitric acid is 65%.

[0092] The ratio of the pretreated biochar, N,N-dimethylformamide, ferric chloride hexahydrate, and 2,5-dimercaptoterephthalic acid used in step B2 is 0.1 g: 50 mL: 4.05 g: 1.236 g.

[0093] The amount of isocyanate-propyltrimethoxysilane used in step B3 is 1% of the mass of the modified biochar.

[0094] Comparative Example 1: In this comparative example, intermediate 7 is replaced by intermediate 6, while the other steps are the same as in Example 1.

[0095] Comparative Example 2: In this comparative example, intermediate 4 is replaced by intermediate 1, while the other steps are the same as in Example 1.

[0096] Comparative Example 3: This comparative example uses pretreated biochar instead of modified biochar, while the other steps are the same as in Example 1.

[0097] Comparative Example 4: This comparative example uses propylene alcohol instead of oleyl alcohol, but the other steps are the same as in Example 1.

[0098] The environmentally friendly polymer sludge dewatering agents prepared in Examples 1-3 and Comparative Examples 1-4 were added to the experimentally prepared sludge. The turbidity of the supernatant, the specific resistance of the sludge, and the moisture content of the sludge cake were measured. The results are shown in Table 1. The selected experimentally prepared sludge was 100g, with a sludge moisture content of 98%, a pH of 6.8, a Zeta potential of -22.5mV, and an organic matter content of 40%. The dosage of the sludge dewatering agent was 10mg / g. The mixture was stirred for 2 minutes at a speed of 500r / min, and then allowed to stand. The turbidity of the supernatant was measured. The mixture was then stirred for 8 minutes at a speed of 150r / min, and the specific resistance of the sludge cake and the moisture content of the sludge cake were measured.

[0099] Table 1

[0100] Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Sludge specific resistance (m / kg) 4.21 x 10 12 ]]> 4.16 x 10 12 ]] 4.09 x 10 12 ]] 2.64 x 10 13 ]] 2.50 x 10 13 ]]> 2.18 x 10 13 ]]> 2.03 x 10 13 ]] Cake moisture content (%) 50.18 48.37 46.45 68.53 65.84 62.48 61.18 Supernatant turbidity (NTU) 2.2 2.0 1.7 3.8 5.6 4.2 3.0

[0101] Table 1 shows that when the environmentally friendly polymer sludge dewatering agents prepared in Examples 1-3 were added to the experimentally prepared sludge, the turbidity of the supernatant was measured to be in the range of 1.7-2.2 NTU. This indicates that the flocs formed by the dewatering agent have excellent shear resistance, can resist mechanical damage, and prevent the shedding of fine particles. The specific resistance of the sludge was 4.09 × 10⁻⁶. 12 -4.21×10 12 Within the range of m / kg, the moisture content of the sludge cake is in the range of 46.45-50.18%, indicating that the present invention has a very good sludge dewatering effect.

[0102] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing an environmentally friendly polymer sludge dewatering agent, characterized in that: Specifically, the steps include the following: Step S1: Mix starch, sodium hydroxide and deionized water evenly, gelatinize, heat, stir and add 3-chloro-2-hydroxypropyltrimethylammonium chloride to react and obtain modified cationic starch. Step S2: Sodium dodecyl sulfate, potassium persulfate, deionized water and modifying additives are mixed and stirred, and modified cationic starch and methacryloyloxyethyltrimethylammonium chloride are added to react and obtain the pretreated polymer. Step S3: Mix the pretreated polymer, dibutyltin dilaurate, acetone and modified filler evenly and react to obtain an environmentally friendly polymer sludge dewatering agent. The ratio of starch, sodium hydroxide, deionized water and 3-chloro-2-hydroxypropyltrimethylammonium chloride used in step S1 is 1g:0.2g:20mL:2g; The ratio of sodium dodecyl sulfate, potassium persulfate, deionized water, modified additive, modified cationic starch and methacryloyloxyethyltrimethylammonium chloride used in step S2 is 0.9g:0.3g:200mL:12g:18g:10g. The ratio of the pretreated polymer to the modified filler in step S3 is 10-14g:2-3g, and the amount of dibutyltin dilaurate is 0.3-0.5% of the mass of the pretreated polymer.

2. The method for preparing an environmentally friendly polymer sludge dewatering agent according to claim 1, characterized in that: The modified additive is prepared by the following steps: Step A1: Hydroxyproline, tetrahydrofuran and sodium hydride are mixed and stirred, 2-bromopyridine is added, the temperature is raised and the reaction is carried out to obtain intermediate 1. Intermediate 1, epichlorohydrin and N,N-dimethylformamide are mixed evenly and reacted. Sodium hydroxide solution is added and the reaction is carried out to obtain intermediate 2. Step A2: Mix intermediate 2, aminopropyltriethoxysilane and tetrahydrofuran evenly and react to obtain intermediate 3. Mix intermediate 3, tert-butyldimethylsilyl ether, imidazole and N,N-dimethylformamide evenly and react to obtain intermediate 4. Mix intermediate 4, 1-hydroxybenzotriazole and dichloromethane and stir, then add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and react. Heat, stir and add oleyl alcohol and triethylamine, and react for 4-6 hours to obtain intermediate 5. Step A3: Mix intermediate 5, tetrabutylammonium fluoride and tetrahydrofuran evenly and react to obtain intermediate 6. Mix intermediate 6, sodium chloroacetate and N,N-dimethylformamide evenly and react to obtain intermediate 7. Mix aluminum trichloride and deionized water, stir and add intermediate 7 and sodium hydroxide, and react to obtain the modified additive.

3. The method for preparing an environmentally friendly polymer sludge dewatering agent according to claim 2, characterized in that: The ratio of hydroxyproline, sodium hydride and 2-bromopyridine used in step A1 is 1 mmol: 1.1 mmol: 1 mmol, and the ratio of intermediate 1, epichlorohydrin and sodium hydroxide solution is 1 mmol: 1.1-1.5 mmol: 1.2 mmol.

4. The preparation method of the environmentally friendly polymer sludge dewatering agent according to claim 2, characterized in that: The amount of aminopropyltriethoxysilane used in step A2 is 2-4% of the mass of intermediate 2. The molar ratio of intermediate 3, tert-butyldimethylsilyl ether and imidazole is 1 mmol:1.2 mmol:2.5 mmol. The molar ratio of intermediate 4, 1-hydroxybenzotriazole, dichloromethane, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, oleyl alcohol and triethylamine is 1.2 mmol:1.5 mmol:5-10 mL:1.5 mmol:1 mmol:3 mmol.

5. The method for preparing an environmentally friendly polymer sludge dewatering agent according to claim 2, characterized in that: The molar ratio of intermediate 5 and tetrabutylammonium fluoride in step A3 is 1 mmol:1.1 mmol, the molar ratio of intermediate 6 and sodium chloroacetate is 1 mmol:4.4 mol, and the molar ratio of aluminum trichloride, deionized water, intermediate 7 and sodium hydroxide is 10 mmol:5 mL:3-4 mmol:2 mg.

6. The method for preparing an environmentally friendly polymer sludge dewatering agent according to claim 1, characterized in that: The modified filler is prepared by the following steps: Step B1: Mix straw, zinc acetate, urea and deionized water evenly, soak and dry, then pyrolyze at high temperature to obtain nitrogen-doped biochar. Mix nitrogen-doped biochar and nitric acid evenly and react to obtain pretreated biochar. Step B2: Disperse the pretreated biochar in N,N-dimethylformamide, add ferric chloride hexahydrate and 2,5-dimercaptoterephthalic acid, sonicate, place in a reaction vessel, and react to obtain modified biochar; Step B3: Disperse the modified biochar in tetrahydrofuran, stir and add isocyanate-propyltrimethoxysilane to carry out the reaction, and obtain the modified filler.

7. The method for preparing an environmentally friendly polymer sludge dewatering agent according to claim 6, characterized in that: The ratio of straw, zinc acetate, urea and deionized water used in step B1 is 20g:0.04mol:0.04mmol:200mL, and the ratio of nitrogen-doped biochar and nitric acid is 1g:15mL.

8. The method for preparing an environmentally friendly polymer sludge dewatering agent according to claim 6, characterized in that: The ratio of the pretreated biochar, N,N-dimethylformamide, ferric chloride hexahydrate, and 2,5-dimercaptoterephthalic acid used in step B2 is 0.1 g: 50 mL: 4.05 g: 1.236 g.

9. The method for preparing an environmentally friendly polymer sludge dewatering agent according to claim 6, characterized in that: The amount of isocyanate-based propyltrimethoxysilane used in step B3 is 0.5-1% of the mass of the modified biochar.

10. An environmentally friendly polymer sludge dewatering agent, characterized in that: Prepared according to any one of the preparation methods described in claims 1-9.