Composite sewage treatment agent and preparation method thereof

Abstract

The invention discloses a composite sewage treatment agent and a preparation method thereof, and belongs to the technical field of sewage treatment. The composite sewage treatment agent disclosed by the invention is prepared from the following raw material components in parts by mass: 10 to 12 parts of starch-based flocculating agent, 0.8 to 1.2 parts of modified bimetallic biochar and 0.7 to 0.8 part of 2, 4, 6-tri (4-ethynyl phenyl)-1, 3, 5-triazine, wherein the starch flocculant is obtained by carrying out graft copolymerization on an active monomer and amylopectin and then introducing carbazole through Ullmann reaction, and the active monomer at least comprises acrylamide, methacryloyloxyethyl trimethyl ammonium chloride, acryloyloxyethyl trimethyl ammonium chloride and N, N-diallylaniline; the modified bimetal biochar is prepared from bimetal biochar modified by 3-bromopropyl trimethoxy silane, and the modified bimetal biochar is prepared from the modified bimetal biochar modified by the 3-bromopropyl trimethoxy silane modified bimetal biochar. The bimetallic biochar is obtained by loading nano-iron and molybdenum disulfide in two steps through a calcination method and a hydrothermal method by taking straw biomass as a raw material.

Description

Technical Field

[0001] This invention relates to composite wastewater treatment agents and their preparation methods. Background Technology

[0002] With the accelerating pace of industrialization and urbanization, the discharge of various types of industrial and domestic wastewater continues to increase, leading to increasingly severe water pollution problems. Wastewater not only contains large amounts of recalcitrant organic pollutants, such as dyes, pesticides, and drug residues, but also often contains various inorganic suspended particulate matter. Montmorillonite, a typical layered silicate mineral, is widely present in wastewater from industries such as drilling fluids, coatings, papermaking, and bentonite processing. These inorganic suspended solids not only increase water turbidity and affect the effectiveness of subsequent treatment processes, but may also adsorb or complex toxic and harmful substances, further exacerbating the risk of water pollution.

[0003] Currently, commonly used physicochemical methods for wastewater treatment mainly include coagulation sedimentation, adsorption filtration, and advanced oxidation. Traditional single treatment agents such as polyaluminum chloride and ferric sulfate can effectively remove some suspended solids and some organic matter, but their removal efficiency for organic pollutants is relatively low.

[0004] To address the aforementioned issues, the applicant developed a composite wastewater treatment agent. Summary of the Invention

[0005] The purpose of this invention is to provide a composite wastewater treatment agent and its preparation method to solve the technical problems mentioned in the background section.

[0006] The technical solution to achieve the objective of this invention is:

[0007] In a first aspect, the present invention provides a composite wastewater treatment agent, wherein, by mass parts, the raw material components include 10-12 parts by mass of starch-based flocculant, 0.8-1.2 parts by mass of modified bimetallic biochar, and 0.7-0.8 parts by mass of crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine.

[0008] The composite wastewater treatment agent of this invention introduces a starch-based flocculant, modified bimetallic biochar, and a crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine. The starch-based flocculant adsorbs and flocculates inorganic suspended particles through interactions such as hydrogen bonding and electrostatic interactions. The modified bimetallic biochar enhances the removal efficiency of inorganic suspended solids and organic pollutants in wastewater by adsorbing inorganic suspended particles and organic pollutants.

[0009] Furthermore, the starch flocculant is obtained by graft copolymerization of active monomers and amylopectin followed by the introduction of carbazole via the Ullmann reaction.

[0010] Furthermore, the active monomer includes at least acrylamide, unsaturated quaternary ammonium salt, and N,N-diallylaniline.

[0011] Furthermore, the unsaturated quaternary ammonium salt includes any one of dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and acryloyloxyethyl trimethyl ammonium chloride.

[0012] This invention utilizes microwave-assisted free radical copolymerization to graft active monomers onto amylopectin. Specifically, the active monomers are grafted and copolymerized through the reactive sites of amylopectin, which are located on the C2 or C3 atoms of the glucose ring. A high charge density acrylamide-quaternary ammonium salt copolymer is grafted onto the side of the amylopectin. Through strong electrostatic interaction, supplemented by hydrogen bonding and other interactions, the copolymer interacts with inorganic suspended solids such as montmorillonite, thereby improving the flocculation and sedimentation effect.

[0013] Furthermore, the modified bimetallic biochar is prepared by modifying bimetallic biochar with 3-bromopropyltrimethoxysilane; the bimetallic biochar is obtained by loading nano-iron and molybdenum disulfide onto straw biomass through a two-step process of calcination and hydrothermal loading.

[0014] The bimetallic biochar of this invention is obtained by loading nano-iron and molybdenum disulfide onto straw biomass through a two-step process of calcination and hydrothermal loading. By introducing metallic iron, the composite wastewater treatment agent is given magnetic properties, which facilitates the recovery of the composite wastewater treatment agent through an external magnetic field.

[0015] The present invention modifies bimetallic biochar with 3-bromopropyltrimethoxysilane. On the one hand, it can make the bimetallic biochar and starch flocculant more uniformly mixed and dispersed. On the other hand, the 3-bromopropyltrimethoxysilane-modified bimetallic biochar can react with N,N-diallylaniline in starch-based flocculants to form quaternary ammonium salts, which further increases the charge density of the composite wastewater treatment agent and thus further improves the flocculation and sedimentation effect.

[0016] In a second aspect, the present invention provides a method for preparing the composite wastewater treatment agent according to the first aspect, comprising the following preparation steps:

[0017] (1) Weigh and prepare each raw material component;

[0018] (2) Mix starch-based flocculant and 15-20 parts by weight of dichloromethane evenly. Then, under nitrogen protection and reflux, add modified bimetallic biochar. Stir and react at 20-40°C for 14-16 hours. After cooling, filter and wash with ether 2-4 times. Dry under vacuum to constant weight. Then, under nitrogen protection, add 20-30 parts by weight of a mixture of ethanol and petroleum ether in a volume ratio of 3:1 and stir for 55-65 minutes. Then, add 0.5-0.72 parts by weight of N-bromosuccinimide and stir at 20-30°C for 55-65 minutes. Then, add another 0.5-0.72 parts by weight of N-bromosuccinimide and stir for another 55-65 minutes. Then, add another 0.36-0.5 parts by weight of N-bromosuccinimide and stir for another 3.5-4.5 hours. Then, quench with ice water, extract with ethyl acetate at least 3 times, dry with anhydrous sodium sulfate, and evaporate ethyl acetate to obtain the premix.

[0019] This invention first premixes a starch-based flocculant with modified bimetallic biochar. During this process, the 3-bromopropyltrimethoxysilane-modified bimetallic biochar reacts with N,N-diallylaniline in the starch-based flocculant to form a quaternary ammonium salt, introducing an electron-withdrawing quaternary ammonium salt onto the benzene ring of N,N-diallylaniline. Then, N-bromosuccinimide is introduced for bromination. During this process, the carbazole in the starch-based flocculant is brominated. Subsequently, when mixed and reacted with 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, the brominated carbazole reacts with 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine to form a structure with the triazine ring as the electron acceptor, the alkynyl group as the electron bridge, and N-phenylcarbazole as the electron donor. The D-π-A type conjugated polymer structure of the composite wastewater treatment agent of this invention is used under light irradiation. Under light irradiation, the electron acceptor captures photogenerated electrons, reducing oxygen to hydrogen peroxide. The electron bridge enhances carrier mobility, and the electron donor provides holes to oxidize water to hydrogen peroxide, forming an internal electric field. The formation of electron-withdrawing quaternary ammonium salts can reduce the electron cloud density of carbazole donors, increase the energy level difference between donors and acceptors, improve the driving force for photogenerated carrier separation, and further facilitate electron-hole separation, reducing exciton binding energy and thus promoting exciton separation. This is beneficial for the generation of hydrogen peroxide during wastewater treatment. The Fe-Mo metal-based modified bimetallic biochar synergistically activates hydrogen peroxide to degrade organic pollutants. The synergistic mechanism is as follows:

[0020] 2FeS2 + 7O2 + 2H2O → 2Fe(II) + 4SO4 2- +4H +

[0021] 2Fe(0) + O2 + 4H + →2Fe(II) + 2H₂O

[0022] Fe(II) + H₂O₂ → Fe(III) + ·OH + OH⁻ -

[0023] 2Fe(III) + Fe(O) → 3Fe(II)

[0024] 4·OH→·O2 - +2H2O

[0025] Fe(II) + O2 → Fe(III) + O2 -

[0026] Fe(III) + Mo(IV) → Fe(II) + Mo(V)

[0027] Fe(III) + Mo(V) → Fe(II) + Mo(VI)

[0028] Mo(VI)+·O2 - →Mo(V)+ 1 O2

[0029] Mo(V)+·O2 - →Mo(IV)+ 1 O2

[0030] Organic pollutants +·OH / ·O2 - / 1 O2 → intermediate → CO2 + H2O.

[0031] (3) The premix, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 0.05-0.06 parts by weight of bis(triphenylphosphine)palladium dichloride, and 0.008-0.012 parts by weight of cuprous iodide are mixed, and then 11-12 parts by weight of N,N-dimethylformamide are added. After ultrasonic treatment for 20-40 min, 8-9 parts by weight of triethylamine are added under room temperature and nitrogen protection. Then the mixture is stirred and reacted at 78-82℃ for 47-49 h. After filtration, the mixture is washed 2-4 times with ethanol and deionized water, and then vacuum dried to obtain a composite wastewater treatment agent.

[0032] Furthermore, the preparation steps of the starch-based flocculant are as follows:

[0033] Weigh 1.5 parts by weight of amylopectin and mix with 400-500 parts by weight of ultrapure water. Gelatinize in a water bath at 70-90°C for 55-65 minutes, then cool to 55-65°C. Add 7.4-7.6 parts by weight of active monomers, specifically 6 parts by weight of acrylamide, 0.7-0.8 parts by weight of unsaturated quaternary ammonium salt, and 0.7-0.8 parts by weight of N,N-diallylaniline. Then add 0.5-0.6 parts by weight of urea and 0.25-0.35 parts by weight of... Under nitrogen protection, 0.08–0.09 parts by weight of ammonium persulfate and 0.03–0.04 parts by weight of sodium bisulfite were added as initiators. The mixture was then reacted at 58–62 °C and a microwave frequency of 200 W for 25–35 min. The reaction was followed by extraction with acetone for 23–25 h, and washing multiple times with anhydrous ethanol to remove unreacted monomers. The mixture was then dried in a vacuum oven at 55–65 °C to constant weight, pulverized, and then mixed with water at a volume ratio of 3… Extract with a mixture of 2:1 ethylene glycol and glacial acetic acid for 5–7 h, then wash 4–6 times with anhydrous ethanol, and vacuum dry to constant weight at 55–65 °C. Then add 37–41 parts by mass of a 0.5–1 mol / L thallium trifluoroacetate solution in trifluoroacetic acid, and react at room temperature under infrared lamp irradiation with stirring for 5 days. Next, add a solution containing 1.32–1.34 parts by mass of potassium iodide and 10 parts by mass of water, stir for 10–20 min, and then add 0.8–1.2 parts by mass of sulfur. Sodium sulfate was added and stirred for 10–20 min. The mixture was then washed and filtered 4–6 times with deionized water and dried under vacuum at 55–65 °C to constant weight. The solution was then placed in 90–100 parts by mass of N,N-dimethylformamide containing 1.5–2 parts by mass of carbazole, along with 2.2–3 parts by mass of potassium carbonate and 0.9–1.2 parts by mass of cuprous iodide. The mixture was heated to 115–125 °C and stirred for 39–42 h. After naturally cooling to room temperature, the mixture was filtered to obtain a starch-based flocculant.

[0034] This invention first grafts active monomers, including N,N-diallylaniline, onto amylopectin using microwave-assisted free radical copolymerization. Then, after iodination, carbazole is introduced via a Ullmann reaction to form a starch-based flocculant containing N-phenylcarbazole.

[0035] Furthermore, the preparation steps of the modified bimetallic biochar are as follows:

[0036] 3-Bromopropyltrimethoxysilane, ethanol, and water were mixed in a mass ratio of 20:(71-73):(7-9) to obtain a mixed modified solution. Bimetallic biochar was immersed in the mixed modified solution and stirred and dispersed evenly at room temperature. Then, it was immersed and reacted at 20-40°C for 11-13 hours. After filtration, it was washed with anhydrous ethanol to remove residual 3-bromopropyltrimethoxysilane. Then, it was dried at 45-55°C for 3.5-4.5 hours to obtain modified bimetallic biochar. The mass ratio of 3-bromopropyltrimethoxysilane to bimetallic biochar was (10-12):1.

[0037] Furthermore, the preparation steps of the bimetallic biochar are as follows:

[0038] Solution A is prepared by dissolving 7-8 parts by mass of ferric nitrate nonhydrate in 100 parts by mass of ultrapure water; solution B is prepared by dissolving 0.9-1.1 parts by mass of ammonium molybdate tetrahydrate and 5.5-6.5 parts by mass of thiourea in 160 parts by mass of ultrapure water; solution B is prepared by adding 5 parts by mass of straw powder to solution A and stirring at 85-95°C until completely dry, then calcining at a nitrogen atmosphere at 695-705°C with a heating rate of 5°C / min for 110-130 min, then mixing with solution B and ultrasonically dispersing for 25-35 min to obtain the precursor; the precursor is sealed in a high-pressure autoclave lined with polytetrafluoroethylene, then heated in a drying oven at 195-205°C for 9.5-10.5 h, then collected with a magnet and washed at least 3 times alternately with ethanol and water, then dried in a vacuum freeze dryer, passed through a 40-60 mesh sieve, collected and sealed for storage.

[0039] Furthermore, the dosage of the composite wastewater treatment agent is 1.1–1.3 g / L; the composite wastewater treatment agent is used under light conditions, wherein the light intensity is 100 mW*cm. 2 The wavelength of the light source is controlled between 395 and 400 nm, and the pH of the wastewater is controlled between 7 and 11.

[0040] By adopting the above technical solution, the present invention has the following beneficial effects:

[0041] (1) The composite wastewater treatment agent of the present invention introduces starch-based flocculant, modified bimetallic biochar and crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine. The starch-based flocculant adsorbs and flocculates inorganic suspended particles through hydrogen bonding, electrostatic interaction and other interactions. The modified bimetallic biochar improves the removal effect of inorganic suspended solids and organic pollutants in wastewater by adsorbing inorganic suspended particles and organic pollutants.

[0042] (2) This invention grafts active monomers onto amylopectin using microwave-assisted free radical copolymerization. Specifically, the active monomers are grafted and copolymerized through the reactive sites of amylopectin, with the active sites located on C2 or C3 atoms of the glucose ring. Acrylamide-quaternary ammonium salt copolymers with high charge density are grafted onto the side of amylopectin. Through strong electrostatic interaction, supplemented by hydrogen bonding and other interactions, they interact with inorganic suspended matter such as montmorillonite to improve the flocculation and sedimentation effect. Then, after iodization, carbazole is introduced through the Ullmann reaction to form a starch-based flocculant containing N-phenylcarbazole. This allows the obtained starch flocculant to maintain good performance over a wide temperature range, which helps to enhance the adaptability of the flocculant under different environmental conditions.

[0043] (3) The bimetallic biochar of the present invention is obtained by loading nano-iron and molybdenum disulfide in two steps, namely calcination and hydrothermal method, using straw biomass as raw material. By introducing metallic iron, the composite sewage treatment agent is given magnetic properties, which facilitates the recovery of the composite sewage treatment agent through an external magnetic field.

[0044] (4) The bimetallic biochar modified by 3-bromopropyltrimethoxysilane of the present invention can, on the one hand, make the bimetallic biochar and starch flocculant more uniformly mixed and dispersed, and on the other hand, the bimetallic biochar modified by 3-bromopropyltrimethoxysilane can react with N,N-diallylaniline in starch-based flocculant to form quaternary ammonium salt, which further increases the charge density of the composite wastewater treatment agent and thus further improves the flocculation and sedimentation effect.

[0045] (5) In this invention, starch-based flocculant is first premixed with modified bimetallic biochar. During this process, 3-bromopropyltrimethoxysilane-modified bimetallic biochar can react with N,N-diallylaniline in the starch-based flocculant to form a quaternary ammonium salt. An electron-withdrawing quaternary ammonium salt is introduced onto the benzene ring of N,N-diallylaniline. Then, N-bromosuccinimide is introduced for bromination. During this process, carbazole in the starch-based flocculant is brominated. Subsequently, when it is mixed and reacted with 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, the brominated carbazole reacts and grafts with 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine to form a structure with the triazine ring as the electron acceptor and the ynyl group as the electron acceptor. The N-phenylcarbazole has a D-π-A type conjugated polymer structure as an electron donor. When the composite wastewater treatment agent of this invention is used under light irradiation, the electron acceptor captures photogenerated electrons, reducing oxygen to hydrogen peroxide. The electron bridge enhances carrier mobility, and the electron donor provides holes to oxidize water to hydrogen peroxide. The formation of the electron-withdrawing quaternary ammonium salt reduces the electron cloud density of the carbazole donor, increases the energy level difference between the donor and acceptor, and improves the driving force for photogenerated carrier separation, which is more conducive to electron-hole separation. This further promotes the generation of hydrogen peroxide during wastewater treatment. The Fe-Mo metal group in the modified bimetallic biochar can synergistically activate the hydrogen peroxide oxidation process, achieving the degradation of organic pollutants.

[0046] (6) The flocculant of the present invention uses starch as the main raw material and modified bimetallic biochar uses straw waste as raw material, which has a wide range of sources, low cost, and better economic benefits and environmental protection. Detailed Implementation

[0047] To better understand the above technical solution, the following will provide a detailed explanation of the technical solution in conjunction with specific implementation methods.

[0048] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0049] The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0050] Example 1

[0051] The preparation method of the composite wastewater treatment agent includes the following preparation steps:

[0052] (1) Weigh and prepare each raw material component according to the following mass parts: 10 parts by mass of starch-based flocculant, 0.8 parts by mass of modified bimetallic biochar, and 0.7 parts by mass of crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine;

[0053] (2) Mix starch-based flocculant and 15 parts by mass of dichloromethane evenly. Then add modified bimetallic biochar under nitrogen protection and reflux. Stir and react at 20°C for 14 h. After cooling, filter and wash twice with diethyl ether. Dry under vacuum to constant weight. Then add 20 parts by mass of a mixture of ethanol and petroleum ether in a volume ratio of 3:1 under nitrogen protection and stir for 55 min. Then add 0.5 parts by mass of N-bromosuccinimide and stir at 20°C for 55 min. Then add another 0.5 parts by mass of N-bromosuccinimide and stir for 55-65 min. Then add another 0.5 parts by mass of N-bromosuccinimide and stir for 3.5 h. Then quench with ice water, extract with ethyl acetate three times, dry with anhydrous sodium sulfate, and evaporate ethyl acetate to obtain the premix.

[0054] (3) The premix, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 0.05 parts by weight of bis(triphenylphosphine)palladium dichloride, and 0.008 parts by weight of cuprous iodide were mixed, and then 11 parts by weight of N,N-dimethylformamide were added. After ultrasonic treatment for 20 min, 8 parts by weight of triethylamine were added under room temperature and nitrogen protection. The mixture was then stirred and reacted at 78 °C for 47 h. After filtration, the mixture was washed twice with ethanol and deionized water, and then vacuum dried to obtain a composite wastewater treatment agent.

[0055] The preparation steps of the starch-based flocculant are as follows:

[0056] Weigh 1.5 parts by weight of amylopectin and mix with 400 parts by weight of ultrapure water. Gelatinize in a water bath at 70°C for 55 min, then cool to 55°C. Add 6 parts by weight of acrylamide, 0.7 parts by weight of unsaturated quaternary ammonium salt dimethyl diallyl ammonium chloride, and 0.7 parts by weight of N,N-diallyl aniline. Then add 0.5 parts by weight of urea and 0.25 parts by weight of sodium ethylenediaminetetraacetate. Under nitrogen protection, add 0.08 parts by weight of ammonium persulfate and 0.03 parts by weight of sodium bisulfite as initiators. Then react at 58°C and 200W microwave frequency for 25 min. Then extract with acetone for 23 h, and wash several times with anhydrous ethanol to remove unreacted monomers. Then dry in a vacuum drying oven at 55°C to constant weight. After pulverizing, mix with ethylene glycol and glacial acetic acid in a volume ratio of 3:2. The mixture was extracted for 5 hours, washed four times with anhydrous ethanol, and vacuum dried at 55°C to constant weight. Then, 37 parts by mass of a 0.5 mol / L thallium trifluoroacetate solution was added, and the mixture was stirred at room temperature for 5 days under infrared lamp irradiation. Then, a solution of 1.32 parts by mass of potassium iodide and 10 parts by mass of water was added, and the mixture was stirred for 10 minutes. Then, 0.8 parts by mass of sodium thiosulfate was added, and the mixture was stirred for another 10 minutes. The mixture was then washed and filtered four times with deionized water, and vacuum dried at 55°C to constant weight. Next, the mixture was placed in 90 parts by mass of N,N-dimethylformamide containing 1.5 parts by mass of carbazole, along with 2.2 parts by mass of potassium carbonate and 0.9 parts by mass of cuprous iodide. The mixture was heated to 115°C and stirred for 39 hours. After naturally cooling to room temperature, the mixture was filtered and vacuum dried at 55°C to constant weight to obtain the starch-based flocculant.

[0057] The preparation steps of the modified bimetallic biochar are as follows:

[0058] 3-Bromopropyltrimethoxysilane, ethanol, and water were mixed in a mass ratio of 20:71:9 to obtain a mixed modified solution. Bimetallic biochar was immersed in the mixed modified solution and stirred and dispersed evenly at room temperature. Then, it was immersed and reacted at 20°C for 11 hours. After filtration, it was washed with anhydrous ethanol to remove residual 3-bromopropyltrimethoxysilane and then dried at 45°C for 3.5 hours to obtain modified bimetallic biochar. The mass ratio of 3-bromopropyltrimethoxysilane to bimetallic biochar was 10:1.

[0059] The preparation steps of the bimetallic biochar are as follows:

[0060] Solution A was prepared by dissolving 7 parts by mass of ferric nitrate nonhydrate in 100 parts by mass of ultrapure water. Solution B was prepared by dissolving 0.9 parts by mass of ammonium molybdate tetrahydrate and 5.5 parts by mass of thiourea in 160 parts by mass of ultrapure water. Solution B was prepared by adding 5 parts by mass of straw powder to solution A and stirring at 85°C until completely dry. Then, the mixture was calcined at 695°C under a nitrogen atmosphere at a heating rate of 5°C / min for 110 min. The mixture was then ultrasonically dispersed with solution B for 25 min to obtain the precursor. The precursor was sealed in a high-pressure autoclave lined with polytetrafluoroethylene and heated at 195°C for 9.5 h in a drying oven. The precursor was then collected with a magnet and washed three times alternately with ethanol and water. It was then dried in a vacuum freeze dryer, passed through a 40-mesh sieve, collected, and sealed for storage.

[0061] The dosage of the composite wastewater treatment agent is 1.1 g / L; the composite wastewater treatment agent is used under light conditions, wherein the light intensity is 100 mW*cm. 2 The wavelength of the light source is controlled at 400nm, and the pH of the wastewater is controlled at 7.

[0062] Example 2

[0063] The preparation method of the composite wastewater treatment agent includes the following preparation steps:

[0064] (1) Weigh and prepare each raw material component according to the following mass parts: 11 mass parts of starch-based flocculant, 1 mass part of modified bimetallic biochar, and 0.75 mass parts of crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine.

[0065] (2) Starch-based flocculant and 18 parts by mass of dichloromethane were stirred and mixed evenly. Then, modified bimetallic biochar was added under nitrogen protection and reflux. The mixture was stirred and reacted at 30°C for 15 h. After cooling, the mixture was filtered, washed three times with diethyl ether, and dried under vacuum to constant weight. Then, under nitrogen protection, 25 parts by mass of a mixture of ethanol and petroleum ether in a volume ratio of 3:1 was added and stirred for 60 min. Then, 0.61 parts by mass of N-bromosuccinimide was added and stirred for 60 min at 25°C. Then, another 0.61 parts by mass of N-bromosuccinimide was added and stirred for another 60 min. Then, 0.43 parts by mass of N-bromosuccinimide was added and stirred for another 4 h. The mixture was then quenched with ice water, extracted three times with ethyl acetate, dried with anhydrous sodium sulfate, and the ethyl acetate was evaporated to obtain the premix.

[0066] (3) The premix, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 0.055 parts by weight of bis(triphenylphosphine)palladium dichloride, and 0.01 parts by weight of cuprous iodide were mixed, and then 11.5 parts by weight of N,N-dimethylformamide were added. After ultrasonic treatment for 30 min, 8.5 parts by weight of triethylamine were added under room temperature and nitrogen protection. The mixture was then stirred and reacted at 80 °C for 48 h. After filtration, the mixture was washed three times with ethanol and deionized water, and then vacuum dried to obtain a composite wastewater treatment agent.

[0067] The preparation steps of the starch-based flocculant are as follows:

[0068] Weigh 1.5 parts by weight of amylopectin and mix with 450 parts by weight of ultrapure water. Gelatinize in an 80°C water bath for 60 min, then cool to 60°C. Add 6 parts by weight of acrylamide, 0.75 parts by weight of unsaturated quaternary ammonium salt methacryloyloxyethyltrimethylammonium chloride, and 0.75 parts by weight of N,N-diallylaniline. Then add 0.55 parts by weight of urea and 0.3 parts by weight of sodium ethylenediaminetetraacetate. Under nitrogen protection, add 0.085 parts by weight of ammonium persulfate and 0.035 parts by weight of sodium bisulfite as initiators. Then react at 60°C and 200W microwave frequency for 30 min. Then extract with acetone for 24 h, and wash several times with anhydrous ethanol to remove unreacted monomers. Then dry in a vacuum drying oven at 60°C to constant weight. After pulverizing, use ethylene glycol at a volume ratio of 3:2. Extracted with a mixture of alcohol and glacial acetic acid for 6 h, then washed 5 times with anhydrous ethanol, and dried under vacuum at 60 °C to constant weight. Then, 40 parts by mass of a 0.8 mol / L thallium trifluoroacetate solution in trifluoroacetic acid were added, and the mixture was stirred at room temperature for 5 days under infrared lamp irradiation. Next, a solution of 1.33 parts by mass of potassium iodide in 10 parts by mass of water was added, and the mixture was stirred for 15 min. Then, 1 part by mass of sodium thiosulfate was added, and the mixture was stirred for another 15 min. The mixture was then washed with deionized water and filtered 5 times, and dried under vacuum at 60 °C to constant weight. Next, the mixture was placed in a solution of 1.8 parts by mass of carbazole in 98 parts by mass of N,N-dimethylformamide, along with 2.6 parts by mass of potassium carbonate and 1 part by mass of cuprous iodide. The mixture was heated to 120 °C and stirred for 40 h. After naturally cooling to room temperature, the mixture was filtered and dried under vacuum at 60 °C to constant weight to obtain a starch-based flocculant.

[0069] The preparation steps of the modified bimetallic biochar are as follows:

[0070] 3-Bromopropyltrimethoxysilane, ethanol, and water were mixed in a mass ratio of 20:72:8 to obtain a mixed modified solution. Bimetallic biochar was immersed in the mixed modified solution and stirred and dispersed evenly at room temperature. Then, it was immersed and reacted at 30°C for 12 hours. After filtration, it was washed with anhydrous ethanol to remove residual 3-bromopropyltrimethoxysilane and then dried at 50°C for 4 hours to obtain modified bimetallic biochar. The mass ratio of 3-bromopropyltrimethoxysilane to bimetallic biochar was 11:1.

[0071] The preparation steps of the bimetallic biochar are as follows:

[0072] 7.5 parts by mass of ferric nitrate nonahydrate were dissolved in 100 parts by mass of ultrapure water to obtain solution A; 1 part by mass of ammonium molybdate tetrahydrate and 6 parts by mass of thiourea were dissolved in 160 parts by mass of ultrapure water to obtain solution B; 5 parts by mass of straw powder were added to solution A and mixed, stirred at 90°C until completely dry, then calcined at 700°C under a nitrogen atmosphere at a heating rate of 5°C / min for 120 min, then mixed with solution B and ultrasonically dispersed for 30 min to obtain the precursor; the precursor was sealed in a polytetrafluoroethylene-lined autoclave, then heated at 200°C for 10 h in a drying oven, then collected with a magnet and washed three times alternately with ethanol and water, then placed in a vacuum freeze dryer for drying, passed through a 50-mesh sieve, collected and sealed for storage.

[0073] The dosage of the composite wastewater treatment agent is 1.2 g / L; the composite wastewater treatment agent is used under light conditions, wherein the light intensity is 100 mW*cm. 2 The wavelength of the light source is controlled at 400nm, and the pH of the wastewater is controlled at 9.

[0074] Example 3

[0075] The preparation method of the composite wastewater treatment agent includes the following preparation steps:

[0076] (1) Weigh and prepare each raw material component according to the following mass parts: 11 parts starch-based flocculant, 1.2 parts modified bimetallic biochar, and 0.8 parts crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine.

[0077] (2) Starch-based flocculant and 20 parts by mass of dichloromethane were stirred and mixed evenly. Then, modified bimetallic biochar was added under nitrogen protection and reflux. The mixture was stirred and reacted at 40°C for 16 h. After cooling, the mixture was filtered, washed 4 times with diethyl ether, and dried under vacuum to constant weight. Then, under nitrogen protection, 30 parts by mass of a mixture of ethanol and petroleum ether in a volume ratio of 3:1 was added and stirred for 65 min. Then, 0.72 parts by mass of N-bromosuccinimide was added and stirred at 30°C for 65 min. Then, another 0.72 parts by mass of N-bromosuccinimide was added and stirred for another 65 min. Then, 0.36 parts by mass of N-bromosuccinimide was added and stirred for another 4.5 h. The mixture was then quenched with ice water, extracted 3 times with ethyl acetate, dried with anhydrous sodium sulfate, and the ethyl acetate was evaporated to obtain the premix.

[0078] (3) The premix, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 0.06 parts by weight of bis(triphenylphosphine)palladium dichloride, and 0.012 parts by weight of cuprous iodide were mixed, and then 12 parts by weight of N,N-dimethylformamide were added. After ultrasonic treatment for 40 min, 9 parts by weight of triethylamine were added under room temperature and nitrogen protection. The mixture was then stirred and reacted at 82 °C for 49 h. After filtration, the mixture was washed 4 times with ethanol and deionized water, and then vacuum dried to obtain a composite wastewater treatment agent.

[0079] The preparation steps of the starch-based flocculant are as follows:

[0080] Weigh 1.5 parts by weight of amylopectin and mix with 500 parts by weight of ultrapure water. Gelatinize in a 90°C water bath for 65 min, then cool to 65°C. Add 6 parts by weight of acrylamide, 0.8 parts by weight of unsaturated quaternary ammonium salt acryloyloxyethyltrimethylammonium chloride, and 0.8 parts by weight of N,N-diallylaniline. Then add 0.6 parts by weight of urea and 0.35 parts by weight of sodium ethylenediaminetetraacetate. Under nitrogen protection, add 0.09 parts by weight of ammonium persulfate and 0.04 parts by weight of sodium bisulfite as initiators. Then react at 62°C and 200W microwave frequency for 35 min. Then extract with acetone for 25 h, and wash several times with anhydrous ethanol to remove unreacted monomers. Then dry in a vacuum drying oven at 65°C to constant weight. After pulverizing, mix with ethylene glycol at a volume ratio of 3:2. The mixture of glacial acetic acid was extracted for 7 hours, washed 6 times with anhydrous ethanol, and dried under vacuum at 65°C to constant weight. Then, 41 parts by mass of a 1 mol / L thallium trifluoroacetate solution in trifluoroacetic acid were added, and the mixture was stirred at room temperature under infrared lamp irradiation for 5 days. Then, a solution of 1.34 parts by mass of potassium iodide in 10 parts by mass of water was added, and the mixture was stirred for 20 minutes. Then, 1.2 parts by mass of sodium thiosulfate were added, and the mixture was stirred for another 20 minutes. The mixture was then washed and filtered 6 times with deionized water, and dried under vacuum at 65°C to constant weight. Next, the mixture was placed in 100 parts by mass of N,N-dimethylformamide containing 2 parts by mass of carbazole, along with 3 parts by mass of potassium carbonate and 1.2 parts by mass of cuprous iodide. The mixture was heated to 125°C and stirred for 42 hours. After naturally cooling to room temperature, the mixture was filtered and dried under vacuum at 65°C to constant weight to obtain a starch-based flocculant.

[0081] The preparation steps of the modified bimetallic biochar are as follows:

[0082] 3-Bromopropyltrimethoxysilane, ethanol, and water were mixed in a mass ratio of 20:73:7 to obtain a mixed modified solution. Bimetallic biochar was immersed in the mixed modified solution and stirred to disperse evenly at room temperature. Then, it was immersed and reacted at 40°C for 13 hours. After filtration, it was washed with anhydrous ethanol to remove residual 3-bromopropyltrimethoxysilane and then dried at 55°C for 4.5 hours to obtain modified bimetallic biochar. The mass ratio of 3-bromopropyltrimethoxysilane to bimetallic biochar was 12:1.

[0083] The preparation steps of the bimetallic biochar are as follows:

[0084] Solution A was prepared by dissolving 8 parts by mass of ferric nitrate nonhydrate in 100 parts by mass of ultrapure water. Solution B was prepared by dissolving 1.1 parts by mass of ammonium molybdate tetrahydrate and 6.5 parts by mass of thiourea in 160 parts by mass of ultrapure water. Solution B was prepared by adding 5 parts by mass of straw powder to solution A and stirring at 95°C until completely dry. Then, the mixture was calcined at 705°C under a nitrogen atmosphere at a heating rate of 5°C / min for 130 min. The mixture was then ultrasonically dispersed with solution B for 35 min to obtain the precursor. The precursor was sealed in a high-pressure autoclave lined with polytetrafluoroethylene and heated at 205°C for 10.5 h in a drying oven. The precursor was then collected with a magnet and washed three times alternately with ethanol and water. It was then dried in a vacuum freeze dryer, passed through a 60-mesh sieve, collected, and sealed for storage.

[0085] The dosage of the composite wastewater treatment agent is 1.3 g / L; the composite wastewater treatment agent is used under light conditions, wherein the light intensity is 100 mW*cm. 2 The wavelength of the light source is controlled at 400nm, and the pH of the wastewater is controlled at 11.

[0086] Comparative Example 1

[0087] The difference between Comparative Example 1 and Example 2 is that the starch-based flocculant is obtained by graft copolymerization of acrylamide, unsaturated quaternary ammonium salt and amylopectin, while the other components and steps are the same as in Example 2.

[0088] Comparative Example 2

[0089] The difference between Comparative Example 2 and Example 2 is that the composite wastewater treatment agent is prepared from commercially available cationic polyacrylamide, modified bimetallic biochar, and crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, while the remaining components and steps are the same as in Example 2.

[0090] Comparative Example 3

[0091] The difference between Comparative Example 3 and Example 2 is that the composite wastewater treatment agent is prepared from starch-based flocculant, bimetallic biochar, and crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, while the remaining components and steps are the same as in Example 2.

[0092] Comparative Example 4

[0093] The difference between Comparative Example 4 and Example 2 is that the composite wastewater treatment agent is made from starch-based flocculant and modified bimetallic biochar, while the other components and steps are the same as in Example 2.

[0094] Comparative Example 5

[0095] The difference between Comparative Example 5 and Example 2 lies in step (2), which is as follows: starch-based flocculant and 18 parts by mass of dichloromethane are stirred and mixed evenly, then modified bimetallic biochar is added, and the mixture is stirred and dispersed at room temperature for 4-6 hours. After cooling, it is filtered, washed three times with ether, and vacuum dried to constant weight to obtain a premix. The remaining components and steps are the same as in Example 2.

[0096] Example of effect

[0097] Add 2g of montmorillonite sample to 250mL of deionized water to prepare a slurry with a concentration of 8g / L. Stir at 1000r / min for 15 minutes to form a highly dispersed suspension. Transfer the suspension to a graduated cylinder. Accurately weigh the composite wastewater treatment agent of the examples and comparative examples, add 100mL of ultrapure water and stir thoroughly to dissolve it completely. Add the corresponding amount of composite wastewater treatment agent of the examples and comparative examples to the montmorillonite suspension respectively. Adjust the pH of the montmorillonite suspension to the pH value used in the corresponding examples or comparative examples with 0.1mol / L hydrochloric acid or 0.1mol / L sodium hydroxide. After settling for 20 minutes, test the transmittance of the supernatant.

[0098] 150 mL of 10 mg / L Rhodamine B was placed in a 250 mL beaker, followed by the addition of the composite wastewater treatment agent used in the examples and comparative examples. The beaker was stirred for 30 min under a mechanical stirrer to conduct an adsorption experiment, ensuring that the catalyst was saturated with the target organic matter. The beaker was then stirred under a xenon lamp for 1 h. The xenon lamp was equipped with a 400 nm filter, and the light intensity was 100 mW·cm. The pH was then adjusted to the pH value used in the examples or comparative examples, and the reaction was continued for 15 min. A sample was taken from the reaction system. A quantitative sample was taken out with a syringe and mixed with a certain volume of methanol solution to stop the catalytic oxidation reaction. The mixture sample was then filtered through a 0.22 μm nylon filter membrane, and the concentration of Rhodamine B in the sample was detected by a specific analytical instrument to test the removal rate of Rhodamine B. The experiment was conducted at room temperature (20 °C), and each adsorption-degradation experiment was performed in triplicate.

[0099] Table 1 below shows the performance test results of the composite wastewater treatment agents prepared in the examples and comparative examples:

[0100] Table 1

[0101]

[0102]

[0103] Table 1 shows that the composite wastewater treatment agents in Examples 1-3 have good flocculation and organic pollutant removal effects.

[0104] The difference between Comparative Example 1 and Example 2 is that the starch-based flocculant is obtained by graft copolymerization of acrylamide, unsaturated quaternary ammonium salt and amylopectin. The resulting composite wastewater treatment agent has a weaker flocculation effect and organic pollutant removal effect.

[0105] The difference between Comparative Example 2 and Example 2 is that the composite wastewater treatment agent is prepared from commercially available cationic polyacrylamide, modified bimetallic biochar, and crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine. The composite wastewater treatment agent prepared has a weaker flocculation effect and organic pollutant removal effect.

[0106] The difference between Comparative Example 3 and Example 2 is that the composite wastewater treatment agent is prepared by starch-based flocculant, bimetallic biochar, and crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine. The composite wastewater treatment agent prepared has a weaker flocculation effect and organic pollutant removal effect.

[0107] The difference between Comparative Example 4 and Example 2 is that the composite wastewater treatment agent is made from starch-based flocculant and modified bimetallic biochar, and the resulting organic pollutant removal effect is weaker.

[0108] The difference between Comparative Example 5 and Example 2 lies in step (2), which is as follows: starch-based flocculant and 18 parts by mass of dichloromethane are stirred and mixed evenly, then modified bimetallic biochar is added, and the mixture is stirred and dispersed at room temperature for 4-6 hours. After cooling, it is filtered, washed three times with ether, and vacuum dried to constant weight to obtain a premix. The flocculation effect and organic pollutant removal effect of the prepared composite sewage treatment agent are relatively weak.

[0109] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A composite wastewater treatment agent, characterized in that, By mass, the raw material components include 10-12 parts by mass of starch-based flocculant, 0.8-1.2 parts by mass of modified bimetallic biochar, and 0.7-0.8 parts by mass of crosslinking agent 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine.

2. The composite wastewater treatment agent according to claim 1, characterized in that, The starch flocculant is obtained by graft copolymerization of active monomers and amylopectin followed by the introduction of carbazole via the Ullmann reaction.

3. The composite wastewater treatment agent according to claim 2, characterized in that, The active monomers include at least acrylamide, unsaturated quaternary ammonium salt, and N,N-diallylaniline.

4. The composite wastewater treatment agent according to claim 3, characterized in that, The unsaturated quaternary ammonium salt includes any one of dimethyl diallyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and acryloyloxyethyl trimethyl ammonium chloride.

5. The composite wastewater treatment agent according to claim 1, characterized in that, The modified bimetallic biochar is prepared by modifying bimetallic biochar with 3-bromopropyltrimethoxysilane; the bimetallic biochar is obtained by loading nano-iron and molybdenum disulfide onto straw biomass through a two-step process of calcination and hydrothermal loading.

6. The method for preparing the composite wastewater treatment agent according to any one of claims 1 to 5, characterized in that, The preparation steps include the following: (1) Weigh and prepare each raw material component; (2) Mix starch-based flocculant and 15-20 parts by weight of dichloromethane evenly. Then add modified bimetallic biochar under nitrogen protection and reflux. Stir and react at 20-40°C for 14-16 hours. After cooling, filter, wash with ether, and vacuum dry to constant weight. Then add 20-30 parts by weight of a mixture of ethanol and petroleum ether under nitrogen protection and stir for 55-65 minutes. Then add 0.5-0.72 parts by weight of N-bromosuccinimide and stir and react at 20-30°C for 55-65 minutes. Then add another 0.5-0.72 parts by weight of N-bromosuccinimide and stir for another 55-65 minutes. Then add another 0.36-0.5 parts by weight of N-bromosuccinimide and stir for another 3.5-4.5 hours. Then quench with ice water, extract with ethyl acetate, dry, and evaporate ethyl acetate to obtain the premix. (3) The premix, 2,4,6-tris(4-ethynylphenyl)-1,3,5-triazine, 0.05-0.06 parts by weight of bis(triphenylphosphine)palladium dichloride, and 0.008-0.012 parts by weight of cuprous iodide are mixed, and then 11-12 parts by weight of N,N-dimethylformamide are added. After ultrasonic treatment for 20-40 min, 8-9 parts by weight of triethylamine are added under room temperature and nitrogen protection. Then the mixture is stirred and reacted at 78-82℃ for 47-49 h. After filtration, the mixture is washed with ethanol and deionized water and dried under vacuum to obtain a composite wastewater treatment agent.

7. The method for preparing the composite wastewater treatment agent according to claim 6, characterized in that, The preparation steps of the starch-based flocculant are as follows: After gelatinizing 1.5 parts by weight of amylopectin, the temperature was lowered to 58–62°C. 7.4–7.6 parts by weight of active monomer were added, followed by 0.5–0.6 parts by weight of urea and 0.25–0.35 parts by weight of sodium ethylenediaminetetraacetate. Under nitrogen protection, 0.11–0.13 parts by weight of initiator were added. The mixture was microwaved for 25–35 minutes, then extracted, washed, dried, and pulverized. The pulverized mixture was then added to 37–41 parts by weight of a 0.5–1 mol / L solution of thallium trifluoroacetate in trifluoroacetic acid. The mixture was reacted at room temperature for 5 days under infrared lamp irradiation. Finally, 11… Stir in 12 parts by weight of an 11.66%–11.82% potassium iodide aqueous solution for 10–20 min, then add 0.8–1.2 parts by weight of sodium thiosulfate, continue stirring for 10–20 min, then wash, filter, and dry. Place the solution in 90–100 parts by weight of N,N-dimethylformamide containing 1.5–2 parts by weight of carbazole, add 2.2–3 parts by weight of potassium carbonate and 0.9–1.2 parts by weight of cuprous iodide, heat to 115–125 °C, and stir for 39–42 h to obtain a starch-based flocculant.

8. The method for preparing the composite wastewater treatment agent according to claim 6, characterized in that, The preparation steps of the modified bimetallic biochar are as follows: 3-Bromopropyltrimethoxysilane, ethanol, and water were mixed in a mass ratio of 20:71-73:7-9 to obtain a mixed modified solution. Bimetallic biochar was immersed in the mixed modified solution and stirred and dispersed evenly at room temperature. Then, it was immersed and reacted at 20-40°C for 11-13 hours. After filtration, it was washed with anhydrous ethanol and dried to obtain modified bimetallic biochar. The mass ratio of 3-bromopropyltrimethoxysilane to bimetallic biochar was (10-12):

1.

9. The method for preparing the composite wastewater treatment agent according to claim 8, characterized in that, The preparation steps of the bimetallic biochar are as follows: Solution A is prepared by dissolving 7-8 parts by mass of ferric nitrate nonhydrate in 100 parts by mass of ultrapure water; solution B is prepared by dissolving 0.9-1.1 parts by mass of ammonium molybdate tetrahydrate and 5.5-6.5 parts by mass of thiourea in 160 parts by mass of ultrapure water; solution B is prepared by adding 5 parts by mass of straw powder to solution A and mixing, stirring at 85-95°C until completely dry, then calcining at 695-705°C under a nitrogen atmosphere for 110-130 min, then mixing with solution B and ultrasonically dispersing for 25-35 min to obtain the precursor; the precursor is sealed in an autoclave and heated at 195-205°C for 9.5-10.5 h, then collected with a magnet and washed alternately with ethanol and water, freeze-dried under vacuum, sieved, collected and sealed for storage.

10. The method for preparing the composite wastewater treatment agent according to claim 6, characterized in that, The dosage of the composite wastewater treatment agent is 1.1–1.3 g / L; the composite wastewater treatment agent is used under light conditions, wherein the wavelength of the light source is controlled at 395–400 nm, and the pH of the wastewater is controlled at 7–11.

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