A bio-based green flocculant and a preparation method and application thereof

Abstract

The application relates to the technical field of water treatment, in particular to a bio-based green flocculant and a preparation method and application thereof. The preparation method of the bio-based green flocculant comprises the following steps: mixing a first reaction monomer and a second reaction monomer according to 5-8 g / mL, stirring uniformly after adding water, adding modified magnetic microparticles with a mass fraction of 3-6% of the first reaction monomer, adding a reaction promoter after nitrogen is passed, reacting for 5-8 h under water bath at 45-55 DEG C, filtering, washing, drying, crushing and obtaining; the modified magnetic microparticles are prepared by modifying cis-9-octadecenoic acid; the flocculant is combined with cationic monomers and magnetic microparticles through graft copolymerization, has excellent flocculation performance and magnetic separation performance, has high removal rates of turbidity, chemical oxygen demand and chroma of papermaking wastewater, has short magnetic separation time, has the advantages of environmental friendliness, recyclability and the like, has a simple preparation process, and is suitable for industrialized production.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, specifically to a bio-based green flocculant, its preparation method, and its application. Background Technology

[0002] With the acceleration of industrialization, the discharge of various industrial wastewaters, especially papermaking wastewater, has been increasing year by year, posing a serious threat to the ecological environment and human health. Papermaking wastewater has a complex composition, mainly containing high concentrations of suspended solids, lignin, cellulose, hemicellulose, resin, pigments, and various chemical additives. It is characterized by high chemical oxygen demand (COD), high color, and poor biodegradability. Direct discharge without effective treatment will lead to eutrophication of receiving water bodies, the death of aquatic organisms, and severe disruption of the aquatic ecological balance. Therefore, developing efficient, economical, and environmentally friendly wastewater treatment technologies has become a research hotspot in the current water treatment field.

[0003] Flocculation is widely used in papermaking wastewater treatment due to its advantages such as simple operation, high treatment efficiency, and relatively low cost. Flocculants, as the core of flocculation, directly determine the treatment effect. Traditional flocculants are mainly divided into inorganic flocculants, such as polyaluminum chloride and polyferric sulfate, and organic synthetic polymer flocculants, such as polyacrylamide. Although inorganic flocculants are inexpensive, they have problems such as large dosage, large amount of sludge production, and high levels of aluminum or iron ion residues in the treated water, which may cause secondary pollution to the environment and human health. Organic synthetic polymer flocculants have advantages such as fast flocculation speed and low dosage, but most are difficult to biodegrade, and their monomer residues, such as acrylamide monomer, often have neurotoxicity and teratogenicity, posing significant environmental safety risks.

[0004] In recent years, with the increasing awareness of environmental protection and the development of green chemistry, the development of environmentally friendly bio-based flocculants has become a research hotspot. Bio-based flocculants are mainly derived from natural polymers or their modified products, and have advantages such as wide availability of raw materials, biodegradability, and non-toxicity. However, single natural polymer flocculants often have disadvantages such as low molecular weight, low charge density, and unstable flocculation activity, which limit their practical application. By introducing synthetic polymer chains into the natural polymer backbone through chemical modification methods such as graft copolymerization, composite flocculants with both good flocculation performance and biodegradability can be obtained.

[0005] On the other hand, traditional flocculants are often difficult to separate and recover from water after application, which not only wastes resources but may also cause new environmental problems. In recent years, magnetic separation technology has attracted attention due to its advantages such as fast separation speed, simple operation, and no need for complex equipment. Introducing magnetic particles into flocculants to prepare magnetically responsive flocculants can achieve rapid separation and recycling of flocculants under the action of an external magnetic field, significantly reducing treatment costs and secondary pollution. However, most of the magnetic flocculants reported so far suffer from problems such as poor dispersion of magnetic particles, weak bonding with organic matrices, and complex preparation processes, which limit their large-scale application.

[0006] Therefore, the present invention provides a bio-based green flocculant, its preparation method and application, to solve the above-mentioned technical problems. Summary of the Invention

[0007] This invention provides a bio-based green flocculant, its preparation method, and its application. The prepared flocculant combines cationic monomers with magnetic microparticles through graft copolymerization, exhibiting both excellent flocculation and magnetic separation performance. It has high removal rates of turbidity, chemical oxygen demand, and color in papermaking wastewater, short magnetic separation time, and advantages such as environmental friendliness and recyclability. The preparation process is simple and suitable for industrial production.

[0008] To achieve the above objectives, the present invention provides the following technical solution: On the one hand, the present invention provides a method for preparing a bio-based green flocculant, comprising the following steps: mixing a first reactive monomer and a second reactive monomer at a dosage ratio of 5-8 g / mL, then adding deionized water at a volume of 30-50 times that of the second reactive monomer, mixing and stirring at a speed of 300-500 r / min for 20-30 min, then adding modified magnetic microparticles at a mass of 3-6% of the first reactive monomer, dispersing them evenly, and then introducing nitrogen gas into the mixture, adding a reaction promoter after 20-40 min, and then stirring and reacting in a water bath at 45-55℃ for 5-8 h; after the reaction is completed, filtering the reaction solution, washing the filter cake with acetone 3-5 times, transferring it to a vacuum drying device, vacuum drying at a temperature of 60-80℃, and then pulverizing it to obtain the final bio-based green flocculant.

[0009] Furthermore, the first reaction monomer is any one of acrylamide, methacrylamide, N,N-dimethylacrylamide, and dimethylaminopropylacrylamide.

[0010] Furthermore, the second reaction monomer is any one of acryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, methacryloyloxyethyltrimethylammonium chloride, and dimethylaminoethyl methacrylate.

[0011] Furthermore, the reaction promoter is composed of an oxidant and a reducing agent, and the amount of the oxidant added is 0.05-0.1% of the mass of the first reaction monomer, and the amount of the reducing agent added is 2-5% of the mass of the first reaction monomer.

[0012] Furthermore, the oxidant is any one of potassium persulfate, ammonium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide.

[0013] Furthermore, the reducing agent is any one of sodium bisulfite, sodium metabisulfite, and sodium thiosulfate.

[0014] Furthermore, the modified magnetic microparticles are prepared by the following method: magnetic microparticles are added to deionized water at a dosage ratio of 5-8 g / mL, ultrasonically dispersed for 20-30 min, and then cis-9-+octadecenoic acid (1-1.5 times the volume of deionized water) is slowly added to the resulting dispersion. After uniform dispersion, the temperature of the resulting mixed phase is raised to 55-65℃, and the mixture is kept at this temperature and shaken for 20-30 h. After the reaction is completed, the reaction solution is filtered, and the resulting filter cake is washed with acetone 3-5 times. Then, it is transferred to a vacuum drying device and vacuum dried at 60-80℃ for 20-30 h to obtain the modified magnetic microparticles.

[0015] Furthermore, the magnetic microparticles are prepared by the following method: ferric chloride, ferrous chloride, and deionized water are mixed and stirred evenly in a mass ratio of 6-10:2-5:80-120. Under nitrogen protection, the temperature of the resulting mixed solution is raised to 65-75°C and kept at this temperature for 30-50 minutes. Then, 20-30 wt% deionized water and 20-30% ammonia solution are added to the reaction solution, and the reaction is carried out at 65-75°C for 30-50 minutes. Next, the temperature of the reaction solution is raised to 85-95°C and kept at this temperature for 60-80 minutes. The reactants are then filtered, washed with deionized water, magnetically screened, and vacuum dried sequentially to obtain the magnetic microparticles.

[0016] On the other hand, the present invention provides a bio-based green flocculant, which is prepared by the above-described preparation method.

[0017] Thirdly, the application of the bio-based green flocculant prepared by this invention in the treatment of papermaking wastewater.

[0018] Compared with the prior art, the beneficial effects of the present invention are: 1. The bio-based green flocculant prepared by this invention has excellent flocculation performance. By copolymerizing the cationic second reactive monomer with the first reactive monomer, a high density of positively charged groups is introduced into the flocculant molecular chain. This enables the effective adsorption of suspended particles, colloidal substances, and dissolved organic matter in negatively charged papermaking wastewater through charge neutralization. At the same time, the bridging effect of the polymer chains aggregates fine flocs into large and dense flocs, significantly improving the removal efficiency of turbidity, color, and chemical oxygen demand.

[0019] 2. The flocculant of this invention also possesses highly efficient magnetic separation performance. By introducing cis-9-octadecenoic acid-modified magnetic microparticles in situ during the polymerization reaction, a strong bond between the magnetic microparticles and the polymer matrix is ​​achieved. The carboxyl groups in the cis-9-octadecenoic acid molecule form coordination bonds with the iron atoms on the surface of the magnetic microparticles, while the long-chain alkyl groups and carbon-carbon double bonds can undergo hydrophobic interactions and copolymerization reactions with the polymer chains, thereby ensuring the uniform dispersion and stable anchoring of the magnetic microparticles in the flocculant. Under the action of an external magnetic field, this flocculant can be rapidly separated from the treated water, exhibiting high magnetic separation efficiency, significantly shortening the solid-liquid separation time, reducing treatment costs, and avoiding secondary pollution caused by flocculant residue.

[0020] 3. The flocculant of this invention exhibits excellent environmental friendliness and biodegradability. The selected first and second reactant monomers introduce biodegradable amide and ester bonds into the polymer backbone formed after polymerization, allowing for gradual degradation into smaller molecules by microorganisms in the natural environment. Simultaneously, the cis-9-octadecenoic acid on the surface of the modified magnetic microparticles is a natural fatty acid, and the magnetic microparticles themselves are iron(III) oxide, demonstrating good biocompatibility. The entire flocculant system avoids the use of toxic and harmful monomers, conforming to the principles of green chemistry.

[0021] 4. This invention employs an aqueous free radical polymerization system, resulting in a lower reaction temperature, eliminating the need for high pressure or strong acid / alkali conditions, and thus offering low energy consumption and high safety. The redox initiation system effectively initiates the polymerization reaction at lower temperatures, avoiding side reactions and excessively broad molecular weight distributions that may occur with high-temperature polymerization. Each step is simple to operate, and all reagents used are common chemicals, which helps reduce production costs and enable large-scale production.

[0022] 5. The flocculant of this invention is recyclable and reusable, offering excellent economic benefits. Thanks to its superior magnetic response performance, the used flocculant can be efficiently recovered under the influence of a magnetic field. After simple regeneration, it can be reused for flocculation treatment of papermaking wastewater, significantly reducing the cost of flocculant use and demonstrating significant economic and environmental benefits. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] Example 1 A method for preparing a bio-based green flocculant includes the following steps: mixing a first reactive monomer and a second reactive monomer at a ratio of 5 g / mL, then adding deionized water at a volume of 30 times that of the second reactive monomer, mixing and stirring at 300 r / min for 30 min, then adding modified magnetic microparticles at a mass of 3% of the first reactive monomer, dispersing them evenly, then introducing nitrogen gas, adding a reaction promoter after 20 min, and then stirring and reacting in a water bath at 45℃ for 8 h; after the reaction is complete, filtering the reaction solution, washing the filter cake three times with acetone, transferring it to a vacuum drying device, vacuum drying at 60℃, and then pulverizing it to obtain the final bio-based green flocculant; The first reactant monomer is acrylamide; the second reactant monomer is acryloyloxyethyltrimethylammonium chloride.

[0025] The reaction promoter consists of potassium persulfate and sodium bisulfite, with the amount of potassium persulfate added being 0.05% of the mass of the first reaction monomer and the amount of sodium bisulfite added being 2% of the mass of the first reaction monomer.

[0026] The modified magnetic microparticles were prepared by the following method: magnetic microparticles were added to deionized water at a dosage ratio of 5 g / mL, and ultrasonically dispersed for 20 min. Then, cis-9-+octadecenoic acid was slowly added to the resulting dispersion in an equal volume to deionized water. After uniform dispersion, the temperature of the resulting mixed phase was raised to 55℃ and kept at this temperature with shaking for 20 h. After the reaction was completed, the reaction solution was filtered first. The resulting filter cake was washed three times with acetone and then transferred to a vacuum drying device. After vacuum drying at 60℃ for 30 h, the modified magnetic microparticles were obtained.

[0027] Magnetic microparticles were prepared by the following method: Ferric chloride, ferrous chloride, and deionized water were mixed and stirred evenly in a mass ratio of 6:2:80. Under nitrogen protection, the temperature of the resulting mixed solution was raised to 65°C and kept at this temperature for 50 min. Then, 20 wt% deionized water and 20% ammonia solution were added to the reaction solution, and the reaction was carried out at 65°C for 50 min. The temperature of the reaction solution was then raised to 85°C and kept at this temperature for 80 min. The reactants were then filtered, washed with deionized water, magnetically screened, and vacuum dried sequentially to obtain the magnetic microparticles.

[0028] Example 2 A method for preparing a bio-based green flocculant includes the following steps: mixing a first reactive monomer and a second reactive monomer at a ratio of 6 g / mL, then adding deionized water at a volume of 40 times that of the second reactive monomer, mixing and stirring at 400 r / min for 25 min, then adding modified magnetic microparticles at a mass of 5% of the first reactive monomer, dispersing them evenly, then introducing nitrogen gas, adding a reaction promoter after 30 min, and then stirring and reacting in a water bath at 50℃ for 6 h; after the reaction is complete, filtering the reaction solution, washing the filter cake four times with acetone, transferring it to a vacuum drying device, vacuum drying at 70℃, and then pulverizing it to obtain the final bio-based green flocculant; The first reactant monomer is methacrylamide; the second reactant monomer is dimethyl diallyl ammonium chloride.

[0029] The reaction promoter consists of ammonium persulfate and sodium metabisulfite, with the amount of ammonium persulfate added being 0.08% of the mass of the first reaction monomer and the amount of sodium metabisulfite added being 3% of the mass of the first reaction monomer.

[0030] The modified magnetic microparticles were prepared by the following method: magnetic microparticles were added to deionized water at a dosage ratio of 6 g / mL, and ultrasonically dispersed for 25 min. Then, cis-9-+octadecenoic acid with a volume of 1.5 times that of deionized water was slowly added to the resulting dispersion. After uniform dispersion, the temperature of the resulting mixed phase was raised to 60℃ and kept at this temperature with shaking for 25 h. After the reaction was completed, the reaction solution was filtered first. The resulting filter cake was washed 4 times with acetone and then transferred to a vacuum drying device. After vacuum drying at 70℃ for 25 h, the modified magnetic microparticles were obtained.

[0031] Magnetic microparticles were prepared by the following method: Ferric chloride, ferrous chloride, and deionized water were mixed and stirred evenly in a mass ratio of 8:3:100. Under nitrogen protection, the temperature of the resulting mixed solution was raised to 70°C and kept at this temperature for 40 min. Then, 25 wt% deionized water and 25% ammonia solution were added to the reaction solution, and the reaction was carried out at 70°C for 40 min. The temperature of the reaction solution was then raised to 90°C and kept at this temperature for 70 min. The reactants were then filtered, washed with deionized water, magnetically screened, and vacuum dried sequentially to obtain the magnetic microparticles.

[0032] Example 3 A method for preparing a bio-based green flocculant includes the following steps: mixing a first reactive monomer and a second reactive monomer at a ratio of 8 g / mL, then adding deionized water at a volume of 50 times that of the second reactive monomer, mixing and stirring at 500 r / min for 20 min, then adding modified magnetic microparticles at a mass of 6% of the first reactive monomer, dispersing them evenly, then introducing nitrogen gas, adding a reaction promoter after 40 min, and then stirring and reacting in a water bath at 55℃ for 5 h; after the reaction is complete, filtering the reaction solution, washing the filter cake five times with acetone, transferring it to a vacuum drying device, vacuum drying at 80℃, and then pulverizing it to obtain the final bio-based green flocculant; The first reactant monomer is N,N-dimethylacrylamide; the second reactant monomer is methacryloyloxyethyltrimethylammonium chloride.

[0033] The reaction promoter consists of hydrogen peroxide and sodium calomel, with the amount of hydrogen peroxide added being 0.1% of the mass of the first reaction monomer and the amount of sodium calomel added being 5% of the mass of the first reaction monomer.

[0034] The modified magnetic microparticles were prepared by the following method: magnetic microparticles were added to deionized water at a dosage ratio of 8 g / mL, and ultrasonically dispersed for 30 min. Then, cis-9-+octadecenoic acid with a volume of 1.5 times that of deionized water was slowly added to the resulting dispersion. After uniform dispersion, the temperature of the resulting mixed phase was raised to 65℃, and the mixture was kept at this temperature and shaken for 20 h. After the reaction was completed, the reaction solution was filtered first. The resulting filter cake was washed 5 times with acetone and then transferred to a vacuum drying device. After vacuum drying at 80℃ for 20 h, the modified magnetic microparticles were obtained.

[0035] Magnetic microparticles were prepared by the following method: Ferric chloride, ferrous chloride, and deionized water were mixed and stirred evenly in a mass ratio of 10:5:120. Under nitrogen protection, the temperature of the resulting mixed solution was raised to 75°C and kept at this temperature for 30 min. Then, 30 wt% deionized water and 30% ammonia solution were added to the reaction solution, and the reaction was carried out at 75°C for 30 min. The temperature of the reaction solution was then raised to 95°C and kept at this temperature for 60 min. The reactants were then filtered, washed with deionized water, magnetically screened, and vacuum dried sequentially to obtain the magnetic microparticles.

[0036] Comparative Example: The difference between this comparative example and Example 1 is that an equal amount of magnetic microparticles are used instead of modified magnetic microparticles in this comparative example.

[0037] Performance testing: The bio-based green flocculant samples prepared in Examples 1-3 and the comparative examples were tested as follows: 1. Flocculation performance test of papermaking wastewater treatment Wastewater source: Combined wastewater from a paper mill; water quality indicators are as follows: Turbidity: 850 NTU Chemical oxygen demand (COD): 1200 mg / L Color intensity: 320 times (dilution ratio method) pH value: 7.2 Test method: Take 500 mL of papermaking wastewater and add the bio-based green flocculant sample to be tested at a dosage of 20 mg / L. Stir rapidly at 200 rpm for 1 min on a six-stage stirrer, then slowly stir at 40 rpm for 10 min. After stirring, apply an external magnetic field (magnetic field strength 0.2 T) to the flocculation system containing magnetic particles for magnetic separation. The separation time is recorded as the time required for the flocs to be completely attracted to the magnetic source side. For the control group without magnetic particles, allow natural sedimentation for 30 min. Then, take the supernatant at 2 cm from the liquid surface and measure the turbidity, COD, and color to calculate the removal rate.

[0038] The turbidity removal rate (%) is calculated as follows: (Initial turbidity - Treated turbidity) / Initial turbidity × 100% COD removal rate / % = (Initial COD - Treated COD) / Initial COD × 100% Color removal rate / % = (Initial color - Processed color) / Initial color × 100% 2. Magnetic separation efficiency test Test method: After the flocculation reaction is completed, place the reaction container above a magnet with a magnetic field strength of 0.2T, let it stand for 5 minutes, take a water sample 1 cm away from the liquid surface, measure the concentration of suspended solids, and calculate the magnetic separation efficiency according to the following formula. Wherein, magnetic separation efficiency / % = (initial suspended solids concentration - suspended solids concentration after separation) / initial suspended solids concentration × 100% 3. Flocculant recovery rate and reuse performance test Test Method: After initial use, the bio-based green flocculant sample was collected under a magnetic field, washed three times with deionized water, and then vacuum-dried to constant weight at 60°C. The recovered flocculant was then reused for flocculation treatment of the same wastewater (dosage 20 mg / L), repeating the flocculation and magnetic separation operations. The recovery rate (recovered mass / dosage mass × 100%) and flocculation performance (turbidity removal rate) were recorded each time until the flocculation performance significantly decreased (turbidity removal rate below 80%).

[0039] 4. Observation of the dispersibility of magnetic particles Test method: The prepared bio-based green flocculant sample was prepared into a 0.1 wt% aqueous solution, dropped onto a copper grid, and after negative staining with phosphotungstic acid, the dispersion state of magnetic particles in the polymer matrix was observed under a transmission electron microscope (TEM, accelerating voltage 120 kV).

[0040] The test data obtained above is recorded in the table below:

[0041] By comparing and analyzing the relevant data in the table, it can be seen that the flocculant prepared by this invention combines cationic monomers with magnetic microparticles through graft copolymerization, exhibiting both excellent flocculation and magnetic separation performance. It demonstrates high removal rates of turbidity, chemical oxygen demand, and color from papermaking wastewater, short magnetic separation time, and advantages such as environmental friendliness and recyclability. Furthermore, the preparation process is simple and suitable for industrial production. Therefore, this invention provides a bio-based green flocculant, its preparation method, and its application, which have broader market prospects and are more suitable for widespread application.

[0042] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0043] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A process for the preparation of a bio-based green flocculant, characterized by, Includes the following steps: Mix the first and second reactants at a ratio of 5-8 g / mL, then add 30-50 times the volume of the second reactant in deionized water. Mix and stir at 300-500 r / min for 20-30 min until homogeneous. Add 3-6% by mass of the first reactant modified magnetic microparticles, disperse them evenly, and then purge with nitrogen gas. After 20-40 min, add the reaction promoter, and then stir and react in a water bath at 45-55℃ for 5-8 h. After the reaction is complete, filter the reaction solution, wash the filter cake with acetone 3-5 times, and then transfer it to a vacuum drying device. After vacuum drying at 60-80℃, it is then pulverized to obtain the final bio-based green flocculant.

2. A process for the preparation of a bio-based green flocculant according to claim 1, characterized by: The first reaction monomer is any one of acrylamide, methacrylamide, N,N-dimethylacrylamide, and dimethylaminopropylacrylamide.

3. The method for preparing a bio-based green flocculant according to claim 1, characterized in that: The second reaction monomer is any one of acryloyloxyethyltrimethylammonium chloride, dimethyl diallyl ammonium chloride, methacryloyloxyethyltrimethylammonium chloride, and dimethylaminoethyl methacrylate.

4. The method for preparing a bio-based green flocculant according to claim 1, characterized in that: The reaction promoter is composed of an oxidant and a reducing agent, and the amount of the oxidant added is 0.05-0.1% of the mass of the first reaction monomer, and the amount of the reducing agent added is 2-5% of the mass of the first reaction monomer.

5. The method for preparing a bio-based green flocculant according to claim 4, characterized in that: The oxidant is any one of potassium persulfate, ammonium persulfate, hydrogen peroxide, and tert-butyl hydroperoxide.

6. The method for preparing a bio-based green flocculant according to claim 4, characterized in that: The reducing agent is any one of sodium bisulfite, sodium metabisulfite, and sodium thiosulfate.

7. The method for preparing a bio-based green flocculant according to claim 1, characterized in that, The modified magnetic microparticles are prepared by the following method: magnetic microparticles are added to deionized water at a dosage ratio of 5-8 g / mL, and ultrasonically dispersed for 20-30 min. Then, cis-9-+octadecenoic acid with a volume of 1-1.5 times that of deionized water is slowly added to the resulting dispersion. After uniform dispersion, the temperature of the resulting mixed phase is raised to 55-65℃, and the mixture is kept at this temperature and shaken for 20-30 h. After the reaction is completed, the reaction solution is filtered first. The resulting filter cake is washed with acetone 3-5 times and then transferred to a vacuum drying device. After vacuum drying at 60-80℃ for 20-30 h, the modified magnetic microparticles are obtained.

8. The method for preparing a bio-based green flocculant according to claim 7, characterized in that, The magnetic microparticles are prepared by the following method: ferric chloride, ferrous chloride, and deionized water are mixed and stirred evenly in a mass ratio of 6-10:2-5:80-120. Under nitrogen protection, the temperature of the resulting mixed solution is raised to 65-75℃ and kept at this temperature for 30-50 minutes. Then, 20-30 wt% deionized water and 20-30% ammonia solution are added to the reaction solution, and the reaction is carried out at 65-75℃ for 30-50 minutes. Next, the temperature of the reaction solution is raised to 85-95℃ and kept at this temperature for 60-80 minutes. The reactants are then filtered, washed with deionized water, magnetically screened, and vacuum dried sequentially to obtain the magnetic microparticles.

9. A bio-based green flocculant, characterized in that: It is prepared by the preparation method according to any one of claims 1-8.

10. The application of a bio-based green flocculant as described in claim 9 in the treatment of papermaking wastewater.

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