Multi-element functional polyacrylamide-chitosan derivative composite flocculant and preparation method thereof

Abstract

The invention provides a multi-element functional polyacrylamide-chitosan derivative composite flocculant. The structural formula of the multi-element functional polyacrylamide-chitosan derivative composite flocculant is shown in the following formula (I): (I), wherein R1 is an anionic monomer, R2 is a cationic monomer, R3 is acrylamide, and R4 is a coupling monomer; the composite flocculant comprises the following raw materials in parts by weight: 85-92 parts of multi-component copolymerized polyacrylamide dry powder, 1-3 parts of a surface protective agent and 5-15 parts of a chitosan derivative. According to the composite flocculant, the removal rate of various heavy metal ions in high-concentration beneficiation wastewater can reach 95% or above, the removal rate of suspended solids exceeds 98%, and the composite flocculant also has a remarkable adsorption and removal effect on residual flotation reagents; the formed floc is thick, dense and high in settling velocity; the product is wide in application range, can maintain high efficiency performance in a pH value range of 3-10, and is low in dosage and low in cost.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a multifunctional polyacrylamide-chitosan derivative composite flocculant and its preparation method. Background Technology

[0002] In my country, wastewater from mining and mineral processing accounts for approximately 10% of all industrial wastewater annually. This massive volume of wastewater, with its complex composition including high levels of heavy metal ions, residual flotation reagents, and suspended particles, poses a serious threat to aquatic bodies and the surrounding ecological environment. Efficient purification of this wastewater has become a key challenge for the green and sustainable development of the non-ferrous metals industry. Currently, commonly used methods for treating mineral processing wastewater include physical, chemical, physicochemical, and biological methods. Among these, flocculation and sedimentation are widely adopted due to their good treatment effect, low cost, and wide applicability; the core of this method lies in the performance of the flocculant.

[0003] Organic polymeric flocculants, especially polyacrylamides, are important agents in mineral processing wastewater treatment. Traditional polyacrylamide flocculants include anionic, cationic, nonionic, and amphoteric types. However, mineral processing wastewater is complex in quality and has high pollutant concentrations. Single-ionic or single-function flocculants are insufficient to achieve simultaneous and efficient removal of heavy metal ions, suspended solids, and organic pollutants, often resulting in unstable flocculation, poor settling performance, and high sludge moisture content. These issues make it difficult to meet the requirements for deep purification and reuse of high-concentration wastewater.

[0004] Therefore, developing a composite flocculant that can remove multiple pollutants, is highly adaptable, efficient, and environmentally friendly is of great significance for promoting the advancement of mineral processing wastewater treatment technology and realizing the green transformation of the industry. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a multifunctional polyacrylamide-chitosan derivative composite flocculant and its preparation method. By utilizing the synergistic effects of charge neutralization, adsorption bridging and metal coupling, it improves the treatment efficiency of high-concentration mineral processing wastewater, removes heavy metals, suspended solid particles and residual flotation reagents from the wastewater through flocculation, and achieves efficient, green and safe purification effect.

[0006] This invention is achieved through the following technical solution:

[0007] On the one hand, a multifunctional polyacrylamide-chitosan derivative composite flocculant is provided, the structural formula of which is as follows (Ⅰ):

[0008] (I); R1 is an anionic monomer, R2 is a cationic monomer, R3 is acrylamide, and R4 is a coupling monomer; The composite flocculant comprises the following raw materials in parts by weight: 85-92 parts of multi-component copolymer polyacrylamide dry powder, 1-3 parts of surface protectant and 5-15 parts of chitosan derivative; The chitosan derivative has the following structural formula (II):

[0009] (II); R is any one of the graft copolymerization of carboxymethyl, hydroxyethyl, acyl, hydroxypropyl, quaternary ammonium, or other groups.

[0010] Furthermore, the surface protectant is selected from one or more of white oil, liquid paraffin, fatty alcohol polyoxyethylene ether, sorbitan fatty acid ester and its polyoxyethylene ether derivatives.

[0011] Further, the multi-component copolymer polyacrylamide dry powder comprises the following raw materials in weight percentage: 10-35% acrylamide monomer, 0.5%-20% anionic monomer, 0.5%-20% cationic monomer, 0.5%-10% coupling monomer, 0.5%-3% surfactant, 1%-5% cosolvent, 0.005%-0.05% chain transfer agent, 0.001%-0.03% redox initiator, 0.015%-0.2% azo initiator, and the balance being deionized water.

[0012] Another method for preparing the above-mentioned multifunctional polyacrylamide-chitosan derivative composite flocculant includes the following steps: Step S1: Weigh the raw materials according to the above mass percentages, and mix the acrylamide monomer, anionic monomer, cationic monomer, coupling monomer, surfactant and deionized water to obtain a mixed monomer aqueous solution; Step S2: Add a cosolvent to the obtained mixed monomer aqueous solution, adjust the pH value to 3.5-7 with acid solution, introduce inert gas, and then add azo initiator, chain transfer agent and redox initiator in sequence. Step S3: Initiate the polymerization reaction at 0-5℃. After the temperature of the reaction system rises to 60-95℃, maintain the temperature for 3-5 hours to obtain multi-component copolymer polyacrylamide blocks. Crush and granulate the obtained multi-component copolymer polyacrylamide blocks, dry and grind them at 70-100℃ to obtain multi-component copolymer polyacrylamide dry powder. Step S4: Mix the obtained multi-component copolymer polyacrylamide dry powder with a surface protectant to obtain functionalized polyacrylamide, and then mix it with chitosan derivatives to obtain the multi-component functionalized polyacrylamide-chitosan derivative composite flocculant.

[0013] This invention introduces chitosan derivatives into multifunctional polyacrylamide, enabling the two to form an interwoven network in the aqueous environment. This enhances the coupling and charge neutralization effect of the multifunctional polyacrylamide, thereby improving the removal efficiency of heavy metal ions in mineral processing wastewater. Furthermore, the surface protection treatment prevents the two from reacting during mixed storage, thus avoiding problems such as dissolution difficulties and dispersion in the aqueous system, and provides good barrier protection.

[0014] This invention uses acrylamide as the main chain backbone, combined with specific anionic / cationic monomers with adjustable charge density, and introduces functional coupling monomers containing electron-donating atoms such as nitrogen, oxygen, and sulfur, giving the polymer strong heavy metal chelating sites. At the same time, by utilizing a specific ratio between anionic monomers, cationic monomers, coupling monomers and acrylamide monomers, the charge distribution, spatial conformation and functional group density of the polymer chain are optimized, thereby giving it good charge neutralization, bridging adsorption and selective heavy metal capture capabilities, overcoming the shortcomings of traditional amphoteric polymers such as easy charge shielding and single function.

[0015] Furthermore, the anionic monomer is selected from one or more unsaturated organic acids and their alkali metal salts; the cationic monomer is selected from one or more unsaturated quaternary ammonium salts / tertiary amine salts.

[0016] Furthermore, the coupling monomer is selected from one or more of ureas containing an amino group or hydroxylamines containing a double bond.

[0017] Furthermore, the co-solvent is one or more of urea, sodium chloride, sodium sulfate, ammonium sulfate, and ammonium chloride.

[0018] Further, in step S2, the acid solution is any one of hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, and adipic acid.

[0019] Furthermore, the azo initiator is selected from one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptane, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 2,2-azo[2-(2-imidazolin-2-yl)propane] dihydrochloride, azobis(2,5-dimethyl-6-carboxy)hexane, and 4,4-azobis(4-cyanopentanoic acid).

[0020] Furthermore, the chitosan derivative is a derivative formed by chemical modification of chitosan, such as carboxymethylation, hydroxypropylation, quaternization, or graft copolymerization.

[0021] The beneficial effects of this invention are: (1) The composite flocculant of the present invention can remove more than 95% of various heavy metal ions in high-concentration mineral processing wastewater, remove more than 98% of suspended solids, and also has a significant adsorption and removal effect on residual flotation reagents; the flocs formed are large and dense, and the settling speed is fast. The main body can usually be settling within 5-15 minutes. The sludge volume is small and the water content is low. The product has a wide range of applications and can maintain high efficiency in the pH range of 3-10. The dosage is low and the treatment cost is low.

[0022] (2) The preparation method of this invention adopts a stepwise polymerization combined with a physical composite process, which is fundamentally different from existing one-step chemical grafting or photocatalytic synthesis techniques. In this invention, a multi-component copolymer polyacrylamide with tunable charge and structure is first synthesized, and then its powder is physically compounded with chitosan derivatives, rather than directly involving chitosan in the copolymerization. The charge neutralization and bridging ability of the product are precisely controlled during the polymerization stage. The introduction of chitosan further enhances the adsorption and biocompatibility of the product. Through surface protection treatment, the resulting composite flocculant is not prone to moisture absorption, clumping or degradation, and has a broad spectrum of pollutant removal capabilities and wide pH adaptability. This preparation method effectively avoids the problems of poor product uniformity and difficult process control commonly found in chemical grafting processes, and provides a new path for developing efficient, multifunctional and easily industrialized environmentally friendly flocculants.

[0023] (3) In the composite flocculant of the present invention, the anionic and cationic groups on the polymer chain can adaptively adjust their ionization state according to the pH of the water, neutralizing the surface charge of colloidal particles; the interwoven network formed by the long-chain polymer and chitosan derivative can strongly adsorb multiple particles, forming large and dense flocs; the functional groups such as carboxyl groups, amino groups, hydroxyl groups, catechol groups, and dithiocarbamate groups on the polymer chain and chitosan can react with heavy metal ions (such as Cu²⁺). + Pb² + Cd² + Zn² + (etc.) form stable five- or six-membered cyclic chelates, thereby converting them from the dissolved state to the solid phase for removal. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the preparation method of the multifunctional polyacrylamide-chitosan derivative composite flocculant in Example 1 of the present invention.

[0025] Figure 2 This is a schematic diagram of the polymerization process of multi-component copolymer polyacrylamide. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments. 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.

[0027] Example 1 A method for preparing a multifunctional polyacrylamide-chitosan derivative composite flocculant includes the following steps: Weigh the following raw materials by mass percentage: 21.25% acrylamide monomer, 3.10% N-hydroxymethylacrylamide, 3.10% 2-acrylamido-2-methylpropanesulfonic acid, 1.55% acryloyloxyethyltrimethylammonium chloride, 1.0% fatty alcohol polyoxyethylene ether (AEO-9), 2.0% urea, 0.005% chain transfer agent sodium hypophosphite, 0.002% ammonium persulfate, 0.002% sodium bisulfite, 0.08% azobisisobutyrazoline hydrochloride, and the balance is deionized water.

[0028] Acrylamide, N-hydroxymethylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acryloyloxyethyltrimethylammonium chloride, and fatty alcohol polyoxyethylene ether (AEO-9) were added to a reactor, followed by deionized water. The mixture was stirred until completely dissolved to form a homogeneous monomer aqueous solution. Urea was added to the obtained monomer aqueous solution, and the pH was adjusted to 4.0 with hydrochloric acid solution. Nitrogen gas was purged for 15 minutes to ensure complete air replacement. Then, azobisisobutyrazoline hydrochloride, chain transfer agent sodium hypophosphite, ammonium persulfate, and sodium bisulfite were added sequentially, and the reactor was sealed. The reactor was kept at 2°C to initiate the polymerization reaction. After about 150 minutes, the system temperature was naturally raised to 85°C and maintained at this temperature for 3-5 hours to obtain a transparent multi-component copolymer polyacrylamide block. The block was pulverized and granulated, continuously dried in a fluidized bed at 95°C to constant weight, and then ground to obtain a multi-component copolymer polyacrylamide dry powder. 88 parts of multi-component copolymer polyacrylamide dry powder were mixed with 2 parts of surface protectant (white oil: OP-10 = 4:1) to obtain functionalized polyacrylamide, which was then uniformly compounded with 12 parts of carboxymethyl chitosan in a mixer to obtain the finished product.

[0029] Example 2 A method for preparing a multifunctional polyacrylamide-chitosan derivative composite flocculant includes the following steps: Weigh the following raw materials by mass percentage: 20.00% acrylamide monomer, 1.50% hydroxyethyl methacrylate, 5.00% 2-acrylamide-2-methylpropanesulfonic acid, 3.50% methacryloyloxyethyltrimethylammonium chloride, 0.8% alkylphenol polyoxyethylene ether (OP-10), 2.0% urea, 0.002% ammonium persulfate, 0.002% sodium bisulfite, 0.06% azobisisobutyrazoline hydrochloride, with the balance being deionized water.

[0030] Acrylamide, hydroxyethyl methacrylate, 2-acrylamido-2-methylpropanesulfonic acid, methacryloyloxyethyltrimethylammonium chloride, and alkylphenol polyoxyethylene ether (OP-10) were added to a reactor, followed by deionized water. The mixture was stirred until completely dissolved to form a homogeneous monomer aqueous solution. Urea was added to the obtained monomer aqueous solution, and the pH was adjusted to 5.0 with hydrochloric acid solution. Nitrogen gas was purged for 15 minutes to ensure complete air replacement. Then, azobisisobutyrazoline hydrochloride, ammonium persulfate, and sodium bisulfite were added sequentially, and the reactor was sealed. The reactor was kept at 5°C to initiate the polymerization reaction. After approximately 120 minutes, the system temperature was allowed to rise naturally to 80°C and maintained at this temperature for 3-5 hours to obtain a transparent multi-component copolymer polyacrylamide block. The block was pulverized and granulated, continuously dried in a fluidized bed at 90°C to constant weight, and then ground to obtain a multi-component copolymer polyacrylamide dry powder. 85 parts of multi-component copolymer polyacrylamide dry powder were mixed with 2 parts of surface protectant (liquid paraffin: Tween-80 = 5:1) to obtain functionalized polyacrylamide, which was then uniformly compounded with 15 parts of quaternized chitosan in a mixer to obtain the finished product.

[0031] Example 3 A method for preparing a multifunctional polyacrylamide-chitosan derivative composite flocculant includes the following steps: Weigh the following raw materials by mass percentage: 20.75% acrylamide monomer, 1.45% N-hydroxymethylacrylamidourea, 1.2% methacrylic acid, 4.35% acryloyloxyethyltrimethylammonium chloride, 1.2% fatty alcohol polyoxyethylene ether (AEO-9), 2.0% urea, 0.06% azobisisopropylimidazoline hydrochloride (V-044), 0.003% ammonium persulfate, with the balance being deionized water.

[0032] Acrylamide, methacrylic acid, acryloyloxyethyltrimethylammonium chloride, N-hydroxymethylacrylamidourea, fatty alcohol polyoxyethylene ether, and urea were added sequentially to a reactor, followed by deionized water. Under stirring and the action of surfactants, a homogeneous and stable monomer dispersion was formed. The pH of the obtained monomer dispersion was adjusted to 5.5 with adipic acid solution, and nitrogen gas was purged for 15 minutes to replace the air. Azobisisopropylimidazoline hydrochloride (V-044) and ammonium persulfate were added sequentially, and the reactor was sealed. The reactor was heated to 40°C to initiate the copolymerization reaction. Polymerization was carried out at this temperature for 240 minutes to obtain a multi-component copolymer polyacrylamide block. The colloid was pulverized and granulated, then placed in a forced-air drying oven and continuously and carefully dried at 80°C until constant weight. Finally, the dried product was ground and granulated to obtain a multi-component copolymer polyacrylamide powder. 92 parts of multi-component copolymer polyacrylamide dry powder were mixed with 2.5 parts of surface protectant (liquid paraffin: Span-80 = 3:1) to obtain functionalized polyacrylamide, which was then uniformly compounded with 8 parts of hydroxypropyl chitosan in a mixer to obtain the finished product.

[0033] Example 4 A method for preparing a multifunctional polyacrylamide-chitosan derivative composite flocculant includes the following steps: Weigh the following raw materials by mass percentage: 25.05% acrylamide monomer, 1.60% acrylamide urea, 3.20% acrylic acid, 1.60% acryloyloxyethyltrimethylammonium chloride, 0.5% fatty alcohol polyoxyethylene ether (AEO-9), 1.0% urea, 0.01% chain transfer agent sodium formate, 0.06% azobisisobutyrazoline hydrochloride, 0.0025% ammonium persulfate, 0.0025% sodium bisulfite, with the balance being deionized water.

[0034] Acrylamide, acrylamide urea, acrylic acid, acryloyloxyethyltrimethylammonium chloride, and fatty alcohol polyoxyethylene ether were added to a reactor, followed by deionized water. The mixture was stirred until completely dissolved to form a homogeneous monomer aqueous solution. Urea was added to the resulting monomer aqueous solution, and the pH was adjusted to 3.8 with hydrochloric acid solution. Nitrogen was purged for 15 minutes to ensure complete air replacement. Then, chain transfer agents sodium formate, azobisisobutyrazoline hydrochloride, ammonium persulfate, and sodium bisulfite were added sequentially, and the reactor was sealed. The copolymerization reaction was initiated in a 10°C ice-water bath. The reaction system was slowly heated, and finally aged at 75°C for 3-5 hours to obtain a transparent multi-component copolymer polyacrylamide block. The block was pulverized and granulated, then continuously dried in a forced-air drying oven or fluidized bed at 95°C until constant weight. The dried product was then ground and granulated to obtain multi-component copolymer polyacrylamide powder. 90 parts of multi-component copolymer polyacrylamide dry powder were mixed with 1.5 parts of white oil to obtain functionalized polyacrylamide, which was then uniformly compounded with 10 parts of industrial-grade carboxymethyl chitosan in a mixer to obtain the finished product.

[0035] Comparative Example 1 A method for preparing a multifunctional polyacrylamide-chitosan derivative composite flocculant includes the following steps: Weigh the following raw materials by mass percentage: 21.25% acrylamide monomer, 3.10% N-hydroxymethylacrylamide, 3.10% 2-acrylamido-2-methylpropanesulfonic acid, 1.55% acryloyloxyethyltrimethylammonium chloride, 12% carboxymethyl chitosan, 1.0% fatty alcohol polyoxyethylene ether (AEO-9), 2.0% urea, 0.005% chain transfer agent sodium hypophosphite, 0.002% ammonium persulfate, 0.002% sodium bisulfite, 0.08% azobisisobutyrazoline hydrochloride, with the balance being deionized water.

[0036] Acrylamide, N-hydroxymethylacrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acryloyloxyethyltrimethylammonium chloride, carboxymethyl chitosan, fatty alcohol polyoxyethylene ether (AEO-9), and some deionized water were added to a reactor and stirred to form a viscous and unevenly mixed dispersion. Urea was added to the dispersion, and the pH was adjusted to 4.0 with hydrochloric acid solution. After purging with nitrogen for 15 minutes to replace the air, azobisisobutyrazoline hydrochloride, chain transfer agent sodium hypophosphite, ammonium persulfate, and sodium bisulfite were added sequentially, and the reactor was sealed. Polymerization was initiated by holding the reactor at 2°C. The polymerization reaction was slow and exothermic. After about 200 minutes of reaction, the system temperature slowly rose to 80°C and was aged at this temperature for 5 hours to obtain a product with uneven color and localized gel-like structure. The obtained product was pulverized and granulated, and dried at 95°C. After drying, the product showed severe agglomeration and high hardness. After vigorous grinding, a powder with uneven particle size and poor flowability was obtained. The powder was mixed with 2.0% of a surface protectant (white oil: OP-10 = 4:1) to obtain the control sample.

[0037] Effect Example For Example 1 The physicochemical properties of the samples obtained in Example 4 and Comparative Example 1 were characterized, and the test data are shown in Table 1 below: Table 1 Example 1 Characterization of physicochemical properties of samples obtained in Example 4 and Comparative Example 1

[0038] As shown in Table 1, in Comparative Example 1, the carboxymethyl chitosan macromolecules exhibit steric hindrance and chain transfer effects in the polymerization system, hindering the chain growth reaction of monomers such as acrylamide, resulting in a product molecular weight that is much lower than that in Example 1.

[0039] Example 1 The samples obtained from Example 4 and Comparative Example 1 were used to treat simulated mineral processing wastewater. The specific test conditions and results are shown in Table 2 below: Table 2 Example 1 The samples obtained from Example 4 and Comparative Example 1 were used to treat simulated mineral processing wastewater.

[0040] As shown in Table 2, the multifunctional polyacrylamide-chitosan derivative composite flocculant sample prepared in Example 1 of this invention exhibits a strong and specific adsorption capacity for high-concentration heavy metal ions. The sample in Example 2 demonstrates excellent stability and adaptability within a wide pH range (3-11). The sample in Example 3 shows a synergistic and enhanced treatment effect on complex wastewater with high suspended solids and high heavy metal concentrations. The sample in Example 4 achieves excellent cost-effectiveness while maintaining sufficient ionicity and functional groups. In contrast, Comparative Example 1 suffers from poor flocculation performance due to problems such as low molecular weight, product heterogeneity, and poor solubility caused by its preparation process. The coupling monomers of this invention provide abundant coordination sites, achieving efficient capture by forming stable complexes with heavy metal ions. At the same time, the anion and cation ratios ensure the synergistic effect of charge neutralization and bridging during the flocculation process. The anionic and cationic monomers provide balanced and pH-independent permanent charges, enabling the polymer to maintain molecular chain extension and effective charge neutralization capacity even under extreme pH conditions, overcoming the defect of traditional flocculants being easily deactivated in non-neutral environments.

[0041] The composite flocculant of this invention can achieve a removal rate of over 95% for multiple heavy metal ions in high-concentration mineral processing wastewater, a removal rate of over 98% for suspended solids (SS), and also has a significant adsorption and removal effect on residual flotation reagents. The formed flocs are large and dense, with fast settling speed, small sludge volume, and low water content. The product has a wide range of applications, can maintain high efficiency in the pH range of 3-10, and has a low dosage, resulting in economical treatment costs.

[0042] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. 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 multifunctional polyacrylamide-chitosan derivative composite flocculant, characterized in that, Its structural formula is as follows (Ⅰ): （Ⅰ）； R1 is an anionic monomer, R2 is a cationic monomer, R3 is acrylamide, and R4 is a coupling monomer; The composite flocculant comprises the following raw materials in parts by weight: 85-92 parts of multi-component copolymer polyacrylamide dry powder, 1-3 parts of surface protectant and 5-15 parts of chitosan derivative; The chitosan derivative has the following structural formula (II): （Ⅱ）； R is any one of the graft copolymerization of carboxymethyl, hydroxyethyl, acyl, hydroxypropyl, quaternary ammonium, or other groups.

2. The multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 1, characterized in that, The surface protectant is selected from one or more of white oil, liquid paraffin, fatty alcohol polyoxyethylene ether, sorbitan fatty acid ester and its polyoxyethylene ether derivatives.

3. The multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 1, characterized in that, The multi-component copolymer polyacrylamide dry powder comprises the following raw materials in weight percentage: 10-35% acrylamide monomer, 0.5%-20% anionic monomer, 0.5%-20% cationic monomer, 0.5%-10% coupling monomer, 0.5%-3% surfactant, 1%-5% cosolvent, 0.005%-0.05% chain transfer agent, 0.001%-0.03% redox initiator, 0.015%-0.2% azo initiator, and the balance being deionized water.

4. A method for preparing the multifunctional polyacrylamide-chitosan derivative composite flocculant as described in claims 1-3, characterized in that, Includes the following steps: Step S1: Weigh the raw materials according to the above mass percentages, and mix the acrylamide monomer, anionic monomer, cationic monomer, coupling monomer, surfactant and deionized water to obtain a mixed monomer aqueous solution; Step S2: Add a cosolvent to the obtained mixed monomer aqueous solution, adjust the pH value to 3.5-7 with acid solution, introduce inert gas, and then add azo initiator, chain transfer agent and redox initiator in sequence. Step S3: Initiate the polymerization reaction at 0-5℃. After the temperature of the reaction system rises to 60-95℃, maintain the temperature for 3-5 hours, pulverize and granulate, and dry and grind at 70-100℃ to obtain multi-component copolymer polyacrylamide dry powder. Step S4: Mix the obtained multi-component copolymer polyacrylamide dry powder with a surface protectant to obtain functionalized polyacrylamide, and then mix it with chitosan derivatives to obtain the multi-component functionalized polyacrylamide-chitosan derivative composite flocculant.

5. The multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 4, characterized in that, The anionic monomer is selected from one or more unsaturated organic acids and their alkali metal salts; the cationic monomer is selected from one or more unsaturated quaternary ammonium salts / tertiary amine salts.

6. The multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 4, characterized in that, The coupling monomer is selected from one or more of ureas containing an amino group or hydroxylamines containing a double bond.

7. The preparation method of the multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 4, characterized in that, The co-solvent is one or more of urea, sodium chloride, sodium sulfate, ammonium sulfate, and ammonium chloride.

8. The preparation method of the multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 4, characterized in that, In step S2, the acid solution is any one of hydrochloric acid, phosphoric acid, sulfuric acid, acetic acid, and adipic acid.

9. The preparation method of the multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 4, characterized in that, The azo initiator is selected from one or more of azobisisobutyronitrile, azobisisovalerate, azobisisoheptane, dimethyl azobisisobutyrate, azobisisobutylamidine hydrochloride, 2,2-azo[2-(2-imidazolin-2-yl)propane] dihydrochloride, azobis(2,5-dimethyl-6-carboxy)hexane, and 4,4-azobis(4-cyanopentanoic acid).

10. The multifunctional polyacrylamide-chitosan derivative composite flocculant according to claim 4, characterized in that, The chitosan derivatives are derivatives formed by chemical modification of chitosan, such as carboxymethylation, hydroxypropylation, quaternization, or graft copolymerization.

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