A branched polyacrylamide flocculant and a method for its preparation

Abstract

This invention relates to a branched polyacrylamide flocculant and its preparation method. The raw materials for preparing the polyacrylamide flocculant include, by parts: 170-280 parts acrylamide crystals, 5-25 parts methacrylamide propyltrimethylammonium chloride, 30-95 parts cationic monomer, 0.1-0.7 parts triallyl isocyanurate, 2-15 parts perfluoroalkyl acrylate monomer, 0.3-1.5 parts crosslinking agent, 0.5-3 parts co-solvent, 1-6 parts allylamine, 1.5-7.5 parts polyether monomer, 550-670 parts water, 0.05-1.8 parts chain transfer agent, and 0.001-0.5 parts mixed initiator. The branched polyacrylamide flocculant of this invention has advantages such as high flocculation efficiency, high floc strength, strong anti-interference ability, and wide applicability. It can effectively improve separation efficiency and separation quality, and can be mass-produced, thus having significant industrial application value.

Description

Technical Field

[0001] This invention relates to the field of composite materials technology, and in particular to a branched polyacrylamide flocculant and its preparation method. Background Technology

[0002] With the explosive growth of the global new energy industry, lithium, as a core strategic resource, has a large market demand. Currently, the industrial development of lepidolite mines mainly adopts the process of "flotation enrichment - acid leaching lithium extraction - solid-liquid separation". Among them, flocculants are the core auxiliary agents connecting "leaching" and "separation", and their performance directly determines the lithium oxide recovery rate and sludge treatment cost.

[0003] In the existing technology, the flocculants used in lithium mica mining are mostly traditional linear polyacrylamide derivatives, which have the following significant technical defects: low lithium oxide recovery efficiency and serious resource waste; poor sludge dewatering performance; poor connection between flotation and flocculation processes; traditional flocculants lack functional groups for regulating foam performance, which can easily lead to "flotation foam breaking too quickly" or "foam carrying sludge during flocculation", affecting the overall process efficiency. In summary, existing technologies cannot simultaneously achieve the goals of "high lithium recovery rate, low sludge moisture content, and strong process synergy." Developing a targeted and optimized branched polyacrylamide flocculant is key to breaking through the bottleneck of efficient development of lithium mica mines. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing flocculants have poor flocculation effect, low efficiency in the recovery of lepidolite ore, and are not easy to separate the actual products after flocculation.

[0005] To address the aforementioned technical problems, this invention provides a polyacrylamide flocculant. The raw materials for preparing the polyacrylamide flocculant, by parts, include: 170-280 parts of acrylamide crystals, 5-25 parts of methacrylamide propyltrimethylammonium chloride, 30-95 parts of cationic monomer, 0.1-0.7 parts of triallyl isocyanurate, 2-15 parts of perfluoroalkyl acrylate monomer, 0.3-1.5 parts of crosslinking agent, 0.5-3 parts of prosolvent, 1-6 parts of allylamine, 1.5-7.5 parts of polyether monomer, 550-670 parts of water, 0.05-1.8 parts of chain transfer agent, and 0.001-0.5 parts of mixed initiator.

[0006] The acrylamide crystals described in this invention are 170 to 280 parts, for example, 170 parts, 180 parts, 200 parts, 220 parts, 240 parts, or 280 parts.

[0007] The methacrylamide propyltrimethylammonium chloride of the present invention is 5 to 25 parts, for example, 5 parts, 10 parts, 15 parts or 25 parts, etc.

[0008] The cationic monomer of the present invention is 30 to 95 parts, for example, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts or 95 parts, etc.

[0009] Preferably, the cationic monomer includes at least two of (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride, (meth)acryloyloxyethyl trimethyl ammonium chloride, or diallylamine hydrochloride; more preferably, it is a combination of methacryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and diallylamine hydrochloride.

[0010] In some embodiments, the complexation ability of flocculants on metal ions on the surface of lepidolite is improved by introducing cationic groups such as methacryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and diallylamine hydrochloride.

[0011] In some embodiments, compared to a single cationic monomer, a combination of multiple cationic monomers can avoid the defects of uneven charge distribution and limited complexing ability that exist with a single cationic monomer. This allows the flocculant to achieve both rapid flocculation and efficient complexation of metal ions in complex lithium mica slurry systems, thereby improving separation efficiency and quality.

[0012] The chain transfer agent described in this invention is used in quantities of 0.05 to 1.8 parts, for example, 0.05 parts, 0.1 parts, 0.5 parts, 1 part, 1.2 parts, or 1.8 parts.

[0013] Preferably, the chain transfer agent comprises any one or a combination of at least two of sodium formate, isopropanol, sodium hypophosphite, and sodium methacrylate sulfonate, with sodium methacrylate sulfonate being the most preferred.

[0014] The mixed initiator described in this invention is 0.001 to 0.5 parts, for example, it can be 0.001 parts, 0.1 parts, 0.2 parts, 0.3 parts, 0.4 parts or 0.5 parts, etc.

[0015] Preferably, the mixed initiator is a combination of an azo initiator and a redox initiator. In this invention, the ratio of the azo initiator to the redox initiator is sufficient to initiate the reaction, and the combination is appropriate.

[0016] The azo initiator includes any one or a combination of at least two of azobisisobutyramidine dihydrochloride, azobisisoheptanenitrile, azobisisobutyramidonitrile, and 4,4'-azobis(4-cyanopentanoic acid), preferably azobisisobutyramidine dihydrochloride.

[0017] The redox initiator includes any one or a combination of at least two of benzoyl peroxide, ammonium persulfate, potassium persulfate, sodium bisulfite, formaldehyde, ferrous sulfate, or sodium bisulfite, preferably ammonium persulfate and sodium bisulfite.

[0018] The amount of triallyl isocyanurate is 0.1 to 0.7 parts, for example, 0.1 parts, 0.2 parts, 0.5 parts or 0.7 parts, etc.

[0019] In this invention, triallyl isocyanurate, as an auxiliary crosslinking monomer, can form a mild crosslinking structure with the main monomer, taking into account both the water solubility and adsorption activity of the flocculant, and avoiding the problem of decreased solubility caused by excessive crosslinking.

[0020] The perfluoroalkyl acrylate monomer of the present invention is 2 to 15 parts, for example, 2 parts, 5 parts, 10 parts or 15 parts, etc.

[0021] Preferably, the perfluoroalkyl acrylate monomer is perfluorododecylethyl acrylate.

[0022] In this invention, perfluorododecyl ethyl acrylate is used as the key modifying monomer. Perfluoroalkyl groups possess extremely strong hydrophobicity and surface activity, enabling them to form a hydrophobic layer on the surface of flocculant molecules. This enhances the flocculant's adsorption capacity for hydrophobic impurities in the slurry, expands the flocculant's applicability, and solves the problems of weak adsorption capacity and incomplete separation of hydrophobic impurities in existing flocculants. Simultaneously, the introduction of perfluoroalkyl groups improves the hydrophobicity of the flocs, reduces floc dispersion in water, accelerates floc settling speed, and improves solid-liquid separation efficiency. Compared to other perfluoroalkyl acrylate monomers, perfluorododecyl ethyl acrylate has a suitable carbon chain length, ensuring both hydrophobic effect and preventing a decrease in flocculant solubility due to excessively long carbon chains, thus achieving a balance between hydrophobic properties and water solubility.

[0023] The crosslinking agent described in this invention is 0.3 to 1.5 parts, for example, 0.3 parts, 0.5 parts, 0.8 parts, 1 part, 1.2 parts, or 1.5 parts.

[0024] Preferably, the crosslinking agent is trimethylolpropane triacrylate.

[0025] In some embodiments, the addition of crosslinking agents with specific structures can significantly improve flocculation speed and efficiency: linear polyacrylamide relies solely on single-chain adsorption of particles, while the branched and network structures formed by crosslinking have more "adsorption sites," enabling the simultaneous capture of multiple slurry particles or colloids, allowing flocs to aggregate rapidly. It can also enhance floc strength and stability: the crosslinked molecular structure forms a "network skeleton," resulting in denser flocs that are less prone to breakage. In subsequent plate and frame filtration, pump conveying, and other processes, the flocs will not disintegrate due to external shear forces.

[0026] The co-solvent used in this invention is 0.5 to 3 parts, for example, it can be 0.5 parts, 1 part, 2 parts or 3 parts, etc.

[0027] Preferably, the co-solvent includes at least two of N,N-dimethylformamide, N,N-dimethylacetamide, urea, or sodium dodecylbenzenesulfonate, and more preferably N,N-dimethylformamide and urea.

[0028] The allylamine described in this invention is in the form of 1 to 6 parts, for example, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, or 6 parts.

[0029] The polyether monomer of the present invention is 1.5 to 7.5 parts, for example, it can be 1.5 parts, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts or 7.5 parts, etc.

[0030] Preferably, the polyether monomer comprises dodecylamine polyoxyethylene ether and / or laurylamine polyoxyethylene ether, with dodecylamine polyoxyethylene ether being the most preferred.

[0031] The branched polyacrylamide flocculant provided by this invention is particularly suitable for the flocculation of lepidolite ore.

[0032] In a second aspect, the present invention provides a method for preparing a branched polyacrylamide flocculant as described in the first aspect, the method comprising the following steps: (1) Acrylamide crystals, methacrylamide propyltrimethylammonium chloride, cationic monomer, triallyl isocyanurate, perfluoroalkyl acrylate monomer, crosslinking agent, co-solvent, allylamine, polyether monomer, and water are mixed and the pH value is adjusted to obtain a mixed solution. (2) Add chain transfer agent and mixed initiator to the mixed solution obtained in step (1) to carry out copolymerization reaction. After the copolymerization reaction is completed, granulate, dry and sieve the product to obtain the branched polyacrylamide flocculant.

[0033] In the preparation process of this invention, after the components described in step (1) are mixed, they can be ultrasonically treated for 20 minutes under stirring at 250-300 rpm to form a homogeneous and transparent solution. In step (2), the copolymerization reaction is carried out by nitrogen purging to remove oxygen: high-purity nitrogen gas is introduced into the mixture for 15-30 minutes, with dissolved oxygen measured every 5 minutes during this period. The final drying conditions are: the particles are transferred to a drying oven and dried at 60-80℃ for 2-4 hours, controlling the moisture content of the finished product to ≤8%.

[0034] Preferably, the pH value in step (1) is 3.5 to 4.5, for example, it can be 3.5, 3.8, 4, 4.2 or 4.5.

[0035] Preferably, the temperature of the copolymerization reaction in step (2) is 0~2℃ and the reaction time is 4~5h.

[0036] Preferably, the particle size of the granulation in step (2) is 2~6mm, for example, it can be 2mm, 3mm, 4mm, 5mm, 6mm, etc.

[0037] The implementation of this invention has the following beneficial effects: Conventional polyacrylamide flocculants in existing technologies are mostly linear structures, which have poor adaptability to slurry systems with fine particles and high dispersion of lepidolite, resulting in problems such as slow settling speed, easy floc breakage, and incomplete solid-liquid separation. This invention enhances the charge neutralization capacity of lepidolite particles through the synergistic effect of the charge of composite cationic monomers; simultaneously, it introduces trimethylolpropane triacrylate to construct a branched cross-linked structure, improving molecular chain bridging efficiency, resulting in flocs with high density and strength, capable of rapidly capturing finely dispersed particles in the slurry and significantly accelerating the settling rate. The introduction of perfluorododecyl ethyl acrylate monomer endows the flocculant with good pollution resistance and interfacial activity, reducing the interference of impurity ions and organic pollutants in the slurry on the flocculation effect, and adapting it to the complex media environment of lepidolite slurry.

[0038] The branched polyacrylamide flocculant of this invention has advantages such as high flocculation efficiency, high floc strength, strong anti-interference ability, and wide applicability. It is especially suitable for solid-liquid separation of complex systems such as lithium mica slurry, which can effectively improve separation efficiency and quality, reduce production costs, and the preparation method is simple and controllable, enabling large-scale production and having important industrial application value. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1 This embodiment provides a branched polyacrylamide flocculant. The composition includes 220 parts of acrylamide crystals, 8 parts of methacrylamide propyltrimethylammonium chloride, 15 parts of methacryloxyethyl dimethylbenzylammonium chloride, 20 parts of methacryloxyethyl trimethylammonium chloride, 16 parts of diallylamine hydrochloride, 0.2 parts of triallyl isocyanurate, 3.5 parts of perfluorododecyl ethyl acrylate, 0.46 parts of trimethylolpropane triacrylate, 0.5 parts of N,N-dimethylformamide, 1.5 parts of urea, 1.5 parts of allylamine, 2.8 parts of dodecylamine polyoxyethylene ether, 590 parts of water, 0.8 parts of sodium methacrylate sulfonate, 0.2 parts of azobisisobutyramidine dihydrochloride, 0.015 parts of ammonium persulfate, and 0.02 parts of sodium bisulfite.

[0041] Preparation process: (1) Preparation of the mixture: Add the following to the polymerization reactor: acrylamide crystals, methacrylamide propyltrimethylammonium chloride, methacryloxyethyl dimethylbenzylammonium chloride, methacryloxyethyl trimethylammonium chloride, diallylamine hydrochloride, triallyl isocyanurate, perfluorododecyl ethyl acrylate, trimethylolpropane triacrylate, N,N-dimethylformamide, urea, allylamine, dodecylamine polyoxyethylene ether, and deionized water; Stirring and dispersion: Sonicate at 250-300 rpm for 20 min to form a homogeneous and transparent solution; adjust the pH to 3.5-4.5 using hydrochloric acid. Adjust the temperature to 0-2℃.

[0042] (2) Copolymerization: Nitrogen purging for oxygen removal: High-purity nitrogen gas is purged into the mixture for 25 minutes, with dissolved oxygen measured every 5 minutes during this period; polymerization is initiated by adding sodium methacrylate sulfonate, azobisisobutyramidine dihydrochloride, ammonium persulfate, and sodium bisulfite, and the reaction ends when the temperature stops rising after 5 hours. Granulation: The polymer blocks obtained from the copolymerization reaction are fed into a granulator for granulation, with a particle size of 2-6 mm.

[0043] Drying: Transfer the granules into a drying oven and dry at 60-80℃ for 2-4 hours, controlling the moisture content of the finished product to ≤8%; Grinding and sieving: The dried particles are ground by a pulverizer and then passed through an 80-mesh standard sieve. The material passing through the sieve is collected, which is the finished product of lepidolite branched polyacrylamide flocculant.

[0044] Example 2 This embodiment provides a branched polyacrylamide flocculant. The composition includes 185 parts of acrylamide crystals, 22 parts of methacrylamide propyltrimethylammonium chloride, 15 parts of methacryloxyethyl dimethylbenzylammonium chloride, 10 parts of acryloyloxyethyl dimethylbenzylammonium chloride, 27 parts of acryloyloxyethyl trimethylammonium chloride, 10 parts of diallylamine hydrochloride, 0.3 parts of triallyl isocyanurate, 3.5 parts of perfluorododecyl ethyl acrylate, 0.7 parts of trimethylolpropane triacrylate, 0.7 parts of N,N-dimethylformamide, 2 parts of urea, 3 parts of allylamine, 2.8 parts of dodecylamine polyoxyethylene ether, 570 parts of water, 0.6 parts of sodium methacrylate sulfonate, 0.2 parts of azobisisobutyramidine dihydrochloride, 0.015 parts of ammonium persulfate, and 0.02 parts of sodium bisulfite.

[0045] The preparation process is the same as in Example 1.

[0046] Example 3 This embodiment provides a branched polyacrylamide flocculant. The composition includes 180 parts of acrylamide crystals, 15 parts of methacrylamide propyltrimethylammonium chloride, 15 parts of methacryloxyethyl dimethylbenzylammonium chloride, 33 parts of acryloyloxyethyl trimethylammonium chloride, 12 parts of diallylamine hydrochloride, 0.1 parts of triallyl isocyanate, 2 parts of perfluorododecyl ethyl acrylate, 0.2 parts of trimethylolpropane triacrylate, 0.6 parts of N,N-dimethylformamide, 1 part of urea, 3 parts of allylamine, 2.8 parts of dodecylamine polyoxyethylene ether, 600 parts of water, 0.9 parts of sodium methacrylate sulfonate, 0.25 parts of azobisisobutyramidine dihydrochloride, 0.015 parts of ammonium persulfate, and 0.025 parts of sodium bisulfite.

[0047] The preparation process is the same as in Example 1.

[0048] Comparative Example 1 The difference between this comparative example and Example 1 is that some components are different, but the preparation process is the same. Acrylamide crystals 220 parts, methacrylamide propyltrimethylammonium chloride 8 parts, methacryloxyethyl dimethylbenzylammonium chloride 41 parts, triallyl isocyanurate 0.2 parts, perfluorododecyl ethyl acrylate 3.5 parts, trimethylolpropane triacrylate 0.25 parts, N,N-dimethylformamide 0.5 parts, urea 1.5 parts, allylamine 1.5 parts, dodecylamine polyoxyethylene ether 2.8 parts, deionized water 590 parts, sodium methacrylate sulfonate 0.8 parts, azobisisobutyramidine dihydrochloride 0.2 parts, ammonium persulfate 0.015 parts, sodium bisulfite 0.02 parts.

[0049] Comparative Example 2 The difference between this comparative example and Example 1 is that no crosslinking agent is added, the initiator is adjusted, but the preparation process is the same. The composition includes: 220 parts acrylamide crystals, 8 parts methacrylamide propyltrimethylammonium chloride, 15 parts methacryloxyethyl dimethylbenzylammonium chloride, 20 parts methacryloxyethyl trimethylammonium chloride, 16 parts diallylamine hydrochloride, 0.2 parts triallyl isocyanate, 3.5 parts perfluorododecyl ethyl acrylate, 0.5 parts N,N-dimethylformamide, 1.5 parts urea, 1.5 parts allylamine, 2.8 parts dodecylamine polyoxyethylene ether, 590 parts deionized water, 0.5 parts sodium methacrylate sulfonate, 0.15 parts azobisisobutyramidine dihydrochloride, 0.013 parts ammonium persulfate, and 0.015 parts sodium bisulfite.

[0050] Comparative Example 3 The difference between this comparative example and Example 3 lies in the components; triallyl isocyanurate and perfluorododecyl ethyl acrylate are not added, and the initiator is adjusted, but the preparation process is the same. The composition includes 220 parts of acrylamide crystals, 8 parts of methacrylamide propyltrimethylammonium chloride, 15 parts of methacryloxyethyl dimethylbenzylammonium chloride, 20 parts of methacryloxyethyl trimethylammonium chloride, 16 parts of diallylamine hydrochloride, 0.46 parts of trimethylolpropane triacrylate, 0.5 parts of N,N-dimethylformamide, 1.5 parts of urea, 1.5 parts of allylamine, 2.8 parts of dodecylamine polyoxyethylene ether, 590 parts of deionized water, 1.2 parts of sodium methacrylate sulfonate, 0.3 parts of azobisisobutyramidine dihydrochloride, 0.015 parts of ammonium persulfate, and 0.03 parts of sodium bisulfite.

[0051] Comparative Example 4 The difference between this comparative example and Example 1 is that methacryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and diallylamine hydrochloride are replaced with acryloyloxyethyl trimethyl ammonium chloride, while the preparation process is the same.

[0052] Comparative Example 5 The difference between this comparative example and Example 1 is that trimethylolpropane triacrylate is replaced with N,N′-methylenebisacrylamide, while the preparation process is the same.

[0053] Performance testing: 1. Relative molecular mass, cationicity, and water-insoluble matter The relative molecular mass M, cationicity (%), and water-insoluble matter (%) were tested according to the test methods in the national standard GB / T 31246-2025.

[0054] 2. Settling time, supernatant turbidity, and floc characteristics A) Preparation of flocculant mother liquor Weigh (1.000±0.001) g of polyacrylamide (PAM) powder and slowly add it to a beaker containing approximately 500 mL of pure water. Simultaneously, stir continuously at 200–400 r / min to ensure uniform dispersion of the powder (avoid clumping). After the powder is completely wetted and dispersed, continue stirring for at least 1 hour until fully dissolved. After cooling, transfer the solution to a 500 mL volumetric flask and dilute to the mark with pure water to obtain a 0.2% (w / v) PAM stock solution. This stock solution should be prepared and used immediately; it should not be stored at room temperature for more than 2 hours. B) Preparation of simulated lithium mica tailings water 1) Mineral sample pretreatment Feldspar and quartz raw materials were manually sorted, crushed, and ground, and then screened to obtain single mineral samples with a particle size of 0.1~0.15mm (purity ≥90%) for later use. 2) Simulated tailings water preparation Weigh pretreated feldspar and quartz single mineral samples at a mass ratio of 1:1 and mix them to prepare artificial mixed tailings. Accurately weigh 60g of this mixed tailings and add it to a beaker containing 1000mL of pure water. Stir with a magnetic stirrer at 500 r / min for 5 minutes to ensure that the mineral particles are completely dispersed, thus obtaining simulated lepidolite tailings water. C) Flocculant sedimentation performance test 1) Sampling Take 500 mL of simulated lepidolite tailings water after uniform stirring and transfer it into six clean 500 mL stoppered graduated cylinders to ensure that the liquid volume in each cylinder is consistent. 2) Add flocculant Using a pipette or micropipette, precisely add 2 mL of 0.2% (w / v) PAM stock solution to each graduated cylinder. 3) Mixed flocculation Tighten the stopper of the measuring cylinder and rotate it up and down 10 times with uniform force and frequency (the whole process takes about 30 seconds) to ensure that the flocculant and the simulated tailings water are fully mixed. 4) Settling under static conditions Place the graduated cylinder vertically and stably on the experimental table, immediately start the stopwatch, and avoid touching the graduated cylinder during the resting process. 5) Observation and Recording Settling time: The time (t, unit: s) required for the solid-liquid interface to descend from the 500mL mark to the 300mL mark (cumulative settling volume 200mL); Turbidity of the supernatant: After standing for 5 minutes, slowly aspirate about 50 mL of the supernatant from the top of the graduated cylinder using the siphon method (avoid disturbing the lower flocs), and measure its turbidity (unit: NTU) using a turbidimeter. Floc characteristics: The size, density, and solid-liquid interface clarity of the flocs were qualitatively described and recorded. The obtained performance data are shown in Table 1 below: Table 1 The experimental data above show that when the crosslinking agent, cationic monomer, etc. of the present invention change, the flocs will change, the flocculation effect will be worse, the solid-liquid interface will be unclear during flocculation, which is not conducive to practical application.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A branched polyacrylamide flocculant, characterized in that, The raw materials for preparing the polyacrylamide flocculant include, by parts: 170-280 parts acrylamide crystals, 5-25 parts methacrylamide propyltrimethylammonium chloride, 30-95 parts cationic monomer, 0.1-0.7 parts triallyl isocyanurate, 2-15 parts perfluoroalkyl acrylate monomer, 0.3-1.5 parts crosslinking agent, 0.5-3 parts prosolvent, 1-6 parts allylamine, 1.5-7.5 parts polyether monomer, 550-670 parts water, 0.05-1.8 parts chain transfer agent, and 0.001-0.5 parts mixed initiator.

2. The branched polyacrylamide flocculant according to claim 1, characterized in that, The cationic monomer includes at least two of (meth)acryloyloxyethyl dimethyl benzyl ammonium chloride, (meth)acryloyloxyethyl trimethyl ammonium chloride, or diallylamine hydrochloride; preferably a combination of methacryloyloxyethyl dimethyl benzyl ammonium chloride, methacryloyloxyethyl trimethyl ammonium chloride, and diallylamine hydrochloride.

3. The branched polyacrylamide flocculant according to claim 1, characterized in that, The chain transfer agent includes any one or a combination of at least two of sodium formate, isopropanol, sodium hypophosphite, and sodium methacrylate sulfonate, preferably sodium methacrylate sulfonate.

4. The branched polyacrylamide flocculant according to claim 1, characterized in that, The mixed initiator is a combination of an azo initiator and a redox initiator; The azo initiator includes any one or a combination of at least two of azobisisobutyramidine dihydrochloride, azobisisoheptanenitrile, azobisisobutyramidonitrile, and 4,4'-azobis(4-cyanopentanoic acid), preferably azobisisobutyramidine dihydrochloride; The redox initiator includes any one or a combination of at least two of benzoyl peroxide, ammonium persulfate, potassium persulfate, sodium bisulfite, formaldehyde, ferrous sulfate, or sodium bisulfite, preferably ammonium persulfate and sodium bisulfite.

5. The branched polyacrylamide flocculant according to claim 1, characterized in that, The perfluoroalkyl acrylate monomer is perfluorododecylethyl acrylate.

6. The branched polyacrylamide flocculant according to claim 1, characterized in that, The crosslinking agent is trimethylolpropane triacrylate.

7. The branched polyacrylamide flocculant according to claim 1, characterized in that, The co-solvent includes at least two of N,N-dimethylformamide, N,N-dimethylacetamide, urea, or sodium dodecylbenzenesulfonate, preferably N,N-dimethylformamide and urea.

8. The branched polyacrylamide flocculant according to claim 1, characterized in that, The polyether monomer includes dodecylamine polyoxyethylene ether and / or laurylamine polyoxyethylene ether, preferably dodecylamine polyoxyethylene ether.

9. The method for preparing the branched polyacrylamide flocculant according to any one of claims 1 to 8, characterized in that, The preparation method includes the following steps: (1) Acrylamide crystals, methacrylamide propyltrimethylammonium chloride, cationic monomer, triallyl isocyanurate, perfluoroalkyl acrylate monomer, crosslinking agent, co-solvent, allylamine, polyether monomer, and water are mixed and the pH value is adjusted to obtain a mixed solution. (2) Add chain transfer agent and mixed initiator to the mixed solution obtained in step (1) to carry out copolymerization reaction. After the copolymerization reaction is completed, granulate, dry and sieve the product to obtain the branched polyacrylamide flocculant.

10. The preparation method according to claim 9, characterized in that, The pH value mentioned in step (1) is 3.5~4.5; Preferably, the temperature of the copolymerization reaction in step (2) is 0~2℃ and the reaction time is 4~5h; Preferably, the particle size of the granulation in step (2) is 2~6 mm.

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