Multifunctional nanocellulose-based polymer water clarifier and preparation method thereof

Abstract

The invention discloses a multifunctional nanocellulose-based polymer water clarifier and a preparation method thereof. The preparation method comprises the following steps: firstly, screening out nano cellulose which is easily dispersed on an oil-water interface, carrying out etherification modification on the nano cellulose through an alkyl methyl ester etherifying agent and a quaternary ammonium salt type etherifying agent, and introducing alkyl methyl ester and cationic quaternary ammonium salt groups; the prepared modified nanocellulose has a relatively strong breaking effect and a clear water oil removal effect on an oil-in-water emulsion; meanwhile, an oleophylic long-chain cationic polymer side group is introduced through a graft copolymerization reaction, so that the modified nanocellulose further obtains strong charge adsorption and flocculation effects on oil-containing colloid in water, and fine floc floating is formed. Nano cellulose is subjected to etherification modification and graft copolymerization modification, a multifunctional nano cellulose-based polymer water clarifier product with reverse demulsification, water clarification and flocculation effects is prepared, and the multifunctional nano cellulose-based polymer water clarifier has a wide application prospect in the field of oil-water separation of offshore oilfields.

Description

Technical Field

[0001] The invention relates to the technical field of natural macromolecular polymer modification, and in particular to a multifunctional nano-cellulose-based polymer water purifier and a preparation method thereof. Background Art

[0002] In recent years, as people pay more and more attention to the transformation and utilization of renewable biomass resources, nanocellulose has received widespread attention due to its unique properties. Nanocellulose has the characteristics of wide sources, renewable, easy to degrade, nano-size effect and functional modification. In the modified nanocellulose-based polymer water-purifying agent, the cyclic hydrophobic groups of nanocellulose have a natural ability to capture crude oil, and after the modified charge squeezing, bridging and network sweeping effects, it is easy to form fine crude oil flocs and float up. In addition, the nanocellulose-based polymer has a low viscosity in water and is not easy to form difficult-to-recycle colloids. The development of such nano-scale polymer water-purifying agents is of great significance.

[0003] The space of offshore oil platforms is limited, and the crude oil processing process of offshore oil fields is short, which requires efficient oil-water separation agents. The conventional process requires the addition of a front-end low molecular weight polymer water-clearing agent and a back-end high molecular weight water-clearing agent to form an oil-water separation system to achieve rapid oil-water separation. Therefore, it is necessary to develop a multifunctional nanocellulose-based polymer water-clearing agent composed of low molecular weight and high molecular weight for demulsification and flocculation oil-water separation to simplify the process. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a multifunctional nano-cellulose-based polymer water purifier and a preparation method thereof.

[0005] In a first aspect, the present invention provides a method for preparing a multifunctional nanocellulose-based polymer water-purifying agent, which is achieved by adopting the following technical scheme.

[0006] A method for preparing a multifunctional nanocellulose-based polymer water-clearing agent, the water-clearing agent comprising the following raw materials in parts by weight: 200-230 parts of nanocellulose, 5-6 parts of alkyl methyl ester etherifying agents, 30-35 parts of etherification promoters in total, 15-18 parts of quaternary ammonium salt etherifying agents, 0.2-0.5 parts of pH regulators, 50-60 parts of acrylamide, 80-90 parts of cationic monomers, 0.3-0.5 parts of initiators, 0.3-0.4 parts of reducing agents, and 380-410 parts of deionized water in total;

[0007] The preparation method of the water purifier comprises the following steps:

[0008] S1. Mix nanocellulose, alkyl methyl ester etherifying agent and deionized water, and stir to dissolve;

[0009] S2. Raise the temperature to 60-65 degrees, drop the etherification promoter, adjust the pH value of the system to 9-9.5, and react for 3-4 hours;

[0010] S3. Under stirring, the quaternary ammonium salt etherifying agent and the etherification promoter are added to the reaction system, and the reaction is continued with stirring for 2 to 3 hours;

[0011] S4. Adjust the pH value to 9.5-10 with an etherification promoter, then raise the temperature to 70-75 degrees and continue the reaction for 1.5-2 hours;

[0012] S5. Cool down to 45-50 degrees, adjust the pH of the system to 5-6 with a pH adjuster, and add acrylamide, cationic monomer, and initiator to the system;

[0013] S6. Nitrogen is filled and deoxygenated for 1-1.5 hours, and the reducing agent solution is added dropwise. After the addition is completed, the reaction is kept at 60 degrees for 3-3.5 hours;

[0014] S7. Cool down to about 30-35 degrees, dilute with water to a content of 15%-18%, and obtain a multifunctional nano-cellulose-based polymer water purifier product.

[0015] Furthermore, the nanocellulose is prepared from coniferous wood fibers, and the diameter of the nanocellulose is 40nm-100nm; and the solid content is 2-2.5%.

[0016] By adopting the above technical scheme, the present invention preferably selects the nanocellulose width diameter to be 40nm-100nm. When the nanocellulose diameter is less than 40nm, the fluidity of the nanocellulose deteriorates, it is inconvenient to modify and use on site, and it is impossible to prepare a modified nanocellulose water-purifying agent with a sufficient concentration; in addition, when the nanocellulose diameter is greater than 100nm, the modified nanocellulose diffuses slowly at the oil-water interface, and the water-purifying effect will be reduced; therefore, nanocellulose with a diameter of 40nm to 100nm is preferred, which is conducive to obtaining modified nanocellulose with good fluidity and good dispersion in oil and water.

[0017] Furthermore, the alkyl methyl ester etherifying agent is a mixture of methyl chloropropionate and methyl chlorobutyrate, and the compounding mass ratio is 1:1.

[0018] By adopting the above technical scheme, nanocellulose is etherified and modified by using alkyl methyl ester etherifying agents, and the etherification modification conditions of alkyl methyl ester etherifying agents are studied. The modified nanocellulose obtained has a strong breaking effect on water-in-oil emulsions. At the same time, the nanocellulose is modified by composite etherification with two alkyl methyl ester etherifying agents with different chain lengths. The modified nanocellulose obtained has a good breaking effect on water-in-oil bubbles of different specifications.

[0019] Furthermore, the quaternary ammonium salt type etherifying agent is a composite of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 2,3-epoxypropyltrimethylammonium chloride, and the mass ratio of the two is 1:1.

[0020] By adopting the above technical scheme, cationic quaternary ammonium salt type side groups are introduced through etherification reaction, so that the modified nanocellulose can further obtain strong charge adsorption effect on oil-containing colloids in water, forming fine flocs that float on the surface; nanocellulose is modified by etherification with alkyl methyl ester and quaternary ammonium salt to prepare modified nanocellulose-based polymers with better clear water deoiling effect.

[0021] Furthermore, the etherification promoter is a compound of 30% sodium hydroxide and 30% potassium hydroxide, and the weight ratio is 1:2.

[0022] Furthermore, the mass ratio of the etherification promoter added in step S2 and step S3 is (7-9):(23-26).

[0023] Furthermore, the acrylamide is selected from an aqueous solution of acrylamide with a content of 50%.

[0024] Furthermore, the cationic monomer is an aqueous solution of methacryloyloxyethyl dimethylbenzyl ammonium chloride with a solid content of 80%.

[0025] By adopting the above technical scheme, nanocellulose is functionally modified by graft copolymerization, and amide groups and long-chain lipophilic cationic groups are introduced to obtain a multifunctional nanocellulose-based polymer water-purifying agent with strong cationic water-purifying, high molecular weight bridging and sweeping high-efficiency oil removal effects.

[0026] Furthermore, the pH adjuster is selected from acetic acid or oxalic acid.

[0027] Furthermore, the initiator is a complex of ammonium persulfate and azobisisobutylamidine hydrochloride, and the mass ratio of the two is 5:1.

[0028] Furthermore, the reducing agent is a composite of sodium sulfite and sodium pyrosulfite, and the composite mass ratio is 1:1.

[0029] Furthermore, the ratio of water used in step S1 to step S7 is (20-30):(360-380).

[0030] In a second aspect, the present invention provides a multifunctional nanocellulose-based polymer water-purifying agent, which is achieved by adopting the following technical scheme.

[0031] A multifunctional nanocellulose-based polymer water-purifying agent prepared by the above preparation method has a bulk viscosity of less than 200cp and a solid content of more than 15%, and has the functions of reverse demulsification, water purification and flocculation. It can be used as a flocculant to treat organic industrial wastewater and as a water-purifying agent to treat oily wastewater.

[0032] The present invention achieves the following beneficial effects.

[0033] (1) The present invention optimizes the nanocellulose width to be 40 nm to 100 nm, which is beneficial for obtaining a nanocellulose matrix with good fluidity and good dispersion in oil and water, and is also beneficial for etherification modification and graft copolymerization modification;

[0034] (2) Nanocellulose was etherified by using alkyl methyl ester etherifying agents, and the etherification modification conditions of alkyl methyl ester etherifying agents were studied. The modified nanocellulose obtained had a strong breaking effect on oil-in-water emulsions. At the same time, nanocellulose was modified by using two alkyl methyl ester etherifying agents with different chain lengths to compositely etherify. The modified nanocellulose obtained had a good breaking effect on oil-in-water emulsions of different specifications.

[0035] (3) The present invention introduces cationic quaternary ammonium salt side groups through etherification reaction, so that the modified nanocellulose can further obtain strong charge adsorption effect on oil-containing colloids in water, forming fine flocs that float upward; nanocellulose can be further improved in oil-water separation performance of nanocellulose-based polymer products after alkyl methyl ester modification and quaternization modification;

[0036] (4) functional modification of nanocellulose by graft copolymerization, introduction of amide groups and long-chain lipophilic cationic groups, and obtaining a multifunctional nanocellulose-based polymer water-cleaning agent with strong cationic water-cleaning, high molecular weight bridging and sweeping high-efficiency oil removal effects;

[0037] (5) The modified nanocellulose prepared by the present invention has good flowability and oil-water interface dispersion performance by controlling the width and aspect ratio of the nanocellulose, and has a viscosity of less than 200cp and a solid content of more than 15%, which is convenient for on-site injection and use;

[0038] In summary, the multifunctional nanocellulose-based polymer water-purifying agent prepared by the present invention has the characteristics of strong lipophilicity, fast diffusion speed, low bulk viscosity, good low temperature resistance, rapid solubility and storage stability.

[0039] Instruction Manual

[0040] Figure 1 This is the oil-water separation effect of the multifunctional nano-cellulose-based polymer water-clearing agent of the present invention (water-clearing effect diagram after standing in a water bath for 20 minutes, from left to right are Examples 1-7. DETAILED DESCRIPTION

[0041] The technical solution of the present invention will be clearly and completely described below through specific implementation methods.

[0042] The nanocellulose used in the examples of the present application is prepared from coniferous wood fibers and purchased from China Pulp and Paper Research Institute Co., Ltd.

[0043] Example 1

[0044] A method for preparing a multifunctional nanocellulose-based polymer water-purifying agent comprises the following steps:

[0045] 200 g of nanocellulose, 5 g of alkyl methyl ester etherifying agent (methyl chloropropionate and methyl chlorobutyrate are mixed in a mass ratio of 1:1) and 20 g of deionized water are added to a reactor and stirred and dissolved; the temperature is slowly raised to 62 degrees, 8 g of etherification promoter (30% sodium hydroxide and 30% potassium hydroxide are mixed in a weight ratio of 1:2) is slowly dripped, the pH value of the system is adjusted to 9.2, and the reaction is carried out for 3 hours; while continuing to stir, 16 g of quaternary ammonium salt etherifying agent (3-chloro-2-hydroxypropyltrimethylammonium chloride and 2,3-epoxypropyltrimethylammonium chloride are mixed in a mass ratio of 1:1) and 22 g of etherification promoter (30% sodium hydroxide and 30% potassium hydroxide are mixed in a weight ratio of 1:2) are slowly added to the reactor, and the reaction is continued to stir for 3 hours; the pH is adjusted with the etherification promoter The value is 9.6, and then the temperature is raised to 70 degrees to continue the reaction for 2 hours; the temperature is slowly lowered to 46 degrees, the pH of the system is adjusted to 5 with a pH regulator glacial acetic acid, 54g of acrylamide, 90g of a cationic monomer (aqueous solution of methacryloyloxyethyl dimethylbenzyl ammonium chloride with a solid content of 80%), and 0.5g of an initiator (ammonium persulfate and azobisisobutylamidine hydrochloride mixed in a mass ratio of 5:1) are added to the system; nitrogen is filled and deoxygenated for 1.1 hours, and 0.3g of a reducing agent solution (sodium sulfite and sodium pyrosulfite mixed in a mass ratio of 1:1) is slowly added dropwise. After the reducing agent solution is added dropwise, the reaction is kept at 60 degrees for 3 hours; the temperature is slowly lowered to 32 degrees, and 365g of water is used to dilute the solid content to 15.2%, and a multifunctional nano-cellulose-based polymer water-purifying agent with a viscosity of 158cp is obtained.

[0046] Example 2

[0047] A method for preparing a multifunctional nanocellulose-based polymer water-purifying agent comprises the following steps:

[0048] Add 210g of nanocellulose, 6g of alkyl methyl ester etherifying agent and 23g of deionized water into a reactor and stir to dissolve; slowly heat up to 62 degrees, slowly drop 9g of etherification promoter, adjust the pH value of the system to 9.3, and react for 3 hours; while continuing to stir, slowly add 17g of quaternary ammonium salt etherifying agent and 23g of etherification promoter into the reactor, continue stirring and react for 3 hours; adjust the pH value to 9.7 with the etherification promoter, then heat up to 70 degrees and continue to react for 2 hours; The temperature was slowly lowered to 47 degrees, and the pH of the system was adjusted to 5 with pH regulator glacial acetic acid. 60 g of acrylamide, 86 g of cationic monomer, and 0.4 g of initiator were added to the system. Nitrogen was filled and deoxygenated for 1.2 hours, and 0.3 g of reducing agent solution was slowly added dropwise. After the reducing agent solution was added dropwise, the system was kept warm at 60 degrees for 3 hours. The temperature was slowly lowered to 33 degrees, and the system was diluted with 380 g of water to a solid content of 15.8%, to obtain a multifunctional nano-cellulose-based polymer water-purifying agent with a viscosity of 165 cp.

[0049] The specific components and proportions of the alkyl methyl ester etherifying agent, etherification accelerator, quaternary ammonium salt etherifying agent, pH adjuster, cationic monomer, initiator, and reducing agent in this embodiment are the same as those in Example 1.

[0050] Example 3

[0051] A method for preparing a multifunctional nanocellulose-based polymer water-purifying agent comprises the following steps:

[0052] 220 g of nanocellulose, 6 g of alkyl methyl ester etherifying agent and 25 g of deionized water were added to the reactor and stirred thoroughly to dissolve; the temperature was slowly raised to 62 degrees, 8 g of etherification promoter was slowly added dropwise, the pH value of the system was adjusted to 9.3, and the reaction was continued for 3 hours; 17 g of quaternary ammonium salt etherifying agent and 24 g of etherification promoter were slowly added to the reactor while stirring, and the reaction was continued with stirring for 3.2 hours; the pH value was adjusted to 9.6 with the etherification promoter, and then the temperature was raised to 72 degrees and the reaction was continued for 1.8 hours. hours; slowly cool down to 48 degrees, adjust the pH of the system to 5 with pH regulator glacial acetic acid, add 56g of acrylamide, 88g of cationic monomer, and 0.5g of initiator to the system; nitrogen filling and deoxygenation for 1 hour, slowly drop 0.3g of reducing agent solution, after the dropping of the reducing agent solution, keep warm at 60 degrees for 3 hours; slowly cool down to 33 degrees, dilute with 360g of water to a solid content of 16.1%, and obtain a multifunctional nano-cellulose-based polymer water-clearing agent with a viscosity of 173cp.

[0053] The specific components and proportions of the alkyl methyl ester etherifying agent, etherification accelerator, quaternary ammonium salt etherifying agent, pH adjuster, cationic monomer, initiator, and reducing agent in this embodiment are the same as those in Example 1.

[0054] Example 4

[0055] A method for preparing a multifunctional nanocellulose-based polymer water-purifying agent comprises the following steps:

[0056] Add 230g of nanocellulose, 6g of alkyl methyl ester etherifying agent and 26g of deionized water into the reactor and stir to dissolve; slowly heat up to 62 degrees, slowly drop 9g of etherification promoter, adjust the pH value of the system to 9.3, and react for 3 hours; while continuing to stir, slowly add 18g of quaternary ammonium salt etherifying agent and 25g of etherification promoter into the reactor, continue stirring and react for 3.5 hours; adjust the pH value to 9.7 with etherification promoter, then heat up to 75 degrees and continue to react for 2 hours slowly cool down to 49 degrees, adjust the pH of the system to 5 with pH regulator glacial acetic acid, add 57g of acrylamide, 89g of cationic monomer and 0.5g of initiator to the system; nitrogen deoxygenation for 1 hour, slowly drop 0.4g of reducing agent solution, after the addition of reducing agent solution, keep warm at 60 degrees for 3 hours; slowly cool down to 30 degrees, dilute with 368g of water to a solid content of 15.9%, and obtain a multifunctional nano-cellulose-based polymer water-clearing agent with a viscosity of 171cp.

[0057] The specific components and proportions of the alkyl methyl ester etherifying agent, etherification accelerator, quaternary ammonium salt etherifying agent, pH adjuster, cationic monomer, initiator, and reducing agent in this embodiment are the same as those in Example 1.

[0058] Example 5

[0059] A method for preparing a multifunctional nanocellulose-based polymer water-purifying agent comprises the following steps:

[0060] Add 220g of nanocellulose, 5g of alkyl methyl ester etherifying agent and 26g of deionized water into the reactor and stir to dissolve; slowly heat up to 62 degrees, slowly drop 8g of etherification promoter, adjust the pH value of the system to 9.2, and react for 3 hours; while continuing to stir, slowly add 17g of quaternary ammonium salt etherifying agent and 24g of etherification promoter into the reactor, continue stirring and react for 3 hours; adjust the pH value to 9.7 with etherification promoter, then heat up to 73 degrees and continue to react for 1.8 hours ; Slowly cool to 49 degrees, adjust the pH of the system to 5 with pH regulator glacial acetic acid, add 56g of acrylamide, 90g of cationic monomer, and 0.5g of initiator to the system; nitrogen filling and deoxygenation for 1.2 hours, slowly add 0.3g of reducing agent solution, after adding the reducing agent solution, keep warm at 60 degrees for 3 hours; slowly cool to 33 degrees, dilute with 370g of water to a solid content of 15.6%, and obtain a multifunctional nano-cellulose-based polymer water-purifying agent with a viscosity of 169cp.

[0061] The specific components and proportions of the alkyl methyl ester etherifying agent, etherification accelerator, quaternary ammonium salt etherifying agent, pH adjuster, cationic monomer, initiator, and reducing agent in this embodiment are the same as those in Example 1.

[0062] Example 6

[0063] A method for preparing a multifunctional nanocellulose-based polymer water-purifying agent comprises the following steps:

[0064] 210 g of nanocellulose, 5 g of alkyl methyl ester etherifying agent and 25 g of deionized water were added to the reactor and stirred thoroughly to dissolve; the temperature was slowly raised to 62 degrees, 8 g of etherification promoter was slowly added dropwise, the pH value of the system was adjusted to 9.1, and the reaction was continued for 3.5 hours; 18 g of quaternary ammonium salt etherifying agent and 25 g of etherification promoter were slowly added to the reactor while stirring, and the reaction was continued for 3 hours; the pH value was adjusted to 9.8 with the etherification promoter, and then the temperature was raised to 74 degrees and the reaction was continued for 1.5 hours; slowly cool down to 50 degrees, adjust the pH of the system to 5 with pH regulator glacial acetic acid, add 58g of acrylamide, 86g of cationic monomer, and 0.5g of initiator to the system; nitrogen filling and deoxygenation for 1 hour, slowly drop 0.3g of reducing agent solution, after the dropping of the reducing agent solution, keep warm at 60 degrees for 3 hours; slowly cool down to 33 degrees, dilute with 370g of water to a solid content of 15.8%, and obtain a multifunctional nano-cellulose-based polymer water-clearing agent with a viscosity of 171cp.

[0065] The specific components and proportions of the alkyl methyl ester etherifying agent, etherification accelerator, quaternary ammonium salt etherifying agent, pH adjuster, cationic monomer, initiator, and reducing agent in this embodiment are the same as those in Example 1.

[0066] Example 7

[0067] A method for preparing a multifunctional nanocellulose-based polymer water-purifying agent comprises the following steps:

[0068] 220g of nanocellulose, 6g of alkyl methyl ester etherifying agent and 22g of deionized water are added into a reactor and stirred and dissolved thoroughly; the temperature is slowly raised to 62 degrees, 9g of etherification promoter is slowly dripped, the pH value of the system is adjusted to 9.2, and the reaction is carried out for 4 hours; 18g of quaternary ammonium salt etherifying agent and 26g of etherification promoter are slowly added into the reactor while stirring, and the stirring reaction is continued for 3 hours; the pH value is adjusted to 9.8 with the etherification promoter, and then the temperature is raised to 73 degrees and the reaction is continued for 2 hours; the temperature is slowly lowered to 49 degrees, the pH value of the system is adjusted to 6 with the pH regulator glacial acetic acid, and 59g of acrylamide, 82g of cationic monomer and 0.4g of initiator are added into the system; nitrogen is filled and deoxygenated for 1 hour, 0.4g of reducing agent solution is slowly dripped, and after the reducing agent solution is dripped, the temperature is kept at 60 degrees for 3 hours; the temperature is slowly lowered to 33 degrees, and 372g of water is used to dilute the solid content to 16.2%, and a multifunctional nanocellulose-based polymer water-purifying agent with a viscosity of 164cp is obtained.

[0069] The specific components and proportions of the alkyl methyl ester etherifying agent, etherification accelerator, quaternary ammonium salt etherifying agent, pH adjuster, cationic monomer, initiator, and reducing agent in this embodiment are the same as those in Example 1.

[0070] Performance Testing

[0071] The multifunctional nanocellulose-based polymer water-clearing agent prepared in the present embodiment was tested for oil-water separation effect. The testing method was based on the industry standard SY / T 5797-1993 "Method for evaluating the performance of water-in-oil emulsion demulsifiers". The experimental results are shown in Tables 1 and Figure 1 .

[0072] Table 1 Oil-water separation effect of multifunctional nanocellulose-based polymer water purifier

[0073]

[0074] Note: A+, A, A-: clear; B+, B, B-: fair; C+, C, C-: poor

[0075] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in the field should fall within the protection scope of the present invention. The technical contents for which protection is sought in the present invention have been fully recorded in the technical requirements.

Claims

1. A method for preparing a multifunctional nanocellulose-based polymer water purifier, characterized in that: The water purifier comprises the following raw materials in parts by weight: 200-230 parts of nanocellulose, 5-6 parts of alkyl methyl ester etherifying agent, 30-35 parts of etherification accelerator, 15-18 parts of quaternary ammonium salt etherifying agent, 0.2-0.5 parts of pH regulator, 50-60 parts of acrylamide, 80-90 parts of cationic monomer, 0.3-0.5 parts of initiator, 0.3-0.4 parts of reducing agent and 380-410 parts of deionized water; The preparation method of the water purifier comprises the following steps: S1. Mix nanocellulose, alkyl methyl ester etherifying agent and deionized water, and stir to dissolve; S2. Raise the temperature to 60-65 degrees, drop the etherification promoter, adjust the pH value of the system to 9-9.5, and react for 3-4 hours; S3. Under stirring, the quaternary ammonium salt etherifying agent and the etherification promoter are added to the reaction system, and the reaction is continued with stirring for 2 to 3 hours; S4. Adjust the pH value to 9.5-10 with an etherification promoter, then raise the temperature to 70-75 degrees and continue the reaction for 1.5-2 hours; S5. Cool down to 45-50 degrees, adjust the pH of the system to 5-6 with a pH adjuster, and add acrylamide, cationic monomer, and initiator to the system; S6. Nitrogen is filled and deoxygenated for 1-1.5 hours, and the reducing agent solution is added dropwise. After the addition is completed, the reaction is kept at 60 degrees for 3-3.5 hours; S7. Cool down to 30-35 degrees, dilute with water to a content of 15%-18%, and obtain a multifunctional nano-cellulose-based polymer water purifier product.

2. The method for preparing a multifunctional nanocellulose-based polymer water purifier according to claim 1, characterized in that: The nanocellulose is prepared from coniferous wood fibers, and the diameter of the nanocellulose is 40nm-100nm; the solid content is 2-2.5%.

3. The method for preparing a multifunctional nanocellulose-based polymer water-purifying agent according to claim 1, characterized in that: The alkyl methyl ester etherifying agent is a mixture of methyl chloropropionate and methyl chlorobutyrate, and the compounding mass ratio is 1:

1.

4. The method for preparing a multifunctional nanocellulose-based polymer water purifier according to claim 1, characterized in that: The quaternary ammonium salt type etherifying agent is a composite of 3-chloro-2-hydroxypropyltrimethylammonium chloride and 2,3-epoxypropyltrimethylammonium chloride, and the mass ratio of the two is 1:

1.

5. The method for preparing a multifunctional nanocellulose-based polymer water purifier according to claim 1, characterized in that: The etherification accelerator is a compound of 30% sodium hydroxide and 30% potassium hydroxide, and the weight ratio is 1:

2.

6. The method for preparing a multifunctional nanocellulose-based polymer water purifier according to claim 1, characterized in that: The cationic monomer is a methacryloyloxyethyl dimethylbenzyl ammonium chloride aqueous solution with a solid content of 80%.

7. The method for preparing a multifunctional nanocellulose-based polymer water-purifying agent according to claim 1, characterized in that: The pH regulator is selected from acetic acid or oxalic acid.

8. The method for preparing a multifunctional nanocellulose-based polymer water-purifying agent according to claim 1, characterized in that: The initiator is a complex of ammonium persulfate and azobisisobutylamidine hydrochloride, and the mass ratio of the two is 5:

1.

9. The method for preparing a multifunctional nanocellulose-based polymer water-purifying agent according to claim 1, characterized in that: The reducing agent is a composite of sodium sulfite and sodium pyrosulfite, and the composite mass ratio is 1:

1.

10. A multifunctional nanocellulose-based polymer water-purifying agent prepared by the preparation method according to any one of claims 1 to 9.

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