Method for preparing cationic flocculant based on ultraviolet-initiated homogeneous modification of cellulose
Cellulose was modified at room temperature using a high-salt system and UV-initiated graft copolymerization, which disrupted its hydrogen bond network, achieving efficient dissolution and flocculation. This solved the problem of incomplete cellulose modification and improved the flocculation performance of the flocculant and the wastewater treatment effect.
Patent Information
- Application Number
- CN202511850509.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-09
- Publication Date
- 2026-02-27
AI Technical Summary
Existing technologies result in incomplete cellulose modification, low dissolution efficiency, high energy consumption and cost in the modification process, limited flocculation performance, long modification time, and complex production processes.
Cellulose was dissolved in a high-salt system at room temperature, and positively charged groups were introduced onto the cellulose by UV-initiated graft copolymerization, thereby disrupting its hydrogen bond network and achieving uniform modification.
It significantly improves the dissolution efficiency and flocculation effect of cellulose. The flocculant can remove turbidity of wastewater by more than 99.8%, remove dye by more than 96.2%, and remove UV254 by more than 93.7%. The process is simple, efficient and economical.
Smart Images
Figure CN121574306A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a water treatment flocculant, specifically to a method for preparing a cationic flocculant based on ultraviolet-induced homogeneous modification of cellulose. Background Technology
[0002] Cationic cellulose flocculants are a class of water treatment agents that use natural high-molecular-weight cellulose as a backbone and introduce cationic groups (such as quaternary ammonium salts and epichlorohydrin derivatives) through chemical modification. They combine the biodegradability of cellulose with the high-efficiency flocculation properties of cationic polymers, and are widely used in dye wastewater decolorization, papermaking retention aids, and sludge dewatering. Cationic cellulose flocculants are typically obtained from bamboo pulp, wood pulp, or microcrystalline cellulose through chemical grafting of cationic monomers. Currently, the main technology for modifying cellulose is to perform non-dissolving surface cationic modification after crushing cellulose into powder. This heterogeneous reaction results in incomplete cellulose modification and low water treatment efficiency. Dissolution modification of cellulose is an effective way to improve its modification efficiency. However, due to the strong hydrogen bond network between and within molecules of natural cellulose, dissolving it in traditional solvent systems (such as NaOH / urea, LiCl / DMAc) suffers from low dissolution efficiency, long dissolution time, significant environmental pollution, and high cost. Furthermore, it is impossible to dissolve cellulose materials at room temperature. It is often necessary to dissolve cellulose materials under strong alkali and low temperature conditions. Therefore, the dissolution grafting modification process has high energy consumption and poor uniformity, which limits the modification efficiency and flocculation performance. At the same time, there are also problems such as long modification time, complex production process and high cost.
[0003] Therefore, in order to overcome the above-mentioned technical problems, a simpler and more efficient method for preparing modified cellulose flocculants is needed. Summary of the Invention
[0004] In view of this, the purpose of this invention is to provide a method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose, thereby improving the solubility of natural cellulose in solvent systems and preparing cationic cellulose flocculants with good water solubility and excellent flocculation effect in a simple, efficient, uniform and controllable manner.
[0005] The present invention provides a method for preparing cationic flocculants based on ultraviolet-initiated homogeneous modification of cellulose, comprising the following steps: dissolving waste agricultural crop materials at room temperature using a high-salt system to destroy the hydrogen bond network of cellulose, and then grafting positively charged groups onto cellulose by ultraviolet-initiated graft copolymerization.
[0006] Furthermore, the specific steps include:
[0007] S1, Dissolve waste agricultural materials in a high-salt system, then adjust the pH to acidity to obtain a cellulose solution;
[0008] S2, a cationizing agent and a UV initiator are added to the cellulose solution to carry out a graft copolymerization reaction. Then, the supernatant separated by centrifugation is dialyzed to low conductivity and freeze-dried to obtain a cationized cellulose flocculant.
[0009] Furthermore, in step S1, the high-salt system is an aqueous solution of ZnCl2 and AlCl3;
[0010] Furthermore, in step S1, the molar ratio is ZnCl2:AlCl3:H2O = 0.6-1.2:0.05-0.2:4.
[0011] Furthermore, in step S1, the pH value is adjusted to 1-3;
[0012] Furthermore, in step S2, the cationic agent undergoes a graft polymerization reaction with cellulose to change the hydroxyl groups on the cellulose into amino groups or other cationic groups;
[0013] Furthermore, in step S2, the cationic agent is trimethacrylamide propyl ammonium chloride, and the mass ratio of the cationic agent to cellulose is 0.2-0.7:1;
[0014] Furthermore, in step S2, the UV initiator used for graft copolymerization is 2-hydroxy-2-methylphenylacetone.
[0015] The beneficial effects of this invention are as follows: This invention provides a method for preparing cationic flocculants based on UV-initiated homogeneous modification of cellulose. By employing a high-salt system to effectively disrupt the hydrogen bond network of cellulose, its dissolution efficiency is significantly improved, achieving high solubility of cellulose at room temperature. It can dissolve cellulose materials with a polymerization degree of 0-4000. Subsequently, positively charged groups are introduced through photo-initiated graft copolymerization, enhancing its adsorption capacity for negatively charged pollutants and thus improving the flocculation effect. The process of this invention is simple, efficient, uniform, and controllable, while also saving economic costs. The prepared flocculant can achieve a turbidity removal rate of over 99.8% for wastewater, a dye removal rate of over 96.2%, and a UV254 removal rate of over 93.7%. Attached Figure Description
[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments:
[0017] Figure 1 This is a diagram showing the effect of cationic flocculants on turbidity removal in wastewater.
[0018] Figure 2 This is a diagram showing the effect of cationic flocculants on dye decolorization.
[0019] Figure 3 This is a diagram showing the effect of cationic flocculants on the removal of organic matter. Detailed Implementation
[0020] This invention discloses a method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose, comprising the following steps: dissolving waste agricultural materials at room temperature using a high-salt system to disrupt the hydrogen bond network of cellulose; then grafting positively charged groups onto the cellulose via UV-induced graft copolymerization. In its natural state or after processing, cellulose molecules stack and crystallize to form microcrystalline cellulose or cellulose particles. These aggregates often exhibit a clump-like (aggregated) structure under a microscope or scanning electron microscope. Therefore, it is difficult for ordinary ionic systems to dissolve cellulose. This invention utilizes a high-salt system to partially or completely break the original three-dimensional hydrogen bond network of cellulose through multiple pathways, including direct ion participation in hydrogen bonding, shielding electrostatics, weakening the bridging effect of water, and altering the solvent microenvironment. This opens the clump-like (aggregated) structure of cellulose, thereby improving its solubility in a shorter time. Then, by introducing positively charged groups through graft copolymerization, its adsorption capacity for negatively charged colloids can be enhanced, thereby improving the flocculation effect. A high-salt system refers to a system containing a high concentration of salt ions, such as Zn²⁺, Ca²⁺, Cl⁻, and Al. 3+ Etc. The present invention preferably uses an aqueous solution of ZnCl2 and AlCl3 with a concentration of not less than 15%, which can achieve high solubility at room temperature without heating.
[0021] This embodiment specifically includes the following steps:
[0022] S1 involves dissolving waste agricultural materials in a high-salt system, then adjusting the pH to acidity to obtain a cellulose solvent. Waste agricultural materials (such as rice straw, corn stalks, and sugarcane bagasse) are not only byproducts of agricultural production but also vast natural cellulose reservoirs. Lignin and hemicellulose can be degraded using acids, alkalis, or biological enzymes to release pure cellulose; this is existing technology and will not be elaborated upon here. The preferred pH setting is 1-3.
[0023] S2, a graft copolymerization reaction was carried out by adding a cationic agent and a UV initiator to a cellulose solution. After the reaction, a certain amount of water was added, followed by centrifugation. The supernatant was dialyzed to low conductivity and then lyophilized to obtain a cationic cellulose flocculant. After adding a UV initiator, the reaction was carried out under 365 nm UV light for 1-2 h to form a cationic cellulose flocculant. The product was then purified and dried: the product was precipitated with ethanol, washed with water, dialyzed, and lyophilized to obtain a cationic cellulose flocculant powder. Graft modification introduces positively charged groups into the open structure of the fiber. The cationic agent is an amine group or other water-soluble group. Because the cellulose undergoes a high-salt system that breaks the hydrogen bond network structure, the grafting reaction can penetrate into the interior of the cellulose crystal region, improving grafting uniformity, enhancing modification depth, and increasing the grafting rate. Centrifugation, dialysis, and lyophilization all employ conventional techniques from existing technologies, which will not be elaborated here.
[0024] The existing reaction formula is as follows:
[0025] .
[0026] In this embodiment, in step S1, the high-salt system is an aqueous solution of ZnCl2 and AlCl3; the molar ratio of ZnCl2:AlCl3:H2O is 0.6-1.2:0.05-0.2:4; this can better disrupt the original three-dimensional hydrogen bond network of cellulose and completely open the cellulose's aggregated structure.
[0027] In this embodiment, in step S2, the cationic agent undergoes a graft polymerization reaction with cellulose to change the hydroxyl groups on the cellulose into amino groups or other cationic groups; the cationic agent is trimethylacrylamidopropylammonium chloride, and the mass ratio of the cationic agent to cellulose is 0.2-0.7:1; the ultraviolet initiator used in the graft copolymerization is 2-hydroxy-2-methylphenylacetone.
[0028] Example 1
[0029] The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose in this embodiment involves crushing straw into 100-mesh sieves, soaking it in 2wt% sodium hydroxide at 60°C for 1 hour to remove impurities, then washing and drying it for later use.
[0030] 5g of straw cellulose was weighed and dissolved in a zinc chloride and aluminum chloride solvent system (molar ratio ZnCl2:AlCl3:H2O=0.9:0.1:4). The mixture was stirred for 10 min, and then the solution value was adjusted to 1.6. Trimethylacrylamidopropylammonium chloride was added to the solution as a cationic agent (cationic agent / cellulose mass ratio of 0.5), and 2-hydroxy-2-methylphenylacetone was used as an initiator. The reaction was carried out at a UV wavelength of 365 nm for 1.5 hours. After the reaction was completed, a certain amount of water was added, and then the mixture was centrifuged. The supernatant was dialyzed to a low conductivity and then freeze-dried to obtain the target cationic cellulose flocculant.
[0031] Example 2
[0032] The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose in this embodiment involves crushing straw into 100-mesh sieves, soaking it in 2wt% sodium hydroxide at 60°C for 1 hour to remove impurities, then washing and drying it for later use.
[0033] 4g of straw cellulose was weighed and dissolved in a zinc chloride and aluminum chloride solvent system (molar ratio ZnCl2:AlCl3:H2O=0.6:0.05:4), stirred for 10min, and then the solution pH was adjusted to 1. Trimethylacrylamidopropylammonium chloride was added to the solution as a cationic agent (cationic agent / cellulose mass ratio of 0.2), and 2-hydroxy-2-methylphenylacetone was used as an initiator. The reaction was carried out at a UV wavelength of 365nm for 1.8 hours. After the reaction was completed, a certain amount of water was added, and then the mixture was centrifuged. The supernatant was dialyzed to a low conductivity and then freeze-dried to obtain the target cationic cellulose flocculant.
[0034] Example 3
[0035] The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose in this embodiment involves crushing straw into 100-mesh sieves, soaking it in 2wt% sodium hydroxide at 60°C for 1 hour to remove impurities, then washing and drying it for later use.
[0036] 6g of straw cellulose was weighed and dissolved in a zinc chloride and aluminum chloride solvent system (molar ratio ZnCl2:AlCl3:H2O=1.2:0.2:4). The mixture was stirred for 10 min, and the pH of the solution was adjusted to 2. Trimethylacrylamidopropylammonium chloride was then added to the solution as a cationic agent (cationic agent / cellulose mass ratio of 0.7), and 2-hydroxy-2-methylphenylacetone was used as an initiator. The reaction was carried out at a UV wavelength of 365 nm for 1.3 hours. After the reaction was completed, a certain amount of water was added, and the mixture was centrifuged. The supernatant was dialyzed to a low conductivity and then freeze-dried to obtain the target cationic cellulose flocculant.
[0037] Example 4
[0038] The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose in this embodiment involves crushing straw into 100-mesh sieves, soaking it in 2wt% sodium hydroxide at 60°C for 1 hour to remove impurities, then washing and drying it for later use.
[0039] 5g of straw cellulose was weighed and dissolved in a zinc chloride and aluminum chloride solvent system (molar ratio ZnCl2:AlCl3:H2O=1:0.1:4). The mixture was stirred for 10 min, and the pH of the solution was adjusted to 1.8. Trimethylacrylamidopropylammonium chloride was then added to the solution as a cationic agent (cationic agent / cellulose mass ratio of 0.4), and 2-hydroxy-2-methylphenylacetone was used as an initiator. The reaction was carried out at a UV wavelength of 365 nm for 1.6 hours. After the reaction was completed, a certain amount of water was added, and the mixture was centrifuged. The supernatant was dialyzed to a low conductivity and then freeze-dried to obtain the target cationic cellulose flocculant.
[0040] The cationic cellulose flocculant prepared in Example 1 was used to treat domestic sewage and dye wastewater. The cationic cellulose flocculant was added to domestic anhydrous or dye wastewater and stirred continuously. This treatment method is a general wastewater flocculation treatment or dye flocculation treatment method, which will not be described in detail here.
[0041] The main components of secondary effluent from wastewater treatment plants are suspended particulate matter and organic pollutants. This experiment used laboratory-simulated water as the experimental water. A certain amount of kaolin was weighed and added to 800 ml of deionized water. The mixture was magnetically stirred for 30 min, and the resulting liquid was poured into a 1 L graduated cylinder. Deionized water was added to the 1 L mark, and after settling for 30 min, 500-600 ml of the supernatant was siphoned off to obtain the kaolin stock solution. 1 g of humic acid was weighed and added to ultrapure water to a final volume of 1 L to obtain the humic acid stock solution, which was stored at 4℃. The kaolin stock solution and the humic acid stock solution were added together at a specific dosage to prepare a water sample with a turbidity of 25 ± 1 NTU and a humic acid content of 10 mg / L, which was used as the experimental water.
[0042] Preparation of dye wastewater:
[0043] Accurately weigh 1.0 g of methylene blue and dilute it to 1 L in a volumetric flask with distilled water to prepare a 1 g / L methylene blue stock solution. Dilute to different concentrations before use and store protected from light. Mix kaolin stock solution with distilled water to prepare a water sample with a turbidity of 25 ± 1, then add a certain amount of methylene blue stock solution to prepare the experimental water. Measure the absorbance at 664 nm using a UV-Vis spectrophotometer.
[0044] As shown in the figure, the turbidity removal rate increases rapidly with increasing flocculant dosage, reaching a maximum of 99.2% at a dosage of 40 mg / L, indicating excellent particulate matter removal. Regarding decolorization, the effect also increases with increasing flocculant dosage, reaching a maximum of 97.1% at a dosage of 40 mg / L, before slightly decreasing. For organic matter removal, the removal effect increases rapidly with increasing flocculant dosage, reaching over 80% at dosages above 20 mg / L, and reaching 92.6% at 40 mg / L. Cationic cellulose flocculants possess strong adsorption bridging and charge neutralization capabilities, resulting in good pollutant removal performance.
[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.
Claims
1. A method for preparing cationic flocculants based on ultraviolet-induced homogeneous modification of cellulose, characterized in that: Includes the following steps: Waste agricultural materials are dissolved at room temperature using a high-salt system to disrupt the hydrogen bond network of cellulose. Then, positively charged groups are grafted onto the cellulose through UV-initiated graft copolymerization.
2. The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose according to claim 1, characterized in that: Specifically, the following steps are included: S1, Dissolve waste agricultural materials in a high-salt system, then adjust the pH to acidity to obtain a cellulose solution; S2, a cationic agent and a UV initiator are added to the solution to carry out a graft copolymerization reaction. Then, the supernatant separated by centrifugation is dialyzed to low conductivity and dehydrated to obtain a solid cationic cellulose flocculant.
3. The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose according to claim 2, characterized in that: In step S1, the high-salt system is an aqueous solution of ZnCl2 and AlCl3.
4. The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose according to claim 2, characterized in that: In step S1, the molar ratio is ZnCl2:AlCl3:H2O = 0.6-1.2:0.05-0.2:
4.
5. The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose according to claim 2, characterized in that: In step S1, the pH value is adjusted to 1-3.
6. The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose according to claim 2, characterized in that: In step S2, the cationic agent undergoes a graft polymerization reaction with cellulose to change the hydroxyl groups on the cellulose into amino groups or other cationic groups.
7. The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose according to claim 2, characterized in that: In step S2, the cationic agent is trimethylacrylamidopropylammonium chloride, and the mass ratio of the cationic agent to cellulose is 0.2-0.7:
1.
8. The method for preparing cationic flocculants based on UV-induced homogeneous modification of cellulose according to claim 2, characterized in that: In step S2, the UV initiator used for graft copolymerization is 2-hydroxy-2-methylphenylacetone.