Hydrophilic anti-pollution coating and preparation method thereof
By coating the surface of the ultrafiltration membrane with a high charge density polyelectrolyte and cross-linking it to form a hydrophilic and antifouling coating, the problems of flux reduction and shortened lifespan of traditional ultrafiltration membranes in the treatment of highly oily wastewater are solved, achieving a permanent hydrophilic and oleophobic effect. This provides a solution with high efficiency separation and low maintenance costs suitable for complex wastewater environments.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGSU BANGTEC ENVIRONMENTAL SCI TECH CO LTD
- Filing Date
- 2025-12-31
- Publication Date
- 2026-04-17
AI Technical Summary
Traditional ultrafiltration membranes are prone to forming a dense fouling layer in the treatment of highly oily wastewater, which leads to a decrease in membrane flux and difficulty in cleaning and recovery, resulting in a shortened service life. Existing hydrophilic polymers are lost during use and cannot achieve permanent hydrophilic and oleophobic effects.
A high-charge-density styrene copolymer polyelectrolyte is coated on the surface of an ultrafiltration porous membrane, and a permanent hydrophilic antifouling coating is formed through a phosphorus pentoxide/methanesulfonic acid crosslinking reaction, which uses electrostatic repulsion to block oily pollutants.
It significantly improves the oil resistance of ultrafiltration membranes, extends service life, reduces flux decay, and increases cleaning flux recovery rate. It is suitable for complex wastewater environments and has the advantages of high-efficiency separation and low maintenance costs.
Smart Images
Figure CN121869103A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of water treatment technology, specifically a hydrophilic anti-fouling coating and its preparation method. Background Technology
[0002] Ultrafiltration membrane technology, as a core process in water treatment, plays a vital role in industrial wastewater treatment. In oily wastewater treatment, it efficiently removes oil droplets and suspended solids through physical sieving, achieving oil-water separation. Its core advantages include the elimination of chemical reagents, high degree of automation, and adaptability to various complex water qualities. For example, in the petrochemical industry, ultrafiltration membranes can effectively treat oily wastewater, reducing the oil content in the effluent to below 5 mg / L. Furthermore, it exhibits strong chemical stability, resistance to high temperatures and acids / alkalis, making it suitable for harsh environments such as high-salt and high-turbidity conditions.
[0003] Currently, ultrafiltration membranes face severe challenges in the application of high-oil-content wastewater. Traditional ultrafiltration membranes are made of hydrophobic polymer materials, such as polysulfone, polyvinylidene fluoride, and polyacrylonitrile. These materials have high surface energy and lack the ability to repel oily substances. The large amounts of emulsified oil and animal and vegetable oils contained in the wastewater can easily spread on the membrane surface to form a dense fouling layer. Tiny oil droplets can even directly enter the micropores of the ultrafiltration membrane, causing a sharp drop in membrane flux. This fouling is extremely difficult to clean and restore, greatly shortening the membrane's lifespan and significantly increasing treatment costs.
[0004] To address this issue, the industry typically adds hydrophilic polymers, such as polyethylene glycol and polyvinylpyrrolidone, to the ultrafiltration casting solution to enhance hydrophilicity. However, after phase inversion to form the membrane, the hydrophilic polymers gradually leach into the water during use, and the membrane surface reverts to the original hydrophobic properties of the substrate. Therefore, developing ultrafiltration membranes with permanently hydrophilic and oleophobic surfaces to improve their oil resistance and extend their service life has become an urgent industry need.
[0005] Therefore, a hydrophilic anti-fouling coating and its preparation method are provided. Summary of the Invention
[0006] To address the aforementioned problems in the prior art, this invention provides a hydrophilic antifouling coating and its preparation method, which actively blocks oily pollutants through electrostatic repulsion, thereby achieving long-term stability and antifouling performance of the membrane.
[0007] The technical solution to achieve the above objectives is: One of the present inventions provides a hydrophilic antifouling coating comprising: Ultrafiltration porous membrane with benzenesulfonate groups; The surface of the ultrafiltration porous membrane is coated with a polyelectrolyte of charged styrene copolymer; Then, a layer of styrene copolymer polyelectrolyte with the opposite charge is coated on the surface of the ultrafiltration porous base membrane coated with styrene copolymer, or multiple layers of polyelectrolyte are alternately coated.
[0008] Preferably, the ultrafiltration porous base membrane is made of sulfonated polysulfone, with a sulfonation degree between 1% and 50%.
[0009] Preferably, the polyelectrolyte of the styrene copolymer is an anionic copolymer of styrene and sodium styrene sulfonate, or a cationic copolymer of styrene and styrene quaternary ammonium salt; wherein the molar percentage of styrene in the copolymer ranges from 5% to 85%, and the molar percentage of charged monomers in the copolymer ranges from 15% to 95%.
[0010] Preferably, the polyelectrolyte coated on the outermost surface is selected to have the same charge as the surface charge of the oil phase contaminant being treated.
[0011] Preferably, the coated ultrafiltration porous base membrane is immersed in a mixed solution of phosphorus pentoxide / methanesulfonic acid for cross-linking, thereby obtaining a permanent hydrophilic antifouling coating.
[0012] A method for preparing a hydrophilic antifouling coating according to a second aspect of the present invention includes: Step S1: Prepare an ultrafiltration porous membrane with benzenesulfonate groups; Step S2: Coating the surface of the ultrafiltration porous base membrane with a charged polyelectrolyte of styrene copolymer; Step S3: Then, coat the surface of the ultrafiltration porous base membrane coated with styrene copolymer with a layer of styrene copolymer polyelectrolyte with opposite charge, or alternately coat multiple layers of polyelectrolyte. Step S4: Immerse the coated ultrafiltration porous base membrane in a mixed solution of phosphorus pentoxide / methanesulfonic acid for cross-linking to obtain a permanent hydrophilic antifouling coating.
[0013] Preferably, in step S1, the ultrafiltration porous membrane is made of sulfonated polysulfone, and its degree of sulfonation is between 1% and 50%.
[0014] Preferably, in step S2, the polyelectrolyte of the styrene copolymer is an anionic copolymer of styrene and sodium styrene sulfonate, or a cationic copolymer of styrene and styrene quaternary ammonium salt; wherein the molar percentage of styrene in the copolymer ranges from 5% to 85%, and the molar percentage of charged monomers in the copolymer ranges from 15% to 95%.
[0015] Preferably, in step S2 or step S3, the coating method is any one of scraping, spraying, dipping, or precision coating.
[0016] Preferably, in step S4, the crosslinking reaction temperature is in the range of room temperature to 100 degrees Celsius.
[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention focuses on the problem of fouling of ultrafiltration membranes in highly oily wastewater. By introducing a high charge density polyelectrolyte coating, a permanent hydrophilic and oleophobic surface is constructed through a one-step crosslinking reaction. The high charge density polyelectrolyte coating significantly improves the anti-oil performance of the ultrafiltration membrane, and the superhydrophilic properties of the surface reduce the contact angle, effectively repelling oily substances, reducing oil adsorption, effectively delaying flux decay, and achieving a high flux recovery rate after cleaning. At the same time, the bonding strength between the coating and the base membrane is significantly improved through the crosslinking system, greatly extending the service life. It is suitable for complex wastewater environments, combining the advantages of high-efficiency separation and low maintenance costs, providing an efficient, economical, and environmentally friendly solution for industrial oily wastewater treatment, and has broad prospects for industrial application. Attached Figure Description
[0018] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a flowchart of a method for preparing a hydrophilic antifouling coating according to the present invention; Figure 2 This is a schematic diagram of the structure of the hydrophilic antifouling coating of the present invention; Figure 3 This is a schematic diagram of the chemical structure of sulfonated polysulfone in this invention; Figure 4 This is a schematic diagram of the polyelectrolyte chemical structure of the styrene copolymer in this invention; Figure 5 This is a schematic diagram of the chemical structure of the styrene-sodium styrene sulfonate copolymer in this invention; Figure 6 This is a schematic diagram of the chemical structure of the styrene-styrene quaternary ammonium salt copolymer in this invention.
[0019] In the diagram, R represents anionic groups such as -SO3H, -COOH, and -PO3H, or cationic groups such as quaternary ammonium salts, quaternary phosphonium salts, imidazole salts, and pyrrole salts. Detailed Implementation
[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.
[0021] A hydrophilic antifouling coating, chemical structure diagram as shown below Figure 2 As shown, it includes: The ultrafiltration porous membrane contains benzenesulfonate groups. The ultrafiltration porous membrane is made of sulfonated polysulfone with a sulfonation degree between 1-50%, preferably between 10-30%. The chemical structure of the sulfonated polysulfone is as follows: Figure 3 As shown; The surface of the ultrafiltration porous membrane is coated with a charged styrene copolymer polyelectrolyte, the chemical structure of which is shown in the figure below. Figure 4 As shown; Then, a layer of styrene copolymer polyelectrolyte with the opposite charge is coated on the surface of the ultrafiltration porous base membrane coated with styrene copolymer, or multiple layers of polyelectrolyte are alternately coated.
[0022] In the examples, the polyelectrolyte of the styrene copolymer is an anionic copolymer of styrene and sodium styrene sulfonate, and the chemical structure of the styrene and sodium styrene sulfonate copolymer is as follows: Figure 5 As shown, or a cationic copolymer of styrene and styrene quaternary ammonium salt, the chemical structure of the styrene-styrene quaternary ammonium salt copolymer is as follows. Figure 6 As shown; wherein the molar percentage of styrene in the copolymer ranges from 5% to 85%, preferably from 20% to 60%, and the molar percentage of charged monomers in the copolymer ranges from 15% to 95%, preferably from 40% to 80%.
[0023] In the embodiments, after coating a polyelectrolyte based on a polystyrene structure, a polyelectrolyte with the opposite charge can also be coated, or multiple polyelectrolytes can be coated alternately to improve the surface charge density and hydrophilic and oleophobic properties. In addition, the polyelectrolyte coated on the outermost surface can be selected with the same charge according to the surface charge of the oil phase contaminants being treated. For example, four groups of cationic polystyrene copolymers and anionic polystyrene copolymers can be coated alternately, with the outermost surface being anionic polyelectrolyte, which can effectively prevent contamination by anionic oil droplets on the surface.
[0024] In the embodiments, the coated ultrafiltration porous base membrane is immersed in a mixed solution of phosphorus pentoxide / methanesulfonic acid for crosslinking. A sulfonated styrene crosslinking system with stable chemical bonds is formed at the interface between the polyelectrolyte and the sulfonated polysulfone base membrane, as well as between the polyelectrolyte molecular chains, thereby obtaining a permanent hydrophilic antifouling coating.
[0025] like Figure 1 As shown, a method for preparing a hydrophilic antifouling coating includes: Step S1: Prepare an ultrafiltration porous membrane with benzenesulfonate groups; In the examples, the ultrafiltration porous membrane is made of sulfonated polysulfone with a sulfonation degree between 1% and 50%.
[0026] Step S2: Coating the surface of the ultrafiltration porous base membrane with a charged polyelectrolyte of styrene copolymer; In the embodiments, the polyelectrolyte of the styrene copolymer is an anionic copolymer of styrene and sodium styrene sulfonate, or a cationic copolymer of styrene and styrene quaternary ammonium salt; wherein the molar percentage of styrene in the copolymer ranges from 5% to 85%, and the molar percentage of charged monomers in the copolymer ranges from 15% to 95%.
[0027] Step S3: Then, coat the surface of the ultrafiltration porous base membrane coated with styrene copolymer with a layer of styrene copolymer polyelectrolyte with opposite charge, or alternately coat multiple layers of polyelectrolyte. In the embodiments, the coating method is any one of scraping, spraying, dip coating, and precision coating.
[0028] Step S4: Immerse the coated ultrafiltration porous base membrane in a mixed solution of phosphorus pentoxide / methanesulfonic acid for cross-linking to obtain a permanent hydrophilic antifouling coating.
[0029] In the examples, the crosslinking reaction temperature was in the range of room temperature to 100 degrees Celsius.
[0030] Example 1 (1) Prepare a DMF mixed solution of 16.5wt% polysulfone and 1.5wt% sulfonated polysulfone (sulfonated polysulfone sulfonation degree is 20%), and form an ultrafiltration membrane by phase inversion in 15% DMF aqueous solution. The membrane has an average pore size of 20nm and a surface contact angle of 10°.
[0031] (2) Spray the surface of this ultrafiltration membrane with 0.1% cationic copolymer ethanol solution (molar ratio of styrene and styrene quaternary ammonium salt 3:7) and dry it at 60 degrees Celsius. Then spray it with 0.1% anionic copolymer ethanol solution (molar ratio of styrene and sodium styrene sulfonate 2:8) and dry it again.
[0032] (3) The coated ultrafiltration membrane was immersed in a mixed solution of phosphorus pentoxide / methanesulfonic acid at 80°C for 20 min. After the cross-linking reaction, the membrane was cooled to room temperature and then washed with deionized water until neutral to obtain a permanent hydrophilic and oleophobic membrane with a water surface contact angle of <5° and a chlorobenzene oil droplet surface contact angle of >170° in water.
[0033] In comparison, the surface contact angle of the chlorobenzene oil droplets on the uncoated ultrafiltration membrane was 30°. This indicates that the oleophobic properties of the ultrafiltration layer are significantly improved after coating with polyelectrolyte, effectively resisting oil contamination.
[0034] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are 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 hydrophilic, anti-fouling coating, characterized in that, include: Ultrafiltration porous membrane with benzenesulfonate groups; The surface of the ultrafiltration porous membrane is coated with a polyelectrolyte of charged styrene copolymer; Then, a layer of styrene copolymer polyelectrolyte with the opposite charge is coated on the surface of the ultrafiltration porous base membrane coated with styrene copolymer, or multiple layers of polyelectrolyte are alternately coated.
2. The hydrophilic antifouling coating according to claim 1, characterized in that, The ultrafiltration porous base membrane uses sulfonated polysulfone, with a sulfonation degree between 1% and 50%.
3. The hydrophilic anti-fouling coating according to claim 1, characterized in that, The polyelectrolyte of the styrene copolymer is an anionic copolymer of styrene and sodium styrene sulfonate, or a cationic copolymer of styrene and styrene quaternary ammonium salt; wherein the molar percentage of styrene in the copolymer ranges from 5% to 85%, and the molar percentage of charged monomers in the copolymer ranges from 15% to 95%.
4. The hydrophilic antifouling coating according to claim 1, characterized in that, Based on the surface charge of the oil phase contaminants being treated, the polyelectrolyte coating the outermost surface is selected to have the same charge.
5. The hydrophilic antifouling coating according to claim 1, characterized in that, The coated ultrafiltration porous base membrane is immersed in a mixed solution of phosphorus pentoxide / methanesulfonic acid for cross-linking, thereby obtaining a permanent hydrophilic antifouling coating.
6. A method for preparing a hydrophilic antifouling coating, characterized in that, include: Step S1: Prepare an ultrafiltration porous membrane with benzenesulfonate groups; Step S2: Coating the surface of the ultrafiltration porous base membrane with a charged polyelectrolyte of styrene copolymer; Step S3: Then, coat the surface of the ultrafiltration porous base membrane coated with styrene copolymer with a layer of styrene copolymer polyelectrolyte with opposite charge, or alternately coat multiple layers of polyelectrolyte. Step S4: Immerse the coated ultrafiltration porous base membrane in a mixed solution of phosphorus pentoxide / methanesulfonic acid for cross-linking to obtain a permanent hydrophilic antifouling coating.
7. The method for preparing a hydrophilic antifouling coating according to claim 6, characterized in that, In step S1, the ultrafiltration porous membrane is made of sulfonated polysulfone, with a sulfonation degree between 1% and 50%.
8. The method for preparing a hydrophilic antifouling coating according to claim 6, characterized in that, In step S2, the polyelectrolyte of the styrene copolymer is an anionic copolymer of styrene and sodium styrene sulfonate, or a cationic copolymer of styrene and styrene quaternary ammonium salt; wherein the molar percentage of styrene in the copolymer ranges from 5% to 85%, and the molar percentage of charged monomers in the copolymer ranges from 15% to 95%.
9. The method for preparing a hydrophilic antifouling coating according to claim 6, characterized in that, In step S2 or step S3, the coating method is any one of scraping, spraying, dipping, or precision coating.
10. The method for preparing a hydrophilic antifouling coating according to claim 6, characterized in that, In step S4, the crosslinking reaction temperature is in the range of room temperature to 100 degrees Celsius.