Preparation method of underwater super-oleophobic cotton fabric and application of underwater super-oleophobic cotton fabric in oil-water separation

Abstract

The application discloses a preparation method and application of underwater super-oleophobic cotton fabric for oil-water separation, and relates to the fields of functional textile material preparation and oil-water separation technology.The preparation method comprises the following steps: dissolving sodium alginate in deionized water, adding dopamine hydrochloride and Tris-HCl buffer, adjusting the pH value to make dopamine oxidize and polymerize and form PDA-SA composite coating with sodium alginate; after pretreatment of cotton fabric through cleaning and drying, the composite coating is coated on the cotton fabric and dried to obtain PDA-SA pre-coated cotton fabric; then the cotton fabric is immersed in a calcium chloride solution for crosslinking treatment, and after cleaning and drying, the underwater super-oleophobic cotton fabric is obtained.The obtained cotton fabric has super-hydrophilicity in air, has a high contact angle to various oils under water, and has good acid, alkali, salt and ultraviolet stabilities.The cotton fabric can be used for oil-water mixture separation and oil-in-water emulsion separation, the separation process can be driven by gravity, and the cotton fabric has the characteristics of simple process, easily available raw materials and good environmental friendliness.

Description

Technical Field

[0001] This invention relates to the field of functional textile material preparation and oil-water separation technology, specifically to a method for preparing underwater superoleophobic cotton fabric for oil-water separation and its application. Background Technology

[0002] With the development of industries such as petrochemicals, machinery manufacturing, food processing, and marine transportation, a large amount of oily wastewater is generated during the production process. Meanwhile, sudden events such as oil spills at sea can also cause serious water pollution. Oily pollutants typically exist in the form of floating oil, dispersed oil, and emulsified oil. Among these, emulsified oil is particularly difficult to separate due to its small droplet size and high system stability.

[0003] Existing oil-water separation methods mainly include gravity sedimentation, centrifugation, adsorption, chemical demulsification, and membrane separation. In practical applications, these methods suffer from varying degrees of problems, such as high energy consumption, complex processing procedures, limited separation efficiency, susceptibility to secondary pollution, or insufficient material stability. Especially for oil-water mixtures and emulsion systems in complex aquatic environments, there is still room for improvement in their treatment effectiveness.

[0004] In recent years, interface materials with special wettability have attracted widespread attention due to their ability to selectively permeate aqueous or oil phases. Among them, superhydrophilic / underwater superoleophobic materials can repel oil droplets in an aqueous environment, making them suitable for achieving efficient oil-water separation. Existing related materials sometimes employ fluorinated compounds to construct low surface energy layers, resulting in insufficient environmental friendliness; others utilize complex etching, photolithography, or multi-step surface modification processes, leading to high preparation costs, complex processes, and difficulties in large-scale scalability. Furthermore, some materials exhibit poor stability under strong acid, strong alkali, high salt, or ultraviolet irradiation conditions, limiting their application range.

[0005] Polydopamine (PDA) exhibits excellent interfacial adhesion, enabling it to form stable coatings on various substrates. Sodium alginate (SA), a natural polymer, possesses excellent hydrophilicity and can undergo cross-linking reactions with divalent metal ions. Combining PDA with sodium alginate to construct a stable composite coating on a fiber substrate, and further enhancing structural stability through calcium ion cross-linking, promises to obtain a separation material that combines excellent hydrophilicity, environmental stability, and underwater superoleophobic properties.

[0006] Therefore, developing an underwater superoleophobic cotton fabric with simple preparation process, readily available raw materials, environmental friendliness, high separation efficiency, and good stability has high application value. Summary of the Invention

[0007] The purpose of this invention is to provide a method for preparing underwater superoleophobic cotton fabric for oil-water separation, so as to solve the problems of complex preparation process, insufficient environmental adaptability or poor separation performance stability of existing oil-water separation materials.

[0008] Another object of the present invention is to provide an underwater superoleophobic cotton fabric prepared by the above method.

[0009] Another object of the present invention is to provide the application of the above-mentioned underwater superoleophobic cotton fabric in the separation of oil-water mixtures and the separation of oil-in-water emulsions.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing an underwater superoleophobic cotton fabric for oil-water separation includes the following steps: (1) Preparation of PDA-SA composite coating: Sodium alginate was added to deionized water and stirred until dissolved. Then, dopamine hydrochloride and Tris-HCl buffer were added to adjust the pH value of the system, so that dopamine would undergo oxidative polymerization and the resulting polydopamine would form a composite system with sodium alginate to obtain PDA-SA composite coating. (2) Pretreatment of cotton fabric: After cutting the cotton fabric, place it in anhydrous ethanol for ultrasonic cleaning to remove surface impurities, and then dry it. (3) Coating and curing: The PDA-SA composite coating is applied to the surface of the pretreated cotton fabric and dried to obtain a cotton fabric with a PDA-SA pre-coating. (4) Calcium ion crosslinking: The cotton fabric obtained in step (3) is immersed in calcium chloride solution for crosslinking treatment, taken out, washed and dried to obtain underwater superoleophobic cotton fabric.

[0011] Preferably, in step (1), the concentration of sodium alginate solution is 0.5% to 1.5% (mass-volume ratio).

[0012] Preferably, in step (1), the amount of dopamine hydrochloride and Tris-HCl added is 0.4-0.8 g and 0.24-0.5 g, respectively; the pH value of the system is adjusted to 8-9, and the reaction time is 18-30 h.

[0013] Preferably, in step (1), the stirring rate is 300-500 r / min; the system is in contact with air during the reaction to facilitate the oxidative polymerization of dopamine.

[0014] Preferably, in step (3), the coating method is any one of dip coating, brush coating or spray coating; the coating amount is 50 to 100 g / m².

[0015] Preferably, the drying temperature in step (3) is 80-85℃.

[0016] Preferably, in step (4), the concentration of calcium chloride solution is 0.02-0.04 mol / L, and the crosslinking time is 3-5 min.

[0017] The present invention also provides an underwater superoleophobic cotton fabric prepared by the above-described method, wherein the surface of the cotton fabric has PDA-SA-Ca 2+ Composite coating.

[0018] Preferably, in the composite coating, sodium alginate and Ca... 2+ The formation of a cross-linked structure improves the stability of the coating and the roughness of the cotton fabric surface.

[0019] Preferably, the underwater superoleophobic cotton fabric exhibits superhydrophilicity in air, with a water contact angle close to 0°; and has a contact angle greater than 155° underwater for one or more oils selected from dichloromethane, chloroform, n-hexane, toluene, and xylene.

[0020] Preferably, the underwater superoleophobic cotton fabric retains high underwater oleophobic properties even after treatment under acidic, alkaline, high-salt, or ultraviolet irradiation conditions.

[0021] The present invention also provides the application of the above-mentioned underwater superoleophobic cotton fabric in oil-water separation, the application including oil-water mixture separation and oil-in-water emulsion separation.

[0022] Preferably, the oil-water separation process is a gravity-driven separation process.

[0023] Preferably, the oil phase is at least one selected from dichloromethane, chloroform, n-hexane, toluene, xylene, and petroleum ether.

[0024] Compared with the prior art, the present invention has the following significant advantages: (1) This invention uses cotton fabric as the substrate and utilizes the interfacial adhesion of PDA and the hydrophilic properties of SA to construct a composite coating on the substrate surface. The process steps are few and the operation is relatively simple. (2) Crosslinking with calcium ions helps to improve the bonding stability between the coating and the substrate, and improves the environmental resistance of the material under acid, alkali, salt and ultraviolet conditions. (3) The cotton fabric obtained has good hydrophilicity in the air and exhibits a high contact angle with a variety of organic oil phases underwater. It can be used for the separation of oil-water mixtures and oil-in-water emulsions. (4) Sodium alginate, a natural polymer, is used in the raw materials of this invention. Water is the main solvent in the preparation process, which has good environmental friendliness and is suitable for further promotion and application. Attached Figure Description

[0025] Figure 1 Scanning electron microscope images of different cotton fabric surface morphologies; Figure 2 The PDA-SA-Ca obtained in the embodiments of the present invention 2+ Figure 1 shows the contact angle test results of cotton fabrics with different organic oil phases underwater. Figure 3 The PDA-SA-Ca obtained in the embodiments of the present invention 2+ Images showing the appearance and microscopic observation results of cotton fabric before and after separation of oil-in-water emulsion. Detailed Implementation

[0026] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the invention will be further described below with reference to embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0027] Example 1 A method for preparing an underwater superoleophobic cotton fabric for oil-water separation includes the following steps: (1) Preparation of PDA-SA composite coating: Weigh 1 g sodium alginate and add it to 100 mL of deionized water. Stir at 400 r / min for 30 min until completely dissolved. Then add 0.4 g dopamine hydrochloride and 0.24 g Tris-HCl buffer to adjust the pH of the system to 8.5. Continue stirring at room temperature for 24 h to obtain dark brown PDA-SA composite coating. (2) Pretreatment of cotton fabric: Commercial cotton fabric was cut into 5 cm × 5 cm samples, placed in anhydrous ethanol, ultrasonically cleaned at 120W power for 20 min, taken out and rinsed 3 times with deionized water, and then placed in an 80℃ oven to dry for 2 h for later use. (3) Coating and curing: The pretreated cotton fabric is immersed in the PDA-SA composite coating by dip coating. After soaking for 5 minutes, it is taken out and excess coating is drained off. The coating amount is controlled to be 80 g / m². Then it is dried at 80℃ for 1 h to obtain PDA-SA pre-coated cotton fabric. (4) Calcium ion crosslinking: The PDA-SA pre-coated cotton fabric is immersed in 0.03 mol / L calcium chloride solution and crosslinked at room temperature for 1 min. After being taken out, the surface residual solution is rinsed with deionized water and then dried at 80℃ for 2 h to obtain underwater superoleophobic cotton fabric.

[0028] Example 2 This embodiment is basically the same as embodiment 1, except that in step (3), a spraying method is used for coating, and the coating amount is controlled to be 60 g / m². 2 The remaining conditions are the same as in Example 1.

[0029] Comparative Example 1 Commercial cotton fabrics were selected, ultrasonically cleaned with anhydrous ethanol for 20 min, and dried at 80℃ for 2 h, and then used directly as unmodified cotton fabric samples.

[0030] Comparative Example 2 This comparative example is basically the same as Example 1, except that the calcium ion crosslinking treatment in step (4) is omitted, and the PDA-SA pre-coated cotton fabric obtained in step (3) is used directly as the test sample.

[0031] Performance Testing and Result Analysis To verify the surface morphology, wettability, stability, and oil-water separation performance of the underwater superoleophobic cotton fabric obtained by the present invention, the samples obtained in the examples and comparative examples were tested as follows.

[0032] Surface morphology analysis The samples obtained from Comparative Example 1, Comparative Example 2, and Example 1 were observed using a scanning electron microscope, and the results are as follows: Figure 1 As shown. The surface of the unmodified cotton fabric (Comparative Example 1) is relatively smooth, with obvious pores between fibers; the PDA-SA coated cotton fabric (Comparative Example 2) shows a certain adhesion layer on the surface, but still has many pores; the fabric treated with Ca... 2+ After cross-linking, + A relatively uniform composite coating was formed on the surface of the cotton fabric (Example 1), and the porosity between fibers was significantly reduced. These results indicate that the PDA-SA composite coating and Ca... 2+ After cross-linking treatment, the surface structure of cotton fabric changes, which is conducive to the formation of an underwater superoleophobic interface.

[0033] Surface wettability test The air water contact angle of each sample was tested, and the results are shown in Table 1. The air water contact angle of Comparative Example 1 was 131.0°±1.5°, and that of Comparative Example 2 was 110.0°±1.2°. Both Examples 1 and 2 showed rapid wetting with water contact angles close to 0°, indicating that the cotton fabric surface treated by the method of the present invention has good hydrophilicity.

[0034] Table 1. Air contact angle of different cotton fabrics

[0035] Underwater oleophobic performance test The contact angles of the cotton fabric obtained in Example 1 with dichloromethane, trichloromethane, toluene, xylene, and n-hexane were tested underwater, and the results are as follows: Figure 2 As shown, the underwater contact angles of the aforementioned organic solvents are all greater than 155°, indicating that the cotton fabric has good underwater superoleophobic properties for different types of oil phases.

[0036] Stability test The cotton fabric obtained in Example 1 was immersed in hydrochloric acid solution with pH=1, sodium hydroxide solution with pH=14, and sodium chloride solution with 1 mol / L, and irradiated under 365 nm ultraviolet light. The underwater oil contact angle was tested after 0 h, 24 h, 48 h and 96 h. The results are shown in Table 2.

[0037] Table 2 PDA-SA-Ca 2+ Underwater oil contact angle of cotton fabrics after treatment under different conditions

[0038] The above results show that after treatment with acid, alkali, high salt and ultraviolet conditions, the underwater oil contact angle of the cotton fabric obtained by the present invention is still maintained above 155°, indicating that the cotton fabric has good environmental stability.

[0039] Oil-water mixture separation performance test The cotton fabric obtained in Example 2 was used as the separation medium to perform gravity-driven separation of mixed systems of dichloromethane / water, trichloromethane / water, toluene / water, xylene / water, and petroleum ether / water, with an oil-to-water volume ratio of 1:1. The separation flux and separation efficiency results are shown in Table 3.

[0040] Table 3 PDA-SA-Ca 2+ The separation performance of cotton fabrics for different oil-water mixtures

[0041] The above results show that the cotton fabric obtained by the present invention has good separation performance for different oil-water mixtures.

[0042] Water-in-oil emulsion separation performance test The toluene oil-in-water emulsion and the chloroform oil-in-water emulsion were separated by gravity using the cotton fabric obtained in Example 1. The oil-in-water emulsion was prepared as follows: 1 mL of organic solvent, 0.1 wt% Tween 80 and 99 mL of deionized water were mixed and stirred at 400 r / min for 4 h to obtain a stable emulsion.

[0043] Before separation, the emulsion appeared cloudy, and numerous dispersed oil droplets were visible under a microscope; after separation, the liquid transparency significantly improved, and no obvious oil droplet residue was observed under a microscope. Figure 3 As shown in the figure. The above results demonstrate that the cotton fabric obtained by this invention has a good separation effect on oil-in-water emulsions.

[0044] It should be noted that the present invention is not limited to the specific embodiments described above. Equivalent substitutions, simple modifications, or combined optimizations made by those skilled in the art to the technical solutions of the present invention without departing from the spirit and essence of the invention should all fall within the protection scope of the present invention.

Claims

1. A method for preparing an underwater superoleophobic cotton fabric, characterized in that, Includes the following steps: (1) Preparation of PDA-SA composite coating: Sodium alginate was added to deionized water and stirred until dissolved. Then, dopamine hydrochloride and Tris-HCl buffer were added to adjust the pH value of the system, so that dopamine would undergo oxidative polymerization and the resulting polydopamine would form a composite system with sodium alginate to obtain PDA-SA composite coating. (2) Pretreatment of cotton fabric: After cutting the cotton fabric, place it in anhydrous ethanol for ultrasonic cleaning to remove surface impurities, and then dry it. (3) Coating and curing: The PDA-SA composite coating is applied to the surface of the pretreated cotton fabric and dried to obtain a cotton fabric with a PDA-SA pre-coating. (4) Calcium ion crosslinking: The cotton fabric obtained in step (3) is immersed in calcium chloride solution for crosslinking treatment, taken out, washed and dried to obtain underwater superoleophobic cotton fabric.

2. The preparation method according to claim 1, characterized in that, In step (1), the concentration of sodium alginate solution is 0.5% to 1.5% by mass-volume ratio.

3. The preparation method according to claim 1, characterized in that, In step (1), the amounts of dopamine hydrochloride and Tris-HCl added are 0.4–0.8 g and 0.24–0.5 g, respectively; the pH of the system is 8–9, and the reaction time is 18–30 h.

4. The preparation method according to claim 1, characterized in that, In step (1), the stirring rate is 300-500 r / min; the system is in contact with air during the reaction.

5. The preparation method according to claim 1, characterized in that, In step (3), the coating method is any one of dip coating, brush coating or spray coating; the coating amount is 50 to 100 g / m².

6. The preparation method according to claim 1, characterized in that, In step (4), the concentration of calcium chloride solution is 0.02-0.04 mol / L, and the cross-linking time is 3-5 min.

7. An underwater superoleophobic cotton fabric, characterized in that, The underwater superoleophobic cotton fabric is prepared by the method described in any one of claims 1 to 6, and the surface of the cotton fabric has PDA-SA-Ca 2+ Composite coating.

8. The underwater superoleophobic cotton fabric according to claim 7, characterized in that, The cotton fabric exhibits superhydrophilicity in air, with a water contact angle close to 0°; underwater, it has a contact angle greater than 155° with one or more oils selected from dichloromethane, chloroform, n-hexane, toluene, and xylene.

9. The underwater superoleophobic cotton fabric according to claim 7, characterized in that, The cotton fabric, after being treated under acidic, alkaline, high-salt, or ultraviolet irradiation conditions, still maintains an underwater oil contact angle of over 155°.

10. The application of the underwater superoleophobic cotton fabric according to any one of claims 7 to 9 in oil-water separation, characterized in that, The applications include oil-water mixture separation and oil-in-water emulsion separation.

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