Preparation method of super hydrophilic / underwater super oleophobic separation membrane for kitchen wastewater treatment

Abstract

The present invention discloses a method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane for treating food wastewater. The preparation method comprises the following steps: firstly, alkali etching is performed to generate two functional groups, carboxyl and hydroxyl, on the surface of a polymer fiber fabric; then, under alkaline conditions, dopamine is used as an adhesive to fix Cu(OH)2 nanoparticles on the surface of the fabric; and finally, a super-hydrophilic / underwater super-oleophobic separation membrane is obtained. The super-hydrophilic / underwater super-oleophobic separation membrane of the present invention can be applied to the oil-water separation treatment of food waste wastewater. The preparation process of the present invention is simple, the raw materials are readily available, and the obtained super-hydrophilic / underwater super-oleophobic separation membrane has good stability, high separation efficiency and high reuse rate.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment materials, and in particular to a method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane. Background Art

[0002] With the improvement of living standards and the development of the catering industry, the production of food waste has been increasing rapidly, now accounting for nearly 20% of total municipal solid waste. The pretreatment process of food waste generates a large amount of food wastewater, which is characterized by a high oil content. Currently, the mainstream treatment technology for food wastewater is biochemical treatment, but the high oil content in the wastewater reduces the effectiveness of subsequent treatment.

[0003] Traditional oil-water separation methods include adsorption, skimming, gravity separation, biological treatment, flotation, and centrifugation. Compared to traditional separation technologies, membrane separation offers high efficiency and simplified operation, making it suitable for separating various oily wastewaters, particularly surfactant-stabilized oil / water emulsions. Oil-water functional separation membrane materials can be categorized based on their superwettability: "water removal" superhydrophobic / superoleophilic separation membranes, "oil removal" superhydrophilic / superoleophobic separation membranes, and stimuli-responsive separation membranes.

[0004] The Chinese invention patent with publication number CN103357276A discloses a UV-cured super-hydrophilic and underwater super-oleophobic oil-water separation membrane. This mesh membrane uses a fabric mesh as a substrate and adsorbs a layer of water-based UV-cured hybrid coating on it. Although it has good oil-water separation effect and oil pollution resistance, the thicker membrane coating reduces the water flux, and the membrane water resistance and chemical resistance are poor. The Chinese invention patent with publication number CN109012217A discloses a preparation method of a pH-responsive cross-linked multilayer membrane for oil-water separation. Its preparation method is relatively complicated and uses polyacrylic acid, which belongs to Class 3 carcinogens and has greater irritation to the eyes, respiratory system and skin. The Chinese invention patent with publication number CN105964014A discloses a preparation method of a hydrophilic and oleophobic stainless steel mesh membrane for oil-water separation. Although the oil-water separation efficiency of the oil-water separation membrane is high, the stainless steel mesh membrane is easily corroded and destroyed in an environment with higher salinity.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The present invention addresses the shortcomings of the prior art by proposing innovative solutions, particularly a method for preparing a superhydrophilic / underwater superoleophobic separation membrane. The membrane prepared by this method exhibits excellent stability, superhydrophilicity, and underwater superoleophobicity, high oil-water separation efficiency, and high reusability.

[0007] To solve the above problems, the present invention adopts the following solution: a method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane for treating food wastewater, characterized by comprising the following steps:

[0008] (1) Ultrasonic cleaning of the polymer membrane in an ethanol solution to remove impurities on the surface;

[0009] (2) The clean polymer mesh is placed in an alkaline etching solution for etching, and then taken out, rinsed with deionized water, and dried. Through the etching treatment, two functional groups, carboxyl and hydroxyl, are generated on the surface of the polymer fiber fabric;

[0010] (3) Dissolve CuCl2 powder in an ammonia solution, then add dopamine (DA), and stir the mixture under ultrasonication to obtain a PDA-copper ammonia solution.

[0011] (4) Immersing the polymer mesh obtained in step (2) in a PDA-copper ammonia solution, then drying to remove residual ammonia, thereby obtaining a polymer mesh containing copper hydroxide and dopamine. Finally, the polymer mesh is repeatedly washed with deionized water to remove any residual NaOH that may have remained in step (2), and then dried to obtain a superhydrophilic / underwater superoleophobic separation membrane.

[0012] Furthermore, the method for preparing the superhydrophilic / underwater superoleophobic separation membrane for treating kitchen wastewater is characterized in that the polymer mesh membrane in step (1) is a polyester, polypropylene or nylon fabric, and the concentration of the ethanol solution is 95%.

[0013] Furthermore, the method for preparing the superhydrophilic / underwater superoleophobic separation membrane for treating food wastewater is characterized in that the alkaline etching solution in step (2) is a NaOH solution with a concentration of 10 g / L; the temperature of the alkaline etching solution is maintained at 70-80°C during the etching treatment for at least 1 hour; and the drying method is drying at 50°C for half an hour.

[0014] Furthermore, the method for preparing the superhydrophilic / underwater superoleophobic separation membrane for treating kitchen wastewater is characterized in that the pH of the ammonia solution in step (3) is 9, and the CuCl2 powder, dopamine and ammonia solution are mixed in a ratio of (0.2~1 g): (1~2 g): 1L.

[0015] Furthermore, the method for preparing the superhydrophilic / underwater superoleophobic separation membrane for treating kitchen wastewater is characterized in that in step (4), the immersion time of the polymer mesh membrane in the PDA-copper ammonia solution is 10 min, the number of immersions is 4 times, and the drying temperature is 50°C.

[0016] The technical effects of the present invention are as follows: (1) The present invention modifies PDA and Cu(OH)2 nanoparticles on the surface of polymer fabrics through etching and impregnation methods to construct a micro-nano layered rough structure, wherein PDA not only strengthens the adhesion of Cu(OH)2 nanoparticles to the fabric, but also enhances the hydrophilicity of the fabric.

[0017] (2) The superhydrophilic / underwater superoleophobic separation membrane prepared by the present invention has good stability, high separation efficiency and reuse rate, and can be used in environments with high salinity.

[0018] (3) The preparation process of the present invention is simple, the raw materials are readily available, and large-scale production is possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a diagram of the preparation steps of the superhydrophilic / underwater superoleophobic separation membrane.

[0020] Figure 2 This is a diagram showing the oil-water separation efficiency of the superhydrophilic / underwater superoleophobic separation membrane prepared in Example 1 for use in kitchen wastewater.

[0021] Figure 3 This is a diagram showing the oil-water separation efficiency of the separation membrane prepared in the comparative example when used for food wastewater. Implementation Method

[0022] The present invention will be further described in detail below with reference to the accompanying drawings.

[0023] The present invention uses a polymer fabric as a substrate and first undergoes an alkali etching process to generate two functional groups, carboxyl and hydroxyl, on the fabric surface. Under alkaline conditions, NH3H2O ​​not only promotes the polymerization of DA, but also forms copper ammonia ions. Due to the presence of abundant catechol groups and amino groups, PDA can serve as a bridge between the polymer fabric and the copper ammonia ions, thereby creating a layered surface structure. After the impregnation process, the hydroxyl groups on the fabric surface form hydrogen bonds with PDA, while the carboxyl groups on the surface complex with copper ammonia, forming a strong bond between PDA-copper ammonia ions and the fabric. After the drying process, the copper ammonia decomposes, the ammonia evaporates, and copper hydroxide is deposited on the fabric surface. Through this method, PDA and Cu(OH)2 nanoparticles can be tightly combined on the fabric surface to obtain a super hydrophilic / underwater super oleophobic separation membrane. Example

[0024] (1) Cut the polyester fabric into 5 cm × 5 cm size, clean the surface impurities, and ultrasonically clean it in 95% ethanol solution for 20 min.

[0025] (2) Place the pre-cleaned polyester fabric in a 10 g / L NaOH solution and heat it in a water bath at 80°C for 1 hour. After taking it out, wash it with deionized water to remove the NaOH on the surface, and then place it in a constant temperature drying oven at 50°C for half an hour.

[0026] (3) Preparation of PDA-copper ammonia solution: Dissolve CuCl2 in ammonia solution with a pH of 9 to a concentration of 1 g / L, then add dopamine to a concentration of 2 g / L. After ultrasonic dispersion for 30 min, the PDA-copper ammonia solution is obtained.

[0027] (4) The polyester fabric obtained in step (2) was immersed in a PDA-copper ammonia solution for 10 min, and then immersed four times, and then dried at 50°C to remove ammonia on the surface. Finally, it was rinsed with deionized water and dried to obtain a superhydrophilic / underwater superoleophobic separation membrane. Example

[0028] (1) Cut the polyester fabric into 5 cm × 5 cm size, clean the surface impurities, and ultrasonically clean it in 95% ethanol solution for 20 min.

[0029] (2) Place the pre-cleaned polyester fabric in a 10 g / L NaOH solution and heat it in a water bath at 80°C for 1 hour. After taking it out, wash it with deionized water to remove the NaOH on the surface, and then place it in a constant temperature drying oven at 50°C for half an hour.

[0030] (3) Preparation of PDA-copper ammonia solution: Dissolve CuCl2 in ammonia solution with a pH of 9 to a concentration of 0.5 g / L, then add dopamine to a concentration of 1.5 g / L. After ultrasonic dispersion for 30 min, the PDA-copper ammonia solution is obtained.

[0031] (4) The polyester fabric obtained in step (2) was immersed in a PDA-copper ammonia solution for 10 min, and then immersed four times, and then dried at 50°C to remove ammonia on the surface. Finally, it was rinsed with deionized water and dried to obtain a superhydrophilic / underwater superoleophobic separation membrane. Example

[0032] (1) Cut the polyester fabric into 5 cm × 5 cm size, clean the surface impurities, and ultrasonically clean it in 95% ethanol solution for 20 min.

[0033] (2) Place the pre-cleaned polyester fabric in a 10 g / L NaOH solution and heat it in a water bath at 80°C for 1 hour. After taking it out, wash it with deionized water to remove the NaOH on the surface, and then place it in a constant temperature drying oven at 50°C for half an hour.

[0034] (3) Preparation of PDA-copper ammonia solution: Dissolve CuCl2 in ammonia solution with a pH of 9 to a concentration of 0.2 g / L, then add dopamine to a concentration of 1 g / L. After ultrasonic dispersion for 30 min, the PDA-copper ammonia solution is obtained.

[0035] (4) The polyester fabric obtained in step (2) was immersed in a PDA-copper ammonia solution for 10 min, and then immersed four times, and then dried at 50°C to remove ammonia on the surface. Finally, it was rinsed with deionized water and dried to obtain a superhydrophilic / underwater superoleophobic separation membrane.

[0036] Comparative Example:

[0037] To demonstrate the stability of the superhydrophilic / underwater superoleophobic separation membrane prepared in the present invention for oil-water separation from food wastewater, a comparative experiment was conducted with a separation membrane prepared by referring to a method for preparing a high-strength, high-efficiency oil-water separation filter paper disclosed in Chinese patent CN 112982020 A.

Claims

1. A method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane for treating kitchen wastewater, characterized in that: The following steps are involved: (1) Ultrasonic cleaning of the polymer membrane in an ethanol solution to remove impurities on the surface; (2) The clean polymer mesh is placed in an alkaline etching solution for etching, and then taken out, rinsed with deionized water, and dried. Through the etching treatment, two functional groups, carboxyl and hydroxyl, are generated on the surface of the polymer fiber fabric; (3) Dissolve CuCl2 powder in an ammonia solution, then add dopamine (DA), and stir the mixture under ultrasonication to obtain a PDA-copper ammonia solution. (4) The polymer mesh obtained in step (2) is immersed in a PDA-copper ammonia solution, and then dried to remove residual ammonia to obtain a polymer mesh containing copper hydroxide and dopamine. Finally, the polymer mesh is repeatedly washed with deionized water to remove residual NaOH, and dried to obtain a superhydrophilic / underwater superoleophobic separation membrane.

2. The method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane for treating kitchen wastewater according to claim 1, characterized in that: The polymer mesh in step (1) is polyester, polypropylene or nylon fabric, and the concentration of the ethanol solution is 95%.

3. The method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane for treating food wastewater according to claim 1, characterized in that: The alkaline etching solution in step (2) is a NaOH solution with a concentration of 10 g / L; the temperature of the alkaline etching solution is maintained at 70-80°C during the etching process for at least 1 hour; The drying method is to dry the mixture at 50°C for half an hour.

4. The method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane for treating food wastewater according to claim 1, wherein: The pH of the ammonia solution in step (3) is 9, and the CuCl2 powder, dopamine and ammonia solution are mixed in a ratio of (0.2-1 g): (1-2 g): 1 L.

5. The method for preparing a super-hydrophilic / underwater super-oleophobic separation membrane for treating food wastewater according to claim 1, wherein: In step (4), the polymer mesh membrane is immersed in the PDA-copper ammonia solution for 10 minutes, the number of immersions is 4 times, and the drying temperature is 50°C.

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