Ca3(po4)2 crystal reinforced zwitterionic hydrogel membrane and preparation method and application thereof

Abstract

The application relates to a Ca3(PO4)2 crystal reinforced zwitterionic hydrogel membrane and a preparation method and application thereof, the application uses PVDF as a base film, the material is low in price, good in mechanical performance, friendly to the environment and good in recycling performance. Through a polyphenol-metal dual autocatalysis method, a layer of zwitterionic hydrogel is simply and efficiently grafted on the surface of the PVDF film without heating and ultraviolet irradiation. Through a mineralization technology, the zwitterionic hydrogel membrane reinforced by inorganic crystals is used for constructing an inorganic crystal reinforced zwitterionic hydrogel membrane, preparing an oil-water separation membrane which is resistant to pollution, good in mechanical performance and long-term stable and cyclic. The inorganic crystal reinforced zwitterionic hydrogel membrane has the advantages of strong hydration performance and high mechanical stability, has a high separation efficiency on oil-in-water emulsion, shows obvious anti-pollution performance and good cyclic stability. The preparation method is simple, convenient to operate, low in energy consumption, easy to handle and free of secondary pollution, meets the green chemistry concept and has a good application prospect in the field of oil-water separation.

Description

Technical Field

[0001] This invention relates to a Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel membrane, its preparation method and application, belonging to the field of environmental functional material preparation technology. Background Technology

[0002] Water is the source of life and the most precious resource on Earth. With industrialization and urbanization, the treatment of oily wastewater has become a challenge. Oily wastewater often exists in the form of oil-in-water (O / W) emulsions, which are difficult to treat, severely damage the ecological environment, and affect people's lives. Therefore, there is an urgent need for efficient oil-water separation technology to treat oily wastewater, purify water resources, and simultaneously achieve water reuse.

[0003] Membrane separation technology has attracted much attention due to its high efficiency, but hydrophobic membranes are prone to fouling. In recent years, researchers have developed TA-APTES coatings based on tannic acid (TA) and 3-aminopropyltriethoxysilane (APTES), which have advantages such as simple preparation, low cost, and wide applicability, but suffer from poor stability and cycling performance.

[0004] Meanwhile, the hydration properties of membrane materials are crucial for their resistance to oil contamination. Membrane materials with strong hydration properties form a hydration layer on their surface in water. This hydration layer effectively prevents oil and other contaminants from directly contacting and adhering to the membrane surface, thereby reducing oil contamination of the separation membrane. Currently, hydrogel materials and zwitterionic polymers are used to construct antifouling separation membranes due to their strong hydration capabilities. Hydrogel materials are polymers with a three-dimensional network structure formed by the cross-linking of hydrophilic compounds rich in hydrogen-bonded groups such as -COOH, -OH, and -NH2 through chemical and physical processes. They possess super-strong hydration properties and have been reported to exhibit antifouling properties against various oils. Zwitterionic polymers utilize the equal amounts of positive and negatively charged functional groups in each structural unit to bind with numerous water molecules through charge, forming a strong and stable hydration layer on the membrane surface through electrostatic interactions, thus strengthening the "fouling resistance" mechanism on the membrane surface. Therefore, a polyphenol-metal dual autocatalytic system was used to initiate the polymerization of sulfobetaine-type amphiphilic monomers on the surface of TA-APTES-coated PVDF membranes, resulting in sulfobetaine-type amphiphilic nanogel-grafted modified PVDF porous membranes (PSBMA@TA-APTES@PVDF gel membranes), providing an effective means to solve the membrane fouling problem. However, due to the low Young's modulus and generally poor mechanical properties of hydrogels, their effectiveness in practical applications is severely limited. Especially in pressure-driven oil / water separation processes, hydrogels are prone to deformation and collapse under flow shear, leading to a decrease in the oil repellency and antifouling functions of hydrogel-modified membranes.

[0005] Unlike most polymers, some inorganic materials inherently possess excellent mechanical strength, chemical stability, and hydrophilicity, which is conducive to the formation of stable hydrophilic membrane structures. Combining the advantages of small pore size in polymer membranes and the stable oil-repellent properties of rigid inorganic materials, polymer / inorganic hybrid membranes with excellent hydrophilicity can achieve efficient separation of oil-water emulsions. Therefore, polymer / inorganic nanoparticle hybrid membranes can be constructed using mineralization technology. During the mineralization process, inorganic materials nucleate and grow at the molecular level and in confined positions, which is beneficial to the uniform dispersion of inorganic particles on the polymer membrane and greatly improves the membrane's hydrophilicity. Therefore, mineralizing the prepared PSBMA@TA-APTES@PVDF hydrogel membrane can successfully solve the problems of low mechanical strength and reduced antifouling performance in the oil-water separation process of zwitterionic hydrogel membranes.

[0006] Currently, there are relatively few research reports in this area. This invention combines multiple technologies, utilizing micro / nanosphere coatings, polyphenol-metal dual autocatalytic polymer technology, and mineralization technology, to prepare a novel Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel membrane. This membrane is not only simple to operate and has a short modification reaction time, but also possesses a superhydrophilic surface and excellent antifouling properties, allowing for long-term stable operation. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to overcome their technical defects. This invention utilizes polyphenol modification as a secondary reaction platform to initiate the polymerization of sulfobetaine-type amphiphilic monomers onto a PVDF membrane via a polyphenol-metal dual autocatalysis method, thus preparing a PSBMA@TA-APTES@PVDF hydrogel membrane. Based on this membrane, Ca3(PO4)2 crystals are used for mineralization, solving problems such as fouling, low flux, and poor mechanical properties of traditional separation membranes. This results in a novel membrane capable of separating various oil-water emulsions, significantly improving separation efficiency and circulation performance.

[0008] A method for preparing a Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel membrane includes the following steps:

[0009] (1) Pretreatment of PVDF base film: Wet with a certain amount of ethanol.

[0010] (2) Preparation of TA-APTES@PVDF membrane:

[0011] Dissolve TA (40-60 mg) in deionized water (20-30 mL), then add 500-1000 μL of APTES, place the pretreated PVDF base membrane in the solution, and react in a water bath at room temperature for 30 min-1 h with shaking to obtain a surface-roughened modified membrane with a micro-nanosphere coating.

[0012] (3) Preparation of PSBMA@TA-APTES@PVDF membrane:

[0013] Dissolve 0.058g FeCl3·6H2O, 0.005-0.025g ammonium persulfate, 0.01-0.02g N,N-methylenebisacrylamide and 0.1-0.5g methacrylic acid sulfobetaine in 5-10mL of deionized water to form a solution. Place the membrane obtained in step (2) into the solution and react with shaking in a water bath at room temperature for 1-3 hours to obtain a zwitterionic hydrogel membrane.

[0014] (4) Preparation of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane:

[0015] Dissolve 50–200 mg of anhydrous CaCl2 in 20 mL of deionized water, immerse the membrane obtained in step (3) in the solution for 10–30 min; then immerse it in water for 5–10 min; finally transfer the membrane to a prepared KH2PO4 solution of 60 mg / 20 mL–80 mg / 20 mL and immerse it for 10–30 min to obtain a zwitterionic hydrogel membrane reinforced with Ca3(PO4)2 crystals.

[0016] The above-mentioned Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel membrane was applied to oil-water separation experiments:

[0017] In this experiment, the oil-water emulsion used had a water-to-oil volume ratio of 99:1, and 20 mg of an ionic surfactant was added. The emulsion was stirred for 12 hours to form a stable emulsion, and then oil-water separation was performed using a vacuum filtration device. The concentration of the emulsion before separation was C0, and the concentration after separation was C... p Calculate the separation efficiency R.

[0018]

[0019] Figure 6 The substances to be separated, namely cyclohexane, dichloroethane, toluene, hexane, and petroleum ether, refer to the statistical data on the separation of these substances from an emulsion with a volume ratio of 1:99 to water.

[0020] The beneficial effects of this invention are as follows:

[0021] (1) The present invention uses PVDF as the base film, which is inexpensive, has good mechanical properties, is environmentally friendly, and has good recyclability.

[0022] (2) A zwitterionic hydrogel is grafted onto the surface of a PVDF membrane using a polyphenol-metal dual autocatalysis method without heating or ultraviolet light. This method is simple and efficient.

[0023] (3) Mineralization technology is used to construct inorganic crystal-reinforced zwitterionic hydrogel membranes to prepare oil-water separation membranes that are resistant to fouling, have good mechanical properties, and are stable in long-term cycling. These inorganic crystal-reinforced zwitterionic hydrogel membranes have the advantages of strong hydration performance and high mechanical stability, and have high separation efficiency for oil-in-water emulsions, exhibiting significant anti-fouling performance and good cycling stability.

[0024] (4) The preparation method of the present invention is simple, easy to operate, low in energy consumption, easy to process, and free from secondary pollution. It conforms to the concept of green chemistry and has a good application prospect in the field of oil-water separation. Attached Figure Description

[0025] Figure 1 This is a scanning electron microscope image of a hydrophobic PVDF-based film.

[0026] Figure 2 Scanning electron microscope image of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane.

[0027] Figure 3 This is a cross-sectional scanning electron microscope image of the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane.

[0028] Figure 4 The middle value represents the water contact angle in air of the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane.

[0029] Figure 5 The underwater oil contact angle of the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane is shown in the middle.

[0030] Figure 6 The rejection rates of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membranes for cyclohexane, dichloroethane, toluene, n-hexane, and petroleum ether, as well as the oil-water flux, are given.

[0031] Figure 7 The change in pure water flux (W) of the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane during circulation testing.

[0032] Figure 8 The flux (O) change of the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane in oil and water during the circulation test. Detailed Implementation

[0033] The embodiments of the present invention will be described in detail below:

[0034] This embodiment is implemented based on the technical solution of the present invention, and provides a detailed operation process and specific reaction conditions, but the scope of protection of the present invention is not limited to the following embodiment.

[0035] Example 1

[0036] Step 1: Pretreatment of PVDF base film: Wet with a certain amount of ethanol, the amount of ethanol used should be enough to cover the PVDF base film.

[0037] Step 2: Preparation of TA-APTES@PVDF membrane:

[0038] 50 mg of TA (tannic acid) was dissolved in 25 mL of deionized water, and then 700 μL of APTES (3-aminopropyltriethoxysilane) was added. The mixture was then placed in a pretreated PVDF-based membrane (polyvinylidene fluoride membrane) and reacted in a water bath at room temperature with shaking for 40 min to obtain a modified membrane with a roughened surface and a micro / nanosphere coating. The preferred room temperature is 15°C to 25°C.

[0039] Step 3: Preparation of PSBMA@TA-APTES@PVDF membrane:

[0040] 0.058g FeCl3·6H2O, 0.01g ammonium persulfate, 0.012g N,N-methylenebisacrylamide and 0.1g methacrylic acid sulfobetaine were dissolved in 6mL of deionized water to form a solution. The membrane obtained in step (2) was placed in this solution and reacted in a water bath at room temperature for 2h with shaking to obtain a zwitterionic hydrogel membrane.

[0041] Step 4: Preparation of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane:

[0042] Dissolve 50 mg of anhydrous CaCl2 in 20 mL of deionized water and immerse the membrane obtained in step 3 in the solution for 30 min; then immerse it in water for 10 min; finally, transfer the membrane to a prepared 69.6 mg / 20 mL KH2PO4 solution and immerse it for 30 min to obtain a zwitterionic hydrogel membrane reinforced with Ca3(PO4)2 crystals.

[0043] Figure 1 It can be seen that the surface of the hydrophobic PVDF base film is relatively smooth and the pore size is sparse.

[0044] Figure 2 The presence of inorganic nanoparticles in the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane indicates successful mineralization.

[0045] Figure 3It can be seen that inorganic nanoparticles are successfully embedded in the pores of the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane.

[0046] Figure 4 It can be seen that the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane exhibits superhydrophilic properties.

[0047] Figure 5 It can be seen that the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane exhibits underwater superoleophobic properties.

[0048] Figure 6 It can be seen that the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane can achieve a separation efficiency of over 99% for different types of oil-water emulsions with high throughput. Specifically, the separation efficiency for cyclohexane is close to 40%, for dichloroethane it reaches 99%, for toluene it is 90%, for n-hexane it is 70%, and for petroleum ether it is 52%.

[0049] Figure 7 It can be seen that the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane has good water circulation performance.

[0050] Figure 8 It can be seen that the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane has good emulsion circulation performance.

[0051] Example 2:

[0052] Step 1: Pretreatment of PVDF base film: Wet with a certain amount of ethanol.

[0053] Step 2: Preparation of TA-APTES@PVDF membrane:

[0054] Dissolve TA (50 mg) in 25 mL of deionized water, then add 700 μL of APTES, place the pretreated PVDF base membrane in the solution, and react in a water bath at room temperature for 40 min with shaking to obtain a modified membrane with a rough surface modified by a micro-nanosphere coating.

[0055] Step 3: Preparation of PSBMA@TA-APTES@PVDF membrane:

[0056] 0.058g FeCl3·6H2O, 0.01g ammonium persulfate, 0.012g N,N-methylenebisacrylamide and 0.1g methacrylic acid sulfobetaine were dissolved in 6mL of deionized water to form a solution. The membrane obtained in step (2) was placed in this solution and reacted in a water bath at room temperature for 2h with shaking to obtain a zwitterionic hydrogel membrane.

[0057] Step 4: Preparation of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane:

[0058] Dissolve 100 mg of anhydrous CaCl2 in 20 mL of deionized water and immerse the membrane obtained in step (3) in it for 30 min; then immerse it in water for 10 min; finally transfer the membrane to a prepared 69.6 mg / 20 mL KH2PO4 solution and immerse it for 30 min to obtain a zwitterionic hydrogel membrane reinforced with Ca3(PO4)2 crystals.

[0059] Example 3:

[0060] Step 1: Pretreatment of PVDF base film: Wet with a certain amount of ethanol.

[0061] Step 2: Preparation of TA-APTES@PVDF membrane:

[0062] Dissolve TA (50 mg) in 25 mL of deionized water, then add 700 μL of APTES, place the pretreated PVDF base membrane in the solution, and react in a water bath at room temperature for 40 min with shaking to obtain a modified membrane with a rough surface modified by a micro-nanosphere coating.

[0063] Step 3: Preparation of PSBMA@TA-APTES@PVDF membrane:

[0064] 0.058g FeCl3·6H2O, 0.01g ammonium persulfate, 0.012g N,N-methylenebisacrylamide and 0.2g methacrylic acid sulfobetaine were dissolved in 6mL of deionized water to form a solution. The membrane obtained in step (2) was placed in this solution and reacted in a water bath at room temperature for 2h with shaking to obtain a zwitterionic hydrogel membrane.

[0065] Step 4: Preparation of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane:

[0066] Dissolve 50 mg of anhydrous CaCl2 in 20 mL of deionized water and immerse the membrane obtained in step (3) in it for 30 min; then immerse it in water for 10 min; finally transfer the membrane to a prepared 69.6 mg / 20 mL KH2PO4 solution and immerse it for 30 min to obtain a zwitterionic hydrogel membrane reinforced with Ca3(PO4)2 crystals.

[0067] Example 4:

[0068] Step 1: Pretreatment of PVDF base film: Wet with a certain amount of ethanol.

[0069] Step 2: Preparation of TA-APTES@PVDF membrane:

[0070] Dissolve TA (50 mg) in 25 mL of deionized water, then add 500 μL of APTES, place the pretreated PVDF base membrane in the solution, and react in a water bath at room temperature for 40 min with shaking to obtain a modified membrane with a rough surface modified by a micro-nanosphere coating.

[0071] Step 3: Preparation of PSBMA@TA-APTES@PVDF membrane:

[0072] 0.058g FeCl3·6H2O, 0.01g ammonium persulfate, 0.012g N,N-methylenebisacrylamide and 0.1g methacrylic acid sulfobetaine were dissolved in 6mL of deionized water to form a solution. The membrane obtained in step (2) was placed in this solution and reacted in a water bath at room temperature for 2h with shaking to obtain a zwitterionic hydrogel membrane.

[0073] Step 4: Preparation of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane:

[0074] Dissolve 50 mg of anhydrous CaCl2 in 20 mL of deionized water and immerse the membrane obtained in step (3) in it for 30 min; then immerse it in water for 10 min; finally transfer the membrane to a prepared 69.6 mg / 20 mL KH2PO4 solution and immerse it for 30 min to obtain a zwitterionic hydrogel membrane reinforced with Ca3(PO4)2 crystals.

[0075] Example 5:

[0076] Step 1: Pretreatment of PVDF base film: Wet with a certain amount of ethanol.

[0077] Step 2: Preparation of TA-APTES@PVDF membrane:

[0078] Dissolve TA (50 mg) in 25 mL of deionized water, then add 700 μL of APTES, place the pretreated PVDF base membrane in the solution, and react in a water bath at room temperature for 40 min with shaking to obtain a modified membrane with a rough surface modified by a micro-nanosphere coating.

[0079] Step 3: Preparation of PSBMA@TA-APTES@PVDF membrane:

[0080] 0.058g FeCl3·6H2O, 0.01g ammonium persulfate, 0.012g N,N-methylenebisacrylamide and 0.1g methacrylic acid sulfobetaine were dissolved in 6mL of deionized water to form a solution. The membrane obtained in step (2) was placed in this solution and reacted in a water bath at room temperature for 2h with shaking to obtain a zwitterionic hydrogel membrane.

[0081] Step 4: Preparation of Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane:

[0082] Dissolve 50 mg of anhydrous CaCl2 in 20 mL of deionized water and immerse the membrane obtained in step (3) in it for 30 min; then immerse it in water for 10 min; finally transfer the membrane to a prepared 80.0 mg / 20 mL KH2PO4 solution and immerse it for 30 min to obtain a zwitterionic hydrogel membrane reinforced with Ca3(PO4)2 crystals.

[0083] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel film, characterized by: The Ca3(PO4)2 crystal enhanced zwitterionic hydrogel membrane is prepared by using a PVDF separation membrane as a base membrane, preparing a micro-nano sphere coating modified membrane through TA-APTES, and then polymerizing zwitterionic monomer methacrylic acid sulfobetaine through a phenol-metal dual autocatalysis method to obtain a zwitterionic hydrogel membrane, and then mineralizing and modifying the zwitterionic hydrogel membrane through Ca3(PO4)2.

2. The method for preparing a Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel membrane according to claim 1, characterized in that: The PVDF base membrane used is a hydrophobic membrane.

3. The method for preparing a Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel membrane according to claim 1, characterized in that: The micro-nano sphere coating modified membrane used has a rough surface, and tannic acid used in the preparation process can be used as a catalyst for zwitterionic radical reaction in the next step.

4. The method for preparing a Ca3(PO4)2 crystal-reinforced zwitterionic hydrogel membrane according to claim 1, characterized in that: The prepared zwitterionic hydrogel membrane is polymerized by using a polyphenol-metal dual autocatalysis method to initiate zwitterionic monomer methacrylic acid sulfobetaine, and the reaction is carried out at room temperature.

5. A method of preparing a Ca3(P04)2 crystal reinforced zwitterionic hydrogel film according to any one of claims 1-4, characterized in that: The method comprises the following steps: Step 1: Pretreatment of the PVDF base membrane: wetting with ethanol; Step 2: Preparation of the TA-APTES@PVDF membrane: Dissolve TA in deionized water, then add APTES, put the pretreated PVDF base membrane into the solution, and carry out water bath oscillation reaction at room temperature to obtain a micro-nano sphere coating modified membrane with a rough surface; Step 3: Preparation of the PSBMA@TA-APTES@PVDF membrane: Dissolve FeCl3·6H2O, ammonium persulfate, N,N-methylene bisacrylamide and methacrylic acid sulfobetaine in deionized water to form a solution, put the membrane obtained in step 2 into the solution, and carry out water bath oscillation reaction at room temperature to obtain a zwitterionic hydrogel membrane; Step 4: Preparation of the Ca3(PO4)2 / PSBMA@TA-APTES@PVDF membrane: Dissolve anhydrous CaCl2 in deionized water, soak the membrane obtained in step 3 in the solution, then soak it in water, and finally transfer the membrane to a KH2PO4 solution to soak, to obtain a Ca3(PO4)2 crystal enhanced zwitterionic hydrogel membrane.

6. The method for preparing a Ca3(PO4)2 crystal enhanced zwitterionic hydrogel membrane according to claim 5, characterized in that, Dissolve 40-60 mg of TA in 20-30 mL of deionized water, then add 500-1000 μL of APTES, put the pretreated PVDF base membrane into the solution, and carry out water bath oscillation reaction at room temperature for 30 min-1 h to obtain a micro-nano sphere coating modified membrane with a rough surface; Dissolve 0.058 g of FeCl3·6H2O, 0.005-0.025 g of ammonium persulfate, 0.01-0.02 g of N,N-methylene bisacrylamide and 0.1-0.5 g of methacrylic acid sulfobetaine in 5-10 mL of deionized water; Carry out water bath oscillation reaction for 1-3 h; Dissolve 50-200 mg of anhydrous CaCl2 in 20 mL of deionized water, soak the membrane obtained in step 3 in the solution for 10-30 min, then soak it in water for 5-10 min, and finally transfer the membrane to a prepared KH2PO4 solution of 60 mg / 20 mL-80 mg / 20 mL to soak for 10-30 min.

7. A Ca3(PO4)2 crystal reinforced zwitterionic hydrogel film, characterized in that, The Ca3(PO4)2 crystal enhanced zwitterionic hydrogel membrane is obtained by using the preparation method according to any one of claims 1-6.

8. Use of the Ca3(PO4)2 crystal reinforced zwitterionic hydrogel membrane of claim 7 for the separation of oil-water emulsions.

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