Super-hydrophilic-underwater oleophobic ceramic membrane as well as preparation method and application thereof

Abstract

The invention discloses a super-hydrophilic-underwater oleophobic ceramic membrane as well as a preparation method and application thereof, and relates to the technical field of ceramic membrane preparation, a ceramic support is soaked in TiO2-SiO2-ZrO2 ternary hydrophilic sol in a certain proportion for a certain time by a soaking method, and low-temperature sintering is performed after drying so as to increase the roughness of the membrane surface and membrane pore channels to improve the hydrophilicity of the membrane, so that the super-hydrophilic-underwater oleophobic ceramic membrane is prepared. And chemically grafting a chitosan oleophobic layer through a surface coating method to prepare the super-hydrophilic-underwater oleophobic ceramic membrane. The surface of the ceramic membrane and the interiors of pore channels have super-hydrophilicity, the contact angle is 2 degrees, the surface of the ceramic membrane is endowed with underwater oleophobicity through a surface coating method of the oleophobic coating liquid, the contact angle with soybean oil underwater is 151 degrees, the ceramic membrane is prevented from being in direct contact with grease during oil-water separation, membrane layer pollution is reduced, and the running flux is improved.

Description

Technical Field

[0001] This invention relates to the field of ceramic membrane preparation technology, and in particular to a superhydrophilic-underwater oleophobic ceramic membrane, its preparation method and application. Background Technology

[0002] Oil-water mixtures exist in chemical industries, food processing, petroleum production, refining, and other related fields. They pose a significant threat to human health and the natural environment. Emulsified oil, due to the action of surfactants, exists in an emulsified state in water, with small oil droplet sizes, generally between 0.1-10 μm. It can be relatively stably dispersed in water and is difficult to spontaneously aggregate into larger oil droplets. Compared with other types of oil-water mixtures, such as floating oil and dispersed oil, it is more difficult to separate and remove from water.

[0003] Membrane filtration technology belongs to fine filtration technology and can efficiently separate stable emulsified oil in wastewater. Ceramic membranes have broad application prospects in various industrial and scientific fields. Their excellent filtration and separation performance, as well as chemical stability and mechanical strength, make them an ideal choice for various complex separation and purification processes. However, due to their inorganic materials and porous structure, the surface wettability of most ceramic membranes is hydrophilic-lipophilic. This leads to problems such as low oil-water selectivity, low operating flux, and weak resistance to oil fouling in traditional ceramic membrane oil-water separation treatment. Patent CN107213801A discloses a method for wettability modification by growing nano-scale columnar TiO2 on the membrane surface to prepare a superhydrophilic-ocean-water-repellent ceramic membrane. However, the columnar TiO2 arranged on the membrane surface has not undergone a high-temperature sintering phase transformation process, resulting in weak bonding between the membrane surface and the columnar TiO2. Furthermore, the membrane thickness is significantly increased due to the columnar TiO2, affecting the flux of the ceramic membrane. Patent CN105948817A discloses a method for surface modification by immersing a substrate in methylated chitosan with SiO2 to prepare a superhydrophilic-ocean-water-repellent ceramic flat sheet membrane. However, the instability of the SiO2 solution affects the modification effect and efficiency of chitosan. Moreover, by immersing, the ceramic membrane and chitosan crosslink, and the chitosan macromolecules enter the pores of the ceramic membrane, further clogging the pores and causing a decrease in flux. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a superhydrophilic-underwater oleophobic ceramic membrane and its preparation method and application. The method achieves hydrophilic modification of the membrane surface and pores by significantly roughening the support surface and pores, and imparts underwater oleophobic properties to the ceramic membrane surface by cross-linking chitosan oleophobic coating through surface coating method, thus preparing a special ceramic membrane for emulsified oil-water separation in superhydrophilic-underwater oleophobic applications.

[0005] In a first aspect, the present invention provides a method for preparing a superhydrophilic-underwater oleophobic ceramic membrane, specifically comprising the following steps:

[0006] 1) Preparation of TiO2-SiO2-ZrO2 ternary hydrophilic sol: Titanium precursor, silicon precursor, zirconium precursor, water, inhibitor, pH adjuster and solvent are mixed and stirred at room temperature for 1-3 hours, and then heated in a water bath at 40-60℃ for 6-8 hours. Through the hydrolysis and polymerization reaction of titanium precursor, silicon precursor and zirconium precursor, TiO2-SiO2-ZrO2 ternary hydrophilic sol is obtained.

[0007] 2) Preparation of roughened ceramic film: The ceramic support is immersed in the TiO2-SiO2-ZrO2 ternary hydrophilic sol prepared in step 1), and then dried and sintered to roughen the surface and the interior of the pores of the film layer, thus obtaining a roughened ceramic film.

[0008] 3) Preparation of chitosan oleophobic coating solution: Disperse chitosan powder in an acidic solution, add a thickener, stir to dissolve, and obtain chitosan oleophobic coating solution;

[0009] 4) Preparation of ceramic membrane loaded with NQ-62: The roughened ceramic membrane obtained in step 2) is immersed in an acid solution for activation treatment for 2 hours to give the ceramic membrane active sites and active pores. Then it is dried at 60°C. Then the silane coupling agent NQ-62 is uniformly coated on the surface of the ceramic membrane to obtain a ceramic membrane loaded with NQ-62.

[0010] 5) Crosslinked chitosan oleophobic layer on ceramic membrane surface: The chitosan oleophobic coating solution prepared in step 3) is uniformly coated on the surface of the ceramic membrane loaded with NQ-62 prepared in step 4) to form a chitosan coating layer. After drying at room temperature, a superhydrophilic-underwater oleophobic ceramic membrane is obtained.

[0011] This invention employs an impregnation method, in which a ceramic support is immersed in a certain proportion of TiO2-SiO2-ZrO2 ternary hydrophilic sol for a certain period of time, dried, and then sintered at low temperature to increase the surface roughness and pore roughness of the membrane, thereby improving its hydrophilicity. Then, a chitosan oleophobic layer is chemically grafted onto the surface using a surface coating method. The hydrophilic groups and excellent film-forming properties of chitosan allow it to form a water film on its surface underwater. The water film of polar molecules is incompatible with oils and greases, thus endowing the ceramic membrane surface with underwater oleophobic properties.

[0012] In conjunction with the first aspect, in some embodiments, the molar ratio of the titanium precursor, silicon precursor, zirconium precursor, water, inhibitor, pH adjuster, and solvent in step 1) is 1:(0.5-1):(0.5-1):(5-10):(0.1-0.2):(0.5-1):(80-100).

[0013] In conjunction with the first aspect, in some embodiments, the titanium precursor in step 1) is one or more of titanium tetrabutyl titanate, titanium isopropoxide, titanium sec-butoxide, and titanium tert-butoxide.

[0014] The silicon precursor is one or more of tetraethyl orthosilicate and tetraethyl orthosilicate;

[0015] The zirconium precursor is one or more of zirconium n-butoxide, zirconium isopropoxide, and zirconium sec-butoxide.

[0016] The inhibitor is one of diethanolamine and acetylacetone;

[0017] The pH adjuster is either hydrochloric acid or nitric acid;

[0018] The solvent is one of ethanol and isobutanol.

[0019] In conjunction with the first aspect, in some embodiments, the ceramic support described in step 2) has a pore size of 0.5 μm and an impregnation time of 6-8 h.

[0020] In conjunction with the first aspect, in some embodiments, the drying temperature in step 2) is 100-120°C and the drying time is 30-90 min, and the sintering temperature is 400-500°C and the sintering time is 20-40 min.

[0021] In conjunction with the first aspect, in some embodiments, the chitosan content in step 3) is 5-10 wt%, the acid solution is one of acetic acid aqueous solution and citric acid aqueous solution, the volume concentration of the acid solution is 1-2%, and the thickener is one of polyvinyl alcohol and hydroxymethyl cellulose, the mass concentration of the thickener is 0.1-0.2 wt%.

[0022] In conjunction with the first aspect, in some embodiments, the acid solution in step 4) is one of nitric acid aqueous solution, acetic acid aqueous solution, and citric acid aqueous solution, with a volume concentration of 1-5%.

[0023] In conjunction with the first aspect, in some embodiments, the chitosan oleophobic coating method in step 5) is either spraying or scraping.

[0024] Secondly, the present invention provides a superhydrophilic-underwater oleophobic ceramic membrane, which is prepared by the preparation method described above.

[0025] Thirdly, the present invention provides the application of the above-mentioned superhydrophilic-underwater oleophobic ceramic membrane in oil-water separation.

[0026] The beneficial effects of this invention are:

[0027] 1. This invention is based on the good hydrophilicity of TiO2, SiO2 and ZrO2. By adjusting the ratio, a TiO2-SiO2-ZrO2 ternary hydrophilic sol is prepared. The nano-TiO2, SiO2 and ZrO2 particles with different particle sizes and disordered distribution can effectively improve the surface roughness and pore roughness of the membrane after sintering phase transformation, optimize the hydrophilicity of the ceramic membrane and improve the operating throughput of oil-water separation.

[0028] 2. This invention improves the superhydrophilicity of the ceramic membrane surface and pore interior by impregnating it with a hydrophilic sol, with a contact angle of 2°. The surface coating method of the oleophobic coating liquid imparts underwater oleophobicity to the ceramic membrane surface, with a contact angle of 151° with soybean oil underwater. This prevents the ceramic membrane from directly contacting the oil during oil-water separation, reducing membrane contamination and increasing operating throughput.

[0029] 3. The oil-water separation method based on the superhydrophilic-underwater oleophobic ceramic membrane of this invention achieves an oil rejection rate of over 99%, and the flux does not decrease significantly after 40 minutes of operation, demonstrating excellent oil-water separation stability. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of the roughened film surface prepared in Example 1 of this invention;

[0031] Figure 2 This is a scanning electron microscope (SEM) image of the cross-section of the roughened film layer prepared in Example 1 of this invention.

[0032] Figure 3 This is a hydrophilicity test image of the ceramic membrane with roughened surface and pore interior prepared in Example 1 of the present invention.

[0033] Figure 4 This is an underwater oleophobicity test image of the superhydrophilic-underwater oleophobic ceramic membrane prepared in Example 1 of this invention;

[0034] Figure 5 This is a schematic diagram of the cross-flow filtration oil-water separation device constructed in an embodiment of the present invention, wherein: 1. 500mg / L soybean oil emulsified oil; 2. water pump; 3. pressure gauge; 4. superhydrophilic-underwater oleophobic ceramic membrane and membrane module; 5. back pressure valve; 6. online balance. Detailed Implementation

[0035] 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.

[0036] Unless otherwise specified in the following examples, the conditions are as per standard conditions or the manufacturer's recommendations. Raw materials, equipment, or instruments whose manufacturers are not specified are all commercially available products.

[0037] This invention proposes a superhydrophilic-underwater oleophobic ceramic membrane, its preparation method, and its application. A certain proportion of TiO2-SiO2-ZrO2 ternary hydrophilic sol is prepared by doping with phase change nanocrystals of different types and sizes. A support is then immersed in this sol and sintered at low temperature. This significantly roughens the surface and pores of the support, achieving hydrophilic modification of the membrane surface and pores. A chitosan oleophobic coating is then applied via surface coating to impart underwater oleophobic properties to the ceramic membrane surface. This results in a superhydrophilic-underwater oleophobic ceramic membrane specifically designed for emulsified oil-water separation. It exhibits advantages such as high oil rejection rate, high separation efficiency, and strong antifouling properties, showing potential for application in the separation of various emulsified oil-containing wastewaters.

[0038] The present invention provides a method for preparing a high-performance nano-electrospun meltblown hydrophilic material for leukocyte filtration, comprising the following steps:

[0039] 1) Preparation of TiO2-SiO2-ZrO2 ternary hydrophilic sol: Mix titanium precursor, silicon precursor, zirconium precursor, water, inhibitor, pH adjuster and solvent. After water bath heating and stirring, the titanium, silicon and zirconium precursors undergo hydrolysis and polymerization reactions to obtain TiO2-SiO2-ZrO2 ternary hydrophilic sol for later use. The titanium precursor is one or more of tetrabutyl titanate, titanium isopropoxide, titanium sec-butoxide, and titanium tert-butoxide; the silicon precursor is one or more of tetraethyl orthosilicate and tetraethyl orthosilicate; the zirconium precursor is one or more of zirconium n-butoxide, zirconium isopropoxide, and zirconium sec-butoxide; the inhibitor is one of diethanolamine and acetylacetone; the pH adjuster is one of hydrochloric acid and nitric acid; and the solvent is one of ethanol and isobutanol. The molar ratio of the titanium precursor, silicon precursor, zirconium precursor, water, inhibitor, pH adjuster, and solvent is 1:(0.5-1):(0.5-1):(5-10):(0.1-0.2):(0.5-1):(80-100).

[0040] 2) Ceramic support impregnation, drying, and sintering: The ceramic support is impregnated in the above-mentioned TiO2-SiO2-ZrO2 ternary hydrophilic sol, dried, and sintered for later use. The ceramic support has a pore size of 0.5 μm, an impregnation time of 6-8 h, a drying temperature of 100-120℃, a drying time of 30-90 min, and a sintering temperature of 400-500℃ for 20-40 min.

[0041] 3) Preparation of chitosan oleophobic coating solution: Disperse chitosan powder in an acidic solution, add a thickener, stir to dissolve, and set aside. The chitosan content is 5-10 wt%, the acidic solution is either an aqueous solution of acetic acid or an aqueous solution of citric acid with a volume concentration of 1-2%, and the thickener is either polyvinyl alcohol or hydroxymethyl cellulose with a mass concentration of 0.1-0.2 wt%.

[0042] 4) Activation of ceramic membrane and coating with silane coupling agent: The roughened ceramic membrane prepared in step 2) is immersed in an acid solution for activation treatment to obtain a ceramic membrane with active sites and active pores. The silane coupling agent NQ-62 is uniformly coated on the surface of the ceramic membrane for later use. The acid solution is one of acetic acid aqueous solution or citric acid aqueous solution with a volume concentration of 4-5%, or the acid solution is 1% nitric acid aqueous solution.

[0043] 5) Cross-linked chitosan oleophobic layer on ceramic membrane surface: A chitosan oleophobic coating is uniformly applied to the surface of the ceramic membrane to form a chitosan coating layer, which is then dried at room temperature to obtain a superhydrophilic-underwater oleophobic ceramic membrane. The coating method is either spraying or blade coating.

[0044] The following examples 1-10 provide a detailed description of a superhydrophilic-underwater oleophobic ceramic membrane of the present invention, its preparation method, and its application.

[0045] Example 1

[0046] This embodiment provides a method for preparing a superhydrophilic-underwater oleophobic ceramic membrane, the steps of which are as follows:

[0047] 1) Add 1.0g of tetrabutyl titanate to 80g of ethanol, add 5g of water, and while stirring, add 0.5g of hydrochloric acid with a volume concentration of 5%. Stir at room temperature for 1h, then add 0.5g of tetraethyl orthosilicate, 0.5g of zirconium sec-butoxide, and 0.5g of acetylacetone in sequence. Heat in a water bath at 40℃ for 6h to obtain TiO2-SiO2-ZrO2 ternary hydrophilic sol for later use.

[0048] 2) The ceramic support with a pore size of 0.5 μm was completely immersed in the above TiO2-SiO2-ZrO2 ternary hydrophilic sol for 6 h, then dried at 100 °C for 30 min, and then sintered in a muffle furnace at 400 °C for 20 min to obtain a ceramic film with roughened surface and pore interior, for later use.

[0049] 3) Weigh 1.2g of chitosan and slowly add it to 8g of 1% glacial acetic acid solution while stirring. Add 0.1wt% polyvinyl alcohol and stir to dissolve to obtain chitosan oleophobic coating solution for later use.

[0050] 4) The surface and pores of the roughened ceramic film are immersed in a 4% citric acid solution for 2 hours and dried at 60°C. The silane coupling agent NQ-62 is then uniformly coated on the surface of the ceramic film by spraying and set aside.

[0051] 5) The chitosan oleophobic coating solution was uniformly sprayed onto the surface of the ceramic membrane loaded with NQ-62 and dried at room temperature to obtain a superhydrophilic-underwater oleophobic ceramic membrane.

[0052] Example 2

[0053] This embodiment provides a method for preparing a superhydrophilic-underwater oleophobic ceramic membrane, the steps of which are as follows:

[0054] 1) Add 1.0g of titanium sec-butoxide to 80g of ethanol, add 5g of water, and while stirring, add 0.5g of hydrochloric acid with a volume concentration of 5%. Stir at room temperature for 2h, then add 0.6g of tetraethyl orthosilicate, 0.6g of zirconium isopropoxide, and 0.5g of acetylacetone in sequence. Heat in a water bath at 50℃ for 7h to obtain TiO2-SiO2-ZrO2 ternary hydrophilic sol for later use.

[0055] 2) The ceramic support with a pore size of 0.5 μm was completely immersed in the above TiO2-SiO2-ZrO2 ternary hydrophilic sol for 7 h, dried at 110 °C for 60 min, and then sintered in a muffle furnace at 450 °C for 30 min to obtain a ceramic film with roughened surface and pore interior, for later use.

[0056] 3) Weigh 1.2g of chitosan and slowly add it to 8g of 2% glacial acetic acid solution while stirring. Add 0.2wt% polyvinyl alcohol and stir to dissolve to obtain chitosan oleophobic coating solution for later use.

[0057] 4) Immerse the surface and pores of the roughened ceramic film in a 5% citric acid solution for 2 hours, dry at 60°C, and then uniformly coat the ceramic film surface with silane coupling agent NQ-62 by spraying for later use.

[0058] 5) The chitosan oleophobic coating solution was uniformly sprayed onto the surface of the ceramic membrane loaded with NQ-62 and dried at room temperature to obtain a superhydrophilic-underwater oleophobic ceramic membrane.

[0059] Example 3

[0060] This embodiment provides a method for preparing a superhydrophilic-underwater oleophobic ceramic membrane, the steps of which are as follows:

[0061] 1) Add 1.0g of tetrabutyl titanate to 80g of ethanol, add 5g of water, and while stirring, add 0.5g of hydrochloric acid with a volume concentration of 5%. Stir at room temperature for 3h, then add 0.8g of tetraethyl orthosilicate, 0.8g of zirconium sec-butoxide, and 0.5g of acetylacetone in sequence. Heat in a water bath at 60℃ for 8h to obtain TiO2-SiO2-ZrO2 ternary hydrophilic sol for later use.

[0062] 2) The ceramic support with a pore size of 0.5 μm was completely immersed in the above TiO2-SiO2-ZrO2 ternary hydrophilic sol for 8 hours, then dried at 120℃ for 90 min, and then sintered in a muffle furnace at 500℃ for 40 min to obtain a ceramic film with roughened surface and pore interior, for later use.

[0063] 3) Weigh 1.2g of chitosan and slowly add it to 8g of 2% glacial acetic acid solution while stirring. Add 0.1wt% polyvinyl alcohol and stir to dissolve to obtain chitosan oleophobic coating solution for later use.

[0064] 4) Immerse the surface and pores of the roughened ceramic film in a 5% citric acid solution for 2 hours, dry at 60°C, and then uniformly coat the ceramic film surface with silane coupling agent NQ-62 by spraying for later use.

[0065] 5) The chitosan oleophobic coating solution was uniformly sprayed onto the surface of the ceramic membrane loaded with NQ-62 and dried at room temperature to obtain a superhydrophilic-underwater oleophobic ceramic membrane.

[0066] Example 4

[0067] The difference between this embodiment and embodiment 2 is that step 4) in this embodiment is: soaking the ceramic membrane in 1% nitric acid for 2 hours, drying it at 100°C, and then uniformly coating the surface of the ceramic membrane with silane coupling agent NQ-62 by spraying, for later use.

[0068] Example 5

[0069] The difference between this embodiment and Embodiment 2 is that in step 1) of this embodiment: the titanium precursor is titanium isopropoxide, the silicon precursor is tetraethyl silicate, the zirconium precursor is zirconium n-butoxide, the inhibitor is diethanolamine, the pH adjuster is nitric acid, and the solvent is isobutanol.

[0070] Example 6

[0071] The difference between this embodiment and Embodiment 2 is that in step 1) of this embodiment: the titanium precursor is titanium sec-butoxide, the silicon precursor is tetraethyl orthosilicate, the zirconium precursor is zirconium isopropoxide, the inhibitor is diethanolamine, the pH adjuster is hydrochloric acid, and the solvent is ethanol.

[0072] Example 7

[0073] The difference between this embodiment and embodiment 2 is that in step 1) of this embodiment: the titanium precursor is titanium tert-butoxide, the silicon precursor is tetraethyl orthosilicate, the zirconium precursor is zirconium sec-butoxide, the inhibitor is acetylacetone, the pH adjuster is hydrochloric acid, and the solvent is ethanol.

[0074] Example 8

[0075] The difference between this embodiment and embodiment 2 is that in step 3) of this embodiment: the acid solution is an aqueous solution of citric acid, and the thickener is hydroxymethyl cellulose.

[0076] Example 9

[0077] The difference between this embodiment and embodiment 2 is that in step 3) of this embodiment: the acid solution is an aqueous solution of citric acid, and the thickener is hydroxymethyl cellulose.

[0078] Example 10

[0079] The difference between this embodiment and embodiment 2 is that in step 5) of this embodiment, the chitosan oleophobic coating is applied by scraping.

[0080] The superhydrophilic-underwater oleophobic ceramic membrane prepared in Example 1 was tested as follows:

[0081] The contact angles of the roughened ceramic membrane surface and pore interior prepared in Example 1 with water in air were measured at room temperature using a contact angle meter. The test results are shown in the attached figure. Figure 3 As shown, the test results show that the ceramic membrane with roughened surface and pore interior prepared in Example 1 has a contact angle of 2° in air, which belongs to the category of superhydrophilic ceramic membranes.

[0082] The superhydrophilic-underwater oleophobic ceramic membrane prepared in Example 1 was immersed in a beaker filled with water at room temperature. Soybean oil was dropped onto the membrane surface using a bent needle. The contact angle between the ceramic membrane and the soybean oil underwater was measured using a contact angle meter. The test results are shown in the attached figure. Figure 4 As shown in the test results, the superhydrophilic-underwater oleophobic ceramic membrane prepared in Example 1 has a contact angle of 151° with soybean oil underwater, which is an oleophobic ceramic membrane.

[0083] Therefore, the superhydrophilic-underwater oleophobic ceramic membrane prepared by this invention has superhydrophilicity on the surface and underwater oleophobicity in the pores, which prevents the ceramic membrane from directly contacting oil during oil-water separation, reducing membrane fouling and reduced operating flux, and can be applied to the separation of various wastewater containing emulsified oil.

[0084] The following are the tests conducted on the emulsified oil-water separation of the superhydrophilic-underwater oleophobic ceramic membranes obtained in Examples 1 to 4:

[0085] Using soybean oil emulsion with an oil concentration of 500 mg / L as the feed liquid, and with... Figure 3 A cross-flow filtration oil-water separation device was constructed. A water pump introduced soybean oil emulsion with a certain pressure into the membrane module. Part of the soybean oil emulsion returned to the feed tank through the back pressure valve, while the other part was filtered by the membrane layer and flowed into the permeate side. The operating flux was measured with an online balance. The COD value of emulsions with different oil concentrations was tested, and a COD-oil concentration standard curve of soybean oil emulsion was plotted. The concentration was calculated based on the COD value of the permeate side, and the oil rejection rate was calculated using the following formula. The test results are shown in Table 1 below. The operating flux was also tested at different time periods, and the test results are shown in Table 2 below.

[0086] R = (1 - C1 / C2) * 100%

[0087] Where R is the oil rejection rate, C1 is the oil concentration on the permeation side, and C2 is the oil concentration on the feed side.

[0088] Table 1

[0089] <![CDATA[Membrane area (m 2 )]]> Oil concentration on the permeate side (mg / L) Operating pressure (bar) Oil cut-off rate Example 1 0.02 4.56 2 99.1％ Example 2 0.02 5.20 2 99.0％ Example 3 0.02 5.43 2 99.1％ Example 4 0.02 3.81 2 99.2％

[0090] Table 2

[0091]

[0092] As shown in Tables 1 and 2, the superhydrophilic-underwater oleophobic ceramic membrane prepared by this invention has an oil-water separation oil rejection rate of over 99%, and the flux does not decrease significantly after a period of operation, demonstrating excellent oil-water separation stability. It can effectively avoid direct contact with grease during oil-water separation, reduce membrane contamination, and improve operating flux.

[0093] 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 present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention. Technologies not described in detail in this invention are known technologies.

Claims

1. A method for preparing a superhydrophilic-underwater oleophobic ceramic membrane, characterized in that, Specifically, the following steps are included: 1) Preparation of TiO2-SiO2-ZrO2 ternary hydrophilic sol: Titanium precursor, silicon precursor, zirconium precursor, water, inhibitor, pH adjuster and solvent are mixed and stirred at room temperature for 1-3 hours, and then heated in a water bath at 40-60℃ for 6-8 hours. Through the hydrolysis and polymerization reaction of titanium precursor, silicon precursor and zirconium precursor, TiO2-SiO2-ZrO2 ternary hydrophilic sol is obtained. 2) Preparation of roughened ceramic film: The ceramic support is immersed in the TiO2-SiO2-ZrO2 ternary hydrophilic sol prepared in step 1), and then dried and sintered to roughen the surface and the interior of the pores of the film layer, thus obtaining a roughened ceramic film. 3) Preparation of chitosan oleophobic coating solution: Disperse chitosan powder in an acid solution, add a thickener, stir to dissolve, and obtain chitosan oleophobic coating solution; 4) Preparation of ceramic membrane loaded with NQ-62: The roughened ceramic membrane obtained in step 2) is immersed in an acid solution for activation treatment for 2 hours to give the ceramic membrane active sites and active pores. Then it is dried at 60°C. Then the silane coupling agent NQ-62 is uniformly coated on the surface of the ceramic membrane to obtain a ceramic membrane loaded with NQ-62. 5) Crosslinked chitosan oleophobic layer on ceramic membrane surface: The chitosan oleophobic coating solution prepared in step 3) is uniformly coated on the surface of the ceramic membrane loaded with NQ-62 prepared in step 4) to form a chitosan coating layer. After drying at room temperature, a superhydrophilic-underwater oleophobic ceramic membrane is obtained.

2. The preparation method according to claim 1, characterized in that, The molar ratio of titanium precursor, silicon precursor, zirconium precursor, water, inhibitor, pH adjuster and solvent in step 1) is 1:(0.5-1):(0.5-1):(5-10):(0.1-0.2):(0.5-1):(80-100).

3. The preparation method according to claim 2, characterized in that, The titanium precursor mentioned in step 1) is one or more of titanium tetrabutyl titanate, titanium isopropoxide, titanium sec-butoxide, and titanium tert-butoxide. The silicon precursor is one or more of tetraethyl orthosilicate and tetraethyl orthosilicate; The zirconium precursor is one or more of zirconium n-butoxide, zirconium isopropoxide, and zirconium sec-butoxide. The inhibitor is one of diethanolamine and acetylacetone; The pH adjuster is either hydrochloric acid or nitric acid; The solvent is one of ethanol and isobutanol.

4. The preparation method according to claim 3, characterized in that, The ceramic support described in step 2) has a pore size of 0.5 μm and an immersion time of 6-8 h.

5. The preparation method according to claim 4, characterized in that, The drying temperature in step 2) is 100-120℃ and the drying time is 30-90 min. The sintering temperature is 400-500℃ and the sintering time is 20-40 min.

6. The preparation method according to claim 5, characterized in that, In step 3), the chitosan content is 5-10 wt%, the acid solution is one of acetic acid aqueous solution and citric acid aqueous solution, the volume concentration of the acid solution is 1-2%, and the thickener is one of polyvinyl alcohol and hydroxymethyl cellulose, the mass concentration of the thickener is 0.1-0.2 wt%.

7. The preparation method according to claim 6, characterized in that, The acid solution mentioned in step 4) is one of nitric acid aqueous solution, acetic acid aqueous solution, or citric acid aqueous solution, with a volume concentration of 1-5%.

8. The preparation method according to claim 7, characterized in that, The chitosan oleophobic coating method described in step 5) is either spraying or scraping.

9. A superhydrophilic-underwater oleophobic ceramic membrane, characterized in that, The superhydrophilic-underwater oleophobic ceramic membrane is prepared by the preparation method described in any one of claims 1-8.

10. The application of the superhydrophilic-underwater oleophobic ceramic membrane as described in claim 9 in oil-water separation.

Images