A hydrophilic, superoleophobic ceramic membrane and a preparation method and application thereof

Abstract

The application discloses a kind of hydrophilic, super oleophobic ceramic membrane and its preparation method and application, belong to ceramic membrane technical field, the hydrophilic, super oleophobic ceramic membrane including support layer, transition layer being supported on the surface of support layer and iron oxide film layer being supported on the surface of transition layer, the average pore size of the iron oxide film layer is 2~100nm.The application is by regulating Fe (OH) 3 sol film forming liquid viscosity and particle size, with the pore size of microporous ceramic membrane surface transition layer is matched, and new complete iron oxide separation layer is formed on its surface.The hydrophilic, super oleophobic ceramic membrane of the application in the membrane flux and flux recovery rate of oil-water system separation is far superior to original microporous ceramic membrane, it is applied to high concentration oil-water system oil-water separation process, with the advantages of anti-membrane pollution, high membrane flux, high oil-water separation efficiency.

Description

Technical Field

[0001] This invention relates to the field of ceramic membrane technology, specifically to a hydrophilic, superoleophobic ceramic membrane, its preparation method, and its application. Background Technology

[0002] Oily wastewater exists in almost every industry, with the majority of the world's oily wastewater generated during oil and gas extraction. Various treatment technologies have been developed to address this issue. However, traditional separation technologies have several drawbacks.

[0003] In recent years, membrane technology has emerged as a novel water treatment technology and is considered one of the most promising methods for treating oily wastewater. Ceramic membranes, in particular, have found wide application in harsh environments such as the petroleum and chemical industries due to their advantages including good chemical stability, high mechanical strength, acid and alkali resistance, and high temperature resistance. Generally speaking, a smooth membrane surface helps reduce scaling. Fe2O3 is considered a naturally hydrophilic material, and its abundant and inexpensive sources, combined with the high hydrophilicity of nano-iron oxide particles, result in minimal scaling tendency when Fe2O3 nanoparticles are deposited on the membrane surface.Patent CN 113926321A describes the modification of Fe2O3 onto the surface of a ceramic microfiltration membrane to obtain an antifouling ceramic membrane. However, this patent explicitly states that Fe2O3 was only modified onto the surface of the ceramic microfiltration membrane. The iron hydroxide sol particles prepared in Example 2 of this patent have a particle size of only 40-50 nm. Under these conditions, a complete iron oxide film layer cannot be formed on the surface of a ceramic support with a pore size of 100 nm. Therefore, this patent lacks supporting data such as the pore size of the iron oxide film layer. Similarly, Barati N et al. (Barati N, Husein MM, Azaiez J. Modifying ceramic membranes with in situ grown iron oxide nanoparticles and their use for oilywater treatment[J]. Journal of Membrane Science, 2020, 617: 118641.) and Karnik BS et al. (Karnik BS, Baumann MJ, Masten SJ, et al. AFM and SEM characterization of iron oxide coated ceramic membranes[J]. Journal of Materials Science, 2006, 41(20):6861-6870.) also modified the ceramic film surface with iron oxide nanoparticles, but the ceramic film surface disclosed in these literatures did not form a complete iron oxide film layer (Barati N et al. directly stated in the 8th and 9th lines of the 4th paragraph of Section 3.1.2 in their literature that they did not observe the formation of an additional layer composed only of nano-iron oxide; Karnik BS et al. showed the EDS energy spectrum of the iron oxide coated ceramic film prepared according to the method in the literature (Fig. 9b). It can be clearly seen from the figure that the surface of the modified ceramic film is mixed with chemical substances of different sizes and shapes (titanium dioxide, zirconium oxide, iron oxide and aluminum oxide), and the EDS energy spectrum signal response of Fe element is not uniform, indicating that the ceramic film is only modified with iron oxide on the surface. If a complete film layer is formed, the surface of the modified ceramic film should be composed of chemical substances of uniform size and similar shape, and the Fe element signal response in the EDS energy spectrum of Fe element should be uniform).

[0004] Traditional methods for preparing iron oxide membranes involve coating a suspension of iron oxide particles with a diameter of a few nanometers onto a small-pore ultrafiltration membrane. According to the Hagen-Poisson equation, the flux of small-pore ceramic membranes is not very high, and this low flux limits their ability to separate oil from oily wastewater. Summary of the Invention

[0005] The technical problem to be solved by this invention is the poor antifouling effect, low flux, and poor oil-water separation effect of ceramic membranes prepared by existing technologies in the oil-water separation process of oily wastewater. This invention provides a hydrophilic, superoleophobic ceramic membrane, its preparation method, and its application. A complete high-flux iron oxide membrane is prepared on a microfiltration membrane. High-flux hydrophilic, superoleophobic ceramic membranes are promising for the separation of oil-water systems. Improving the sol-gel process and controlling the particle size of the iron hydroxide sol to prepare a high-flux iron oxide ceramic ultrafiltration membrane on a large-pore microfiltration membrane is a meaningful design solution.

[0006] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0007] A hydrophilic and superoleophobic ceramic membrane is provided, wherein a complete α-Fe2O3 film layer is formed on the surface of a microporous ceramic membrane; the α-Fe2O3 film layer has an average pore size of 2-100 nm, a porosity of 35-40%, and a film thickness of 1-2 micrometers.

[0008] The microporous ceramic membrane comprises a support and a transition layer loaded on the surface of the support. The materials of the support and the transition layer are independently selected from any one or a combination of several of the following: alumina, zirconium oxide, magnesium oxide, silicon oxide, titanium oxide, cerium oxide, yttrium oxide, barium titanate, cordierite, andalusite, forsterite, block talc, silica-alumina-nitrogen ceramics, zircon, ferrates, silicon nitride, aluminum nitride, silicon carbide, hydroxyapatite, carbon, silicon, clay, clay minerals, ceramic slag, silica sand, ceramic stone, feldspar, and white sand.

[0009] The transition layer has an average pore size of 0.1–1 μm, preferably 100–300 nm.

[0010] This invention also discloses a method for preparing the aforementioned hydrophilic and superoleophobic ceramic membrane, comprising the following steps:

[0011] Step 1: Ferric chloride aqueous solution is subjected to high-temperature hydrolysis to obtain ferric hydroxide sol, which is then cooled to 70-90°C. Polyvinyl alcohol (PVA) is added to the ferric hydroxide sol to obtain a ferric hydroxide sol film-forming solution; wherein the polyvinyl alcohol is polyvinyl alcohol type 124; the content of polyvinyl alcohol in the ferric hydroxide sol film-forming solution is 0.05-2.5 wt%, and the solid content of ferric hydroxide is 0.1-0.6 wt%.

[0012] Step 2: Immerse the microporous ceramic membrane in the ferric hydroxide sol film-forming solution obtained in Step 1 for 1-60 seconds, then remove, dry, and calcine to obtain the final product.

[0013] In step 1, the ferric chloride aqueous solution is any one of anhydrous FeCl3, FeCl3·6H2O, 2FeCl3·7H2O, and 2FeCl3·5H2O; the high-temperature hydrolysis reaction is as follows: the ferric chloride aqueous solution is added dropwise to boiling water and reacted at a temperature of 90-100℃ for 0.1-12 hours.

[0014] In step 1, after adding polyvinyl alcohol aqueous solution to the ferric hydroxide sol, the mixture is reacted for 10 to 30 minutes under stirring and a temperature of 70 to 90°C to obtain the ferric hydroxide sol film-forming solution.

[0015] In step 1, the particle size of the ferric hydroxide colloid in the ferric hydroxide sol film-forming solution is 100-200 nm.

[0016] In step 2, the microporous ceramic membrane is a microporous ceramic membrane that includes the support layer and the transition layer, and the microporous ceramic membrane can be purchased from the market.

[0017] In step 2, the drying temperature is 25-110℃ and the drying time is 1-48h, preferably 12h; the calcination temperature is 450-1000℃ and the calcination time is 1-24h, preferably calcination at 700℃ for 2h.

[0018] The present invention also discloses the application of the aforementioned hydrophilic and superoleophobic ceramic membrane in oil-water separation of oil-water mixed systems.

[0019] The oil-water mixture system is a mixture of emulsified oil and water. The emulsified oil exists in a stable state (does not float or agglomerate) as tiny oil droplets, and the oil includes, but is not limited to, vegetable oil, industrial cutting oil, mineral oil, and artificial chemical synthetic oil (such as lubricating oil, silicone oil, etc.).

[0020] When using the aforementioned hydrophilic and superoleophobic ceramic membrane for oil-water separation, the flow velocity at the membrane surface is 1–4 m / s. -1 The transmembrane pressure difference is 1–3 bar, and the temperature is 20–60 °C.

[0021] Beneficial effects:

[0022] (1) The present invention uses polyvinyl alcohol to regulate the hydration particle size and viscosity of ferric hydroxide sol, coats the ferric hydroxide sol onto the surface of a microporous ceramic membrane, and forms a new and complete ferric oxide separation layer on the surface of the microporous ceramic membrane by matching the structure-property relationship between the particle size of the ferric hydroxide sol and the pore size of the transition layer on the surface of the microfiltration membrane, thereby enhancing the oleophobic properties of the membrane surface and reducing the degree of fouling on the membrane surface.

[0023] (2) The surface of the hydrophilic and superoleophobic ceramic membrane of the present invention is formed by iron oxide nanoparticles to form a complete iron oxide film layer, which significantly reduces the isoelectric point of the membrane surface. Due to the existence of electrostatic repulsion, the scaling degree of the iron oxide membrane in the oil-water system is significantly reduced, the permeation flux is significantly improved, and the oil-water separation effect is excellent.

[0024] (3) The present invention improves the bonding strength of iron oxide nanoparticles on the surface of ceramic film by drying and calcining the ceramic film coated with iron hydroxide sol, thereby improving the operational stability. Attached Figure Description

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0026] Figure 1 The images show scanning electron microscope (SEM) images of the original alumina ceramic film and the ceramic films prepared in Examples 1, 1, and 2. Image a shows the SEM images of the surface (left) and cross-section (right) of the original alumina ceramic film; image b shows the SEM images of the surface (left) and cross-section (right) of the ceramic film prepared in Comparative Example 1; image c shows the SEM images of the surface (left) and cross-section (right) of the ceramic film prepared in Comparative Example 2; and image d shows the SEM images of the surface (left) and cross-section (right) of the ceramic film prepared in Example 1.

[0027] Figure 2 The images show the elemental distribution map and EDS spectrum obtained from the EDS scan of the ceramic film prepared in Example 1; where, a is the Fe elemental distribution map of the ceramic film surface; b is the Al elemental distribution map of the ceramic film surface; and c is the EDS spectrum obtained from the energy dispersive spectroscopy scan of the ceramic film surface.

[0028] Figure 3 The images show the underwater oil contact angles of the original alumina ceramic film and the ceramic film prepared in Example 1; where, Figure a is the underwater oil contact angle image of the original alumina ceramic film surface; and Figure b is the underwater oil contact angle image of the ceramic film prepared in Example 1.

[0029] Figure 4 The images show the underwater oil adhesion force on the surface of the original alumina ceramic film and the ceramic film prepared in Example 1; wherein, Figure a is the underwater oil adhesion force image on the surface of the original alumina ceramic film; and Figure b is the underwater oil adhesion force image on the surface of the ceramic film prepared in Example 1.

[0030] Figure 5 The ceramic membrane prepared in Example 1 was soaked in water with pH values ​​of 1, 3, and 5, and then Fe... 3+ The leaching volume statistics chart.

[0031] Figure 6The graph shows the zeta potential of the original alumina ceramic film under different pH conditions in Example 3 and the ceramic film prepared in Example 1.

[0032] Figure 7 This is a statistical chart showing the membrane flux during the oil-water separation process of the original alumina ceramic membrane in Example 4 and the ceramic membrane prepared in Example 1.

[0033] Figure 8 This is a statistical chart showing the membrane flux recovery rate after oil-water separation of the original alumina ceramic membrane in Example 4 and the ceramic membrane prepared in Example 1.

[0034] Figure 9 This is a flowchart of the extraction process of 9α-hydroxyandrostenedione in Example 5. Detailed Implementation

[0035] The present invention will be further described below with reference to the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0036] For any specific techniques or conditions not specified in the examples, the techniques or conditions described in the literature in this field, or the product instructions, shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0037] Example 1

[0038] Accurately weigh 1.29 g of FeCl3·6H2O compound and add it to 50 mL of deionized water. Sonicate for 5 min to dissolve completely. Then, add it dropwise to 40 mL of pre-boiled deionized water and heat in an oil bath to 100 °C. Continue the reaction for 3 h, then cool to 80 °C to obtain ferric hydroxide sol. Next, take 10 mL of 10 wt% PVA (type 124) aqueous solution and add it dropwise to the ferric hydroxide sol. React at 80 °C for 20 min, and finally cool naturally to room temperature to obtain a ferric hydroxide sol film-forming solution with a solid content of 0.5%. Mix it in a mixer-deaerator for 3 min, deaerate for 5 min, and repeat the mixing and deaeration process 3 times. The particle size of the ferric hydroxide colloid was measured to be 100–200 nm. A sheet-type alumina ceramic membrane with an average pore size of 100 nm (purchased from Nanjing Membrane Materials Industry Technology Research Institute Co., Ltd., diameter 3 cm, membrane thickness 2 mm) was cleaned with deionized water and dried at 110 °C for 4 h. After immersing the cleaned alumina ceramic membrane in ferric hydroxide sol film-forming solution for 1 minute, it is taken out at a speed of 10 mm / s, air-dried naturally, and then placed in constant temperature and humidity ovens at 70℃ and 110℃ for 24 hours. Finally, it is calcined at 700℃ in a tube furnace for 2 hours to obtain the hydrophilic and superoleophobic ceramic membrane of the present invention.

[0039] The microstructure of the original alumina ceramic film and the hydrophilic, superoleophobic ceramic film prepared in this embodiment were analyzed using scanning electron microscopy (SEM). The results are as follows: Figure 1 Figure a (sheet-type alumina ceramic membrane) and Figure d (hydrophilic and superoleophobic ceramic membrane prepared in this embodiment) show the microstructure of the ceramic membrane surface before and after coating with the film-forming solution. It was found that compared to the original alumina ceramic membrane, a new 1.2 μm thick α-Fe₂O₃ film layer was formed on the surface of the hydrophilic and superoleophobic ceramic membrane. This new film layer has smaller nanoparticles and a smoother surface. The α-Fe₂O₃ film layer in the hydrophilic and superoleophobic ceramic membrane prepared in this embodiment has a pore size of 103.1 nm and a porosity of 36.9%.

[0040] Surface EDS energy dispersive spectroscopy analysis was performed on the original alumina ceramic film and the hydrophilic and superoleophobic ceramic film prepared in this embodiment. The results are as follows: Figure 2 As shown, comparing the elements on the surface of the original alumina ceramic film and the hydrophilic and superoleophobic ceramic film prepared in this embodiment, it was found that since the surface of the hydrophilic and superoleophobic ceramic film is a new iron oxide film layer, there is an obvious Fe element signal response on its surface, with the Fe element accounting for 45.7 wt%.

[0041] Comparative Example 1

[0042] Accurately weigh 1.29 g of FeCl3·6H2O compound and add it to 50 mL of deionized water. Sonicate for 5 min to dissolve completely. Then, add it dropwise to 40 mL of pre-boiled deionized water and heat in an oil bath to 100 °C. Continue the reaction for 3 h, then cool to 80 °C to obtain ferric hydroxide sol. Next, take 10 mL of 10 wt% PVA (type 2488) solution and add it dropwise to the ferric hydroxide sol. React at 80 °C for 20 min, and finally cool naturally to room temperature to obtain a ferric hydroxide sol film-forming solution with a solid content of 0.5%. Mix it in a mixer-deaerator for 3 min and deaerator for 5 min. Repeat the mixing and deaerator process 3 times. The particle size of the ferric hydroxide colloid was measured to be 350–450 nm. A sheet-type alumina ceramic membrane with an average pore size of 100 nm (purchased from Nanjing Membrane Materials Industry Technology Research Institute Co., Ltd., diameter 3 cm, membrane thickness 2 mm) was cleaned with deionized water and dried at 110 °C for 4 h. After immersing the cleaned alumina ceramic film in ferric hydroxide sol film-forming solution for 1 minute, it is taken out at a speed of 10 mm / s, air-dried naturally, and then placed in constant temperature and humidity ovens at 70℃ and 110℃ for 24 hours. Finally, it is calcined at 700℃ in a tube furnace for 2 hours to obtain the ferric oxide modified ceramic film.

[0043] The microstructure of the iron oxide-modified ceramic film prepared in this comparative example was analyzed by SEM. The results are as follows: Figure 1 As shown in Figure b, compared with the original alumina ceramic film ( Figure 1a) The surface microstructure of the iron oxide-modified ceramic film prepared in this comparative example showed no significant change.

[0044] Comparative Example 2

[0045] Accurately weigh 1.29 g of FeCl3·6H2O compound and add it to 50 mL of deionized water. Sonicate for 5 min to dissolve completely. Then, add it dropwise to 40 mL of pre-boiled deionized water and heat in an oil bath to 100 °C. Continue the reaction for 3 h, then cool to 80 °C to obtain ferric hydroxide sol. Next, take 10 mL of 10 wt% PVA (type 1788) solution and add it dropwise to the ferric hydroxide sol. React at 80 °C for 20 min, and finally cool naturally to room temperature to obtain a ferric hydroxide sol film-forming solution with a solid content of 0.5%. Mix it in a mixer-deaerator for 3 min, deaerate for 5 min, and repeat the mixing and deaeration process 3 times. The particle size of the ferric hydroxide colloid was measured to be 230–340 nm. A sheet-type alumina ceramic membrane with an average pore size of 100 nm (purchased from Nanjing Membrane Materials Industry Technology Research Institute Co., Ltd., diameter 3 cm, membrane thickness 2 mm) was cleaned with deionized water and dried at 110 °C for 4 h. After immersing the cleaned alumina ceramic film in ferric hydroxide sol film-forming solution for 1 minute, it is taken out at a speed of 10 mm / s, air-dried naturally, and then placed in constant temperature and humidity ovens at 70℃ and 110℃ for 24 hours. Finally, it is calcined at 700℃ in a tube furnace for 2 hours to obtain the ferric oxide modified ceramic film.

[0046] The microstructure of the iron oxide-modified ceramic film prepared in this comparative example was analyzed by SEM. The results are as follows: Figure 1 As shown in Figure c, compared with the original alumina ceramic film ( Figure 1 a) An iron oxide layer appeared on the surface of the iron oxide-modified ceramic film prepared in this comparative example, but it was not complete.

[0047] Example 2

[0048] Accurately weigh 1.29 g of FeCl3·6H2O compound and add it to 50 mL of deionized water. Sonicate for 5 min to dissolve completely. Then, add it dropwise to 40 mL of pre-boiled deionized water and heat in an oil bath to 100 °C. Continue the reaction for 3 h, then cool to 80 °C to obtain ferric hydroxide sol. Next, take 10 mL of 10 wt% PVA (type 124) aqueous solution and add it dropwise to the ferric hydroxide sol. React at 80 °C for 20 min, and finally cool naturally to room temperature to obtain a ferric hydroxide sol film-forming solution with a solid content of 0.5%. Mix it in a mixer-deaerator for 3 min and deaerator for 5 min. Repeat the mixing and deaerator process 3 times. The particle size of the ferric hydroxide colloid was measured to be 100–200 nm. A sheet-type alumina ceramic membrane with an average pore size of 200 nm (purchased from Nanjing Membrane Materials Industry Technology Research Institute Co., Ltd., diameter 3 cm, membrane thickness 2 mm) was cleaned with deionized water and dried at 110 °C for 4 h. After immersing the cleaned alumina ceramic membrane in ferric hydroxide sol film-forming solution for 1 minute, it is taken out at a speed of 10 mm / s, air-dried naturally, and then placed in constant temperature and humidity ovens at 70℃ and 110℃ for 24 hours. Finally, it is calcined at 700℃ in a tube furnace for 2 hours to obtain the hydrophilic and superoleophobic ceramic membrane of the present invention.

[0049] The hydrophilic and superoleophobic ceramic membrane prepared in this embodiment has an α-Fe2O3 film layer with a thickness of 2 micrometers, a pore size of 130.6 nm, and a porosity of 38%.

[0050] Example 3

[0051] The underwater oleophobic properties of the original alumina ceramic membrane and the hydrophilic, superoleophobic ceramic membrane prepared in Example 1 were analyzed. The results are as follows: Figure 3 As shown, compared to the original alumina ceramic film surface underwater oil contact angle, due to the formation of a new iron oxide film layer on the surface of the hydrophilic and superoleophobic ceramic film, its surface underwater oil contact angle increases from 155° to 162°, and the film surface's resistance to oil droplet wetting is enhanced.

[0052] Underwater oil adhesion was measured on the surfaces of the original alumina ceramic film and the hydrophilic, superoleophobic ceramic film prepared in Example 1. The results are as follows: Figure 4 As shown, compared with the underwater oil adhesion force on the surface of the original alumina ceramic membrane, the underwater oil adhesion force on the surface of the hydrophilic and superoleophobic ceramic membrane decreased from 0.159 mN to 0.075 mN due to the formation of a new iron oxide film layer, a decrease of 52.8%. The membrane surface's resistance to oil droplet adhesion is significantly enhanced, indicating that the hydrophilic and superoleophobic ceramic membrane prepared by this invention has superior anti-fouling performance and oil-water separation performance.

[0053] The hydrophilic and superoleophobic ceramic membrane prepared in Example 1 was subjected to chemical stability analysis by immersing it in water with pH values ​​of 1, 3, and 5 for 1 day, 7 days, and 14 days, respectively, and measuring the Fe content in the water under different conditions. 3+ Content (i.e., Fe) 3+ Leaching amount), results as follows Figure 5 As shown. The hydrophilic, superoleophobic ceramic membrane prepared in Example 1 was soaked in water at pH 1 and then... 3+ The highest leaching concentration was observed, ranging from 0.3 to 0.35 mg / L, under weakly acidic and neutral conditions. (Fe...) 3+ No leaching indicates that the hydrophilic and superoleophobic ceramic membrane of the present invention has excellent chemical stability.

[0054] Zeta potential analysis was performed on the surfaces of the original alumina ceramic film and the hydrophilic, superoleophobic ceramic film prepared in Example 1. The results are as follows: Figure 6 As shown, compared to the original alumina ceramic membrane surface isoelectric point pH=9, the hydrophilic and superoleophobic ceramic membrane prepared in Example 1 has an isoelectric point pH=5.7. Under neutral conditions, the original alumina ceramic membrane surface has a Zeta potential of 2mV, while the hydrophilic and superoleophobic ceramic membrane prepared in Example 1 has an isoelectric point -6mV, indicating that the negative charge on the membrane surface is enhanced.

[0055] The above test results show that the hydrophilic and superoleophobic ceramic membrane prepared in Example 1 has very good hydrophilicity and underwater oleophobicity, which is significantly different from the original membrane, proving that the ceramic membrane prepared by the present invention has a complete iron oxide film layer and excellent performance.

[0056] Example 4

[0057] Oil-water separation experiments were conducted on a 1000 ppm soybean oil-water emulsion using a raw alumina ceramic membrane and a hydrophilic / superoleophobic ceramic membrane prepared in Example 1. The transmembrane pressure difference was 1 bar, the membrane surface velocity was 1 m / s, and the temperature was 20 °C. Membrane flux was measured during the separation process. The experimental results are as follows: Figure 7 As shown, the results indicate that after 60 minutes of operation, the stable flux of the original alumina ceramic membrane is 193 L·m⁻¹. -2 ·h -1 The hydrophilic and superoleophobic ceramic membrane prepared in Example 1 has a stable flux of 493 L·m. -2 ·h -1 The flux of the original ceramic membrane increased by 155%, a significant increase. Furthermore, after oil-water separation, the permeate flux of the hydrophilic and superoleophobic ceramic membrane prepared in Example 1 decreased by only about 10%, while that of the original ceramic membrane decreased by about 43%, indicating that the antifouling ability of the hydrophilic and superoleophobic ceramic membrane of the present invention is significantly enhanced.

[0058] After 60 minutes of oil-water separation experiment, the membrane surface was rinsed with pure water for 30 minutes, and the membrane flux was measured again. The membrane flux recovery rate was calculated. The experimental results are as follows: Figure 8 As shown, the results indicate that the flux recovery rate of the original alumina ceramic membrane was 41%, while the flux recovery rate of the hydrophilic and superoleophobic ceramic membrane prepared in Example 1 increased to 71%, which is 30% higher than that of the original ceramic membrane, and the membrane flux recovery performance was significantly improved.

[0059] Example 5

[0060] The hydrophilic, superoleophobic ceramic membrane (pore size approximately 100 nm, membrane area 0.002 m² during filtration) prepared in Example 1 was used. 2 This is applied to the oil-water separation process of the feed liquid in the extraction process of 9α-hydroxyandrostenedione. The 9α-hydroxyandrostenedione extraction process flow is as follows: Figure 9 As shown, 18 kg of phytosterol fermentation broth (containing 1.8 kg of soybean oil and 14.91 kg of sterols) was pretreated to obtain 4.5 kg of feed liquid. The feed liquid was then subjected to oil-water separation using the hydrophilic, superoleophobic ceramic membrane prepared in Example 1 (the transmembrane pressure difference was 1 bar, the membrane surface flow rate was 1 m / s, and the temperature was 20 °C). 3.6 kg of oil phase concentrate was collected. The oil phase concentrate was extracted twice with 7.2 kg of methanol. After collecting the methanol extract, approximately 13.3 g of 9α-hydroxyandrostenedione was detected under UV light. After evaporation, concentration, and decolorization, 14.2 g of crude 9α-hydroxyandrostenedione was obtained. The product yield was 89.2%, and the purity was 93.7%.

[0061] The hydrophilic and superoleophobic ceramic membrane prepared in Example 1 was applied to the oil-water separation process of the raw material liquid in the extraction process of 9α-hydroxyandrostenedione, which greatly reduced the amount of methanol extractant used and the extraction process time, and reduced the operating energy consumption.

[0062] This invention provides a hydrophilic, superoleophobic ceramic membrane and its preparation method. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing a hydrophilic, superoleophobic ceramic membrane, characterized in that, Includes the following steps: Step 1: Ferric chloride aqueous solution is subjected to high-temperature hydrolysis to obtain ferric hydroxide sol. The solution is cooled to 70-90°C, and polyvinyl alcohol aqueous solution is added to the ferric hydroxide sol to obtain a ferric hydroxide sol film-forming solution. The polyvinyl alcohol is type 124. The polyvinyl alcohol content in the ferric hydroxide sol film-forming solution is 0.05-2.5 wt%, and the solid content of ferric hydroxide is 0.1-0.6 wt%. Step 2: Immerse the microporous ceramic membrane in the ferric hydroxide sol film-forming solution obtained in Step 1 for 1 to 60 seconds, then remove, dry, and calcine to obtain the final product. In step 1, the particle size of the ferric hydroxide colloid in the ferric hydroxide sol film-forming solution is 100 ~ 200 nm; In step 2, the microporous ceramic membrane includes a support and a transition layer loaded on the surface of the support; the transition layer has an average pore size of 0.1 ~ 1 μm.

2. The preparation method according to claim 1, characterized in that, In step 1, the ferric chloride is any one of anhydrous FeCl3, FeCl3·6H2O, 2FeCl3·7H2O, and 2FeCl3·5H2O; the high-temperature hydrolysis reaction is as follows: the ferric chloride aqueous solution is added dropwise to boiling water, and the reaction is carried out at a temperature of 90~100℃ for 0.1~12 h.

3. The preparation method according to claim 1, characterized in that, In step 1, after adding polyvinyl alcohol aqueous solution to the ferric hydroxide sol, the mixture is reacted for 10 to 30 minutes under stirring and at a temperature of 70 to 90°C to obtain the ferric hydroxide sol film-forming solution.

4. The preparation method according to claim 1, characterized in that, In step 2, the drying temperature is 25 ~ 110℃ and the drying time is 1 ~ 48 h; the calcination temperature is 450 ~ 1000℃ and the calcination time is 1 ~ 24 h.

5. The preparation method according to claim 1, characterized in that, In step 2, the materials of the support and the transition layer are independently selected from any one or a combination of several of the following: alumina, zirconium oxide, magnesium oxide, silicon oxide, titanium oxide, cerium oxide, yttrium oxide, barium titanate, cordierite, andalusite, forsterite, block talc, silica-alumina-nitrogen ceramics, zircon, ferrates, silicon nitride, aluminum nitride, silicon carbide, hydroxyapatite, carbon, silicon, clay, clay minerals, ceramic slag, silica sand, ceramic stone, feldspar, and white sand.

6. The hydrophilic and superoleophobic ceramic membrane prepared by the preparation method according to any one of claims 1 to 5.

7. The hydrophilic and superoleophobic ceramic membrane according to claim 6, characterized in that, A complete α-Fe2O3 film layer is formed on the surface of the microporous ceramic membrane; the α-Fe2O3 film layer has an average pore size of 2 ~ 100 nm, a porosity of 35 ~ 40%, and a film thickness of 1 ~ 2 micrometers.

8. The application of the hydrophilic, superoleophobic ceramic membrane according to claim 6 or 7 in oil-water separation of oil-water mixed systems.

9. The application according to claim 8, characterized in that, The oil-water mixture system is a mixture of emulsified oil and water.

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