A modified ceramic membrane, its modification method and application

Abstract

This disclosure relates to a modified ceramic membrane and its modification method and application. The method includes the following steps: (1) impregnating the ceramic membrane in a solvent containing a metal salt to obtain an impregnated ceramic membrane; (2) coordinating a hydroxylated imidazole ligand with the impregnated ceramic membrane to obtain a ceramic membrane containing a hydroxylated imidazole framework material; (3) grafting the ceramic membrane containing the hydroxylated imidazole framework material with a fluorinated silanizing reagent and a first organic solvent; wherein, in step (1), the metal salt is a transition metal salt. The modified ceramic membrane of this disclosure has excellent hydrophobicity and good oleophilicity, with small and relatively uniform surface pore size, overcoming the problems of existing ceramic membranes having extremely hydrophilic surfaces, weak hydrophobic effects after modification, and poor oleophilic effects.

Description

Technical Field

[0001] This disclosure relates to the field of special separation materials, specifically to a modified ceramic membrane, its modification method, and its application. Background Technology

[0002] Ceramic membranes, also known as inorganic ceramic membranes, are solid membrane materials used in membrane separation technology. They are asymmetric membranes with a three-layer structure (porous support layer, transition layer, and separation layer), formed from inorganic ceramic materials such as alumina, zirconium oxide, titanium oxide, and silicon oxide through a special process. Depending on the support, ceramic membranes can be classified into three types: flat sheet, tubular, and multi-channel. Compared with general organic polymer membranes, ceramic membranes have numerous advantages, including stable performance, good chemical stability, resistance to acids and alkalis, resistance to organic solvents, antibacterial properties, high temperature resistance, high mechanical strength, low energy consumption, and long service life. They have been successfully applied in many fields such as food, beverage, plant (pharmaceutical) deep processing, biomedicine, fermentation, and fine chemicals.

[0003] Membrane distillation (MD) separation technology and oil-water separation technology are important components of membrane separation technology, providing new approaches for seawater desalination and industrial wastewater concentration. Polymer membranes are commonly used in both MD and oil-water separation processes due to their low surface energy and good hydrophobicity. They also allow for the easy fabrication of membranes with small pore sizes. However, polymer membranes have low operating temperatures, poor corrosion resistance, and short service lives. In MD, after a period of operation in the feed solution, organic matter and inorganic salts in the feed solution easily deposit on the membrane surface, causing membrane fouling and ultimately leading to a decrease in permeate flux and permeate quality. In oil-water separation, complex oily solvents in the feed solution can damage the structure of the polymer membrane, ultimately causing the membrane to lose its oil-water separation performance. Inorganic ceramic membranes, with their excellent chemical stability and mechanical strength, long service life, easy cleaning, and strong anti-fouling ability, are the most suitable membrane materials for MD and oil-water separation. However, due to the materials and structure used in ceramic membrane preparation, the high hydrophilicity and large pore size of ceramic membranes limit their application in membrane distillation and oil-water separation technologies. Therefore, it is necessary to modify ceramic membranes to be hydrophobic in order to improve their membrane distillation performance.

[0004] Existing ceramic membrane hydrophobic modification technologies have drawbacks such as limited modification methods, weak hydrophobicity imparted by modifiers, insufficient hydrophobicity of the modified ceramic membrane, and lack of good oleophilicity. Summary of the Invention

[0005] The purpose of this disclosure is to provide a device-modified ceramic membrane, a modification method thereon, and its application. This modification method is characterized by mild conditions, simple steps, and high versatility, which is beneficial for the large-scale production of modified ceramic membranes with hydrophobic, oleophilic, and adjustable pore sizes.

[0006] To achieve the above objectives, the first aspect of this disclosure provides a method for modifying a ceramic membrane, the method comprising the following steps:

[0007] (1) The ceramic membrane is immersed in a solvent containing metal salt to obtain the immersed ceramic membrane;

[0008] (2) A coordination reaction is carried out by contacting the impregnated ceramic membrane with the hydroxylated imidazole ligand to obtain a ceramic membrane containing a hydroxylated imidazole framework material.

[0009] (3) The ceramic membrane containing the hydroxylated imidazole framework material is grafted with a fluorinated silanizing agent and a first organic solvent;

[0010] In step (1), the metal salt is a transition metal salt.

[0011] Optionally, in step (1), the immersion time is 0.5 to 24 hours, and the concentration of the metal salt is 0.01 to 1.0 g / ml, preferably 0.05 to 0.1 g / ml;

[0012] The ceramic membrane is made of one or more of alumina, zirconium oxide, magnesium oxide, silicon oxide, yttrium oxide, cerium oxide, titanium oxide, and silicon carbide, preferably alumina; the metal salt is a transition metal salt, selected from one or more inorganic metal salts containing Zn, Cd, Co, Mn, and Cr ions; preferably one or more of zinc nitrate, zinc chloride, zinc acetate, and zinc sulfate, more preferably zinc nitrate.

[0013] Optionally, in step (2), the mass ratio of the hydroxylated imidazole ligand to the metal salt in step (1) is (1-7.5):1, preferably (1.5-4.5):1.

[0014] Optionally, the hydroxylated imidazole ligand is obtained by mixing an imidazole ligand with a hydroxylating reagent and performing a hydroxylation reaction; the mass ratio of the imidazole ligand to the hydroxylating reagent is (0.1-0.85):1;

[0015] The imidazole ligand is selected from one or more of benzimidazole, 2-methylimidazole, 2-ethylimidazole and methimazole, preferably 2-methylimidazole;

[0016] The hydroxylating agent has a boiling point above 70°C, and is preferably one or more of triethylamine, trimethylamine, isopropylamine, and tripropylamine, with triethylamine being more preferred.

[0017] Optionally, in step (2), the conditions for the coordination reaction include: the coordination reaction time is 45 min to 72 h, preferably 12 h to 24 h, and the coordination reaction temperature is 25 to 100 °C, preferably 30 to 60 °C.

[0018] Optionally, in step (3), the ratio of the area of ​​the ceramic film containing the hydroxylated imidazole framework material to the molar amount of the fluorinated silanizing agent is (0.5-5) cm². 2 1 mmol, preferably (0.5–3) cm 2 1 mmol;

[0019] The grafting reaction conditions include: a temperature of 20–60°C, preferably 20–40°C; and a time of 6–96 h, preferably 12–72 h.

[0020] The first organic solvent has a boiling point below 70°C and is selected from one or more of methanol, ethanol, n-hexane, and isopropanol.

[0021] Optionally, in step (3), the fluorine content of the fluorine-containing silanizing agent is 15-90% by mass; and the concentration of the fluorine-containing silanizing agent is 0.2-0.8 mmol / ml.

[0022] The fluorinated silanizing agent is selected from one or more of triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane, trifluoropropyltrichlorosilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, preferably triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane.

[0023] The second aspect of this disclosure provides a modified ceramic membrane obtained by the method described in the first aspect of this disclosure, the modified ceramic membrane comprising a ceramic membrane substrate and an imidazole silane material loaded on the ceramic membrane substrate, the imidazole silane material comprising a hydroxylated imidazole framework material and a fluorinated silane grafted onto the hydroxylated imidazole framework material.

[0024] Optionally, the modified ceramic membrane contains 0.1% to 4.5% fluorine by mass, and the average pore size of the modified ceramic membrane is 50 to 250 nm.

[0025] This third aspect of the disclosure provides the application of the modified ceramic membrane described in the second aspect of the disclosure in the fields of membrane distillation separation technology and oil-water separation.

[0026] Through the above technical solution, this disclosure uses hydroxylated imidazole ligands to perform coordination reactions on the surface of a ceramic membrane to form a ceramic membrane containing a hydroxylated imidazole framework material; the ceramic membrane containing the hydroxylated imidazole framework material is then chemically grafted with a fluorinated silanizing agent to obtain a modified ceramic membrane. This modified ceramic membrane has excellent hydrophobicity and good oleophilicity, and its surface pore size is small and relatively uniform, overcoming the problems of existing ceramic membranes having extremely hydrophilic surfaces, weak hydrophobic effects after modification, and poor oleophilic effects.

[0027] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0028] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0029] Figure 1 These are scanning electron microscope (SEM) images of the surface morphology of the unmodified ceramic membrane (ceramic membrane raw material) disclosed herein, as well as the modified ceramic membranes obtained in Examples 1 and 2.

[0030] Figure 2 This is a graph showing the changes in the infrared spectra of the unmodified ceramic membrane and the modified ceramic membrane in Embodiment 1 of this disclosure.

[0031] Figure 3 The graph shows the results of hydrophobicity tests on the surfaces of the unmodified ceramic membranes of this disclosure and the modified ceramic membranes obtained in Examples 1 and 2.

[0032] Figure 4 This is a graph showing the results of a surface oleophilicity test on the modified ceramic film obtained in Example 1 of this disclosure.

[0033] Figure 5 This is a graph showing the results of a surface oleophilicity test on the modified ceramic film obtained in Example 2 of this disclosure. Detailed Implementation

[0034] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0035] The first aspect of this disclosure provides a method for modifying a ceramic membrane, the method comprising the following steps:

[0036] (1) The ceramic membrane is immersed in a solvent containing metal salt to obtain the immersed ceramic membrane;

[0037] (2) A coordination reaction is carried out by contacting the impregnated ceramic membrane with the hydroxylated imidazole ligand to obtain a ceramic membrane containing a hydroxylated imidazole framework material.

[0038] (3) The ceramic membrane containing the hydroxylated imidazole framework material is grafted with a fluorinated silanizing agent and a first organic solvent;

[0039] In step (1), the metal salt is a transition metal salt.

[0040] The modification method disclosed herein is mild, simple, and highly versatile, which is beneficial for the large-scale production of modified ceramic membranes with hydrophobic, oleophilic, and tunable pore sizes. This disclosure enhances the hydrophobic effect by in-situ growth of a hydroxylated imidazole framework material (ZIF-8-OH) on the ceramic membrane followed by chemical grafting. The fluorinated silanizing agent disclosed herein possesses good oleophilicity, improving both the hydrophobicity and oleophilicity of the ceramic membrane surface. The modified ceramic membrane of this disclosure overcomes the shortcomings of other modified ceramic membranes, such as insufficient hydrophobicity, poor oleophilicity, and difficulty in simultaneously achieving pore size adjustment, thus optimizing the process effect.

[0041] According to one embodiment of this disclosure, in step (1), the immersion time is 0.5–24 h, and the concentration of the metal salt is 0.01–1.0 g / ml, preferably 0.05–0.1 g / ml; the material of the ceramic membrane is selected from one or more of alumina, zirconium oxide, magnesium oxide, silicon oxide, yttrium oxide, cerium oxide, titanium oxide, and silicon carbide, preferably alumina; the metal salt is a transition metal salt, selected from one or more of inorganic metal salts containing Zn, Cd, Co, Mn, and Cr ions; preferably one or more of zinc nitrate, zinc chloride, zinc acetate, and zinc sulfate, more preferably zinc nitrate. The above embodiment facilitates uniform adhesion of the metal salt to the ceramic membrane while avoiding waste of metal salt resources.

[0042] According to one embodiment of this disclosure, in step (2), the mass ratio of the hydroxylated imidazole ligand to the metal salt in step (1) is (1-7.5):1, preferably (1.5-4.5):1. The above embodiment is advantageous for obtaining modified ceramic films with superhydrophobic and oleophilic properties.

[0043] According to one embodiment of this disclosure, the hydroxylated imidazole ligand is obtained by mixing an imidazole ligand with a hydroxylating reagent and performing a hydroxylation reaction; the mass ratio of the imidazole ligand to the hydroxylating reagent is (0.1-0.85):1; the imidazole ligand is selected from one or more of benzimidazole, 2-methylimidazole, 2-ethylimidazole, and methimazole, preferably 2-methylimidazole; the hydroxylating reagent has a boiling point above 70°C, preferably one or more of triethylamine, trimethylamine, isopropylamine, and tripropylamine, more preferably triethylamine. The hydroxylated imidazole ligand obtained by this disclosure is basic in solvent and can combine with various transition metal compounds to generate hydroxylated imidazole framework materials with high yield and fast growth rate.

[0044] According to one embodiment of this disclosure, the conditions for the hydroxylation reaction include: a hydroxylation temperature of 10–60°C, preferably 30–60°C; a hydroxylation time of 10 min–24 h, preferably 12 h–48 h; a concentration of the imidazole ligand of 0.01–1.0 g / ml, preferably 0.08–0.12 g / ml; and a concentration of the hydroxylation reagent of 0.02–2.0 g / ml, preferably 0.1–0.5 g / ml. The above embodiment facilitates the complete hydroxylation of the imidazole ligand, avoids affecting the modification efficiency due to incomplete hydroxylation, and also avoids material waste.

[0045] According to one embodiment of this disclosure, the conditions for the coordination reaction include: a coordination reaction time of 45 min to 72 h, preferably 12 h to 24 h, and a coordination reaction temperature of 25 to 100 °C, preferably 30 to 60 °C. The above embodiment facilitates the uniform growth of the hydroxylated imidazole framework material on the ceramic film, avoiding resource waste caused by long reaction times and high energy consumption.

[0046] According to one embodiment of this disclosure, before step (3), the ceramic membrane containing the hydroxylated imidazole framework material is removed, cleaned with a second organic solvent, and subjected to a first drying treatment. The second organic solvent is not particularly limited and can be one or more of methanol, ethanol, n-hexane, and isopropanol; the first drying conditions can be conventional operating conditions in the art, for example, the first drying temperature can be 60-100°C, and the first drying time can be 0.3-2.5 h.

[0047] According to one embodiment of this disclosure, in step (3), the ratio of the area of ​​the ceramic film containing the hydroxylated imidazole framework material to the molar amount of the fluorinated silanizing agent is (0.5-5) cm². 2 1 mmol, preferably (0.5–3) cm 2The grafting reaction conditions include: a temperature of 20–60°C, preferably 20–40°C; a time of 6–96 h, preferably 12–72 h; and the boiling point of the first organic solvent being below 70°C, selected from one or more of methanol, ethanol, n-hexane, and isopropanol. The above embodiments result in ceramic films containing hydroxylated imidazole framework materials exhibiting better hydrophobicity after grafting, while also possessing good oleophilicity.

[0048] According to one embodiment of this disclosure, in step (3), the fluorine content of the fluorinated silanizing agent is 15-90% by mass; the concentration of the fluorinated silanizing agent is 0.2-0.8 mmol / ml; the fluorinated silanizing agent is selected from one or more of triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane, trifluoropropyltrichlorosilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane, preferably triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane. The above embodiment results in ceramic films containing hydroxylated imidazole framework materials exhibiting better hydrophobicity after grafting, while also possessing good oleophilicity. In this disclosure, a ceramic membrane containing a hydroxylated imidazole framework material is mixed with a fluorinated silanizing agent. The fluorinated silanizing agent, such as a fluorinated silane, is hydrolyzed to obtain silanol, which undergoes dehydration condensation with the hydroxyl groups on the hydroxylated imidazole framework material (ZIF-8-OH) grown on the surface of the ceramic membrane, thus completing the chemical grafting reaction.

[0049] According to one embodiment of this disclosure, after step (3), the grafted ceramic membrane is removed, washed sequentially with a second organic solvent and deionized water, and then subjected to a second drying treatment. The number of washing cycles is not specifically limited and can be two to four times; the second drying conditions can be conventional operating conditions in the art, for example, the second drying temperature can be 60 to 120°C, and the second drying time can be 6 to 18 hours.

[0050] The second aspect of this disclosure provides a modified ceramic membrane obtained by the method described in the first aspect of this disclosure, the modified ceramic membrane comprising a ceramic membrane substrate and an imidazole silane material loaded on the ceramic membrane substrate, the imidazole silane material comprising a hydroxylated imidazole framework material and a fluorinated silane grafted onto the hydroxylated imidazole framework material.

[0051] The modified ceramic membrane disclosed herein has excellent hydrophobicity, good oleophilicity, and customizable pore size. The surface pore size is small and relatively uniform, overcoming the problems of existing ceramic membranes having extremely hydrophilic surfaces, weak hydrophobic effects after modification, and poor oleophilic effects.

[0052] According to one embodiment of this disclosure, the modified ceramic membrane contains 0.1% to 4.5% fluorine by mass, and the average pore size of the modified ceramic membrane is 50 to 250 nm.

[0053] This third aspect of the disclosure provides the application of the modified ceramic membrane described in the second aspect of the disclosure in the fields of membrane distillation separation technology and oil-water separation.

[0054] The present disclosure will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the scope of this disclosure in any way.

[0055] All raw materials used in the examples were obtained commercially and, unless otherwise specified, were of analytical grade. 2-Methylimidazole was purchased from Anhui Zesheng Technology Co., Ltd., under the brand name Anaiji (a standard product). The ceramic microporous membrane had a thickness of approximately 6 mm and an effective area of ​​50 cm². 2 Purchased from Water Treatment Technology Co., Ltd.

[0056] The mass content of fluorine in this disclosure was tested by X-ray photoelectron spectroscopy; scanning electron microscopy was performed on a Hitachi SU-4800 instrument; and infrared spectroscopy was performed on a Thermo Fisher Nicolet-is50 instrument.

[0057] Example 1

[0058] (1) Place the ceramic membrane in ethanol, ultrasonically clean the surface of the ceramic membrane, remove it and place it in 50 ml of 0.05 g / mL zinc nitrate hexahydrate ethanol solution for 0.5 h to obtain the impregnated ceramic membrane;

[0059] (2) Prepare a deionized aqueous solution of 2-methylimidazole with a concentration of 0.08 g / ml in another beaker. After it is fully dissolved, add a deionized aqueous solution of triethylamine with a concentration of 0.1 g / ml and stir continuously. After stirring continuously at room temperature for 12 hours, hydroxylated 2-methylimidazole is obtained. The hydroxylation reaction is shown in formula (1):

[0060]

[0061] 7.5g of hydroxylated 2-methylimidazole was poured into the mixed solution of step (1), and the zinc ions on the impregnated ceramic membrane were subjected to a coordination reaction with the hydroxylated 2-methylimidazole at 40°C for 24h to obtain a ceramic membrane containing a hydroxylated imidazole framework material. The ceramic membrane containing the hydroxylated imidazole framework material was then taken out, washed with methanol, and dried. The mass ratio of the hydroxylated imidazole ligand in step (2) to the metal salt in step (1) was 3:1.

[0062] (3) Take the 50cm obtained in step (2) 2A ceramic membrane containing a hydroxylated imidazole framework was placed in 100 mL of a methanol solution containing 0.2 mmol / mL triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane. After reacting at 20 °C for 72 h, the grafted ceramic membrane was removed, washed three times sequentially with methanol and deionized water, and dried at 60 °C for 12 h to obtain a modified ceramic membrane. The area of ​​the ceramic membrane containing the hydroxylated imidazole framework was 2.5 cm² / cm², representing the molar ratio of the fluorinated silanizing reagent. 2 1 mmol;

[0063] The ceramic membrane raw materials and modified ceramic membrane structures were characterized by SEM electron microscopy, and the results were obtained as follows: Figure 1 The electron microscope image shown. (By...) Figure 1 It can be seen that hydroxylated ZIF-8 crystals are grown in situ on the surface of the ceramic film treated by the method disclosed herein. Infrared spectroscopy was performed on the raw ceramic film and the modified ceramic film, and the resulting infrared spectra are shown below. Figure 2 As shown, 3310cm -1 The absorption peak at 3411 cm⁻¹ corresponds to the OH stretching vibrations that are abundant on the surface of the original ceramic film, while the peak at 3411 cm⁻¹ is clearly visible in the infrared spectrum of the modified ceramic film. -1 1542cm -1 NH stretching vibration and 2365cm -1 The in-plane bending vibration at NH is attributed to the successful in-situ growth of ZIF-8-OH on the surface of the modified ceramic film, 1143 cm⁻¹. -1 The CF stretching vibration is attributed to the successful grafting of the fluorinated silanizing agent. Infrared spectroscopy confirms the successful in-situ growth of hydroxylated ZIF-8 on the ceramic film surface, and the successful grafting of the fluorinated organosilicon alkylating agent onto the hydroxylated ZIF-8 surface.

[0064] Example 2

[0065] (1) Place the ceramic membrane in ethanol, ultrasonically clean the surface of the ceramic membrane, remove it and place it in 125ml of 0.1g / mL zinc nitrate hexahydrate ethanol solution for 1h to obtain the impregnated ceramic membrane.

[0066] (2) Prepare a deionized aqueous solution of 2-methylimidazole with a concentration of 0.12 g / ml in another beaker. After it is fully dissolved, add a deionized aqueous solution of triethylamine with a concentration of 0.5 g / ml and stir continuously. After stirring continuously at room temperature for 24 hours, hydroxylated 2-methylimidazole is obtained.

[0067] 18.75g of hydroxylated 2-methylimidazole was poured into the mixed solution of step (1), and the zinc ions on the impregnated ceramic membrane were subjected to a coordination reaction with the hydroxylated 2-methylimidazole at 40°C for 12h to obtain a ceramic membrane containing a hydroxylated imidazole framework material. The ceramic membrane containing the hydroxylated imidazole framework material was then taken out, washed with methanol, and dried. The mass ratio of the hydroxylated imidazole ligand in step (2) to the metal salt in step (1) was 1.5:1.

[0068] (3) Take the 50cm obtained in step (2) 2 A ceramic membrane containing a hydroxylated imidazole framework material was placed in 75 mL of a methanol solution containing 0.8 mmol / mL of triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane and reacted at 40 °C for 12 h. The ceramic membrane was then removed, washed three times sequentially with methanol and deionized water, and dried at 60 °C for 12 h to obtain a modified ceramic membrane. The molar ratio of the area of ​​the ceramic membrane containing the hydroxylated imidazole framework material to the molar amount of the fluorinated silanizing reagent was 0.83:1.

[0069] Example 3

[0070] The method in this embodiment is the same as that in Example 1, except that the amount of metal salt used in step (1) is 250 ml and 0.05 g / mL zinc nitrate hexahydrate; in step (2), 14.5 g of hydroxylated 2-methylimidazole is poured into the mixed solution in step (1); and the mass ratio of the hydroxylated imidazole ligand to the metal salt in step (1) is 1.16:1.

[0071] Example 4

[0072] The method in this embodiment is the same as that in embodiment 1, except that the coordination reaction time in step (2) is 6 hours and the coordination reaction temperature is 25°C.

[0073] Example 5

[0074] The method in this embodiment is the same as that in Example 1, except that the concentration of triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane in step (3) is 0.05 mmol / ml, and the molar ratio of the area of ​​the ceramic membrane containing the hydroxyl imidazole skeleton material to the molar amount of the fluorinated silanizing reagent is 10:1.

[0075] Example 6

[0076] The method in this embodiment is the same as that in embodiment 1, except that the grafting reaction temperature in step (3) is 20°C and the grafting reaction time is 6h.

[0077] Test Example 1

[0078] The contact angles of the ceramic membrane raw materials and the modified ceramic membranes of Examples 1-6 were tested in water and oil solvents, respectively. The mass content of fluorine and the average pore size were also tested. The results of the water contact angle tests are shown in Table 1 and [Table data missing]. Figure 3 Contact angles for oily solvents are shown in Table 2 and Figures 4-5 .

[0079] Table 1

[0080]

[0081]

[0082] Table 2

[0083]

[0084] Depend on Figure 3 It can be seen that the water contact angle of the ceramic membrane raw material rapidly decreases to 0° within a very short time, meaning it has almost no hydrophobicity; while the water contact angle of the modified ceramic membranes prepared in Examples 1 and 2, after stabilization, is greater than 130°, indicating that the modified ceramic membranes prepared in Examples 1 and 2 have excellent hydrophobicity. Figure 4 and 5 It can be seen that the contact angle of the oily solvent on the surface of the modified ceramic film prepared in Examples 1 and 2 drops rapidly to 0° in a short time, which means that it has oleophilicity.

[0085] According to the results in Tables 1 and 2, the modified ceramic film obtained by the modification method of this disclosure exhibits both superhydrophobicity and superoleophilicity. Furthermore, the preparation method is simple, the preparation requirements are easily met, and it is suitable for large-area preparation. A comparison of Examples 1 and 3 shows that within the mass ratio range of the hydroxylated imidazole ligand to the metal salt disclosed in this disclosure, the modified ceramic film obtained exhibits better hydrophobicity and oleophilicity. A comparison of Examples 1 and 4 shows that within the preferred conditions of the coordination reaction disclosed in this disclosure, the modified ceramic film obtained exhibits better hydrophobicity and oleophilicity. A comparison of Examples 1 and 5 shows that within the ratio range of the area of ​​the ceramic film containing the hydroxylated imidazole framework material to the molar amount of the fluorinated silanizing reagent disclosed in this disclosure, the modified ceramic film obtained exhibits better hydrophobicity and oleophilicity. A comparison of Examples 1 and 6 shows that within the preferred conditions of the chemical grafting reaction disclosed in this disclosure, the modified ceramic film obtained exhibits better hydrophobicity and oleophilicity.

[0086] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0087] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0088] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for modifying a ceramic membrane, characterized in that, The method includes the following steps: (1) The ceramic membrane is immersed in a solvent containing metal salt to obtain the immersed ceramic membrane; (2) The hydroxylated imidazole ligand is brought into contact with the impregnated ceramic membrane to carry out a coordination reaction, thereby obtaining a ceramic membrane containing a hydroxylated imidazole framework material. (3) The ceramic membrane containing the hydroxylated imidazole framework material is grafted with a fluorinated silanizing agent and a first organic solvent; In step (1), the metal salt is a transition metal salt.

2. The method according to claim 1, wherein, In step (1), the immersion time is 0.5~24h, and the concentration of the metal salt is 0.01~1.0 g / ml; The ceramic membrane is made of one or more of the following materials: alumina, zirconium oxide, magnesium oxide, silicon oxide, yttrium oxide, cerium oxide, titanium oxide, and silicon carbide; the metal salt is a transition metal salt and is selected from one or more inorganic metal salts containing Zn, Cd, Co, Mn, and Cr ions.

3. The method according to claim 2, wherein, In step (1), the concentration of the metal salt is 0.05~0.1 g / ml.

4. The method according to claim 2, wherein, In step (1), the ceramic film is made of alumina.

5. The method according to claim 2, wherein, In step (1), the metal salt is one or more of zinc nitrate, zinc chloride, zinc acetate and zinc sulfate.

6. The method according to claim 5, wherein, In step (1), the metal salt is zinc nitrate.

7. The method according to claim 1, wherein, The mass ratio of the hydroxylated imidazole ligand in step (2) to the metal salt in step (1) is (1~7.5):

1.

8. The method according to claim 7, wherein, The mass ratio of the hydroxylated imidazole ligand in step (2) to the metal salt in step (1) is (1.5~4.5):

1.

9. The method according to claim 1, wherein, The hydroxylated imidazole ligand is obtained by mixing an imidazole ligand with a hydroxylating reagent and then performing a hydroxylation reaction; the mass ratio of the imidazole ligand to the hydroxylating reagent is (0.1~0.85):1; The imidazole ligand is selected from one or more of benzimidazole, 2-methylimidazole, 2-ethylimidazole and methimazole; The boiling point of the hydroxylating agent is above 70°C.

10. The method according to claim 9, wherein, The imidazole ligand is 2-methylimidazole.

11. The method according to claim 9, wherein, The hydroxylating agent is one or more of triethylamine, trimethylamine, isopropylamine, and tripropylamine.

12. The method according to claim 11, wherein, The hydroxylating agent is triethylamine.

13. The method according to claim 1, wherein, In step (2), the conditions for the coordination reaction include: the coordination reaction time is 45 min to 72 h, and the coordination reaction temperature is 25 to 100 °C.

14. The method according to claim 13, wherein, In step (2), the conditions for the coordination reaction include: the coordination reaction time is 12h~24h, and the coordination reaction temperature is 30~60℃.

15. The method according to claim 1, wherein, In step (3), the ratio of the area of ​​the ceramic film containing the hydroxylated imidazole framework material to the molar amount of the fluorinated silanizing agent is (0.5~5) cm². 2 1 mmol; The grafting reaction conditions include: a temperature of 20~60℃ and a time of 6~96h; The first organic solvent has a boiling point below 70°C and is selected from one or more of methanol, ethanol, n-hexane, and isopropanol.

16. The method according to claim 15, wherein, In step (3), the ratio of the area of ​​the ceramic film containing the hydroxyl imidazole framework material to the molar amount of the fluorinated silanizing agent is (0.5~3) cm². 2 1 mmol.

17. The method according to claim 15, wherein, In step (3), the conditions for the grafting reaction include: a temperature of 20~40℃ and a time of 12~72h.

18. The method according to claim 1, wherein, In step (3), the fluorine content of the fluorine-containing silanizing agent is 15-90% by mass; the concentration of the fluorine-containing silanizing agent is 0.2-0.8 mmol / ml; The fluorinated silanizing agent is selected from one or more of triethoxy-1H,1H,2H,2H-tridecylfluoro-n-octylsilane, trifluoropropyltrichlorosilane, and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane.

19. The method according to claim 18, wherein, In step (3), the fluorinated silanizing agent is triethoxy-1H,1H,2H,2H-tetrafluoro-n-octylsilane.

20. The modified ceramic membrane obtained by the method according to any one of claims 1 to 19, characterized in that, The modified ceramic membrane comprises a ceramic membrane substrate and an imidazole silane material loaded on the ceramic membrane substrate, wherein the imidazole silane material comprises a hydroxylated imidazole framework material and a fluorinated silane grafted onto the hydroxylated imidazole framework material.

21. The modified ceramic membrane according to claim 20, wherein, The modified ceramic membrane contains 0.1-4.5% fluorine by mass, and the average pore size of the modified ceramic membrane is 50-250 nm.

22. The application of the modified ceramic membrane according to any one of claims 20 to 21 in the fields of membrane distillation separation technology and oil-water separation technology.

Images