Fluorine functionalized composite ceramic membrane as well as preparation method and application thereof

Abstract

The invention discloses a fluorine-functionalized composite ceramic membrane and a preparation method and application thereof, and belongs to the technical field of water treatment.The fluorine-functionalized composite ceramic membrane comprises a ceramic membrane and a catalyst loaded on the surface of the ceramic membrane, and the catalyst is a fluorine-functionalized ZIF-67 compound. Strong selective adsorption is formed by F... F fluorine affinity and PFASs molecules, meanwhile, a surface hydrogen bond network is reconstructed to reduce an energy barrier for generating active hydrogen through water dissociation, adsorption-activation synergistic enhancement is achieved, meanwhile, the mass transfer flux is improved through forced convection by means of a multi-stage pore channel structure of the ceramic membrane, and the adsorption efficiency is improved. The chemical bonding of the fluorine functionalized ZIF-67 and the ceramic substrate ensures the interface electron transfer efficiency and long-term stability, breaks through the double limitations of low mass transfer efficiency and high reaction energy barrier of trace PFASs, and provides a new way for efficient defluorination of PFASs pollutants in complex water.

Description

Technical Field

[0001] The present invention belongs to the technical field of water treatment, and relates to a fluorine-functionalized composite ceramic membrane, a preparation method thereof, and an application thereof, specifically to a fluorine-functionalized composite ceramic membrane, a preparation method thereof, and an application thereof in removing perfluorinated compounds in water bodies. Background Art

[0002] Perfluorinated compounds (PFASs) are a class of persistent pollutants with extremely high chemical stability and bioaccumulation, and are widely present in surface water, groundwater, and industrial wastewater. Their strong C-F bonds make it difficult for traditional redox technologies to effectively degrade them, and the low-concentration characteristics of trace PFASs further exacerbate the difficulty of removal. Electrochemical reduction defluorination technology has become a research hotspot due to its advantages such as green controllability and no need for chemical agents, but it faces multiple challenges in practical applications: on the one hand, the diffusion mass transfer efficiency of trace PFASs in water bodies is limited by the low concentration gradient, and the low conductivity of water significantly inhibits the electron transfer rate; on the other hand, the anionic characteristics of PFASs are prone to form an electrostatic repulsion barrier on the cathode surface, superimposed with the competitive adsorption effect of coexisting anions, resulting in serious obstruction of the interfacial reaction kinetics.

[0003] Existing electrochemical cathode materials mostly rely on non-specific physical or chemical adsorption (such as activated carbon, metal oxides), and their adsorption capacity is easily affected by complex water body environments. In addition, the catalytic active sites and adsorption functions of traditional electrodes lack collaborative design, making it difficult to simultaneously achieve efficient enrichment of pollutants and directional activation of C-F bonds. For example, the static adsorption mechanism cannot adapt to the dynamic mass transfer process, resulting in a sharp drop in the defluorination efficiency under low-concentration conditions; while the modification strategy of simply improving conductivity (such as carbon material loading) can accelerate electron transfer, but it cannot break through the key bottleneck of the coupling of selective adsorption and catalytic path.

[0004] Chinese Patent with Publication No. CN119746930A discloses a fluorinated ZIF-67 / graphene composite catalyst for coal chemical wastewater treatment and a preparation method thereof. The fluorinated ZIF-67 / graphene composite catalyst uses porous graphene as a carrier and loads fluorinated ZIF-67. The fluorinated ZIF-67 / graphene composite catalyst has the ability to highly degrade organic pollutants and is suitable for treating pollutants such as phenols and oils that are difficult to biodegrade in coal chemical wastewater. However, at present, no application of the fluorinated ZIF-67 / graphene composite catalyst in the removal of PFASs has been found. Summary of the Invention

[0005] To address the above problems, the present invention discloses a fluorine-functionalized composite ceramic membrane, its preparation method, and applications. The fluorine-functionalized composite ceramic membrane of the present invention precisely anchors fluorine-functional groups on the material surface, forms strong selective adsorption with PFASs molecules through F…F fluorophilic interactions, and simultaneously reconstructs the surface hydrogen bond network to lower the energy barrier for the hydrolysis dissociation to generate active hydrogen, achieving synergistic enhancement of "adsorption-activation". The multi-level pore structure of the ceramic membrane enhances the mass transfer flux through forced convection, while the chemical bonding between the fluorine-functionalized ZIF-67 and the ceramic substrate ensures the interfacial electron transfer efficiency and long-term stability. This technology breaks through the dual limitations of low mass transfer efficiency and high reaction energy barrier of trace PFASs, providing a new approach for the efficient defluorination of PFASs pollutants in complex water bodies.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a fluorine-functionalized composite ceramic membrane, comprising a ceramic membrane and a catalyst loaded on the surface of the ceramic membrane, wherein the catalyst is a fluorine-functionalized ZIF-67 composite.

[0007] In some embodiments, the loading amount of the catalyst is 0.2 mg / cm 2 - 0.5 mg / cm 2 .

[0008] In some embodiments, the material of the ceramic membrane is one of alumina, zirconia, titania, or silica.

[0009] In some embodiments, the pore size of the ceramic membrane is 50nm - 200nm.

[0010] In some embodiments, the preparation method of the fluorine-functionalized ZIF-67 composite comprises the following steps: S1. Dissolve cobalt nitrate hexahydrate in methanol to form solution A; dissolve 2-methylimidazole in methanol to form solution B; mix solution B with solution A, stir, allow to stand for aging, perform solid-liquid separation, washing, and drying to obtain a ZIF-67 precursor; S2. Add the ZIF-67 precursor to ethanol and pentafluorobenzenethiol, disperse, heat and react, wash, and dry to obtain fluorine-functionalized ZIF-67; S3. Mix and disperse reduced graphene oxide with water to obtain a dispersion; add the fluorine-functionalized ZIF-67 to the dispersion, perform secondary dispersion, solid-liquid separation, washing, and drying to obtain a fluorine-functionalized ZIF-67 composite.

[0011] Preferably, the molar ratio of cobalt nitrate hexahydrate to 2-methylimidazole in step S1 is 1:5 - 10; more preferably 1:7 - 9; even more preferably 1:8.

[0012] Preferably, the stirring time in step S1 is 0.5 h - 2 h; more preferably 1 h - 2 h; even more preferably 1 h.

[0013] Preferably, the standing and aging time in step S1 is 20 h - 30 h; more preferably 24 h - 30 h; even more preferably 24 h.

[0014] Preferably, the washing in step S1 is washing with methanol 1 - 5 times.

[0015] Preferably, the molar ratio of pentafluorobenzenethiol to ZIF-67 precursor in step S2 is 1:1 - 3.

[0016] Preferably, the heating reaction in step S2 is: reacting at 80 °C - 90 °C for 10 h - 14 h.

[0017] Preferably, the washing in step S2 is washing with ethanol and water successively 1 - 5 times after the reaction is completed.

[0018] Preferably, the molar ratio of reduced graphene oxide to fluorine-functionalized ZIF-67 in step S3 is 1:4 - 6.

[0019] Preferably, the washing in step S3 is washing with water 1 - 5 times.

[0020] The solid-liquid separation involved in the present invention aims to separate the solid phase and the liquid phase, which is a conventional solid-liquid separation technical means in the art. Therefore, its specific implementation manner is not limited, and precipitation, centrifugation or suction filtration, etc. can be selected according to actual needs. For example, the solid-liquid separation in step S1 is centrifugation, and the solid-liquid separation in step S3 is vacuum filtration.

[0021] The dispersion involved in the present invention aims to fully disperse the solid in the liquid phase to form a uniform dispersion liquid. Therefore, its specific implementation manner is not limited, and at least one of ultrasonic, stirring and high-pressure homogenization, etc. can be selected according to actual needs. For example, the dispersion in steps S2 and S3 is ultrasonic dispersion, and the dispersion time is 20 min - 60 min.

[0022] The drying involved in the present invention aims to reduce the moisture content of the substance and control the moisture content of the dried substance not to exceed 10%. Conventional drying methods in the art, such as vacuum drying, freeze drying, spray drying, baking, etc., can be used. Therefore, its specific implementation manner is not limited. For example, the drying in steps S1 and S3 is vacuum drying, the temperature is 70 °C - 90 °C, and the drying time is 10 h - 14 h. The drying in step S2 is freeze drying.

[0023] Second aspect, the present invention provides a method for preparing the above-mentioned fluorine-functionalized composite ceramic membrane, which comprises the following steps: dispersing the fluorine-functionalized ZIF-67 composite in a dimethyl sulfoxide solution, loading it onto the surface of the ceramic membrane by suction filtration, and then performing a drying treatment.

[0024] In some embodiments, the concentration of the dimethyl sulfoxide solution is 4 mM - 10 mM.

[0025] In some embodiments, the temperature of the drying is 70°C - 90°C, and the time of the drying is 10 h - 16 h.

[0026] Third aspect, the present invention provides the application of the above-mentioned fluorine-functionalized ZIF-67 composite and fluorine-functionalized composite ceramic membrane in removing perfluorinated compounds in water bodies.

[0027] In some embodiments, the perfluorinated compounds include at least one of perfluorooctanoic acid (PFOA), perfluorobutyric acid (PFBA), perfluoropentanoic acid (PFPeA), perfluorohexanoic acid (PFHxA), perfluoroheptanoic acid (PFHpA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), ammonium perfluoro(2-methyl-3-oxahexanoate) (GenX), perfluorohexane sulfonic acid (PFHxS), and perfluorobutane sulfonic acid (PFBS); preferably at least one of PFOA, PFBA, GenX, and PFHxS.

[0028] In some embodiments, the concentration of the perfluorinated compounds in the water body is 0.1 μg / L - 100 mg / L.

[0029] Fourth aspect, the present invention provides a defluorination device, which comprises an electrocatalytic reaction system with the above-mentioned fluorine-functionalized composite ceramic membrane as the cathode and a Pt-Ti plate as the anode.

[0030] In some embodiments, the defluorination device is a cross-flow filtration type reaction device.

[0031] In some embodiments, the cross-flow filtration type reaction device includes a circulating liquid storage tank, a circulating chamber, a cathode, an anode, a power supply, and a treatment liquid storage tank; The circulating chamber is provided with a water inlet, a circulating liquid outlet, and a treatment liquid outlet. The water inlet and the circulating liquid outlet are respectively connected to the circulating liquid storage tank through pipelines, and the treatment liquid outlet is connected to the treatment liquid storage tank through a pipeline; The circulating chamber is internally provided with a cathode and an anode, and the cathode and the anode are respectively connected to the negative electrode and the positive electrode of the power supply to form an electrocatalytic reaction system; The material of the cathode is the fluorine-functionalized composite ceramic membrane, and the material of the anode is a porous Pt-Ti plate.

[0032] Fourthly, the present invention provides a method for removing perfluorinated compounds from water, comprising the following steps: Using the above fluorine-functionalized composite ceramic membrane as the cathode and a Pt-Ti plate as the anode, an electrochemical defluorination reaction is carried out on the water body containing perfluorinated compounds and sodium sulfate.

[0033] In some embodiments, the concentration of the perfluorinated compound is 0.1 μg / L - 100 mg / L, and the concentration of the sodium sulfate is 0.01 M - 0.5 M.

[0034] In some embodiments, the current density of the electrochemical defluorination reaction is 5 mA / cm² - 100 mA / cm 2 .

[0035] In some embodiments, the flow rate of the water body is 5 mL / min - 100 mL / min.

[0036] The present invention takes the fluorine-functionalized ZIF-67 composite ceramic membrane cathode as the core, collaborates with a cross-flow filtration reaction device, and through the coupling of the "adsorption-reduction" mechanism, significantly improves the defluorination efficiency of trace PFASs, has the advantages of adaptability to complex water bodies, low interfacial resistance energy consumption, and long-term operation stability, and provides an integrated solution for the efficient removal of perfluorinated pollutants in wastewater.

[0037] Compared with the prior art, the present invention has the following advantages: 1. High-efficiency adsorption-reduction synergistic effect: Through fluorine-functionalized design, selective adsorption and synchronous electrocatalytic reduction of trace PFASs pollutants are realized, significantly improving the pollutant removal efficiency; 2. Potential for low-energy consumption operation: The tight combination of the ceramic substrate and the fluorine-functionalized ZIF-67 composite reduces the electrode spacing by 1 - 2 orders of magnitude compared with the conventional one, significantly reducing the interfacial resistance, especially suitable for the treatment of wastewater with low conductivity; 3. Enhanced structural stability: The firm bonding of the ceramic membrane and the catalytic material (fluorine-functionalized ZIF-67 composite) avoids the loss of active components and ensures long-term operation stability. Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of the cross-flow filtration reaction device of the present invention.

[0039] Among them, 1, circulating liquid storage tank; 2, water inlet pipe; 3, pump; 4, water inlet; 5, circulation chamber; 6, fluorine-functionalized composite ceramic membrane cathode; 7, porous Pt-Ti anode; 8, treated liquid outlet; 9, treated liquid outlet pipe; 10, treated liquid storage tank; 11, circulating liquid outlet; 12, power supply.

[0040] Figure 2XPS full spectrum of the fluorine-functionalized ZIF-67 composite powder in Example 1.

[0041] Figure 3 High-magnification SEM and low-magnification SEM images of the fluorine-functionalized ZIF-67 composite ceramic membrane in Example 1.

[0042] Figure 4 EDS image of the fluorine-functionalized ZIF-67 composite ceramic membrane in Example 1. Detailed implementation mode

[0043] In order to more clearly understand the above objects, features, and advantages of the present invention, the following further describes the present invention in conjunction with specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0044] In the following description, many specific details are set forth to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Therefore, the present invention is not limited by the specific embodiments disclosed in the following specification.

[0045] Unless otherwise specified, the solvent for solution preparation in the present invention is deionized water, and the temperature is room temperature (20°C - 25°C).

[0046] Example 1 A fluorine-functionalized ZIF-67 ceramic membrane, the preparation method is as follows: S1. Dissolve 2.9 g of Co(NO3)2·6H2O in 100 mL of methanol to form solution A. Separately, dissolve 6.5 g of 2-methylimidazole in 100 mL of methanol to form solution B. Quickly pour solution B into solution A, stir at room temperature for 1 h, then stand for aging for 24 h, centrifuge to collect the purple precipitate, wash it 3 times with methanol, and vacuum dry it at 80°C for 12 h to obtain the ZIF-67 precursor.

[0047] S2. Take 350 mg of the ZIF-67 precursor, disperse it in 5 mL of ethanol, add 100 μL of pentafluorobenzenethiol and 10 mL of ethanol, ultrasonically disperse for 30 min, then heat and react at 85°C for 14 h. After the reaction is completed, wash it 3 times with ethanol and deionized water in sequence, and freeze-dry to obtain fluorine-functionalized ZIF-67.

[0048] S3. Disperse 40 mg of reduced graphene oxide in 50 mL of deionized water, ultrasonically treat for 30 min to form a homogeneous dispersion, add 200 mg of fluorine-functionalized ZIF-67, continue to ultrasonically disperse for 30 min, then collect the composite by vacuum filtration, wash it 3 times with deionized water, and dry it at 80°C for 12 h to prepare the fluorine-functionalized ZIF-67 composite.

[0049] S4. Disperse 15 mg of the fluorine-functionalized ZIF-67 composite in a DMSO (5 mM) solution, and ultrasonically treat it for 2 h to form a homogeneous dispersion. Then, directionally load the dispersion onto the surface of the ceramic membrane by vacuum filtration, and dry it at 85 °C for 12 h to obtain the fluorine-functionalized ZIF-67 ceramic membrane.

[0050] Figure 2 It is the full XPS spectrum of the fluorine-functionalized ZIF-67 composite powder in Example 1. It can be seen from the figure that the characteristic peaks of elements such as F and Co are present, indicating that fluorine elements are successfully doped into ZIF-67.

[0051] Figure 3 They are the high-magnification SEM image and low-magnification SEM image of the fluorine-functionalized ZIF-67 composite ceramic membrane in Example 1. It can be seen from the figure that there are irregular flaky structures on the ceramic membrane substrate, which are evenly distributed on the surface of the ceramic membrane, indicating that the active components are successfully loaded onto the ceramic membrane.

[0052] Figure 4 It is the EDS diagram of the fluorine-functionalized ZIF-67 composite ceramic membrane in Example 1. In the figure, Al comes from the alumina ceramic membrane substrate, and the presence of F and Co elements further proves that the catalyst is successfully loaded onto the ceramic membrane.

[0053] A defluorination device, as Figure 1 shown, includes a circulating liquid storage tank 1, a circulating chamber 5, a fluorine-functionalized composite ceramic membrane cathode 6, a porous Pt-Ti anode 7, a power supply 12, and a treatment liquid storage tank 10; The circulating chamber 5 is provided with a water inlet 4, a circulating liquid outlet 11, and a treatment liquid outlet 8. The water inlet 4 and the circulating liquid outlet 11 are respectively connected to the circulating liquid storage tank 1 through pipelines, and the treatment liquid outlet 8 is connected to the treatment liquid storage tank 10 through a treatment liquid outlet pipe 9; The circulating chamber 5 is internally provided with a fluorine-functionalized composite ceramic membrane cathode 6 and a porous Pt-Ti anode 7. The fluorine-functionalized composite ceramic membrane cathode 6 and the porous Pt-Ti anode 7 are respectively connected to the negative and positive electrodes of the power supply 12 to form an electrocatalytic reaction system.

[0054] The circulating liquid storage tank 1 is connected to a pump 3 through a water inlet pipe 2, and the pump 3 is connected to the water inlet 4 through a pipeline.

[0055] A method for removing PFOA in water uses a defluorination device as Figure 1 shown, in which a fluorine-functionalized composite ceramic membrane is used as the cathode, an alumina ceramic membrane with a thickness of 3 mm and a membrane layer pore size of 100 nm is used, a porous Pt-Ti plate is used as the anode, and the treatment liquid storage tank 10 is placed below the defluorination device to collect the reaction products.

[0056] The experimental parameters were as follows: a 0.1 M Na2SO4 pollutant solution containing 10 μg / L PFOA was continuously pumped into the defluorination device inlet from a peristaltic pump at a flow rate of 10 mL / min. The power supply was set in the constant current mode, and a current density of 10 mA / cm² was applied to initiate the reaction.

[0057] After testing, the PFOA removal rate was 97.5%, and the PFOA defluorination rate was 97.0%.

[0058] After 10 repeated experiments, the defluorination rate remained at 97.5%.

[0059] Example 2 A fluorine-functionalized ZIF-67 ceramic membrane was prepared by the following method: S1. Dissolve 2.9 g of Co(NO3)2·6H2O in 100 mL of methanol to form solution A; dissolve 5.8 g of 2-methylimidazole in 100 mL of methanol to form solution B. Pour solution B quickly into solution A, stir at room temperature for 1.5 h, and then let it stand and age for 24 h at room temperature. Centrifuge to collect the purple precipitate, wash it 3 times with methanol, and dry it under vacuum at 75 °C for 13 h to obtain the ZIF-67 precursor.

[0060] S②. Disperse 350 mg of the ZIF-67 precursor in 5 mL of ethanol, add 110 μL of pentafluorobenzenethiol and 10 mL of ethanol, ultrasonically disperse for 30 min, and then heat and react at 85 °C for 12 h. After the reaction is completed, wash it 3 times with ethanol and deionized water in sequence, and freeze-dry to obtain fluorine-functionalized ZIF-67.

[0061] S③. Disperse 40 mg of reduced graphene oxide in 50 mL of deionized water, ultrasonically treat for 30 min to form a homogeneous dispersion; add 180 mg of fluorine-functionalized ZIF-67, continue to ultrasonically disperse for 30 min, then collect the composite by vacuum filtration, wash it 3 times with deionized water, and dry it at 70 °C for 12 h to prepare the fluorine-functionalized ZIF-67 composite.

[0062] S④. Disperse 15 mg of the fluorine-functionalized ZIF-67 composite in a DMSO (6 mM) solution, ultrasonically treat for 2 h to form a homogeneous dispersion, and directionally load the dispersion onto the surface of the ceramic membrane by vacuum filtration method, and dry it at 70 °C for 14 h to prepare the fluorine-functionalized ZIF-67 ceramic membrane.

[0063] A method for removing PFBA in water was used, and the defluorination device used was as Figure 1 shown, where a fluorine-functionalized composite ceramic membrane was used as the cathode, a zirconia ceramic membrane substrate with a thickness of 4 mm and a membrane layer pore size of 50 nm was used, a porous Pt-Ti plate was used as the anode, and a treatment liquid storage tank 10 was placed below the defluorination device to collect the reaction products.

[0064] The experimental parameters were as follows: a 0.2 M Na2SO4 pollutant solution containing 100 μg / L PFBA was continuously pumped into the defluorination device inlet by a peristaltic pump at a flow rate of 20 mL / min. The power supply was set to the constant current mode, and a current density of 15 mA / cm² was applied to initiate the reaction.

[0065] After testing, the PFBA removal rate was 98.0%, and the PFBA defluorination rate was 97.8%.

[0066] Example 3 A fluorine-functionalized ZIF-67 ceramic membrane was prepared by the following method: S1. Dissolve 2.9 g of Co(NO3)2·6H2O in 100 mL of methanol to form solution A; dissolve 6.6 g of 2-methylimidazole in 100 mL of methanol to form solution B. Quickly pour solution B into solution A, stir at room temperature for 1 h, then let it stand and age for 24 h. Centrifuge to collect the purple precipitate, wash it 3 times with methanol, and dry it in vacuum at 80 °C for 12 h to obtain the ZIF-67 precursor.

[0067] S2. Take 350 mg of the ZIF-67 precursor and disperse it in 5 mL of ethanol. Add 100 μL of pentafluorobenzenethiol and 10 mL of ethanol, ultrasonically disperse for 30 min, and then heat and react at 85 °C for 14 h. After the reaction is completed, wash it 3 times with ethanol and deionized water in sequence, and freeze-dry to obtain fluorine-functionalized ZIF-67.

[0068] S3. Disperse 40 mg of reduced graphene oxide in 50 mL of deionized water, ultrasonically treat for 30 min to form a homogeneous dispersion; add 220 mg of fluorine-functionalized ZIF-67, continue to ultrasonically disperse for 30 min, then collect the composite by vacuum filtration, wash it 3 times with deionized water, and dry it at 80 °C for 12 h to prepare the fluorine-functionalized ZIF-67 composite.

[0069] S4. Disperse 15 mg of the fluorine-functionalized ZIF-67 composite in a DMSO (8 mM) solution, ultrasonically treat for 2 h to form a homogeneous dispersion, and directionally load the dispersion onto the surface of the ceramic membrane by vacuum filtration method, and dry it at 80 °C for 12 h to prepare the fluorine-functionalized ZIF-67 ceramic membrane.

[0070] A method for defluorinating GenX in a low-conductivity solution, using a defluorination device as Figure 1 shown, where a fluorine-functionalized composite ceramic membrane is used as the cathode, an anatase ceramic membrane substrate with a thickness of 5 mm and a membrane layer pore size of 150 nm, and a porous Pt-Ti plate is used as the anode. The treatment liquid storage tank 10 is placed below the defluorination device to collect the reaction products.

[0071] The experimental parameters were as follows: a 0.05 M Na2SO4 pollutant solution containing 1 mg / L GenX was continuously pumped into the defluorination device inlet by a peristaltic pump at a flow rate of 50 mL / min. The power supply was set to the constant current mode, and a current density of 20 mA / cm² was applied to initiate the reaction.

[0072] After testing, the removal rate of GenX was 97.0%, and the defluorination rate of GenX was 96.8%.

[0073] Example 4 A fluorine-functionalized ZIF-67 ceramic membrane, the preparation method is as follows: S1. Dissolve 2.9 g of Co(NO3)2·6H2O in 100 mL of methanol to form solution A; dissolve 6.1 g of 2-methylimidazole in 100 mL of methanol to form solution B. Quickly pour solution B into solution A, stir at room temperature for 1.2 h, then let it stand and age for 24 h. Centrifuge to collect the purple precipitate, wash it 3 times with methanol, and dry it in vacuum at 85 °C for 14 h to obtain the ZIF-67 precursor.

[0074] S2. Take 350 mg of the ZIF-67 precursor and disperse it in 5 mL of ethanol. Add 90 μL of pentafluorobenzenethiol and 10 mL of ethanol. After ultrasonic dispersion for 30 min, heat and react at 85 °C for 14 h. After the reaction is completed, wash it 3 times with ethanol and deionized water in turn, and freeze-dry to obtain fluorine-functionalized ZIF-67.

[0075] S3. Disperse 40 mg of reduced graphene oxide in 50 mL of deionized water, and ultrasonically treat it for 30 min to form a homogeneous dispersion; add 210 mg of fluorine-functionalized ZIF-67, continue ultrasonic dispersion for 30 min, then collect the composite by vacuum filtration, wash it 3 times with deionized water, and dry it at 85 °C for 12 h to obtain the fluorine-functionalized ZIF-67 composite.

[0076] S4. Disperse 15 mg of the fluorine-functionalized ZIF-67 composite in a DMSO (7 mM) solution, ultrasonically treat it for 2 h to form a homogeneous dispersion, and directionally load the dispersion onto the surface of the ceramic membrane by vacuum filtration method, and dry it at 80 °C for 12 h to obtain the fluorine-functionalized ZIF-67 ceramic membrane.

[0077] A method for removing PFHxS in water, the defluorination device used is as Figure 1 shown, where a fluorine-functionalized composite ceramic membrane is used as the cathode, a silicon oxide ceramic membrane substrate with a thickness of 5 mm and a membrane layer pore size of 200 nm, and a porous Pt-Ti plate is used as the anode. The treatment liquid storage tank 10 is placed below the defluorination device to collect the reaction products.

[0078] The experimental parameters were as follows: a pollutant solution containing 10 mg / L PFHxS and 0.1 M Na2SO4 was continuously pumped into the reactor inlet from a peristaltic pump at a flow rate of 80 mL / min. The power supply was set to the constant current mode, and a current density of 50 mA / cm² was applied to initiate the reaction.

[0079] After testing, the removal rate of PFHxS was 96.0%, and the defluorination rate of PFHxS was 95.6%.

[0080] Comparative Example 1 The difference between this comparative example and Example 1 was that no fluorination functionalization was carried out during the preparation process, and other reaction devices and experimental conditions were the same as those in Example 1; A ZIF-67 ceramic membrane, the specific preparation method is as follows: S1. Dissolve 2.9 g of Co(NO3)2·6H2O in 100 mL of methanol to form solution A; dissolve 6.5 g of 2-methylimidazole in 100 mL of methanol to form solution B. Pour solution B quickly into solution A, stir at room temperature for 1 h, then stand for aging for 24 h, collect the purple precipitate by centrifugation, wash it with methanol three times, and dry it in vacuum at 80 °C for 12 h to obtain the ZIF-67 precursor.

[0081] S2. Disperse 40 mg of reduced graphene oxide in 50 mL of deionized water, and ultrasonically treat it for 30 min to form a homogeneous dispersion; add 200 mg of the ZIF-67 precursor, continue ultrasonic dispersion for 30 min, then collect the composite by vacuum filtration, wash it with deionized water three times, and dry it at 80 °C for 12 h to obtain the ZIF-67 composite.

[0082] S3. Disperse 15 mg of the ZIF-67 composite in a DMSO (5 mM) solution, ultrasonically treat it for 2 h to form a homogeneous dispersion, and directionally load the dispersion onto the surface of the ceramic membrane by vacuum filtration method, and dry it at 85 °C for 12 h to obtain the ZIF-67 ceramic membrane.

[0083] A method for removing PFOA in water, the defluorination device used is as Figure 1 shown, where a fluorination-functionalized composite ceramic membrane is used as the cathode, an alumina ceramic membrane with a thickness of 3 mm and a membrane layer pore size of 100 nm, and a porous Pt-Ti plate is used as the anode. The treatment liquid storage tank 10 is placed below the defluorination device to collect the reaction products.

[0084] The experimental parameters were as follows: a 0.1 M Na2SO4 pollutant solution containing 10 μg / L PFOA was continuously pumped into the defluorination device inlet from a peristaltic pump at a flow rate of 10 mL / min. The power supply was set to the constant current mode, and a current density of 10 mA / cm² was applied to initiate the reaction.

[0085] After testing, the PFOA removal rate was 30.0% and the PFOA defluorination rate was 29.5%.

[0086] Comparative Example 2 The difference between this comparative example and Example 1 is that the preparation method of the fluorine-functionalized composite ceramic membrane is different, and the other reaction devices and experimental conditions are the same as those in Example 1; The fluorine-functionalized composite ceramic membrane of the present invention is prepared by the preparation method of Example 1 in Chinese Patent Publication No. CN119746930A. The specific preparation method is as follows: (1) Accurately weigh 1.161 g of maleic acid and 5.299 g of sodium carbonate, dissolve them in 20 mL of deionized water, ultrasonicate for 8 min, dry at 50 °C for 12 h, take out the dried solid and grind it thoroughly. Move the ground powder into a tube furnace, and heat it to 650 °C at a rate of 5 °C / min for 3 h in an argon atmosphere with a flow rate of 50 mL / min. The product is washed with anhydrous ethanol and deionized water, respectively, and dried in a vacuum at 50 °C for 12 h to obtain porous graphene.

[0087] (2) Accurately weigh 0.436 g of cobalt nitrate hexahydrate and dissolve it in 50 mL of ultrapure water. Stir and mix evenly for 10 min. Add 0.1 g of porous graphene and ultrasonically treat to obtain solution A. Accurately weigh 0.517 g of 2-methylimidazole and 0.105 g of 2-trifluoromethylimidazole and dissolve them in 50 mL of methanol. Ultrasonicate for 10 min to obtain solution B.

[0088] (3) Solution B was slowly added dropwise to solution A while stirring. After standing for 24 hours, the mixture was centrifuged. The precipitate was washed with methanol and deionized water respectively, and dried under vacuum at 50°C for 12 hours to obtain a composite catalyst. (4) 15 mg of the composite catalyst was dispersed in DMSO (5 mM) solution and ultrasonically treated for 2 h to form a uniform dispersion. The dispersion was directionally loaded onto the surface of the ceramic membrane by vacuum filtration and dried at 85 °C for 12 h to obtain a fluorine-functionalized ZIF-67 ceramic membrane.

[0089] A method for removing PFOA from water, using a defluorination device such as Figure 1 As shown, a fluorine-functionalized composite ceramic membrane is used as the cathode, an alumina ceramic membrane is used with a thickness of 3 mm and a pore size of 100 nm, a porous Pt-Ti plate is used as the anode, and a treatment liquid storage tank 10 is placed under the defluorination device to collect the reaction products.

[0090] Experimental parameters were as follows: a 0.1M Na₂SO₄ solution containing 10 μg / L PFOA was continuously pumped into the defluorination device at a flow rate of 10 mL / min via a peristaltic pump. The power supply was set to constant current mode, applying a current density of 10 mA / cm² to initiate the reaction.

[0091] After testing, the PFOA removal rate is 40.0%, and the PFOA defluorination rate is 39.5%.

[0092] The above is a further description of the present invention in combination with specific embodiments, but these embodiments are merely exemplary and do not constitute any limitation to the scope of the present invention. Those skilled in the art should understand that the details and forms of the technical solution of the present invention can be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the protection scope of the present invention.

Claims

1. A fluorine-functionalized composite ceramic membrane, characterized in that, It includes a ceramic membrane and a catalyst loaded on the surface of the ceramic membrane, and the catalyst is a fluorine-functionalized ZIF-67 composite; The loading amount of the catalyst is 0.2 mg / cm² - 0.5 mg / cm²; The material of the ceramic membrane is one of alumina, zirconia, titanium oxide or silica; The preparation method of the fluorine-functionalized ZIF-67 composite includes the following steps: S1. Dissolve cobalt nitrate hexahydrate in methanol to form solution A; dissolve 2-methylimidazole in methanol to form solution B; mix solution B with solution A, stir, stand for aging, separate solid from liquid, wash and dry to obtain a ZIF-67 precursor; S2. Add the ZIF-67 precursor to ethanol and pentafluorobenzenethiol, disperse, heat and react, wash and dry to obtain fluorine-functionalized ZIF-67; S3. Mix and disperse reduced graphene oxide with water to obtain a dispersion; add the fluorine-functionalized ZIF-67 to the dispersion, disperse for the second time, separate solid from liquid, wash and dry to obtain a fluorine-functionalized ZIF-67 composite.

2. The fluorine-functionalized composite ceramic membrane according to claim 1, wherein The pore size of the ceramic membrane is 50nm - 200nm.

3. The fluorine-functionalized composite ceramic membrane according to claim 1, wherein The molar ratio of cobalt nitrate hexahydrate to 2-methylimidazole in step S1 is 1:5 - 10; and / or the molar ratio of pentafluorobenzenethiol to the ZIF-67 precursor in step S2 is 1:1 - 3; and / or the molar ratio of reduced graphene oxide to fluorine-functionalized ZIF-67 in step S3 is 1:4 - 6.

4. The fluorine-functionalized composite ceramic membrane according to claim 1, wherein The standing and aging time in step S1 is 20h - 30h; and / or the heating reaction in step S2 is: reacting at 80°C - 90°C for 10h - 14h.

5. The preparation method of the fluorine-functionalized composite ceramic membrane according to any one of claims 1-4, characterized in that, It includes the following steps: Disperse the fluorine-functionalized ZIF-67 composite in a dimethyl sulfoxide solution, load it onto the surface of the ceramic membrane by suction filtration, and perform a drying treatment; and / or the concentration of the dimethyl sulfoxide solution is 4mM - 10mM.

6. Use of the fluorine-functionalized composite ceramic membrane according to any one of claims 1 to 4 in removing perfluorinated compounds from water, characterized in that, The perfluorinated compound includes at least one of perfluorooctanoic acid, perfluorobutyric acid, perfluoropentanoic acid, perfluorohexanoic acid, perfluoroheptanoic acid, perfluorononanoic acid, perfluorodecanoic acid, ammonium perfluoro(2-methyl-3-oxahexanoate), perfluorohexane sulfonic acid, perfluorobutane sulfonic acid.

7. The application according to claim 6, wherein The concentration of the perfluorinated compound is 0.1μg / L - 100mg / L.

8. A defluorination device, characterized in that, It includes an electrocatalytic reaction system with the fluorine-functionalized composite ceramic membrane described in any one of claims 1 - 4 as the cathode and a Pt-Ti plate as the anode; and / or the defluorination device is a cross-flow filtration type reaction device.

9. A method for removing perfluorinated compounds from water, characterized in that, It includes the following steps: Using the fluorine-functionalized composite ceramic membrane described in any one of claims 1 - 4 as the cathode and a Pt-Ti plate as the anode, perform an electrochemical defluorination reaction on the water body containing perfluorinated compounds and sodium sulfate.

10. The method for removing perfluorinated compounds from water according to claim 9, characterized in that, The concentration of the perfluorinated compound is 0.1μg / L - 100mg / L, and the concentration of sodium sulfate is 0.01M - 0.5M; and / or the current density of the electrochemical defluorination reaction is 5 mA / cm 2 - 100 mA / cm 2 ; and / or the flow rate of the water body is 5mL / min - 100mL / min.

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