Ceramic nanofiber membrane and preparation thereof, catalytic ceramic nanofiber membrane and preparation and application thereof

Abstract

The invention discloses a ceramic nanofiber membrane and preparation thereof, a catalytic ceramic nanofiber membrane and preparation and application thereof. The preparation method of the ceramic nanofiber membrane comprises the following steps: (1) cleaning a particle accumulation state ceramic membrane support body; (2) spraying the mullite fiber membrane layer slurry on one surface of a supporting body for multiple times by using a spraying method, after each spraying, applying negative pressure to a membrane for a preset time, then drying, and after the last drying, forming a spraying layer on one surface of the supporting body; and (3) sintering the obtained membrane at high temperature to obtain the ceramic nanofiber membrane which is provided with a support body and a mullite fiber membrane layer which is stably attached to one surface of the support body and is of a net-shaped structure formed by staggering and stacking mullite fibers. The catalytic ceramic nanofiber membrane comprises a ceramic nanofiber membrane and a catalyst loaded on the surface of the ceramic nanofiber membrane and in membrane holes. The ceramic nanofiber membrane provided by the invention has the advantages of high porosity, high mechanical strength, high membrane flux and the like, and is beneficial to subsequent catalyst loading and application in water treatment.

Description

Technical Field

[0001] The present invention relates to the technical field of membrane water treatment, in particular to a ceramic nanofiber membrane and its preparation, a catalytic ceramic nanofiber membrane and its preparation and application. Background Art

[0002] Advanced oxidation technology based on catalytic ceramic membranes can efficiently remove new pollutants from water by activating oxidants such as ozone, hydrogen peroxide, and persulfate to produce reactive oxygen species (ROS), achieving the goal of effectively treating new pollutants in the water environment. Advanced oxidation technology based on catalytic ceramic membranes not only effectively addresses the problems of powdered catalyst agglomeration and recovery difficulties, but also enhances the mass transfer efficiency of ROS to organic pollutants during the advanced oxidation reaction through the confinement effect of ceramic membrane pores, thereby improving ROS utilization and pollutant removal rates.

[0003] At present, most catalytic ceramic membranes are mainly based on traditional particle-stacked ceramic membranes loaded with monovalent transition metal oxide catalysts. The traditional particle-stacked ceramic membrane structure has problems such as low porosity and high transmembrane pressure, which leads to high membrane filtration operating costs. In recent years, ceramic fiber membranes have attracted attention due to their high porosity and high membrane flux. Traditional catalytic ceramic membranes mostly use traditional high-temperature calcination processes to dope or load monovalent transition metal oxide catalysts onto ceramic membranes. This method of preparing catalytic ceramic membranes has many catalytic application defects. First, high-temperature calcination will change the structure of the active components of the catalyst, resulting in a decrease in active sites and a decrease in catalytic activity. In addition, the high-temperature calcination process has high energy consumption, usually requiring a high temperature of more than 1000°C, which consumes huge amounts of energy.

[0004] It should be noted that the information disclosed in the above background technology section is only used to understand the background of this application, and therefore may include information that does not constitute prior art known to ordinary technicians in this field. Summary of the Invention

[0005] In order to make up for the deficiencies of the prior art, the present invention provides a ceramic nanofiber membrane and its preparation, a catalytic ceramic nanofiber membrane and its preparation and application.

[0006] The present invention adopts the following technical solutions:

[0007] In a first aspect, a method for preparing a ceramic nanofiber membrane is provided, comprising the following steps:

[0008] (1) Cleaning the particle-stacked ceramic membrane support;

[0009] (2) spraying the mullite fiber membrane slurry onto one side of the particle-stacked ceramic membrane support multiple times by a spraying method, applying negative pressure to the obtained membrane for a predetermined time after each spraying, and then drying, and forming a firmly attached spray layer on one side of the particle-stacked ceramic membrane support after the last drying;

[0010] (3) The membrane obtained in step (2) is subjected to high-temperature sintering to obtain the ceramic nanofiber membrane, which comprises a granular ceramic membrane support body and a mullite fiber membrane layer firmly attached to one side of the granular ceramic membrane support body and composed of mullite fibers staggered and stacked into a mesh structure.

[0011] In the second aspect, a ceramic nanofiber membrane prepared by the preparation method described in the first aspect is provided, wherein the ceramic nanofiber membrane has a granular ceramic membrane support body and a mullite fiber membrane layer firmly attached to one side of the granular ceramic membrane support body, which is composed of mullite fibers staggered and stacked into a mesh structure.

[0012] In a third aspect, a method for preparing a catalytic ceramic nanofiber membrane is proposed, comprising the following steps:

[0013] (1) preparing a catalyst precursor ion solution, wherein the catalyst precursor ion solution comprises a transition metal ion of the corresponding catalyst and water, wherein the concentration of the transition metal ion is 0.05-2.0 mol / L;

[0014] (2) completely immersing the ceramic nanofiber membrane prepared by the preparation method described in the first aspect in the catalyst precursor ion solution;

[0015] (3) after treating the system of step (2) under low-temperature hydrothermal conditions for a first predetermined time, adding an alkali precipitant to the catalyst precursor ion solution to obtain an alkali precipitation reaction liquid, continuing to treat under the low-temperature hydrothermal conditions for a second predetermined time, and then removing the film loaded with the catalyst precursor and drying it; wherein the concentration of the alkali precipitant in the alkali precipitation reaction liquid is 0.1-4.0 mol / L;

[0016] (4) After the catalyst precursor particles in the alkali precipitation reaction liquid are fully precipitated, the supernatant is discarded, the catalyst precursor particles are collected and redispersed in water, and ultrasonic dispersion is performed for at least 1 hour to form a suspension containing the catalyst precursor particles;

[0017] (5) immersing the catalyst precursor-loaded membrane dried in step (3) in the suspension of step (4) again, applying negative pressure for at least 30 minutes, and then drying the membrane. Repeating the steps of "immersing in the suspension of step (4), applying negative pressure, and drying" multiple times. Then, after the final drying, the membrane is subjected to a final aging reaction with the suspension at 80-100° C. for 24-48 hours to allow the catalyst to have more defect sites and activity. The membrane is then taken out and fully dried at 35-70° C.;

[0018] (6) calcining the dried membrane obtained in step (5) at 300-600°C for 2-6h to obtain the catalytic ceramic nanofiber membrane, which includes a ceramic nanofiber membrane and a catalyst loaded on the ceramic nanofiber membrane and in the membrane pores, wherein the catalyst is a multi-element transition metal oxide.

[0019] In a fourth aspect, a catalytic ceramic nanofiber membrane prepared by the preparation method described in the third aspect is proposed, comprising the ceramic nanofiber membrane described in the second aspect and a catalyst loaded on the ceramic nanofiber membrane and in the membrane pores.

[0020] In the fifth aspect, an application of the catalytic ceramic nanofiber membrane described in the fourth aspect in oxidative water treatment is proposed. The catalytic ceramic nanofiber membrane is placed in the water to be treated, which can efficiently catalyze the decomposition of oxidants in the water to produce active oxygen species, thereby enhancing the removal of pollutants in the water.

[0021] The present invention has the following beneficial effects:

[0022] In the preparation method of the ceramic nanofiber membrane of the present invention, a mullite fiber membrane layer formed by interlaced stacking of mullite fibers to form a network structure is firmly attached to one side of a particle-stacked ceramic membrane support body by an alternating method of spraying-applying negative pressure-drying. The obtained ceramic nanofiber membrane has high porosity, high mechanical strength and high membrane flux (membrane flux exceeds 2000 L / m 2 / h / bar), low application cost, etc.

[0023] In the preparation method of the catalytic ceramic nanofiber membrane of the present invention, on the basis of preparing the ceramic nanofiber membrane, the metal oxide catalyst is uniformly, stably and largely loaded on the surface and membrane pores of the ceramic nanofiber membrane by adopting the in-situ impregnation-cold sintering (300-600°C) method.

[0024] More specifically, the catalytic ceramic nanofiber membrane of the present invention has the following advantages:

[0025] High membrane flux: The ceramic nanofiber membrane, which is constructed with mullite fiber as the main membrane material and has a mullite fiber membrane layer with a network structure formed by interlaced stacking of mullite fibers, has the advantages of high mechanical strength, high porosity, high membrane flux, etc., giving it the advantage of low-cost membrane filtration.

[0026] Low preparation cost: The cold sintering process is used to achieve enhanced loading of transition metal oxide catalysts on ceramic nanofiber membranes under lower temperature conditions. Its low-temperature characteristics significantly reduce the production cost of catalytic ceramic nanofiber membranes, and it has the energy-saving and environmental protection advantages of low-cost development of high-catalytic activity ceramic membranes.

[0027] High catalytic activity: The catalyst is loaded with enhanced catalyst loading using a low-temperature cold sintering process, which helps preserve catalyst activity and avoids technical drawbacks such as catalyst deactivation and grain growth during high-temperature sintering. This allows for efficient catalytic decomposition of oxidants within a short period of time, generating large amounts of ROS. This powerful catalyst removes recalcitrant organic matter, such as new pollutants, from water via advanced oxidation reactions. Furthermore, the confined space within the pores of the prepared catalytic ceramic nanofiber membrane significantly improves ROS utilization by shortening the mass transfer distance between ROS and organic pollutants.

[0028] Strong catalytic stability: By adopting a cold sintering process and coordinating the dissolution and lubrication of the alkaline liquid phase and the material transfer driven by negative pressure, the transition metal oxide catalyst is strengthened and loaded on the ceramic nanofiber membrane, so that a stronger binding force is formed between the catalyst and the ceramic nanofiber membrane, the stability of the catalyst loading on the ceramic nanofiber membrane is improved, the catalyst is effectively prevented from falling off and the service life is extended. Specifically, the dissolution and lubrication of the alkaline liquid phase can promote the rearrangement of catalyst particles, and the pressure drive can promote the close contact between the catalyst and the ceramic nanofiber membrane and the particles, enhance the van der Waals force and electrostatic force between the catalyst and the ceramic nanofiber membrane, and help the bonding between the catalyst and the ceramic nanofiber membrane. It can achieve the stable sintering of a large amount of catalyst to the ceramic nanofiber membrane under low temperature conditions, while maintaining the high catalytic activity of the catalyst and significantly reducing the energy consumption of the preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a scanning electron microscope image of the membrane surface of the ceramic nanofiber membrane in Example 1 of the present invention.

[0030] Figure 2a This is a scanning electron microscope image of the cross section of the ceramic nanofiber membrane of Example 1 of the present invention.

[0031] Figure 2b This is a scanning electron microscope image of the cross section of the ceramic nanofiber membrane of Comparative Example 1 of the present invention.

[0032] Figure 3A scanning electron microscope image of a cross section of the catalytic ceramic nanofiber membrane of Example 2 of the present application.

[0033] Figure 4 A scanning electron microscope image of a membrane surface of the catalytic ceramic nanofiber membrane in Example 2 of the present application.

[0034] Figure 5 A cross-sectional element content distribution chart of the catalytic ceramic nanofiber membrane in Example 2 of the present application.

[0035] Figure 6 An effect chart of filtering removal of OFX in water and catalytic removal of OFX by H2O2 of the catalytic ceramic nanofiber membrane in Example 3 of the present application.

[0036] Figure 7 An effect chart of filtering removal of OFX in water and catalytic removal of OFX by H2O2 of the white membrane as a comparison in Example 3 of the present application. DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present application in detail. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope of the present application and its applications, and the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. In this article, "room temperature" refers to 20-25℃.

[0038] The specific embodiment of the present application provides a preparation method of a ceramic nanofiber membrane, comprising the following steps:

[0039] (1) washing a granular accumulation state ceramic membrane support body clean;

[0040] (2) spraying the mullite fiber membrane layer slurry on one side of the granular accumulation state ceramic membrane support body by spraying multiple times, after each spraying, applying negative pressure to the obtained membrane piece for a predetermined time, and then drying, after the last drying, forming a stable adhered spraying layer on one side of the granular accumulation state ceramic membrane support body; that is, the method of spraying-negative pressure application-drying alternately is used in step (2) to ensure that each sprayed layer is stably adhered to each other and to the granular accumulation state ceramic membrane support body, and finally the spraying layer is stably adhered to the granular accumulation state ceramic membrane support body;

[0041] (3) sintering the membrane piece obtained in step (2) at high temperature to obtain the ceramic nanofiber membrane, which has a granular accumulation state ceramic membrane support body and a mullite fiber membrane layer formed by mullite fibers interlaced and stacked into a network structure on one side of the granular accumulation state ceramic membrane support body.

[0042] Mullite fiber, as a natural ceramic fiber material, has the advantages of low material cost and high mechanical strength. It can overcome the defects of fiber materials such as attapulgite, such as poor mechanical strength, and can be used as a good fiber material for preparing new ceramic fiber membranes. However, when mullite fiber is combined with a granular ceramic membrane, there are disadvantages such as poor bonding strength and easy shedding of the membrane layer. To address this, the present invention adopts a method of spraying-applying negative pressure-drying alternately to obtain a spray layer and then sintering it at high temperature. In the prepared ceramic nanofiber membrane, the mullite fiber membrane layer is composed of mullite fibers staggered and stacked into a mesh structure that is tightly, uniformly, and firmly attached to one side of the granular ceramic membrane support. The ceramic nanofiber membrane has high porosity, high mechanical strength, and high membrane flux (membrane flux exceeds 2000L / m 2 / h / bar), low application cost, etc., with better catalyst loading basis and longer service life, which can promote the development and application of a new generation of low-cost ceramic membranes.

[0043] In some embodiments, in step (2), the pressure of each negative pressure applied is -0.03 to -0.08 MPa, and the negative pressure is applied for 10 to 60 minutes each time.

[0044] In some embodiments, the thickness of each spraying in step (2) is in the range of 20-50 μm; the thickness of the mullite fiber membrane layer in step (3) is 100-350 μm, and the membrane pore size is less than 100 nm.

[0045] In some embodiments, in step (2), the drying is performed by drying at no more than 70° C. (eg, drying in an oven) for at least 12 h, or air-drying at room temperature for 12-36 h.

[0046] In some embodiments, in step (3), the high-temperature sintering refers to calcining at a temperature of 1200-1350° C. for at least 2-6 hours, wherein the heating rate is controlled at 2-5° C. / min.

[0047] In some embodiments, in step (2), the mullite fiber membrane slurry comprises the following components in the following percentages: 2 wt%-6 wt% of mullite fiber, 0.5 wt%-5 wt% of dispersant, 1 wt%-5 wt% of stabilizer, and the balance being water. The mullite fiber may be natural mullite fiber.

[0048] In some embodiments, the mullite fiber is a mullite nanowire with a diameter of 30-100 nm and a length of 0.6-1.5 μm.

[0049] In some embodiments, the dispersant is at least one of sodium hexametaphosphate, sodium pyrophosphate, trisodium phosphate, tetrasodium phosphate, sodium hexametaphosphate, sodium metasilicate, and sodium disilicate.

[0050] In some embodiments, the stabilizer is at least one of methyl cellulose and carboxymethyl cellulose.

[0051] In some embodiments, ultrasound is first applied followed by continuous physical stirring to form the mullite fiber membrane slurry that is uniformly dispersed and stable. Preferably, the ultrasound time is at least 1 hour, and the continuous physical stirring time is at least 12 hours.

[0052] In some embodiments, the granular-stacked ceramic membrane support in step (1) is formed by high-temperature sintering of alumina particles (commercial micron-sized alumina granular-stacked ceramic membrane support can also be directly used), and the membrane pore size of the granular-stacked ceramic membrane support is 1-5 μm, and the membrane thickness is 1-2 mm.

[0053] A specific embodiment of the present invention also provides a ceramic nanofiber membrane prepared by the preparation method, wherein the ceramic nanofiber membrane has a granular ceramic membrane support body and a mullite fiber membrane layer firmly attached to one side of the granular ceramic membrane support body, which is composed of mullite fibers staggered and stacked into a mesh structure.

[0054] The present invention also provides a method for preparing a catalytic ceramic nanofiber membrane, comprising the following steps:

[0055] (1) preparing a catalyst precursor ion solution, wherein the catalyst precursor ion solution comprises a transition metal ion of the corresponding catalyst and water, wherein the concentration of the transition metal ion is 0.05-2.0 mol / L;

[0056] (2) completely immersing the ceramic nanofiber membrane prepared by the preparation method in the catalyst precursor ion solution;

[0057] (3) After the system of step (2) is treated under low-temperature hydrothermal conditions for a first predetermined time, an alkali precipitant is added to the catalyst precursor ion solution to obtain an alkali precipitation reaction liquid, and the solution is further treated under the low-temperature hydrothermal conditions for a second predetermined time, and then the membrane loaded with the catalyst precursor is taken out and dried; wherein, in the alkali precipitation reaction liquid, the concentration of the alkali precipitant is 0.1-4.0 mol / L; in this step (3), the alkali precipitant is first hydrothermally treated for a predetermined time, and then the alkali precipitant is added to continue the hydrothermal treatment, which can promote the in-situ generation of the catalyst precursor (i.e., the transition metal hydroxide) on the ceramic nanofiber membrane and in the membrane pores;

[0058] (4) After the catalyst precursor particles in the alkali precipitation reaction liquid are fully precipitated, the supernatant is discarded, the catalyst precursor particles are collected and redispersed in water (the volume of water is preferably the same as the volume of water in step (1)), and ultrasonic dispersion is performed for at least 1 hour to form a suspension containing the catalyst precursor particles;

[0059] (5) immersing the catalyst precursor-loaded membrane dried in step (3) in the suspension of step (4) again, applying negative pressure for at least 30 minutes, and then drying the membrane. Repeating the steps of "immersing in the suspension of step (4), applying negative pressure, and drying" multiple times. Then, after the final drying, the membrane is subjected to a final aging reaction with the suspension at 80-100° C. for 24-48 hours to allow the catalyst to have more defect sites and activity. The membrane is then taken out and fully dried at 35-70° C.;

[0060] (6) The dried membrane obtained in step (5) is calcined at 300-600°C for 2-6 hours to obtain the catalytic ceramic nanofiber membrane, which includes a ceramic nanofiber membrane and a catalyst loaded on the ceramic nanofiber membrane and in the membrane pores, wherein the catalyst is a multi-element transition metal oxide catalyst having high catalytic activity.

[0061] In some embodiments, in step (6), the catalyst is a ternary catalyst (including but not limited to CuFeMnO, CuZnMnO, CuTiMnO, CuCoMnO, CuCeMnO, etc.), a quaternary catalyst (including but not limited to CuFeZnMnO, CuFeTiMnO, CuFeCoMnO, CuFeCeMnO, etc.) or a quinary catalyst (including but not limited to CuFeZnTiMnO, CuFeZnCoMnO, CuFeZnCeMnO, etc.). By adopting the above catalysts, the catalytic ceramic nanofiber membrane can have a higher confined catalytic activity. Wherein, the concentration ratio of each transition metal ion in the catalyst precursor ion solution of the ternary catalyst conforms to the metal element ratio of spinel AB2O4 metal oxide, and the concentration ratio of three transition metal ions in the catalyst precursor ion solution of the quaternary or quinary catalyst conforms to the metal element ratio of spinel AB2O4 metal oxide, and the remaining transition metal ions are doped at different concentrations.

[0062] In some embodiments, the immersion treatment in step (2) refers to: oscillating in a shaker at room temperature for at least 12 hours; fully immersing at room temperature for at least 12 hours, so that the catalyst precursor ion solution can fully impregnate the ceramic nanofiber membrane pores, thereby facilitating the subsequent in-situ loading of the target catalyst.

[0063] In some embodiments, the low-temperature hydrothermal conditions in step (3) refer to: a water bath at 60-100° C., the first predetermined time is 5-20 minutes, and the second predetermined time is 0.5-2 hours.

[0064] In some embodiments, the drying in step (3) and step (5) each independently refers to: drying in an oven at 35-70° C. for at least 30 min.

[0065] In some embodiments, the negative pressure applied in step (5) is -0.03 to -0.08 MPa.

[0066] In some embodiments, in step (5), the sufficient drying time after the aging reaction is 24-48 hours.

[0067] A specific embodiment of the present invention further provides a catalytic ceramic nanofiber membrane prepared by the preparation method, which includes the ceramic nanofiber membrane and a catalyst loaded on the surface and in the membrane pores of the ceramic nanofiber membrane.

[0068] The specific embodiment of the present invention also provides an application of the catalytic ceramic nanofiber membrane in advanced oxidation water treatment, wherein the catalytic ceramic nanofiber membrane is placed in the water to be treated, and the oxidants in the catalytic water treatment (including but not limited to hydrogen peroxide, ozone, persulfate and other oxidants) are decomposed to produce reactive oxygen species (including but not limited to hydroxyl radicals, singlet oxygen, superoxide radicals, etc.) to enhance the removal of pollutants in the water. In particular, the supported catalyst has a multivalent metal component, which is beneficial to improving the redox ability and electron transfer rate of the catalytic ceramic nanofiber membrane, thereby efficiently catalyzing the decomposition and producing reactive oxygen species, thereby enhancing the efficient removal of difficult-to-degrade organic matter represented by new pollutants in water by enhancing the catalytic advanced oxidation reaction. The new pollutants include but are not limited to at least one of the following common new pollutants in natural water bodies: ofloxacin, ciprofloxacin, tiamulin, acetaminophen, salicylic acid, ibuprofen, erythromycin, tetracycline, oxytetracycline, roxithromycin, clarithromycin, and azithromycin.

[0069] Specific embodiments of the present invention are further described below.

[0070] Example 1

[0071] The preparation of ceramic nanofiber membrane includes:

[0072] (1) A commercial aluminum oxide particle stacked ceramic membrane with an average pore size of 2 μm and a thickness of 2 mm was used as a support, which was cut to the size required for specific membrane production and cleaned for later use;

[0073] (2) Mullite nanowires with a diameter of 30-100 nm and a length of 0.6-1.5 μm were purchased, and a mullite fiber membrane slurry containing 4 wt% mullite fiber, 1.2 wt% sodium hexametaphosphate, 1 wt% carboxymethyl cellulose, and the balance water was prepared. After ultrasonic dispersion for 1 h, physical stirring was continued for 12 h to form a uniformly dispersed and stable mullite fiber membrane slurry.

[0074] (3) The mullite fiber membrane slurry is evenly sprayed onto the support by spraying. After each spraying, the obtained membrane is placed in a vacuum device and negative pressure (pressure -0.04MPa) is drawn for 30min, and then dried in a 70°C oven for 12h. The spraying-negative pressure-drying process is repeated several times until the thickness of the sprayed layer reaches the predetermined thickness.

[0075] (4) The membrane obtained in step (3) was transferred to a muffle furnace, and the temperature was raised to 1250°C at a rate of 5°C / min and calcined for 2 hours to finally obtain a ceramic nanofiber membrane.

[0076] The ceramic nanofiber membrane prepared in this example comprises a particle-stacked ceramic membrane support body and a mullite fiber membrane layer firmly attached to the particle-stacked ceramic membrane support body, which is composed of mullite fibers staggered and stacked into a network structure.

[0077] like Figure 1 and Figure 2a As shown, the mullite fiber membrane layer in the ceramic nanofiber membrane produced in this example has a thickness of approximately 140 μm and a pore size of less than 100 nm. At a membrane flux of 40 L / m² / h, the pure water permeability of the ceramic nanofiber membrane produced in Example 1 was 2054 L / m² / h / bar, far exceeding the reported permeability of 200-1000 L / m² / h / bar for particle-stacked ceramic membranes with an average pore size of 50-100 nm.

[0078] Comparative Example 1

[0079] The difference from Example 1 is that in step (3), no negative pressure pumping operation is performed in step (3) of Comparative Example 1. The scanning electron microscope image of the cross section of the ceramic nanofiber membrane prepared in Comparative Example 1 is as follows: Figure 2b As shown, it can be seen that there are obvious gaps between the mullite fiber membrane layers formed by multiple spraying in Comparative Example 1, the membrane layer is unstable, easily falls off in a molting state, and has poor mechanical strength. However, in the ceramic nanofiber membrane obtained in Example 1, the connection between the mullite fiber membrane layer and the support body is tighter, more stable and uniform, without obvious gaps, which is beneficial to improving the overall mechanical strength of the ceramic nanofiber membrane and extending its service life.

[0080] Example 2

[0081] The preparation of the catalytic ceramic nanofiber membrane includes: loading a copper-manganese-iron ternary transition metal oxide (CuMnFeO4) catalyst having high Fenton-like catalytic activity on the ceramic nanofiber membrane prepared in Example 1 to obtain a catalytic ceramic nanofiber membrane having high Fenton-like catalytic activity. The specific steps are as follows:

[0082] (1) preparing a Cu0.4Mn0.6Fe2O4 precursor ion aqueous solution with an ion molar ratio of Cu:Mn:Fe=0.4:0.6:2 and a total ion molar concentration of 0.1 mol / L;

[0083] (2) Immersing the ceramic nanofiber membrane prepared in Example 1 in the Cu0.4Mn0.6Fe2O4 precursor ion solution prepared in step (1), placing the immersed membrane and the Cu0.4Mn0.6Fe2O4 precursor ion solution together in a shaker for 12 hours at room temperature, so that the Cu0.4Mn0.6Fe2O4 precursor ion solution fully impregnates the pores of the ceramic nanofiber membrane, thereby facilitating the subsequent in-situ generation and loading of the target catalyst CuMnFeO4;

[0084] (3) The immersed membrane and the Cu0.4Mn0.6Fe2O4 precursor ion solution were placed together in a 90°C water bath and heated for 5 minutes. Then, under low-temperature hydrothermal conditions, NaOH alkali solution was added and quickly mixed to obtain an alkali precipitation reaction solution (in the alkali precipitation reaction solution, the concentration of NaOH was 0.5 mol / L) to uniformly and effectively start the alkali precipitation reaction of the copper manganese iron hydroxide precursor in situ generated on the surface / in the membrane pores of the ceramic nanofiber membrane. After the addition of the alkali solution, the reaction was carried out at a constant temperature for 1 hour in a 90°C water bath to ensure that the alkali precipitation reaction was complete. After the water bath alkali precipitation was completed, the membrane loaded with the copper manganese iron hydroxide precursor was taken out and dried in a 60°C oven for 30 minutes.

[0085] (4) After the copper-manganese-iron hydroxide precursor particles in the remaining alkaline precipitation reaction liquid are fully precipitated after the membrane loaded with the copper-manganese-iron hydroxide precursor is removed, the supernatant is discarded, the copper-manganese-iron hydroxide precursor particles are collected and redispersed in the same volume of pure water as in step (1), and ultrasonic dispersion is performed again for 1 hour to form a suspension containing the copper-manganese-iron hydroxide precursor particles;

[0086] (5) The membrane loaded with the copper manganese iron hydroxide precursor that has been dried in step (3) is immersed in the suspension of step (4) again, and vacuum-drawn negative pressure (pressure -0.04MPa) for 30min, and then the membrane is dried in a 60°C oven for 30min, and the above immersion in the suspension of step (4), vacuum-drawn negative pressure and membrane drying steps are repeated 10 times to perform low-temperature enhanced loading of the catalyst; then after the last drying, the membrane is immersed in the copper manganese iron hydroxide precursor suspension and placed in an 80°C oven for a final aging reaction for 24h to allow the catalyst to have more defect sites and activity, and then the membrane is taken out and fully dried in a 60°C oven for 24h;

[0087] (6) The dried membrane obtained in step (5) is placed in a muffle furnace and calcined at 600°C for 3 hours at a heating rate of 5°C / min to obtain a catalytic ceramic nanofiber membrane, which includes a ceramic nanofiber membrane and a copper-manganese-iron ternary catalyst with high Fenton-like catalytic activity loaded on the ceramic nanofiber membrane and in the membrane pores.

[0088] The thickness of the catalytic ceramic nanofiber membrane prepared by the above method is about 140 μm (such as Figure 3 As shown), the pore size of the membrane is less than 100nm (as shown Figure 4 As shown), the copper-manganese-iron ternary catalyst is uniformly and massively loaded on the ceramic nanofiber membrane and in the membrane pores (as shown Figure 4 and Figure 5 The average particle size of the catalyst is about 20 nm.

[0089] The present invention securely supports the CuFeMnO4 catalyst on a catalytic ceramic nanofiber membrane. By adding an alkaline liquid phase and applying negative pressure, the catalyst adheres tightly to the ceramic nanofiber membrane at low temperatures, maintaining catalyst activity and preventing high-temperature deactivation and grain enlargement. Furthermore, the lubrication and material transfer effects of the alkaline liquid phase enhance the bonding strength, improving the stability and service life of the catalytic ceramic nanofiber membrane. This significantly reduces production costs, offering energy-saving and environmentally friendly advantages.

[0090] Example 3

[0091] The catalytic ceramic nanofiber membrane was applied to water treatment and its performance was tested.

[0092] The catalytic ceramic nanofiber membrane prepared in Example 2 was used to treat a water sample containing 1 mg / L OFX (ofloxacin). Under neutral reaction conditions, the hydrogen peroxide dosage was 5 mM and the flow rate was 30 L / m 2 The catalytic ceramic nanofiber membrane (represented as "catalytic membrane" in the figure) can maintain a high removal rate of nearly 100% of OFX within 100 hours, showing excellent membrane filtration performance and high-efficiency catalytic Fenton activity (such as Figure 6 In contrast, the OFX removal performance of the ceramic nanofiber membrane (white membrane) of Example 1 without catalyst loading was significantly weaker than that of the catalytic ceramic nanofiber membrane of Example 2 under the same experimental conditions. After only 16 hours of operation, the OFX removal performance of the white membrane showed a significant attenuation trend. After 44 hours of operation, the OFX removal rate was only 4% to 17% (as shown in FIG. Figure 7 shown).

[0093] The present invention uses mullite nanowires to construct a ceramic nanofiber membrane at low cost, and combines a cold sintering process with coordinated vacuum extraction, alkali precipitation and other processes to develop a catalytic ceramic nanofiber membrane. The catalyst is stably loaded on the ceramic nanofiber membrane and in the membrane pores in a low-cost manner while maintaining high catalytic activity. It not only has high mechanical strength and high membrane flux, optimizes the filtration performance of the membrane, but also achieves stable loading and uniform distribution of the CuFeMnO4 catalyst on the ceramic nanofiber membrane, significantly improving the Fenton-like catalytic performance of the catalytic ceramic nanofiber membrane, and can efficiently catalytically decompose oxidants such as ozone, hydrogen peroxide, and persulfate to produce ROS. The membrane pores of the catalytic ceramic nanofiber membrane can also further enhance the reaction efficiency and ROS utilization rate through the confinement effect, thereby significantly improving the removal efficiency of difficult-to-degrade organic pollutants in water, represented by new pollutants, and has high catalytic stability, which helps to achieve the goal of low-cost sustainable water pollution control and has broad application prospects.

[0094] The above description further details the present invention in conjunction with specific / preferred embodiments, and the specific implementation of the present invention should not be construed as being limited to these descriptions. Persons skilled in the art will appreciate that, without departing from the spirit of the present invention, they may make various substitutions or modifications to the described embodiments, and these substitutions or modifications should be considered to fall within the scope of protection of the present invention. Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with such embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Persons skilled in the art may combine and assemble the different embodiments or examples described in this specification, as well as features of different embodiments or examples, without conflicting opinions. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications may be made herein without departing from the scope of protection of the patent application.

Claims

1. A method for preparing a ceramic nanofiber membrane, characterized in that: The steps include: (1) Cleaning the particle-stacked ceramic membrane support; (2) spraying the mullite fiber membrane slurry onto one side of the particle-stacked ceramic membrane support multiple times by a spraying method, applying negative pressure to the obtained membrane for a predetermined time after each spraying, and then drying, and forming a firmly attached spray layer on one side of the particle-stacked ceramic membrane support after the last drying; (3) The membrane obtained in step (2) is subjected to high-temperature sintering to obtain the ceramic nanofiber membrane, which comprises a granular ceramic membrane support body and a mullite fiber membrane layer firmly attached to one side of the granular ceramic membrane support body and composed of mullite fibers staggered and stacked into a mesh structure.

2. The preparation method according to claim 1, wherein In step (2), the negative pressure is applied at a pressure of -0.03 to -0.08 MPa, and the negative pressure is applied for 10 to 60 minutes each time.

3. The preparation method according to claim 1, wherein The thickness of each spraying in step (2) is within the range of 20-50 μm; the thickness of the mullite fiber membrane layer in step (3) is 100-350 μm, and the membrane pore size is less than 100 nm.

4. The preparation method according to claim 1, wherein: In step (2), the drying is performed by drying at a temperature not exceeding 70° C. for at least 12 hours, or air-drying at room temperature for 12-36 hours; In step (3), the high-temperature sintering refers to calcining at a temperature of 1200-1350°C for 2-6 hours, wherein the heating rate is controlled at 2-5°C / min.

5. The preparation method according to claim 1, wherein In step (2), the mullite fiber membrane slurry comprises the following components in percentages: 2wt%-6wt% of mullite fiber, 0.5wt%-5wt% of dispersant, 1wt%-5wt% of stabilizer, and the balance being water; Preferably, the mullite fiber is a mullite nanowire with a diameter of 30-100 nm and a length of 0.6-1.5 μm; Preferably, the dispersant is at least one of sodium hexametaphosphate, sodium pyrophosphate, trisodium phosphate, tetrasodium phosphate, sodium hexametaphosphate, sodium metasilicate, and sodium disilicate; Preferably, the stabilizer is at least one of methyl cellulose and carboxymethyl cellulose; Preferably, ultrasound is first applied followed by continuous physical stirring to form the mullite fiber membrane slurry which is uniformly dispersed and stable. Preferably, the ultrasound time is at least 1 hour, and the continuous physical stirring time is at least 12 hours. Preferably, the particle-stacked ceramic membrane support in step (1) is formed by high-temperature sintering of aluminum oxide particles, and the membrane pore size of the particle-stacked ceramic membrane support is 1-5 μm and the membrane thickness is 1-2 mm.

6. A ceramic nanofiber membrane prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The ceramic nanofiber membrane comprises a particle-stacked ceramic membrane support body and a mullite fiber membrane layer firmly attached to one side of the particle-stacked ceramic membrane support body and composed of mullite fibers staggered and stacked into a mesh structure.

7. A method for preparing a catalytic ceramic nanofiber membrane, characterized in that: The steps include: (1) preparing a catalyst precursor ion solution, wherein the catalyst precursor ion solution comprises a transition metal ion of the corresponding catalyst and water, wherein the concentration of the transition metal ion is 0.05-2.0 mol / L; (2) completely immersing the ceramic nanofiber membrane prepared by the preparation method according to any one of claims 1 to 5 in the catalyst precursor ion solution; (3) after treating the system of step (2) under low-temperature hydrothermal conditions for a first predetermined time, adding an alkali precipitant to the catalyst precursor ion solution to obtain an alkali precipitation reaction liquid, continuing to treat under the low-temperature hydrothermal conditions for a second predetermined time, and then removing the film loaded with the catalyst precursor and drying it; wherein the concentration of the alkali precipitant in the alkali precipitation reaction liquid is 0.1-4.0 mol / L; (4) After the catalyst precursor particles in the alkali precipitation reaction liquid are fully precipitated, the supernatant is discarded, the catalyst precursor particles are collected and redispersed in water, and ultrasonic dispersion is performed for at least 1 hour to form a suspension containing the catalyst precursor particles; (5) immersing the catalyst precursor-loaded membrane dried in step (3) in the suspension of step (4) again, applying negative pressure for at least 30 minutes, and then drying the membrane. Repeating the "immersing in the suspension of step (4), applying negative pressure, and drying" steps multiple times. Then, after the final drying, the membrane is subjected to a final aging reaction with the suspension at 80-100° C. for 24-48 hours to allow the catalyst to have more defect sites and activity. The membrane is then taken out and fully dried at 35-70° C.; (6) calcining the dried membrane obtained in step (5) at 300-600°C for 2-6h to obtain the catalytic ceramic nanofiber membrane, which includes a ceramic nanofiber membrane and a catalyst loaded on the ceramic nanofiber membrane and in the membrane pores, wherein the catalyst is a multi-element transition metal oxide catalyst.

8. The preparation method according to claim 7, wherein: In step (6), the catalyst is a ternary, quaternary or quinary catalyst; preferably, the ternary catalyst is at least one of CuFeMnO, CuZnMnO, CuTiMnO, CuCoMnO and CuCeMnO; the quaternary catalyst is at least one of CuFeZnMnO, CuFeTiMnO, CuFeCoMnO and CuFeCeMnO; the quinary catalyst is at least one of CuFeZnTiMnO, CuFeZnCoMnO and CuFeZnCeMnO; The immersion treatment in step (2) refers to: shaking in a shaker at room temperature for at least 12 hours; The low-temperature hydrothermal conditions in step (3) are: a water bath at 60-100°C, the first predetermined time is 5-20 minutes, and the second predetermined time is 0.5-2 hours; The drying in step (3) and step (5) independently refers to: drying in an oven at 35-70°C for at least 30 minutes; The negative pressure applied in step (5) is -0.03 to -0.08 MPa; In step (5), the time for sufficient drying after the aging reaction is 24-48 hours.

9. A catalytic ceramic nanofiber membrane prepared by the preparation method according to any one of claims 7-8, characterized in that: The invention comprises the ceramic nanofiber membrane according to claim 6 and a catalyst supported on the ceramic nanofiber membrane and in the membrane pores.

10. Use of the catalytic ceramic nanofiber membrane according to claim 9 in oxidative water treatment, characterized in that: The catalytic ceramic nanofiber membrane is placed in the water to be treated, which can efficiently catalyze the decomposition of oxidants in the water to produce active oxygen species, thereby enhancing the removal of pollutants in the water.

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