Preparation method of nanoporous dual-functional layer composite ceramic membrane for treating oily emulsified wastewater

Abstract

A method for preparing a nanoporous dual-functional composite ceramic membrane for treating oil-containing emulsified wastewater, which relates to a preparation method and application of a composite ceramic membrane. The present invention aims to solve the problems of poor nanoemulsified oil droplet retention rate of existing ceramic membranes and difficulty in cleaning membrane contamination. Method: 1. Preparation of a substrate coated with a nano / micron alumina ceramic membrane; 2. Preparation of a nanoporous LaMn 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 Preparation of O3 ceramic membrane. The present invention is used for the preparation of nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a composite ceramic membrane. Background Art

[0002] Highly toxic oil-containing emulsified wastewater generated during production processes in industries such as petrochemicals, metallurgy, machining, and biomedicine has become a major issue in water treatment due to its complex colloidal properties and environmental hazards. This type of wastewater is commonly found in emulsified oil droplets with a particle size distribution of nanometers (50nm to 200nm), accompanied by high concentrations of surfactants, forming a kinetically stable dispersion system. Traditional treatment technologies such as adsorption, flotation, centrifugal separation, and chemical demulsification processes have significant limitations in removing nanoscale oil droplets. In particular, the retention efficiency of oil droplets with a particle size of less than 100nm is generally low, making it difficult to meet increasingly stringent emission standards.

[0003] Membrane separation technology is considered the most promising solution due to its efficient separation characteristics, and porous ceramic membranes with excellent hydrophilicity have become a current research hotspot due to their excellent chemical stability. However, due to the colloidal stability caused by the small hydrodynamic radius and high surface charge density of nano-sized oil droplets, conventional ceramic membrane separation technology still faces two key problems in the treatment of oil-containing emulsified wastewater: First, the pore size distribution of conventional ceramic membranes is uneven and the porosity is low, resulting in a large permeation resistance and an inability to effectively remove nano-sized oil droplets in oil-containing emulsified wastewater. Second, membrane fouling formed during long-term operation leads to a significant decrease in the treatment efficiency of oil-containing emulsified wastewater.

[0004] Because the ceramic membrane separation layer plays a crucial role in oil-water emulsion treatment, membrane fouling characteristics, and cleaning efficiency, constructing a nanoporous ceramic membrane separation layer with uniform pore size, high porosity, and enhanced cleaning capabilities is key to overcoming the dual dilemma of retention failure and permeation flux attenuation faced by existing ceramic membranes. Summary of the Invention

[0005] The present invention aims to solve the problems of poor nanoemulsified oil droplet retention rate of existing ceramic membranes and difficulty in cleaning membrane pollution, and further provides a method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater.

[0006] A method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater is carried out according to the following steps:

[0007] 1. Preparation of substrate covered with nano / micro alumina ceramic film:

[0008] ① Using polyvinyl alcohol, micron alumina ceramic powder, nano titanium dioxide, dispersant and water through ball milling and degassing to obtain a micron ceramic powder coating liquid, the micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate and dried, and finally calcined to obtain a substrate covered with a micron alumina ceramic film;

[0009] ②Using nano-alumina ceramic powder, nano-titanium dioxide and anhydrous ethanol through ultrasonic dispersion to obtain a nano-ceramic powder coating liquid, the nano-ceramic powder coating liquid is applied to the surface of the micron alumina ceramic film of the substrate and dried, and finally calcined to obtain a substrate covered with a nano / micron alumina ceramic film;

[0010] 2. Nanoporous LaMn 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 O3 ceramic membrane preparation:

[0011] ① Add the precursor and block copolymer template into a volatile organic solvent for hydrolysis to obtain LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 O3 precursor sol;

[0012] The precursor is LaMn 0.5 Al 0.5 O3 or LaMn 0.5 Al 0.5 O3;

[0013] ② LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 The O3 precursor sol is sequentially coated on the surface of the nano / micro alumina ceramic membrane of the substrate, and then dried and calcined to obtain a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater.

[0014] The beneficial effects of the present invention are:

[0015] Nanoporous LaMn prepared by the present invention 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 The pore size of the O3 dual-functional layer is mainly distributed in the range of 10nm to 30nm, which can achieve high removal efficiency of emulsion nano-oil droplets (removal rate>98%). The nano-pores of the functional layer present a densely arranged structure with a porosity of 65% to 72%, which can achieve high water permeability (638L·h -1 ·m -2 bar-1 ).

[0016] During long-term use, most oil droplets adhere to the surface of composite ceramic membranes, while some penetrate into the pores, making them difficult to remove. A backwash strategy, combining in-situ catalytic oxidation with in-situ gas washing, allows the generated active substances to penetrate deep into the pores, eliminating irreversible membrane fouling and achieving efficient and thorough membrane cleaning. This results in a membrane flux recovery rate exceeding 90%.

[0017] The invention is used for a method for preparing a nano-pore double-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a surface scanning electron microscope image of the DL-LMCA ceramic membrane prepared in Example 1 (magnified 10,000 times);

[0019] Figure 2 This is a scanning electron microscope image of the surface of the DL-LMCA ceramic membrane prepared in Example 1 (magnified 50,000 times);

[0020] Figure 3 LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 X-ray diffraction spectrum of O3 layer;

[0021] Figure 4 LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O3 layer X-ray diffraction spectrum;

[0022] Figure 5 LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 Figure 1: Nitrogen adsorption and desorption of O3 layer;

[0023] Figure 6 LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 Figure 1: Nitrogen adsorption and desorption of O3 layer;

[0024] Figure 7 LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 Pore ​​size distribution diagram of O3 layer;

[0025] Figure 8 LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 Pore ​​size distribution diagram of O3 layer;

[0026] Figure 9 The oil rejection rate of the DL-LMCA ceramic membrane prepared in Examples 1 to 3;

[0027] Figure 10 This is a visual diagram of the oil interception effect of the DL-LMCA ceramic membrane prepared in Examples 1 to 3;

[0028] Figure 11 This is a diagram of the membrane cleaning efficiency of the DL-LMCA ceramic membrane prepared in Example 1;

[0029] Figure 12 Schematic diagram of the DL-LMCA ceramic membrane prepared in Example 1;

[0030] Figure 13 This is the actual process flow chart of the DL-LMCA ceramic membrane prepared in Example 1, ① is the water inlet tank, ② is the valve, ③ is the pressure gauge, ④ is the pressure pump, ⑤ is the ceramic membrane assembly, ⑥ is the water outlet tank, and ⑦ is the backwash water tank. DETAILED DESCRIPTION

[0031] Specific embodiment 1: This embodiment is a method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater, which is carried out according to the following steps:

[0032] 1. Preparation of substrate covered with nano / micro alumina ceramic film:

[0033] ① Using polyvinyl alcohol, micron alumina ceramic powder, nano titanium dioxide, dispersant and water through ball milling and degassing to obtain a micron ceramic powder coating liquid, the micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate and dried, and finally calcined to obtain a substrate covered with a micron alumina ceramic film;

[0034] ②Using nano-alumina ceramic powder, nano-titanium dioxide and anhydrous ethanol through ultrasonic dispersion to obtain a nano-ceramic powder coating liquid, the nano-ceramic powder coating liquid is applied to the surface of the micron alumina ceramic film of the substrate and dried, and finally calcined to obtain a substrate covered with a nano / micron alumina ceramic film;

[0035] 2. Nanoporous LaMn 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 O3 ceramic membrane preparation:

[0036] ① Add the precursor and block copolymer template into a volatile organic solvent for hydrolysis to obtain LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 O3 precursor sol;

[0037] The precursor is LaMn 0.5 Al 0.5 O3 or LaMn 0.5 Al 0.5 O3;

[0038] ② LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 The O3 precursor sol is sequentially coated on the surface of the nano / micro alumina ceramic membrane of the substrate, and then dried and calcined to obtain a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater.

[0039] Preparation principle: In the membrane separation process, the pore structure of the membrane plays a decisive role in the separation performance of the membrane. 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 An O3 precursor and a block copolymer template are added to a volatile organic solvent system to obtain a precursor solution. After evaporation and drying, the solvent forms a gel film. During the evaporation process, the PS-b-PEO microphase separates and self-assembles, forming an ordered mesostructure. A substrate coated with a nano / micron alumina ceramic membrane serves as a hard template to prevent the mesoporous structure from collapsing. The pore structure of the ceramic membrane is primarily regulated by using PS-b-PEO as a template. The molecular weight of the template controls the pore size. The larger the molecular weight of the template, the larger the diameter of the micelles formed during the microphase separation process. Therefore, the pore size formed after calcination to remove the template is also larger.

[0040] Nanoemulsion separation principle: Size screening and surface wettability are considered key factors affecting nanoemulsion separation. Achieving the creation of nanopores ranging from 10nm to 30nm ensures a high degree of retention of nanoemulsions. Uniformly ordered mesopores can also increase specific surface area, improve surface properties, and increase water flux. Numerous studies have shown that catalytic oxidation and backwashing are effective methods for mitigating membrane fouling.

[0041] Catalytic oxidation cleaning principle: LaCu in the double functional layer 0.5 Al 0.5 The Cu-O-Al active sites in the O3 layer catalyze the generation of a large number of hydroxyl radicals (·OH). Due to the spatial restriction of the nanopores, the diffusion time required for ·OH to contact the pollutants in the pores is greatly shortened, effectively improving the degradation efficiency of oil and surfactants in the nanopores. 0.5 Al 0.5The Mn-O-Al active sites in the O3 layer can catalyze H2O2 to quickly generate a large number of nano-O2 bubbles in the pores, forming air pressure in the nano-pores, and achieving efficient air washing of oil stains blocked in the membrane pores and on the surface. 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 The unique catalytic properties of the O3 dual-functional layer simultaneously achieve a highly efficient in-situ catalytic oxidation / gas washing effect on membrane fouling inside and on the surface of the DL-LMCA membrane.

[0042] The beneficial effects of this embodiment are:

[0043] Nanoporous LaMn prepared in this embodiment 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 The pore size of the O3 dual-functional layer is mainly distributed in the range of 10nm to 30nm, which can achieve high removal efficiency of emulsion nano-oil droplets (removal rate>98%). The nano-pores of the functional layer present a densely arranged structure with a porosity of 65% to 72%, which can achieve high water permeability (638L·h -1 ·m -2 bar -1 ).

[0044] During long-term use, most oil droplets adhere to the surface of composite ceramic membranes, while some penetrate into the pores, making them difficult to remove. A backwash strategy, combining in-situ catalytic oxidation with in-situ gas washing, allows the generated active substances to penetrate deep into the pores, eliminating irreversible membrane fouling and achieving efficient and thorough membrane cleaning. This results in a membrane flux recovery rate exceeding 90%.

[0045] Specific embodiment 2: This embodiment differs from the specific embodiment 1 in that the micron ceramic powder coating liquid described in step 1① is specifically prepared according to the following steps:

[0046] a. dissolving polyvinyl alcohol in water at a temperature of 80° C. to 120° C. and a rotation speed of 300 rpm to 500 rpm to obtain a polyvinyl alcohol solution;

[0047] The viscosity of the polyvinyl alcohol is 50mPa·s to 60mPa·s; the concentration of the polyvinyl alcohol in the polyvinyl alcohol solution is 0.95g / mL to 1g / mL;

[0048] b. Dissolve the micron alumina ceramic powder, nano titanium dioxide and dispersant in a polyvinyl alcohol solution, then ball mill for 3 h to 12 h at a rotation speed of 300 rpm to 500 rpm and a ball-to-material mass ratio of 1: (0.2 to 1), and finally degas under vacuum at a vacuum degree of -0.08 MPa to 0.1 MPa for 30 min to 40 min to obtain a micron ceramic powder coating solution;

[0049] The micron ceramic powder coating liquids are respectively 40μm-50μm micron ceramic powder coating liquids, 5μm-15μm micron ceramic powder coating liquids, 1μm-5μm micron ceramic powder coating liquids and 0.1μm-0.3μm micron ceramic powder coating liquids; the particle size of the micron alumina ceramic powder in the 40μm-50μm micron ceramic powder coating liquid is 40μm-50μm; the particle size of the micron alumina ceramic powder in the 5μm-15μm micron ceramic powder coating liquid is 5μm-15μm; the particle size of the micron alumina ceramic powder in the 1μm-5μm micron ceramic powder coating liquid is 1μm-5μm; the particle size of the micron alumina ceramic powder in the 0.1μm-0.3μm micron ceramic powder coating liquid is 0.1μm-0.3μm;

[0050] The concentration of the micron alumina ceramic powder in the micron ceramic powder coating solution is 0.3 g / mL to 0.4 g / mL; the concentration of nano-titanium dioxide in the micron ceramic powder coating solution is 0.05 g / mL to 0.1 g / mL, and the particle size of the nano-titanium dioxide is 100 nm to 200 nm; the concentration of the dispersant in the micron ceramic powder coating solution is 0.03 g / mL to 0.05 g / mL, and the dispersant is DARVAN CN. Other aspects are the same as those in the first embodiment.

[0051] Specific embodiment three: This embodiment differs from either specific embodiment one or two in that: in step one ①, the micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate and dried, specifically by the following steps:

[0052] a. At a speed of 1500 rpm to 2500 rpm and a coating volume of 0.25 mL / cm 2 ~0.3mL / cm 2 Under the conditions of , a 40μm to 50μm micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate for 10s to 25s, and then dried for 1min to 3min at a temperature of 50℃ to 80℃, and the coating and drying are repeated 2 to 3 times;

[0053] The porous ceramic substrate has a pore size of 50 μm to 100 μm, a porosity of 30% to 40%, and a thickness of 2 mm to 5 mm;

[0054] b. Apply 5μm-15μm micron ceramic powder coating solution, 1μm-5μm micron ceramic powder coating solution and 0.1μm-0.3μm micron ceramic powder coating solution in sequence according to step a. Other aspects are the same as those in the first or second embodiment.

[0055] Specific embodiment 4: This embodiment differs from Specific embodiments 1 to 3 in that the calcination in step 1 (1) is performed at a heating rate of 2°C / min to 5°C / min to a temperature of 1100°C to 1500°C, followed by calcination at 1100°C to 1500°C for 5 to 6 hours. Other aspects are the same as Specific embodiments 1 to 3.

[0056] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the nano-ceramic powder coating solution described in step 1 ② is prepared according to the following steps:

[0057] Ultrasonic dispersion of nano-alumina ceramic powder in ethanol and nano-titanium dioxide in ethanol was performed for 1 to 2 hours at a power of 200W to 300W to obtain a mixed dispersion, and anhydrous ethanol was added to the mixed dispersion, and ultrasonic dispersion was performed for 1 to 2 hours at a power of 200W to 300W to obtain a nano-ceramic powder coating solution.

[0058] The concentration of the nano-alumina ceramic powder in the nano-alumina ceramic powder ethanol dispersion is 0.15 g / mL to 0.16 g / mL, and the particle size of the nano-alumina ceramic powder is 100 nm to 200 nm. The concentration of the nano-titanium dioxide in the nano-titanium dioxide ethanol dispersion is 0.15 g / mL to 0.16 g / mL, and the particle size of the nano-titanium dioxide is 100 nm to 200 nm. The concentration of the nano-alumina ceramic powder in the nano-ceramic powder coating solution is 0.10 g / mL to 0.11 g / mL, and the concentration of the nano-titanium dioxide in the nano-ceramic powder coating solution is 0.01 g / mL to 0.02 g / mL. Other aspects are the same as those of Specific Embodiments 1 to 4.

[0059] Specific embodiment 6: This embodiment differs from the specific embodiments 1 to 5 in that: in step 1 ②, the nano ceramic powder coating liquid is applied to the surface of the micron alumina ceramic film of the substrate and dried, specifically by the following steps:

[0060] At a rotation speed of 2000 rpm to 2500 rpm and a coating volume of 0.25 mL / cm 2 ~0.3mL / cm 2Under the conditions of , the nano ceramic powder coating liquid is applied to the surface of the micron alumina ceramic film of the substrate for 15s to 20s, and then dried at a temperature of 50°C to 80°C for 1min to 3min, and the coating and drying are repeated 2 to 3 times. Other steps are the same as those of the first to fifth embodiments.

[0061] Specific embodiment 7: This embodiment differs from Specific embodiments 1 to 6 in that the calcination in step 1 (2) is performed at a heating rate of 2°C / min to 5°C / min to a temperature of 850°C to 1200°C, followed by calcination at 850°C to 1200°C for 3 to 4 hours. Other steps are the same as Specific embodiments 1 to 6.

[0062] Specific embodiment eight: This embodiment differs from any one of the specific embodiments one to seven in that: the LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 The O3 precursor sol is specifically prepared by the following steps: mixing the precursor, citric acid, block copolymer template, concentrated nitric acid and tetrahydrofuran, and then reacting at a temperature of 40°C to 45°C for 10h to 18h; the precursor is LaMn 0.5 Al 0.5 O3 or LaMn 0.5 Al 0.5 O3; the block copolymer template is a PS-b-PEO block copolymer with a number average molecular weight of Mn = 12,000-13,000; the molar ratio of citric acid to precursor is 4:(0.3-0.5); the molar ratio of citric acid to block copolymer template is 4:(0.001-0.005); the molar ratio of citric acid to nitric acid in concentrated nitric acid is 4:(0.2-0.3); the molar ratio of citric acid to tetrahydrofuran is 4:(150-200); and the mass percentage of concentrated nitric acid is 65%-68%. Other aspects are the same as those of Specific Embodiments 1 to 7.

[0063] The PS-b-PEO block copolymer described in this specific embodiment is prepared by atom transfer radical polymerization.

[0064] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: in step 2②, the rotation speed is 1500rpm~2000rpm and the coating amount is 0.25mL / cm 2 ~0.3mL / cm 2 Under the conditions of 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al0.5 The O3 precursor sol is sequentially coated on the surface of the nano / micro alumina ceramic film on the substrate. Other steps are the same as those in the first to eighth embodiments.

[0065] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the drying and calcining described in step 2 ② are specifically carried out according to the following steps:

[0066] First, dry at a temperature of 50°C to 55°C for 12 to 48 hours, then dry at a temperature of 100°C to 150°C for 12 to 48 hours, then heat to 300°C to 500°C at a heating rate of 2°C / min to 5°C / min, and calcine at 300°C to 500°C for 4 to 5 hours, then heat to 750°C to 850°C at a heating rate of 2°C / min to 5°C / min, and calcine at 750°C to 850°C for 5 to 10 minutes, and finally cool to room temperature at a cooling rate of 2°C / min to 5°C / min. Other steps are the same as those in the first to ninth embodiments.

[0067] The following examples are used to verify the beneficial effects of the present invention:

[0068] Example 1:

[0069] A method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater is carried out according to the following steps:

[0070] 1. Preparation of substrate covered with nano / micro alumina ceramic film:

[0071] a. dissolving polyvinyl alcohol in water at a temperature of 95° C. and a rotation speed of 300 rpm to obtain a polyvinyl alcohol solution;

[0072] The viscosity of the polyvinyl alcohol is 50 mPa·s to 60 mPa·s; the concentration of the polyvinyl alcohol in the polyvinyl alcohol solution is 0.98 g / mL;

[0073] b. Dissolve micron alumina ceramic powder, nano titanium dioxide and a dispersant in a polyvinyl alcohol solution, then ball mill at a rotation speed of 400 rpm and a ball-to-material mass ratio of 1:0.2. Finally, vacuum degassing is performed at a vacuum degree of 0.05 MPa for 30 minutes to obtain a micron ceramic powder coating solution;

[0074] The micron ceramic powder coating liquids are respectively 46μm micron ceramic powder coating liquid, 9μm micron ceramic powder coating liquid, 5μm micron ceramic powder coating liquid and 0.3μm micron ceramic powder coating liquid; the particle size of the micron alumina ceramic powder in the 46μm micron ceramic powder coating liquid is 46μm; the particle size of the micron alumina ceramic powder in the 9μm micron ceramic powder coating liquid is 9μm; the particle size of the micron alumina ceramic powder in the 5μm micron ceramic powder coating liquid is 5μm; the particle size of the micron alumina ceramic powder in the 0.3μm micron ceramic powder coating liquid is 0.3μm; and the ball milling times corresponding to different particle sizes are 3h, 8h, 8h and 12h respectively;

[0075] The concentration of the micron alumina ceramic powder in the 46μm micron ceramic powder coating liquid, the 9μm micron ceramic powder coating liquid, the 5μm micron ceramic powder coating liquid and the 0.3μm micron ceramic powder coating liquid is 0.32g / mL; the concentration of nano titanium dioxide in the 46μm micron ceramic powder coating liquid, the 9μm micron ceramic powder coating liquid, the 5μm micron ceramic powder coating liquid and the 0.3μm micron ceramic powder coating liquid is 0.08g / mL, and the particle size of the nano titanium dioxide is 200nm; the concentration of the dispersant in the 46μm micron ceramic powder coating liquid, the 9μm micron ceramic powder coating liquid, the 5μm micron ceramic powder coating liquid and the 0.3μm micron ceramic powder coating liquid is 0.04g / mL, and the dispersant is DARVAN CN;

[0076] c. At a speed of 2000 rpm and a coating volume of 0.25 mL / cm 2 Under the conditions of , 46μm micron ceramic powder coating liquid was applied to one side of the porous ceramic substrate for 15s, and then dried at a temperature of 60℃ for 1min, and the coating and drying were repeated 3 times;

[0077] The porous ceramic substrate has an average pore size of 50 μm, a porosity of 34%, and a thickness of 3 mm;

[0078] d. Apply 9μm micron ceramic powder coating liquid, 5μm micron ceramic powder coating liquid and 0.3μm micron ceramic powder coating liquid in sequence according to step c;

[0079] e. Heating the temperature to 1100° C. at a heating rate of 2° C. / min, and then calcining at 1100° C. for 5 h to obtain a substrate covered with a micronized alumina ceramic film;

[0080] f. Ultrasonic dispersion of nano-alumina ceramic powder ethanol dispersion and nano-titanium dioxide ethanol dispersion at a power of 200 W for 1 h to obtain a mixed dispersion, adding anhydrous ethanol to the mixed dispersion, and ultrasonically dispersing at a power of 200 W for 1 h to obtain a nano-ceramic powder coating solution;

[0081] The concentration of the nano-alumina ceramic powder in the nano-alumina ceramic powder ethanol dispersion is 0.157 g / mL, and the particle size of the nano-alumina ceramic powder is 100 nm; the concentration of the nano-titanium dioxide in the nano-titanium dioxide ethanol dispersion is 0.157 g / mL, and the particle size of the nano-titanium dioxide is 100 nm; the concentration of the nano-alumina ceramic powder in the nano-ceramic powder coating solution is 0.1052 g / mL; the concentration of the nano-titanium dioxide in the nano-ceramic powder coating solution is 0.017 g / mL;

[0082] g, at a rotation speed of 2000 rpm and a coating volume of 0.25 mL / cm 2 Under the conditions of , the nano ceramic powder coating liquid was coated on the surface of the micron alumina ceramic film of the substrate for 25s, and then dried for 1min at a temperature of 60°C, and the coating and drying were repeated 3 times;

[0083] h. heating the substrate to 900° C. at a heating rate of 2° C. / min, and then calcining the substrate at 900° C. for 3 h to obtain a substrate covered with a nano / micro alumina ceramic film;

[0084] 2. Nanoporous LaMn 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 O3 ceramic membrane preparation:

[0085] ① Mix the precursor, citric acid, block copolymer template, concentrated nitric acid and tetrahydrofuran, and then react at 42 ° C for 18 hours to obtain LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 O3 precursor sol; the precursor is LaMn 0.5 Al 0.5 O3 or LaMn 0.5 Al 0.5 O3;

[0086] The block copolymer template is a PS-b-PEO block copolymer with a number average molecular weight of Mn=13000; the molar ratio of citric acid to precursor is 4:0.36; the molar ratio of citric acid to block copolymer template is 4:0.0015; the molar ratio of citric acid to nitric acid in concentrated nitric acid is 4:0.3; the molar ratio of citric acid to tetrahydrofuran is 4:160; and the mass percentage of concentrated nitric acid is 65%.

[0087] ② At a speed of 2000 rpm and a coating volume of 0.3 mL / cm2 Under the conditions of 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 The O3 precursor sol is sequentially coated on the surface of the nano / micron alumina ceramic membrane of the substrate, and then dried at a temperature of 50°C for 12 hours, then dried at a temperature of 110°C for 12 hours, then heated to 400°C at a heating rate of 5°C / minn, and calcined at 400°C for 4 hours, then heated to 850°C at a heating rate of 5°C / min, and calcined at 850°C for 5 minutes, and finally cooled to room temperature at a cooling rate of 5°C / min to obtain a nanoporous dual-functional layer composite ceramic membrane for oil-containing emulsified wastewater treatment, namely, DL-LMCA ceramic membrane.

[0088] Example 2: This example differs from Example 1 in that the concentration of the micron alumina ceramic powder in the 46μm, 9μm, 5μm, and 0.3μm micron ceramic powder coating solutions in step 1b is 0.32g / mL; in step 1e, the temperature is increased to 1250°C at a rate of 5°C / min, followed by calcination at 1250°C for 5 hours to obtain a substrate coated with a micron alumina ceramic film; in step 1h, the temperature is increased to 1000°C at a rate of 5°C / min, followed by calcination at 1000°C for 3 hours to obtain a substrate coated with a nano / micron alumina ceramic film; and in step 2i, the reaction is carried out at 45°C for 10 hours. Other conditions are the same as in Example 1.

[0089] Example 3: The difference between this example and Example 1 is that the concentration of the micron alumina ceramic powder in the 46μm micron ceramic powder coating liquid, 9μm micron ceramic powder coating liquid, 5μm micron ceramic powder coating liquid and 0.3μm micron ceramic powder coating liquid described in step 1b is 0.35g / mL, and the concentration of nano titanium dioxide is 0.08g / mL; in step 1e, the temperature is raised to 1150℃ at a heating rate of 5℃ / min, and then calcined at 1150℃ for 5h to obtain a micron alumina-coated ceramic powder. A ceramic membrane substrate; in step 1, the temperature was raised to 950°C at a heating rate of 5°C / min, followed by calcination at 950°C for 3 hours to obtain a substrate covered with a nano / micron alumina ceramic membrane; in step 2 (1), the molar ratio of citric acid to precursor was 4:0.4; the molar ratio of citric acid to template in step 2 (1) was 4:0.001; the molar ratio of citric acid to nitric acid in concentrated nitric acid in step 2 (1) was 4:0.2; and in step 2 (1), the reaction was carried out at 45°C for 12 hours. Other procedures were the same as in Example 1.

[0090] Figure 1 This is a surface scanning electron microscope image of the DL-LMCA ceramic membrane prepared in Example 1 (magnified 10,000 times); it can be seen from the image that the surface of the double-layer membrane is very smooth and flat without any cracks.

[0091] Figure 2 This is a scanning electron microscope image of the surface of the DL-LMCA ceramic membrane prepared in Example 1 (magnified 50,000 times); as can be seen from the figure, the DL-LMCA ceramic membrane has a nanopore structure that can reach 10nm to 30nm; its porosity can reach 65% to 72%, and it is relatively uniform and dense, with very good coverage.

[0092] In the following experiments, in order to 0.5 Al 0.5 O3 layer or LaMn 0.5 Al 0.5 The O3 layer was tested, and only LaCu was coated in step 2② of Example 1. 0.5 Al 0.5 O3 precursor sol or LaMn 0.5 Al 0.5 O3 precursor sol, and other processes are the same as those in Example 1.

[0093] Figure 3 LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 X-ray diffraction spectrum of the O3 layer; it can be seen from the figure that it has a very narrow and high characteristic peak. Analysis of the position of its characteristic peak shows that it has characteristic crystal planes such as (110), (202), and (024), indicating that it still maintains its original crystal shape during the preparation process of the film and no lattice distortion occurs.

[0094] Figure 4 LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 X-ray diffraction spectrum of O3 layer; it can be seen from the figure that LaMn appears at 33.14°, 48.73°, 59.4° and other positions. 0.5 Al 0.5 The characteristic peaks of O3 prove the integrity of its structure.

[0095] Figure 5 LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 Figure 1: Nitrogen adsorption and desorption of O3 layer; Figure 6 LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5Figure 2 shows nitrogen adsorption and desorption of O3 layer; BET (Brunauer-Emmett-Teller) specific surface area test shows that nitrogen and two materials LaCu 0.5 Al 0.5 O3 and LaMn 0.5 Al 0.5 The interaction force between nitrogen and O3 is weak. Because the C value in the BET formula is less than 2, the C value is generally used to describe the interaction strength between the gas and the material surface. The smaller the C value, the weaker the interaction force between the gas and the material surface. Therefore, there is mainly a weak interaction between nitrogen and these two materials. In addition, a type IV isotherm was observed from the adsorption-desorption isotherm, and a hysteresis loop was present. Type IV isotherms are usually found in mesoporous materials, and the presence of hysteresis loops indicates the presence of a certain amount of pore structure within the material. These pore structures give the DL-LMCA ceramic membrane a high specific surface area, thereby enhancing its adsorption capacity. At the same time, the high specific surface area also provides more active sites for catalytic reactions, so this ceramic membrane exhibits higher efficiency in catalytic reactions. In summary, due to its rich pore structure and high specific surface area, the DL-LMCA ceramic membrane can not only effectively adsorb gases but also exhibit excellent performance in catalytic reactions.

[0096] Figure 7 LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 Pore ​​size distribution diagram of O3 layer; Figure 8 LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 Pore ​​size distribution diagram of the O3 layer; it can be seen from the figure that the pore size of the DL-LMCA ceramic membrane is mainly distributed in the range of 15nm to 25nm, which is consistent with the SEM observation results.

[0097] The DL-LMCA ceramic membranes prepared in Examples 1 to 3 were placed in a ceramic membrane filter cup, and then pure water was added. After sealing, the airtightness was checked. The pressure valve was controlled by a program to start the pure water measurement experiment. The water quality of the ultrafiltration cup was measured by an electronic balance. The instantaneous water output was read from the computer and the pure water flux of the membrane was calculated. By running the test under different pressures, the DL-LMCA ceramic membrane had a high water permeability (638.1L·h -1 ·m -2 bar -1 ).

[0098] The DL-LMCA ceramic membrane prepared in Examples 1 to 3 was placed in a ceramic membrane filter cup, and then the nanoemulsion solution was added and sealed to check for airtightness. The pressure valve was controlled by a program to start the nanoemulsion measurement experiment. The oil water from the ultrafiltration cup was measured by a TOC analyzer. By comparing the TOC in the crude oil water, the retention rate of nanoemulsions with different molecular weights can be obtained. Figure 9 and 10 The nanoemulsion solution is specifically prepared according to the following steps: 100 mL of n-hexane and 1 L of water are placed in a homogenizer, and treated at a rotation speed of 20,000 r / min for 15 minutes to obtain a nanoemulsion solution.

[0099] Figure 9 The oil rejection rate of the DL-LMCA ceramic membranes prepared in Examples 1 to 3 is shown in the figure. As can be seen from the figure, the DL-LMCA ceramic membranes prepared in Examples 1 to 3 all have a nano-oil droplet rejection rate of more than 99%.

[0100] Figure 10 This is a visual diagram of the oil interception effect of the DL-LMCA ceramic membrane prepared in Examples 1 to 3; it can be seen from the figure that the filtration effect is very good, and the oily wastewater has changed from turbid to clear.

[0101] After the membrane was filtered for 1 hour, the membrane was backwashed with ordinary H2O or H2O2 solution (mass percentage of 1%) for 5 minutes from the reverse side at a pressure of 0.5 bar. Figure 11 This is a graph of membrane cleaning efficiency for the DL-LMCA ceramic membrane prepared in Example 1. The graph shows that the emulsifiable concentrate flux at each moment of emulsifiable concentrate filtration is recorded alongside the initial emulsifiable concentrate flux. The J / J0 trend reveals the membrane's performance recovery after different cleaning methods. The cleaning effects of H2O2 and H2O differ significantly, with conventional backwashing resulting in a lower flux recovery rate of approximately 10%. Cleaning with H2O2 can restore flux to 90%, while the cleaning effect of H2O is minimal.

[0102] Figure 12 This is the principle diagram of the DL-LMCA ceramic membrane prepared in Example 1. As can be seen from the figure, when the ceramic membrane is used normally, the nanoemulsion is successfully intercepted. However, when the use time becomes longer and the use cycle becomes more, the membrane will inevitably have the problem of membrane fouling. 0.5 Al 0.5 During the cleaning process of the O3 membrane, the oxidant H2O2 contacts the LaCu 0.5 Al 0.5 The Cu-O-Al active sites in the O3 layer react to produce OH and O2 -The free radicals such as hydroxyl radicals can promote the catalytic degradation of pollutants such as surfactants and oils in the pores. Due to the confinement of the nanopore space, the diffusion time required for OH to contact the pollutants in the pores is greatly shortened, effectively improving the degradation efficiency of oils and surfactants in the nanopores. The residual H2O2 then passes through LaMn 0.5 Al 0.5 The O3 layer is formed, and a large number of nano-O2 bubbles are generated in the pores by the catalysis of the Mn-O-Al active sites, forming an in-situ gas washing effect in the membrane pores and on the membrane surface, and then performing an in-situ backwashing process on the pores that may be blocked by pollutants, which helps to alleviate the membrane fouling problem of DL-LMCA ceramic membrane.

[0103] Figure 13 This is a flow chart of the actual process for preparing the DL-LMCA ceramic membrane in Example 1. ① is the water inlet tank, ② is the valve, ③ is the pressure gauge, ④ is the pressure pump, ⑤ is the ceramic membrane assembly, ⑥ is the water outlet tank, and ⑦ is the backwash tank. Wastewater enters through ①, and after pressure is adjusted by opening the left-hand pressure pump ④, it passes through the inlet pipe at valve ② and enters the ceramic membrane assembly ⑤ for treatment. The treated water is then discharged through the ⑥ water outlet tank. Valve ② at the end of ⑤ can be opened to relieve pressure. As the operating cycle lengthens and membrane fouling occurs, the hydrogen peroxide backwash tank ⑦ is opened, and the water enters the valve at ⑤ for in-situ backwashing of the ceramic membrane. The wastewater can be discharged through valve ② at the end of ⑤.

Claims

1. A method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater, characterized in that It is carried out in the following steps:

1. Preparation of substrate covered with nano / micro alumina ceramic film: ① Using polyvinyl alcohol, micron alumina ceramic powder, nano titanium dioxide, dispersant and water through ball milling and degassing to obtain a micron ceramic powder coating liquid, the micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate and dried, and finally calcined to obtain a substrate covered with a micron alumina ceramic film; ②Using nano-alumina ceramic powder, nano-titanium dioxide and anhydrous ethanol through ultrasonic dispersion to obtain a nano-ceramic powder coating liquid, the nano-ceramic powder coating liquid is applied to the surface of the micron alumina ceramic film of the substrate and dried, and finally calcined to obtain a substrate covered with a nano / micron alumina ceramic film; 2. Nanoporous LaMn 0.5 Al 0.5 O3 / LaCu 0.5 Al 0.5 O3 ceramic membrane preparation: ① Mix the precursor, citric acid, block copolymer template, concentrated nitric acid and tetrahydrofuran, and then react at a temperature of 40℃~45℃ for 10h~18h to obtain LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 O3 precursor sol; The precursor is LaCu 0.5 Al 0.5 O3 or LaMn 0.5 Al 0.5 O3; ② LaCu 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 The O3 precursor sol is sequentially coated on the surface of the nano / micro alumina ceramic membrane of the substrate, and then dried and calcined to obtain a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater.

2. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that The micron ceramic powder coating liquid described in step 1① is specifically prepared according to the following steps: a. dissolving polyvinyl alcohol in water at a temperature of 80° C. to 120° C. and a rotation speed of 300 rpm to 500 rpm to obtain a polyvinyl alcohol solution; The viscosity of the polyvinyl alcohol is 50mPa·s to 60mPa·s; the concentration of the polyvinyl alcohol in the polyvinyl alcohol solution is 0.95g / mL to 1g / mL; b. Dissolve the micron alumina ceramic powder, nano titanium dioxide and dispersant in a polyvinyl alcohol solution, then ball mill for 3 h to 12 h at a rotation speed of 300 rpm to 500 rpm and a ball-to-material mass ratio of 1: (0.2 to 1), and finally degas under vacuum at a vacuum degree of -0.08 MPa to 0.1 MPa for 30 min to 40 min to obtain a micron ceramic powder coating solution; The micron ceramic powder coating liquids are respectively 40μm-50μm micron ceramic powder coating liquids, 5μm-15μm micron ceramic powder coating liquids, 1μm-5μm micron ceramic powder coating liquids and 0.1μm-0.3μm micron ceramic powder coating liquids; the particle size of the micron alumina ceramic powder in the 40μm-50μm micron ceramic powder coating liquid is 40μm-50μm; the particle size of the micron alumina ceramic powder in the 5μm-15μm micron ceramic powder coating liquid is 5μm-15μm; the particle size of the micron alumina ceramic powder in the 1μm-5μm micron ceramic powder coating liquid is 1μm-5μm; the particle size of the micron alumina ceramic powder in the 0.1μm-0.3μm micron ceramic powder coating liquid is 0.1μm-0.3μm; The concentration of the micron alumina ceramic powder in the micron ceramic powder coating liquid is 0.3g / mL to 0.4g / mL; the concentration of nano titanium dioxide in the micron ceramic powder coating liquid is 0.05g / mL to 0.1g / mL, and the particle size of the nano titanium dioxide is 100nm to 200nm; the concentration of the dispersant in the micron ceramic powder coating liquid is 0.03g / mL to 0.05g / mL, and the dispersant is DARVAN CN.

3. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 2, characterized in that In step 1①, the micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate and dried. Specifically, the following steps are performed: a. At a speed of 1500 rpm to 2500 rpm and a coating volume of 0.25 mL / cm 2 ~0.3mL / cm 2 Under the conditions of , a 40μm to 50μm micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate for 10s to 25s, and then dried for 1min to 3min at a temperature of 50℃ to 80℃, and the coating and drying are repeated 2 to 3 times; The porous ceramic substrate has a pore size of 50 μm to 100 μm, a porosity of 30% to 40%, and a thickness of 2 mm to 5 mm; b. Follow the process in step a to apply 5μm~15μm micron ceramic powder coating liquid, 1μm~5μm micron ceramic powder coating liquid and 0.1μm~0.3μm micron ceramic powder coating liquid in sequence.

4. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that The calcination in step 1① is specifically carried out at a heating rate of 2°C / min to 5°C / min, heating to 1100°C to 1500°C, and then calcining at a temperature of 1100°C to 1500°C for 5h to 6h.

5. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that The nano-ceramic powder coating solution described in step 1② is specifically prepared according to the following steps: Ultrasonic dispersion of nano-alumina ceramic powder in ethanol and nano-titanium dioxide in ethanol was performed for 1 to 2 hours at a power of 200W to 300W to obtain a mixed dispersion, and anhydrous ethanol was added to the mixed dispersion, and ultrasonic dispersion was performed for 1 to 2 hours at a power of 200W to 300W to obtain a nano-ceramic powder coating solution. The concentration of the nano-alumina ceramic powder in the nano-alumina ceramic powder ethanol dispersion is 0.15 g / mL to 0.16 g / mL, and the particle size of the nano-alumina ceramic powder is 100 nm to 200 nm; the concentration of the nano-titanium dioxide in the nano-titanium dioxide ethanol dispersion is 0.15 g / mL to 0.16 g / mL, and the particle size of the nano-titanium dioxide is 100 nm to 200 nm; the concentration of the nano-alumina ceramic powder in the nano-ceramic powder coating liquid is 0.10 g / mL to 0.11 g / mL; and the concentration of the nano-titanium dioxide in the nano-ceramic powder coating liquid is 0.01 g / mL to 0.02 g / mL.

6. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that In step 1②, the nano-ceramic powder coating liquid is applied to the surface of the micron alumina ceramic film of the substrate and dried, specifically by the following steps: At a rotation speed of 2000 rpm to 2500 rpm and a coating volume of 0.25 mL / cm 2 ~0.3mL / cm 2 Under the conditions of , the nano ceramic powder coating liquid is applied to the surface of the micron alumina ceramic film of the substrate for 15s to 20s, and then dried for 1min to 3min at a temperature of 50℃ to 80℃, and the coating and drying are repeated 2 to 3 times.

7. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that The calcination in step 1② is specifically carried out at a heating rate of 2°C / min to 5°C / min, heating to 850°C to 1200°C, and then calcining at a temperature of 850°C to 1200°C for 3h to 4h.

8. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that The block copolymer template described in step 2① is a PS-b-PEO block copolymer with a number average molecular weight of Mn=12000-13000; the molar ratio of citric acid to the precursor described in step 2① is 4:(0.3-0.5); the molar ratio of citric acid to the block copolymer template described in step 2① is 4:(0.001-0.005); the molar ratio of citric acid to nitric acid in concentrated nitric acid described in step 2① is 4:(0.2-0.3); the molar ratio of citric acid to tetrahydrofuran described in step 2① is 4:(150-200); the mass percentage of concentrated nitric acid described in step 2① is 65%-68%.

9. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that In step 2②, the rotation speed is 1500rpm~2000rpm and the coating amount is 0.25mL / cm 2 ~0.3mL / cm 2 Under the conditions of 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 The O3 precursor sol is sequentially coated on the surface of the nano / micro alumina ceramic film on the substrate.

10. The method for preparing a nanoporous dual-functional layer composite ceramic membrane for treating oil-containing emulsified wastewater according to claim 1, characterized in that The drying and calcining described in step 2② are specifically carried out according to the following steps: First, dry at a temperature of 50℃~55℃ for 12h~48h, then dry at a temperature of 100℃~150℃ for 12h~48h, then heat to 300℃~500℃ at a heating rate of 2℃ / min~5℃ / min, and calcine at a temperature of 300℃~500℃ for 4h~5h, then heat to 750℃~850℃ at a heating rate of 2℃ / min~5℃ / min, and calcine at a temperature of 750℃~850℃ for 5min~10min, and finally cool to room temperature at a cooling rate of 2℃ / min~5℃ / min.

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