Preparation method of nano-pore-channel double-functional-layer composite ceramic membrane for oil-containing emulsified wastewater treatment

Abstract

The invention relates to a preparation method and application of a composite ceramic membrane, in particular to a preparation method of a nano-pore-channel dual-functional-layer composite ceramic membrane for treating oil-containing emulsified wastewater. The problems that an existing ceramic membrane is poor in nano emulsified oil drop retention rate, and membrane pollution is difficult to clean are solved. The method comprises the following steps: 1, preparing a substrate coated with a nano / micron aluminum oxide ceramic membrane; and 2, preparation of the LaMn < 0.5 > Al < 0.5 > O < 3 > / LaCu < 0.5 > Al < 0.5 > O < 3 > ceramic membrane with nano pore channels. The preparation method is used for preparing the composite ceramic membrane with the nano-pore channel and the double-functional layer for treating the 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 in the production process of industrial fields such as petrochemicals, metallurgy, mechanical processing and biomedicine has become an important topic in the field of water treatment due to its complex colloidal properties and environmental hazards. Emulsified oil droplets with a particle size distribution of nanometers (50nm to 200nm) are common in this type of wastewater, accompanied by high concentrations of surfactants, forming a dispersed system with dynamic stability. Traditional treatment technologies such as adsorption, flotation, centrifugal separation and chemical demulsification processes have significant limitations in dealing with the removal of nano-scale oil droplets, especially for oil droplets with a particle size of less than 100nm. The retention efficiency 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 inability to effectively remove nano-sized oil droplets in oil-containing emulsified wastewater. Second, membrane pollution formed during long-term operation leads to a significant decrease in the treatment efficiency of oil-containing emulsified wastewater.

[0004] Since the ceramic membrane separation layer plays a vital role in the treatment of oil-water emulsions, membrane fouling characteristics and cleaning efficiency, constructing a nanoporous ceramic membrane separation layer with uniform pore size, high porosity and enhanced cleaning function is the key to breaking through the dual dilemma of interception 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 interception 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, coating the micron ceramic powder coating liquid on one side of the porous ceramic substrate and drying, and finally calcining to obtain a substrate covered with a micron alumina ceramic film;

[0009] ②Using nano-alumina ceramic powder, nano-titanium dioxide and anhydrous ethanol to disperse by ultrasonic to obtain nano-ceramic powder coating liquid, coating the nano-ceramic powder coating liquid on the surface of the micron alumina ceramic film of the substrate and drying, and finally calcining to obtain a substrate covered with a nano / micron alumina ceramic film;

[0010] 2. Nanoporous LaMn 0.5 Al 0.5 O 3 / LaCu 0.5 Al 0.5 O 3 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 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3 Precursor sol;

[0012] The precursor is LaMn 0.5 Al 0.5 O 3 or LaMn 0.5 Al 0.5 O 3 ;

[0013] ② LaCu 0.5 Al 0.5 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3 The precursor sol is coated on the surface of the nanometer / micrometer alumina ceramic membrane of the substrate in sequence, and then dried and calcined to obtain a composite ceramic membrane with a nano-pore double functional layer for treating oil-containing emulsified wastewater.

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

[0015] Nano-homogeneous LaMn prepared by the present invention 0.5 Al 0.5 O 3 / LaCu 0.5 Al 0.5 O 3The pore size of the 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, and its porosity can reach 65% to 72%, which can achieve high water permeability (638L·h -1 ·m -2 bar -1 ).

[0016] When the composite ceramic membrane is used for a long time, most of the oil droplets adhere to the surface, and some enter the gaps, which is difficult to relieve. Under the backwash strategy, combined with the in-situ catalytic oxidation and in-situ gas washing concepts, the active substances produced can penetrate deep into the gaps, eliminate irreversible membrane fouling behavior, and achieve efficient and thorough membrane cleaning. The membrane flux recovery rate can reach more than 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 The LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 X-ray diffraction spectrum of the layer;

[0021] Figure 4 The LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Layer X-ray diffraction spectrum;

[0022] Figure 5 The LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Nitrogen absorption and desorption diagram of the layer;

[0023] Figure 6 The LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Nitrogen absorption and desorption diagram of the layer;

[0024] Figure 7 The LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Pore ​​size distribution diagram of the layer;

[0025] Figure 8 The LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Pore ​​size distribution diagram of the layer;

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

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

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

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

[0030] Fig.13 This is the actual process flow chart of the DL-LMCA ceramic membrane prepared in Example 1, wherein 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 implementation method 1: This implementation method 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, coating the micron ceramic powder coating liquid on one side of the porous ceramic substrate and drying, and finally calcining to obtain a substrate covered with a micron alumina ceramic film;

[0034] ②Using nano-alumina ceramic powder, nano-titanium dioxide and anhydrous ethanol to disperse by ultrasonic to obtain nano-ceramic powder coating liquid, coating the nano-ceramic powder coating liquid on the surface of the micron alumina ceramic film of the substrate and drying, and finally calcining to obtain a substrate covered with a nano / micron alumina ceramic film;

[0035] 2. Nanoporous LaMn0.5 Al 0.5 O 3 / LaCu 0.5 Al 0.5 O 3 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 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3 Precursor sol;

[0037] The precursor is LaMn 0.5 Al 0.5 O 3 or LaMn 0.5 Al 0.5 O 3 ;

[0038] ② LaCu 0.5 Al 0.5 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3 The precursor sol is coated on the surface of the nanometer / micrometer alumina ceramic membrane of the substrate in sequence, and then dried and calcined to obtain a composite ceramic membrane with a nano-pore double functional layer 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 O 3 / LaCu 0.5 Al 0.5 O 3 The precursor and block copolymer template are added to a volatile organic solvent system to obtain a precursor solution, and the solvent is evaporated and dried to form a gel film. During the evaporation process, the PS-b-PEO microphase separation is self-assembled to form an ordered mesostructure. The substrate covered with a nano / micron alumina ceramic membrane is used as a hard template to ensure that the mesoporous structure will not collapse. The pore structure of the ceramic membrane is mainly regulated by PS-b-PEO as a template. The molecular weight of the template can control the size of the pore size. The larger the molecular weight of the template, the larger the diameter of the micelle formed during the microphase separation process. Therefore, the pore size formed after calcination to remove the template is larger.

[0040] Nanoemulsion separation principle: Size screening and surface wettability are considered to be the key factors affecting nanoemulsion separation. The establishment of 10nm to 30nm nanopores is the guarantee for highly intercepting nanoemulsions. Uniform and orderly mesopores can also increase specific surface area, improve surface properties, and increase water flux. According to a large number of studies, catalytic oxidation and backwashing are effective ways to alleviate membrane fouling.

[0041] Catalytic oxidation cleaning principle: LaCu in the double functional layer 0.5 Al 0.5 O 3 The Cu-O-Al active sites in the 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 0.5 O 3 The Mn-O-Al active sites in the layer can catalyze H 2 O 2 A large amount of nano-O is rapidly generated in the pores. 2 Bubbles form air pressure in the nanopores, achieving efficient air washing of oil stains blocked in the membrane pores and on the surface. 2 O 2 Under the solution backwash strategy, LaMn 0.5 Al 0.5 O 3 / LaCu 0.5 Al 0.5 O 3 The unique catalytic properties of the dual-functional layer simultaneously achieve a highly efficient in-situ catalytic oxidation / gas washing effect on membrane fouling inside the pores 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 O 3 / LaCu 0.5 Al 0.5 O 3 The pore size of the 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, and its porosity can reach 65% to 72%, which can achieve high water permeability (638L·h -1 ·m -2 bar -1 ).

[0044] When the composite ceramic membrane is used for a long time, most of the oil droplets adhere to the surface, and some enter the gaps, which is difficult to relieve. Under the backwash strategy, combined with the in-situ catalytic oxidation and in-situ gas washing concepts, the active substances produced can penetrate deep into the gaps, eliminate irreversible membrane fouling behavior, and achieve efficient and thorough membrane cleaning. The membrane flux recovery rate can reach more than 90%.

[0045] Specific embodiment 2: This embodiment is different 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 3h to 12h at a rotation speed of 300rpm to 500rpm and a ball-to-material mass ratio of 1:(0.2 to 1), and finally vacuum degas for 30min to 40min at a vacuum degree of -0.08MPa to 0.1MPa to obtain a micron ceramic powder coating liquid;

[0049] The micron ceramic powder coating liquids are 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 respectively; 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 liquid is 0.3g / mL to 0.4g / mL; the concentration of the 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. The rest is the same as the first embodiment.

[0051] Specific implementation method three: This implementation method is different from specific implementation method one or two in that: in step 1①, the micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate and dried, specifically according to 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 condition of , a 40μm-50μm micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate for 10s-25s, and then dried for 1min-3min at a temperature of 50℃-80℃, and the coating and drying are repeated 2-3 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 liquid, 1μm-5μm micron ceramic powder coating liquid and 0.1μm-0.3μm micron ceramic powder coating liquid in sequence according to step a. The rest is the same as the first or second embodiment.

[0055] Specific embodiment 4: This embodiment is different from specific embodiments 1 to 3 in that: the calcination described in step 1① is specifically carried out at a heating rate of 2°C / min to 5°C / min, the temperature is raised to 1100°C to 1500°C, and then calcined at a temperature of 1100°C to 1500°C for 5h to 6h. The rest is the same as specific embodiments 1 to 3.

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

[0057] Under the condition of power of 200W to 300W, the nano-alumina ceramic powder ethanol dispersion and the nano-titanium dioxide ethanol dispersion are ultrasonically dispersed for 1h to 2h to obtain a mixed dispersion, anhydrous ethanol is added to the mixed dispersion, and under the condition of power of 200W to 300W, the dispersion is ultrasonically dispersed for 1h to 2h to obtain a nano-ceramic powder coating liquid;

[0058] The concentration of the nano-alumina ceramic powder in the nano-alumina ceramic powder ethanol dispersion is 0.15g / mL to 0.16g / mL, and the particle size of the nano-alumina ceramic powder is 100nm to 200nm; the concentration of the nano-titanium dioxide in the nano-titanium dioxide ethanol dispersion is 0.15g / mL to 0.16g / mL, and the particle size of the nano-titanium dioxide is 100nm to 200nm; the concentration of the nano-alumina ceramic powder in the nano-ceramic powder coating liquid is 0.10g / mL to 0.11g / mL; the concentration of the nano-titanium dioxide in the nano-ceramic powder coating liquid is 0.01g / mL to 0.02g / mL. Others are the same as the specific embodiments one to four.

[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 coated on the surface of the micron alumina ceramic film of the substrate and dried, specifically according to the following steps:

[0060] At a speed of 2000 rpm to 2500 rpm and a coating volume of 0.25 mL / cm 2 ~0.3mL / cm 2 Under the condition of , the nano ceramic powder coating liquid is coated on 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°C to 80°C, and the coating and drying are repeated 2 to 3 times. The rest is the same as the specific embodiments 1 to 5.

[0061] Specific embodiment 7: This embodiment is different from specific embodiments 1 to 6 in that: the calcination described in step 1② is specifically carried out at a heating rate of 2°C / min to 5°C / min, the temperature is raised to 850°C to 1200°C, and then calcined at a temperature of 850°C to 1200°C for 3h to 4h. The rest is 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 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3The precursor sol is specifically prepared according to the following steps: the precursor, citric acid, block copolymer template, concentrated nitric acid and tetrahydrofuran are mixed, and then reacted at a temperature of 40°C to 45°C for 10h to 18h; the precursor is LaMn 0.5 Al 0.5 O 3 or LaMn 0.5 Al 0.5 O 3 ; The block copolymer template is a PS-b-PEO block copolymer with a number average molecular weight of Mn=12000-13000; 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); the mass percentage of concentrated nitric acid is 65%-68%. Others are the same as those in 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 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3 The precursor sol is sequentially coated on the surface of the nano / micron alumina ceramic film of the substrate. The rest is the same as the specific embodiments 1 to 8.

[0065] Specific embodiment 10: This embodiment differs from specific embodiments 1 to 9 in that the drying and calcining described in step 2② are specifically carried out according to the following steps:

[0066] First, dry at a temperature of 50°C to 55°C for 12h to 48h, then dry at a temperature of 100°C to 150°C for 12h to 48h, then heat to 300°C to 500°C at a heating rate of 2°C / min to 5°C / min, and calcine at a temperature of 300°C to 500°C for 4h to 5h, then heat to 750°C to 850°C at a heating rate of 2°C / min to 5°C / min, and calcine at a temperature of 750°C to 850°C for 5min to 10min, and finally cool to room temperature at a cooling rate of 2°C / min to 5°C / min. Others 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] Embodiment 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 50mPa·s to 60mPa·s; the concentration of the polyvinyl alcohol in the polyvinyl alcohol solution is 0.98g / mL;

[0073] b. Dissolve the micron alumina ceramic powder, nano titanium dioxide and 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, and finally vacuum degas for 30 minutes at a vacuum degree of 0.05 MPa to obtain a micron ceramic powder coating liquid;

[0074] The micron ceramic powder coating liquids are 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 respectively; 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 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 is 0.32g / mL; the concentration of nano titanium dioxide 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 is 0.08g / mL, and the particle size of nano titanium dioxide is 200nm; the concentration of dispersant 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 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 condition of , a 46 μm micron ceramic powder coating liquid was coated on one side of the porous ceramic substrate for 15 seconds, and then dried for 1 minute at a temperature of 60°C, 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 hours to obtain a substrate covered with a micron alumina ceramic film;

[0080] f. Ultrasonic dispersion of nano-alumina ceramic powder ethanol dispersion and nano-titanium dioxide ethanol dispersion for 1 h at a power of 200 W to obtain a mixed dispersion, and anhydrous ethanol is added to the mixed dispersion, and ultrasonic dispersion is performed for 1 h at a power of 200 W to obtain a nano-ceramic powder coating liquid;

[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 liquid is 0.1052 g / mL; the concentration of the nano-titanium dioxide in the nano-ceramic powder coating liquid is 0.017 g / mL;

[0082] g, at a speed of 2000 rpm and a coating volume of 0.25 mL / cm2 Under the condition 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. Raising the temperature to 900° C. at a heating rate of 2° C. / min, and then calcining at 900° C. for 3 hours to obtain a substrate covered with a nano / micron alumina ceramic film;

[0084] 2. Nanoporous LaMn 0.5 Al 0.5 O 3 / LaCu 0.5 Al 0.5 O 3 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 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3 Precursor sol; the precursor is LaMn 0.5 Al 0.5 O 3 or LaMn 0.5 Al 0.5 O 3 ;

[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; 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 / cm 2 Under the conditions of 0.5 Al 0.5 O 3 Precursor sol and LaMn 0.5 Al 0.5 O 3The precursor sol is sequentially coated on the surface of the nano / micron alumina ceramic membrane of the substrate, and then dried at 50°C for 12 hours, then dried at 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, a DL-LMCA ceramic membrane.

[0088] Example 2: This example is different from Example 1 in that the concentration of the micron alumina ceramic powder in the 46μm micron ceramic powder coating solution, 9μm micron ceramic powder coating solution, 5μm micron ceramic powder coating solution and 0.3μm micron ceramic powder coating solution described in step 1b is 0.32g / mL; in step 1e, the temperature is raised to 1250℃ at a heating rate of 5℃ / min, and then calcined at 1250℃ for 5h to obtain a substrate covered with a micron alumina ceramic film; in step 1h, the temperature is raised to 1000℃ at a heating rate of 5℃ / min, and then calcined at 1000℃ for 3h to obtain a substrate covered with a nano / micron alumina ceramic film; in step 2①, the reaction is carried out at a temperature of 45℃ for 10h. The rest is the same as 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, the 9μm micron ceramic powder coating liquid, the 5μm micron ceramic powder coating liquid and the 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 increased to 1150°C at a heating rate of 5°C / min, and then calcined at 1150°C for 5h to obtain a micron alumina ceramic powder coated with The substrate of the ceramic film; in step 1, the temperature is raised to 950°C at a heating rate of 5°C / min, and then calcined at 950°C for 3h to obtain a substrate covered with a nano / micron alumina ceramic film; the molar ratio of citric acid to the precursor in step 2① is 4:0.4; the molar ratio of citric acid to the template in step 2① is 4:0.001; the molar ratio of citric acid to nitric acid in concentrated nitric acid in step 2① is 4:0.2; in step 2①, the reaction is carried out at a temperature of 45°C for 12h. The rest is 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); it can be seen from the figure that 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 O 3 Layer or LaMn 0.5 Al 0.5 O 3 The layer was tested, and only LaCu was coated in step 2② of Example 1. 0.5 Al 0.5 O 3 Precursor sol or LaMn 0.5 Al 0.5 O 3 Precursor sol and other processes are the same as those in Example 1.

[0093] Figure 3 The LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 X-ray diffraction spectrum of the layer; as can be seen from the figure, 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 The LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Layer X-ray diffraction spectrum; 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 O 3 The characteristic peaks of

[0095] Figure 5 The LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Nitrogen absorption and desorption diagram of the layer; Figure 6 The LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O3 The nitrogen absorption and desorption diagram of the layer; through the BET (Brunauer-Emmett-Teller) specific surface area test, it was found that nitrogen and the two materials LaCu 0.5 Al 0.5 O 3 and LaMn 0.5 Al 0.5 O 3 The interaction force between them is weak. Because the C value in the BET formula is less than 2, the C value is usually 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 existed. Type IV isotherms usually appear in mesoporous materials, and the presence of hysteresis loops indicates that there are a certain number of pore structures inside the material. These pore structures give the DL-LMCA ceramic membrane a higher specific surface area, thereby enhancing its adsorption capacity. At the same time, the higher specific surface area also provides more active sites for the catalytic reaction, so this ceramic membrane shows higher efficiency in the catalytic reaction. In summary, the DL-LMCA ceramic membrane can not only effectively adsorb gas due to its rich pore structure and high specific surface area, but also show excellent performance in catalytic reactions.

[0096] Figure 7 The LaCu in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Pore ​​size distribution diagram of the layer; Figure 8 The LaMn in the DL-LMCA ceramic membrane prepared in Example 1 0.5 Al 0.5 O 3 Pore ​​size distribution diagram of the layer; it can be seen from the figure that the pore size of 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 membrane prepared in Examples 1 to 3 was placed in a ceramic membrane filter cup, and then pure water was added. After sealing, the air tightness 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, and the instantaneous water output could be read from the computer to calculate the pure water flux of the membrane. 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 membranes prepared in Examples 1 to 3 were placed in a ceramic membrane filter cup, and then a nano-emulsion solution was added. The airtightness was checked after sealing. By controlling the pressure valve through a program, the measurement experiment of the nano-emulsion was started. The oil and water output from the ultrafiltration cup was measured by a TOC analyzer. By comparing the TOC in the crude oil water, the rejection rates of nano-emulsions with different molecular weights could be obtained, specifically as Fig. 9 and 10 shown. The nano-emulsion solution was specifically prepared according to the following steps: 100 mL of n-hexane and 1 L of water were placed in a homogenizer and treated for 15 min at a rotation speed of 20,000 r / min to obtain a nano-emulsion solution.

[0099] Fig. 9 is the oil rejection rate of the DL-LMCA ceramic membranes prepared in Examples 1 to 3; 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] Fig.10 is the intuitive effect diagram of oil rejection of the DL-LMCA ceramic membranes prepared in Examples 1 to 3; as can be seen from the figure, the filtration effect is very good, and the oily sewage has changed from turbid to clear.

[0101] After the membrane filtered the nano-emulsion solution for 1 hour, from the reverse side of the membrane at a pressure of 0.5 bar, ordinary H 2 O backwashing or H 2 O 2 solution (mass percentage is 1%) was used for backwashing for 5 min; Fig.11 is the membrane cleaning efficiency diagram of the DL-LMCA ceramic membrane prepared in Example 1; as can be seen from the figure, when filtering the emulsion, the emulsion flux at each moment and the initial emulsion flux were recorded. Through the trend of J / J 0 , the performance recovery of the membrane after different cleaning methods can be seen. The cleaning effects of H 2 O 2 and H 2 O have a significant gap. The recovery rate of the ordinary backwashed membrane flux is relatively low, about 10%. The cleaning method of H 2 O 2 can restore its flux to 90%, while the cleaning effect of H 2 O is weak.

[0102] Fig.12 is the schematic 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 nano-emulsion is successfully intercepted. When the usage time becomes longer and the usage cycle becomes more, inevitable problems of the membrane occur - membrane fouling problems. During the cleaning process of the LaCu 0.5 Al 0.5 O 3 membrane, the oxidant H2 O 2 In-situ contact LaCu 0.5 Al 0.5 O 3 The Cu-O-Al active sites in the layer pores react to produce OH, O 2 - The residual H 2 O 2 Then through LaMn 0.5 Al 0.5 O 3 layer, and a large amount of nano-O is produced in the pores catalyzed by the Mn-O-Al active sites. 2 Bubbles are formed in the membrane pores and on the membrane surface to perform an in-situ air washing process, which in turn performs an in-situ backwashing process on the pores that may be blocked by pollutants, helping to alleviate the DL-LMCA ceramic membrane fouling problem.

[0103] Fig.13 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. After the sewage enters from ①, open the left pressure pump ④ to adjust the pressure, and then pass through the inlet pipe of valve ② to enter the ⑤ ceramic membrane assembly for water treatment. The treated water is discharged through the ⑥ water outlet tank. The valve ② at the end of ⑤ can be opened to release the pressure. As the operation cycle becomes longer, membrane contamination occurs, open the ⑦ hydrogen peroxide backwash water tank, and enter ⑤ through the valve to perform in-situ backwashing of the ceramic membrane. The waste liquid after cleaning can be discharged from the 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, coating the micron ceramic powder coating liquid on one side of the porous ceramic substrate and drying, and finally calcining to obtain a substrate covered with a micron alumina ceramic film; ②Using nano-alumina ceramic powder, nano-titanium dioxide and anhydrous ethanol to disperse by ultrasonic to obtain nano-ceramic powder coating liquid, coating the nano-ceramic powder coating liquid on the surface of the micron alumina ceramic film of the substrate and drying, and finally calcining 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 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; The precursor is LaMn 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 double-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 3h to 12h at a rotation speed of 300rpm to 500rpm and a ball-to-material mass ratio of 1:(0.2 to 1), and finally vacuum degas for 30min to 40min at a vacuum degree of -0.08MPa to 0.1MPa to obtain a micron ceramic powder coating liquid; The micron ceramic powder coating liquids are 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 respectively; 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 according to the following steps: 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 condition of , a 40μm-50μm micron ceramic powder coating liquid is applied to one side of the porous ceramic substrate for 10s-25s, and then dried for 1min-3min at a temperature of 50℃-80℃, and the coating and drying are repeated 2-3 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. 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 according to step a.

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 described 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 liquid described in step 1② is specifically prepared according to the following steps: Under the condition of power of 200W to 300W, the nano-alumina ceramic powder ethanol dispersion and the nano-titanium dioxide ethanol dispersion are ultrasonically dispersed for 1h to 2h to obtain a mixed dispersion, anhydrous ethanol is added to the mixed dispersion, and under the condition of power of 200W to 300W, the dispersion is ultrasonically dispersed for 1h to 2h to obtain a nano-ceramic powder coating liquid; The concentration of the nano-alumina ceramic powder in the nano-alumina ceramic powder ethanol dispersion is 0.15g / mL to 0.16g / mL, and the particle size of the nano-alumina ceramic powder is 100nm to 200nm; the concentration of the nano-titanium dioxide in the nano-titanium dioxide ethanol dispersion is 0.15g / mL to 0.16g / mL, and the particle size of the nano-titanium dioxide is 100nm to 200nm; the concentration of the nano-alumina ceramic powder in the nano-ceramic powder coating liquid is 0.10g / mL to 0.11g / mL; the concentration of the nano-titanium dioxide in the nano-ceramic powder coating liquid is 0.01g / mL to 0.02g / 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 according to the following steps: At a speed of 2000 rpm to 2500 rpm and a coating volume of 0.25 mL / cm 2 ~0.3mL / cm 2 Under the condition of , the nano ceramic powder coating liquid is coated on 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 LaCu as described in step 2① 0.5 Al 0.5 O3 precursor sol and LaMn 0.5 Al 0.5 The O3 precursor sol is specifically prepared according to the following steps: the precursor, citric acid, block copolymer template, concentrated nitric acid and tetrahydrofuran are mixed, and then reacted 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=12000-13000; 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); the mass percentage of concentrated nitric acid 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 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 up 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 up 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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