A method and article for simply preparing a ceramic membrane with small pore size, narrow pore size distribution, and high anti-pollution

Abstract

The application provides a method for simply preparing a small-aperture, narrow-aperture-distribution and high-anti-pollution ceramic membrane and an article, and belongs to the technical field of ceramic membrane separation. Specifically, a commercial ceramic membrane with an average aperture of 300-500 nm is used as a base film, ceramic particles with an average particle size of 100-500 nm are used as coating fillers, an inorganic binder is used as a sintering aid, a water-soluble polymer is used as a dispersant, and a surfactant and a defoaming agent are used as auxiliary additives; the above-mentioned components are uniformly mixed to obtain a doctor-blade coating slurry; the slurry is coated on the surface of the commercial ceramic membrane by using a doctor-blade coating method; and a stable ceramic membrane product with chemical bonding between the ceramic particles and the inorganic binder is obtained through sintering treatment. The method has the advantages of simplicity, few steps, easy operation, low sintering temperature, and the prepared membrane has the advantages of small aperture (50-100 nm aperture can be adjusted), narrow aperture distribution (the aperture of 50-100 nm accounts for no less than 95%), excellent separation performance for small-size oil droplets and strong anti-pollution ability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of ceramic membrane separation, and particularly relates to a method for simply preparing a ceramic membrane with small pore size, narrow pore size distribution and high anti-pollution performance and a product thereof. BACKGROUND

[0002] Oil-containing wastewater is commonly generated in the fields of food processing and industrial production, and direct discharge of the wastewater without treatment will pose a serious threat to the ecological system. Oil droplets in the oil-containing wastewater mainly exist in the forms of free oil (>150 μm), dispersed oil (25-150 μm) and emulsified oil (<25 μm), wherein the free oil and the dispersed oil are prone to aggregation and removal under the action of external force; and the emulsified oil droplets are relatively stable due to the adsorption of surfactants on the surface of the emulsified oil droplets, and are not prone to aggregation, thus being difficult to treat. Traditional methods for treating oil-containing wastewater include adsorption, flocculation, biological treatment and gas flotation. However, these methods have poor removal effect on stable small-size emulsified oil droplets, and are difficult to meet the discharge requirements.

[0003] Compared with traditional oil-containing wastewater treatment technologies, membrane separation technology is concerned due to its high separation precision, low cost and low energy consumption. Although the cost of the polymer membrane is low, the polymer membrane is prone to adsorption of oil and thus pollution, which reduces the service life of the polymer membrane, thereby limiting the application of the polymer membrane in oil-containing wastewater. In addition, the emulsified oil droplets are prone to deformation under pressure driving and thus easy to penetrate the membrane with a smaller pore size than the emulsified oil droplets. Compared with the polymer membrane, the inorganic membrane (especially the ceramic membrane) has the advantages of high mechanical strength, good stability, low requirement for the use environment and easy cleaning, but the commercially available ceramic membrane has the problems of large pore size (>200 nm), wide pore size distribution and complex preparation process, which limit the application of the ceramic membrane, and the ceramic membrane has poor separation performance and anti-oil pollution performance for small-size emulsified oil wastewater.

[0004] Currently, the surface layer-by-layer coating-sintering method can effectively reduce the surface layer pore size of ceramic membranes. For example, Chinese invention CN111420562A discloses a preparation method of hollow flat ceramic membrane. The invention uniformly sprays three layers of slurry on the surface of the ceramic support by multiple spraying method, and obtains a ceramic membrane with an average pore size of 40 nm and a porosity of 40% after high temperature sintering. However, the preparation process is complex and requires multiple steps, which limits its application. In addition, the pore size distribution range of the membrane is not clear. CN102701778B patent discloses a preparation method of ceramic membrane with multi-level pore structure. First, ceramic powder and pore-forming agent are used to prepare multiple coating solutions, and a ceramic membrane with gradient distribution of multi-level pore structure is prepared by multiple dipping-coating process. Although the preparation method of this invention can realize the pore size of the third separation layer in the range of 50-100 nm, it has limitations such as long preparation time of the separation layer, high cost, and cannot guarantee the firm combination between multiple separation layers. CN110368818B patent discloses a preparation method of high-flux flat ceramic membrane. The invention uses spraying method to prepare an intermediate transition layer on the surface of the flat ceramic membrane support, and then uses dipping method to prepare a separation membrane layer, and obtains a flat ceramic membrane with an average pore size of 46 nm and a water permeation flux of 420 L m - 2 bar -1 h -1 . However, since the invention requires the combination of spraying technology and dipping process, the preparation process has high technical requirements and multiple steps, which is not suitable for practical application. In addition, for the oil pollution resistance of ceramic membranes, surface modification technology can be used to improve the hydrophilic and hydrophobic properties of the membrane, thereby improving the anti-pollution ability of the ceramic membrane. For example, Chinese invention CN112121647A discloses that ceramic powder is pressed into a ceramic green body by dry pressing method, then immersed in a mixed solution of TEOS and PDMS, and after taking out, it is treated with acid to obtain an oil-water separation ceramic membrane with superhydrophilic and superoleophobic properties. CN116283238A patent discloses a preparation technology of oil-water separation ceramic membrane with stable performance and strong anti-pollution ability. The invention uses alumina and kaolin as main raw materials, and forms an oil-repellent layer on the surface of the ceramic membrane through the catalytic action of ammonium molybdate to construct a mullite whisker, forming a ceramic membrane with superhydrophilic / underwater superoleophobic and good oil-water separation effect. Although the above methods improve the anti-pollution performance of the ceramic membrane, they are limited in application due to complex preparation process, high technical requirements, repeated treatment, and easy decay of hydrophilicity. In addition, the uniformity of the pore size distribution of the membrane and the anti-pollution performance are not clear. In summary, multiple coating processes can reduce the pore size of the membrane, but cannot simplify the pore reduction process, and still have difficulty in solving the bottleneck of wide pore size distribution. Surface modification technology can improve the anti-pollution performance of the membrane, but it is difficult to reduce the pore size of the membrane. Therefore, how to simply and effectively reduce the pore size of the ceramic membrane surface, improve the pore size uniformity and anti-pollution performance is the key to solving the poor oil-water separation efficiency of ceramic membranes.

[0005] On the basis of the above-mentioned limitations, the small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane is prepared by using the doctor blade coating method. Specifically, the commercial ceramic membrane with an average pore size of 300-500 nm is used as the base film, the ceramic particles with an average particle size of 100-500 nm are used as the coating filler, the inorganic binder is used as the sintering aid, the water-soluble polymer is used as the dispersant, and the surfactant and the defoaming agent are used as the auxiliary additives. After mixing, the doctor blade coating slurry is obtained. The slurry is coated on the surface of the commercial ceramic membrane by using the doctor blade coating method, and the sintering treatment is performed to obtain the stable ceramic membrane product with chemical bonding between the ceramic particles and the inorganic binder. The method is simple, has few steps, is easy to operate, has low sintering temperature, and has the advantages of small pore size (50-100 nm pore size can be adjusted), narrow pore size distribution (50-100 nm pore size accounts for not less than 95%), excellent separation performance for small-size oil droplets, and strong anti-pollution ability. SUMMARY

[0006] In view of the existing problems, the present application aims to provide a simple preparation method and product of a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane.

[0007] The technical scheme of the present application is a simple preparation method of a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane. The commercial ceramic membrane with an average pore size of 300-500 nm is used as the base film, the ceramic particles with an average particle size of 100-500 nm are used as the coating filler, the inorganic binder is used as the sintering aid, the water-soluble polymer is used as the dispersant, and the surfactant and the defoaming agent are used as the auxiliary additives. After mixing, the doctor blade coating slurry is obtained. The doctor blade coating method is used to prepare the small-pore ceramic membrane with a pore size in the range of 50-100 nm and a narrow pore size distribution (50-100 nm pore size accounts for not less than 95%).

[0008] The aforementioned simple preparation method of a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane has the following specific steps:

[0009] S1, ceramic particles, inorganic binder, dispersant, surfactant, defoaming agent, and deionized water are mixed in a mass ratio of 20-50:4-30:10-16:0.1-1:0.1-2:25.8-31, and are mixed and stirred in a mixer for 1-5 h to obtain a uniform, viscosity-appropriate coating or coating slurry;

[0010] S2, the obtained slurry is vacuum-deaerated, and is coated on the surface of the ceramic base film under the preset conditions. The coating is dried at 40-100℃ for 12-24 h until the coating is completely dried;

[0011] S3, place the membrane in a muffle furnace and sinter under a set program of 800-1500℃, and keep warm for 1-5h, take out after cooling with the furnace to get the desired ceramic membrane product.

[0012] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the ceramic particles in step S1 are one of alumina, silica, zirconia, silicon carbide, and kaolin.

[0013] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the inorganic binder in step S1 is one of aluminum phosphate, magnesium phosphate, aluminum dihydrogen phosphate, silica sol, and alumina colloid.

[0014] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the dispersant in step S1 is one of polyvinyl alcohol, polyethylene glycol, carboxymethyl cellulose, and polyvinylpyrrolidone.

[0015] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the dissolving temperature of the water-soluble polymer in the ceramic doctoring slurry in step S1 is 35-95℃, and the dissolving time is 1-2h.

[0016] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the surfactant in step S1 is one of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, cetyltrimethylammonium bromide, sodium cetyl sulfate, and sodium octadecyl sulfate.

[0017] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the defoaming agent in step S1 is one of polyethylene glycol fatty alcohol ether, glycerol polyoxypropylene ether, polypropylene glycol, polydimethylsiloxane, and tributyl phosphate.

[0018] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the viscosity control range of the ceramic slurry in step S1 is 300-450mPa s.

[0019] The method for simply preparing a small-pore, narrow-pore-distribution, high-anti-pollution ceramic membrane as described above, the preset conditions of the ceramic coating in step S2 are that the doctoring rate is 30mm-2m min -1 , the ambient temperature is 25-35℃, the ambient humidity is 20%-40%, and the doctoring thickness is 100-500μm.

[0020] The method for simply preparing the ceramic membrane with small pore size, narrow pore size distribution and high anti-pollution according to the foregoing method, the sintering procedure is set in step S3, the sintering temperature of the ceramic membrane is 800-1500 DEG C, the inorganic binder is combined with the ceramic particles through chemical bonds to make the coating and the base membrane firmly connected; wherein, the low-temperature heating stage is room temperature-600 DEG C, the temperature rising rate is 1-2 DEG C / min -1 ; the high-temperature sintering stage is 600 DEG C to the sintering end temperature (800-1500 DEG C) with the temperature rising rate of 1-5 DEG C / min -1 , and the highest temperature is kept for 1-5 h, and the ceramic membrane with small pore size and narrow pore size distribution is obtained after the furnace cooling.

[0021] The product prepared by the method for preparing the ceramic membrane with small pore size, narrow pore size distribution and high anti-pollution according to the foregoing method.

[0022] The beneficial effects of the present application

[0023] The principle of the method for simply preparing the ceramic membrane with small pore size, narrow pore size distribution and high anti-pollution according to the present application is that: in the preparation process of the ceramic membrane with small pore size, narrow pore size distribution and high anti-pollution, the inorganic binder generates M-O oxide rich in covalent bonds at high temperature, and the M-O can be bonded with O and Al in the ceramic particles in the separation layer or the commercially available ceramic base membrane to form covalent bonds, so that the ceramic membrane with small pore size, narrow pore size distribution and high anti-pollution is finally obtained, in which the separation layer and the ceramic base membrane are bonded by covalent bonds, and the large pores on the surface of the base membrane are effectively filled. At the same time, the inorganic binder introduced on the surface of the membrane can bond the ceramic particles at a lower temperature, so that the sintering temperature of the membrane is moderately reduced. In addition, the inorganic binder introduced on the surface of the membrane has strong hydrophilic property and negative charge, so that the membrane has stronger hydrophilic ability and more negative charges. In the oil-water separation process, the surface of the emulsified oil droplets stabilized by the surfactant has a certain amount of negative charges, and when the emulsified oil droplets contact the surface of the membrane, the negative charges on the surface of the membrane will produce electrostatic repulsion to the emulsified oil droplets. Secondly, the pore blocking effect of the inorganic binder can reduce the roughness of the membrane surface and affect the spreading behavior of the emulsified oil droplets on the membrane surface, thereby improving the anti-oil pollution ability of the ceramic membrane. Therefore, the size screening and electrostatic repulsion synergistic effect of the membrane can be utilized to realize the deep treatment of small-size emulsified oil wastewater.

[0024] The advantages and positive effects of this invention are as follows: (1) The operation method is simple. A small-pore ceramic membrane with narrow pore size distribution and high anti-pollution properties (50-100nm pore size adjustable, pore size ratio not less than 95%) can be prepared by a simple scraping method. The method is simple, has few steps, is easy to operate and has obvious effects, and the sintering temperature of the membrane is moderately reduced; (2) The membrane can achieve efficient purification of small-sized emulsified oil wastewater; (3) The membrane's resistance to oil pollution is significantly improved; (4) It effectively solves many limitations in the ceramic preparation process, such as easy detachment of the separation layer, complex preparation process and high sintering temperature. (5) This method is applicable to ceramic membranes of various configurations such as flat plate, tubular, and multi-channel. Detailed Implementation

[0025] The technical approach of this invention in its specific implementation will be described in detail and completely. It should be noted that the implementation process and technical approach mentioned above represent only a small part of the key achievements involved in this invention, and do not list all the technical requirements in detail. Based on specific implementation schemes, all other specific embodiments obtained by those skilled in the art under the technical approach of this invention without creative effort are within the protection scope of this invention.

[0026] Example 1:

[0027] S1. Calculate by mass fraction, take 60 parts of ceramic particles (alumina) with an average particle size of 500nm, 4 parts of inorganic binder (magnesium phosphate), 10 parts of dispersant (polyvinyl alcohol), 0.1 parts of surfactant (sodium dodecyl sulfate), 0.1 parts of defoamer (polyethylene glycol fatty alcohol ether), and 25.8 parts of deionized water, add them to a mixer and mix for 5 hours to obtain a uniform coating or coating slurry with appropriate viscosity;

[0028] S2. After vacuum degassing, the obtained slurry is coated onto the surface of a ceramic substrate at 25°C using a coating speed of 30 mm / min. -1 The ambient humidity was 20%, the film thickness was 100μm, and the coating was dried at 40℃ for 24h until it was completely dry.

[0029] S3. Subsequently, the membrane is placed in a muffle furnace and sintered under the set program; firstly, the low-temperature sintering stage is from room temperature to 600℃, with a heating rate of 1℃ / min. -1 Subsequently, during the high-temperature sintering stage, the temperature was 1℃ min. -1 The heating rate was increased from 600℃ to 800℃, and the temperature was held at 800℃ for 5 hours. After cooling in the furnace, the product was taken out to obtain the desired ceramic film product.

[0030] The 99 nm pore size of the ceramic membrane accounted for 96.2%, the oil-water separation efficiency was 96.4%, and the flux recovery rate after 10 cycles was 95.5%. The 497 nm pore size of the flat ceramic membrane accounted for 27.9%, the oil removal efficiency was 28.4%, and the flux recovery rate after 10 cycles was 30.2%.

[0031] Example 2

[0032] S1, according to the mass fraction, take 55 parts of ceramic particles (zirconium oxide) with an average particle size of 500 nm, 7 parts of inorganic binder (silica sol), 11 parts of dispersing agent (polyethylene glycol), 0.2 parts of surfactant (sodium dodecyl benzene sulfonate), 0.4 parts of defoaming agent (glycerol polyoxypropylene ether) and 26.4 parts of deionized water, add them into a mixer and mix and stir for 4 h to obtain a uniform coating or coating slurry with appropriate viscosity;

[0033] S2, the obtained slurry is vacuum degassed and then scraped on the surface of the ceramic membrane at 28℃, the scraping rate is 100mmmin- 1 , the environmental humidity is 30%, the film thickness is 200μm, and the coating is dried at 50℃ for 22h until it is completely dry;

[0034] S3, then put the membrane in a muffle furnace and sinter it under a set program; first, the low-temperature sintering stage is room temperature-600℃, the heating rate is 1℃ min -1 ; then, in the high-temperature sintering stage, the temperature is heated from 600℃ to 900℃ at a heating rate of 1℃ min -1 , and kept at 900℃ for 5h, then taken out after cooling in the furnace to obtain the desired ceramic membrane product.

[0035] The 97 nm pore size of the ceramic membrane accounted for 95.7%, the oil-water separation efficiency was 96.8%, and the flux recovery rate after 10 cycles was 95.9%. The 497 nm pore size of the flat ceramic membrane accounted for 27.9%, the oil removal efficiency was 28.4%, and the flux recovery rate after 10 cycles was 30.2%.

[0036] Example 3

[0037] S1, according to the mass fraction, take 55 parts of ceramic particles (zirconium oxide) with an average particle size of 500 nm, 7 parts of inorganic binder (silica sol), 11 parts of dispersing agent (polyethylene glycol), 0.2 parts of surfactant (sodium dodecyl benzene sulfonate), 0.4 parts of defoaming agent (glycerol polyoxypropylene ether) and 26.4 parts of deionized water, add them into a mixer and mix and stir for 4 h to obtain a uniform coating or coating slurry with appropriate viscosity;

[0038] S2, the obtained slurry is vacuum degassed and then scraped on the surface of the ceramic membrane at 28℃, the scraping rate is 100mmmin- 1 , the environmental humidity is 30%, the film thickness is 200μm, and the coating is dried at 50℃ for 22h until it is completely dry;

[0034] S3, then put the membrane in a muffle furnace and sinter it under a set program; first, the low-temperature sintering stage is room temperature-600℃, the heating rate is 1℃ min -1 ; then, in the high-temperature sintering stage, the temperature is heated from 600℃ to 900℃ at a heating rate of 1℃ min -1 , and kept at 900℃ for 5h, then taken out after cooling in the furnace to obtain the desired ceramic membrane product.

[0035] The 97 nm pore size of the ceramic membrane accounted for 95.7%, the oil-water separation efficiency was 96.8%, and the flux recovery rate after 10 cycles was 95.9%. The 497 nm pore size of the flat ceramic membrane accounted for 27.9%, the oil removal efficiency was 28.4%, and the flux recovery rate after 10 cycles was 30.2%.

[0036] Example 3

[0037] S1, according to the mass fraction, take 55 parts of ceramic particles (zirconium oxide) with an average particle size of 500 nm, 7 parts of inorganic binder (silica sol), 11 parts of dispersing agent (polyethylene glycol), 0.2 parts of surfactant (sodium dodecyl benzene sulfonate), 0.4 parts of defoaming agent (glycerol polyoxypropylene ether) and 26.4 parts of deionized water, add them into a mixer and mix and stir for 4 h to obtain a uniform coating or coating slurry with appropriate viscosity;-1 , the ambient humidity was 30%, the film thickness was 200 μm, and the coating was dried at 60°C for 20 h until the coating was completely dry;

[0039] S3, the film was then placed in a muffle furnace and sintered under a set program; first, a low-temperature sintering stage was room temperature to 600°C at a temperature increasing rate of 1°C / min -1 ; then, a high-temperature sintering stage was performed, in which the temperature was increased from 600°C to 1000°C at a temperature increasing rate of 2°C / min -1 , and the temperature was kept at 1000°C for 4 h, and the film was removed after furnace cooling to obtain the desired ceramic membrane product.

[0040] It was determined that the ceramic membrane had a pore size of 89 nm, accounting for 97.4%, an oil-water separation efficiency of 98.1%, and a flux recovery rate of 97.3% after ten cycles. The multi-channel flat ceramic membrane used had a pore size of 425 nm, accounting for 37.8%, an oil removal efficiency of 35.4%, and a flux recovery rate of 36.1% after ten cycles.

[0041] Example 4:

[0042] S1, 45 parts of ceramic particles (kaolin) with an average particle size of 400 nm, 13 parts of inorganic binder (aluminum phosphate), 13 parts of dispersant (polyvinyl alcohol), 0.4 parts of surfactant (sodium lauryl sulfate), 1 part of defoaming agent (polydimethylsiloxane), and 27.6 parts of deionized water were mixed and stirred in a mixer for 3 h to obtain a uniform coating or coating slurry with appropriate viscosity;

[0043] S2, the obtained slurry was vacuum degassed and then coated on the surface of the ceramic membrane at 32°C at a coating speed of 500 mm / min -1 , the ambient humidity was 40%, the film thickness was 300 μm, and the coating was dried at 70°C for 18 h until the coating was completely dry;

[0044] S3, the film was then placed in a muffle furnace and sintered under a set program; first, a low-temperature sintering stage was room temperature to 600°C at a temperature increasing rate of 2°C / min -1 ; then, a high-temperature sintering stage was performed, in which the temperature was increased from 600°C to 1100°C at a temperature increasing rate of 2°C / min -1 , and the temperature was kept at 1100°C for 3 h, and the film was removed after furnace cooling to obtain the desired ceramic membrane product.

[0045] It was determined that the ceramic membrane had a pore size of 86 nm, accounting for 96.9%, an oil-water separation efficiency of 98.5%, and a flux recovery rate of 97.4% after ten cycles. The multi-channel flat ceramic membrane used had a pore size of 425 nm, accounting for 37.8%, an oil removal efficiency of 35.4%, and a flux recovery rate of 36.1% after ten cycles.

[0046] Example 5:

[0047] S1, 40 parts of ceramic particles (silicon dioxide) with an average particle size of 300 nm, 16 parts of inorganic binder (aluminum dihydrogen phosphate), 14 parts of dispersant (polyvinylpyrrolidone), 0.5 parts of surfactant (sodium octadecyl sulfate), 1.3 parts of defoaming agent (tributyl phosphate), and 28.2 parts of deionized water were mixed and stirred in a mixer for 2 h to obtain a uniform coating or coating slurry with appropriate viscosity;

[0048] S2, the obtained slurry was vacuum degassed and then coated on the surface of the ceramic base film at 35°C at a coating rate of 800 mm / min -1 , the environmental humidity was 30%, the film thickness was 200 μm, and the coating was dried at 80°C for 16 h until it was completely dry;

[0049] S3, then the film was placed in a muffle furnace and sintered under a set program; first, the low-temperature sintering stage was room temperature to 600°C at a heating rate of 2°C / min -1 ; then, the high-temperature sintering stage was heated from 600°C to 1200°C at a heating rate of 3°C / min -1 , and kept at 1200°C for 2 h, and then removed after cooling in the furnace to obtain the desired ceramic film product.

[0050] It was determined that the ceramic membrane had a pore size of 70 nm accounting for 97.9%, an oil-water separation efficiency of 98.6%, and a flux recovery rate of 97.8% after ten cycles. The flat ceramic base film used had a pore size of 363 nm accounting for 44.1%, an oil removal efficiency of 43.7%, and a flux recovery rate of 40.5% after ten cycles.

[0051] Example 6:

[0052] S1, 40 parts of ceramic particles (silicon dioxide) with an average particle size of 300 nm, 16 parts of inorganic binder (aluminum dihydrogen phosphate), 14 parts of dispersant (polyvinylpyrrolidone), 0.5 parts of surfactant (sodium octadecyl sulfate), 1.3 parts of defoaming agent (tributyl phosphate), and 28.2 parts of deionized water were mixed and stirred in a mixer for 2 h to obtain a uniform coating or coating slurry with appropriate viscosity;

[0053] S2, the obtained slurry was vacuum degassed and then coated on the surface of the ceramic base film at 35°C at a coating rate of 800 mm / min -1 , the environmental humidity was 30%, the film thickness was 200 μm, and the coating was dried at 80°C for 16 h until it was completely dry;

[0054] S3. Subsequently, the membrane is placed in a muffle furnace and sintered under the set program; firstly, the low-temperature sintering stage is from room temperature to 600℃, with a heating rate of 2℃ / min. -1 Subsequently, during the high-temperature sintering stage, the temperature was 3℃ min. -1 The heating rate was increased from 600℃ to 1300℃, and the temperature was held at 1300℃ for 3 hours. After cooling in the furnace, the product was taken out to obtain the desired ceramic film product.

[0055] Measurements showed that the ceramic membrane had a pore size of 68 nm accounting for 97.2%, an oil-water separation efficiency of 99.2%, and a flux recovery rate of 98.5% after ten cycles. In contrast, the flat-panel ceramic membrane used had a pore size of 363 nm accounting for 44.1%, an oil removal efficiency of 43.7%, and a flux recovery rate of 40.5% after ten cycles.

[0056] Example 7:

[0057] S1. Calculate by mass fraction, take 30 parts of ceramic particles (kaolin) with an average particle size of 200nm, 23 parts of inorganic binder (silica sol), 15 parts of dispersant (polyvinylpyrrolidone), 0.7 parts of surfactant (sodium octadecyl sulfate), 1.7 parts of defoamer (polydimethylsiloxane), and 29.6 parts of deionized water, mix and stir in a mixer for 1 hour to obtain a uniform coating or coating slurry with suitable viscosity;

[0058] S2. After vacuum degassing, the obtained slurry is coated onto the surface of a ceramic substrate at 28°C using a coating rate of 1 m / min. -1 The ambient humidity was 30%, the film thickness was 300μm, and it was dried at 90℃ for 14 hours until the coating was completely dry.

[0059] S3. Subsequently, the membrane is placed in a muffle furnace and sintered under the set program; firstly, the low-temperature sintering stage is from room temperature to 600℃, with a heating rate of 2℃ / min. -1 Subsequently, during the high-temperature sintering stage, the temperature was 4℃ min. -1 The heating rate was increased from 600℃ to 1400℃, and the temperature was held at 1400℃ for 2 hours. After cooling in the furnace, the product was taken out to obtain the desired ceramic film product.

[0060] Measurements showed that the ceramic membrane had a pore size of 59nm accounting for 97%, an oil-water separation efficiency of 100%, and a flux recovery rate of 98.6% after ten cycles. In contrast, the flat ceramic membrane used had a pore size of 327nm accounting for 47.2%, an oil removal efficiency of 46.5%, and a flux recovery rate of 41.8% after ten cycles.

[0061] Example 8:

[0062] S1. Calculate by mass fraction, take 25 parts of ceramic particles (zirconia) with an average particle size of 200nm, 26 parts of inorganic binder (aluminum dihydrogen phosphate), 15 parts of dispersant (polyvinyl alcohol), 0.8 parts of surfactant (sodium dodecylbenzene sulfonate), 1.9 parts of defoamer (polyethylene glycol fatty alcohol ether), and 31.3 parts of deionized water, mix and stir in a mixer for 3 hours to obtain a uniform coating or coating slurry with appropriate viscosity;

[0063] S2. After vacuum degassing, the obtained slurry is coated onto the surface of a ceramic substrate at 30°C using a coating rate of 2 m / min. -1 The ambient humidity was 30%, the film thickness was 500μm, and it was dried at 95℃ for 13 hours until the coating was completely dry.

[0064] S3. Subsequently, the membrane is placed in a muffle furnace and sintered under the set program; firstly, the low-temperature sintering stage is from room temperature to 600℃, with a heating rate of 1℃ / min. -1 Subsequently, during the high-temperature sintering stage, the temperature was 4℃ for 4 minutes. -1 The heating rate was increased from 600℃ to 1450℃, and the temperature was held at 1450℃ for 2 hours. After cooling in the furnace, the product was taken out to obtain the desired ceramic film product.

[0065] Measurements showed that the ceramic membrane had a pore size of 57nm accounting for 97.9%, an oil-water separation efficiency of 100%, and a flux recovery rate of 98.1% after ten cycles. In contrast, the flat-panel ceramic-based membrane had a pore size of 327nm accounting for 47.2%, an oil removal efficiency of 46.5%, and a flux recovery rate of 41.8% after ten cycles.

[0066] Example 9:

[0067] S1. Calculate by mass fraction, take 20 parts of ceramic particles (zirconia) with an average particle size of 100nm, 30 parts of inorganic binder (silica sol), 16 parts of dispersant (polyethylene glycol), 1 part of surfactant (sodium hexadecyl sulfate), 2 parts of defoamer (tributyl phosphate) and 31 parts of deionized water, mix and stir in a mixer for 3 hours to obtain a uniform coating or coating slurry with appropriate viscosity;

[0068] S2. After vacuum degassing, the obtained slurry is coated onto the surface of a ceramic substrate at 35°C using a coating rate of 1 m / min. -1 The ambient humidity is 30%, the film thickness is 400 μm, and it is dried at 100℃ for 12 hours until the coating is completely dry.

[0069] S3. Subsequently, the membrane is placed in a muffle furnace and sintered under the set program; firstly, the low-temperature sintering stage is from room temperature to 600℃, with a heating rate of 1℃ / min. -1 Subsequently, during the high-temperature sintering stage, the temperature was 5℃ for 5 minutes. -1The temperature is heated from 600℃ to 1500℃ at a heating rate of 10℃ / min, and the temperature is kept at 1500℃ for 1h, and then the ceramic membrane product is obtained after the furnace is cooled and taken out.

[0070] It is determined that the ceramic membrane aperture of 50nm accounts for 98.3%, the oil-water separation efficiency is 100%, and the flux recovery rate after ten cycles is 98.9%. While the flat ceramic membrane used has an aperture of 305nm accounting for 47.2%, the oil removal efficiency is 49.2%, and the flux recovery rate after ten cycles is 51.8%.

Claims

1. A simple method for preparing ceramic membranes with small pore size, narrow pore size distribution, and high anti-fouling properties, characterized in that: A commercial ceramic membrane with an average pore size of 300-500 nm is used as a base membrane, ceramic particles with an average particle size of 100-500 nm are used as coating fillers, an inorganic binder is used as a sintering aid, a water-soluble polymer is used as a dispersant, and a surfactant and a defoaming agent are used as auxiliary additives. After mixing, a scraping coating slurry is obtained, and a small-pore ceramic membrane is prepared by scraping coating. The proportion of pores with a size of 50-100 nm is not less than 95%.

2. A method for simply preparing a ceramic membrane having a small pore diameter, a narrow pore diameter distribution, and high pollution resistance, characterized by, The specific steps are as follows: S1. Ceramic particles with an average particle size of 100-500 nm, an inorganic binder, a water-soluble polymer, a surfactant, a defoaming agent, and deionized water are mixed in a mass ratio of 20-60:4-30:10-16:0.1-1:0.1-2:25.8-31, added to a mixer, and mixed and stirred for 1-5 h to obtain a uniform ceramic scraping coating slurry with appropriate viscosity. The viscosity control range is 300-450 mPa s; S2. The obtained ceramic scraping coating slurry is vacuum degassed and scraped onto the surface of a commercial ceramic membrane with an average pore size of 300-500 nm under pre-set conditions, and dried at 40-100℃ for 12-24 h until the ceramic coating is completely dry; S3, the film is placed in a muffle furnace and sintered at a set program of 800-1500°C, the low-temperature heating stage is room temperature-600°C, and the temperature rising rate is 1-2°C / min -1 ; The high-temperature sintering stage is 600°C to the sintering end temperature 800-1500°C, using a 1-5°C / min -1 heating rate, and holding for 1-5h, and after furnace cooling, the desired ceramic membrane product is obtained.

3. The method for simply preparing a ceramic membrane with a small pore size, a narrow pore size distribution, and high pollution resistance according to claim 2, characterized in that: The ceramic particles in step S1 are one of alumina, silica, zirconia, silicon carbide, and kaolin.

4. The method for easily preparing a ceramic membrane having a small pore size, a narrow pore size distribution, and high pollution resistance according to claim 2, characterized in that: The inorganic binder in step S1 is one of aluminum phosphate, magnesium phosphate, aluminum dihydrogen phosphate, silica sol, and alumina colloid.

5. The method for easily preparing a ceramic membrane having a small pore size, a narrow pore size distribution, and high pollution resistance according to claim 2, characterized in that: The water-soluble polymer in step S1 is one of polyvinyl alcohol, polyethylene glycol, carboxymethyl cellulose, and polyvinylpyrrolidone.

6. The method for easily preparing a ceramic membrane having a small pore size, a narrow pore size distribution, and high pollution resistance according to claim 2, characterized in that: The water-soluble polymer in the ceramic scraping coating slurry in step S1 has a dissolution temperature of 35-95℃ and a dissolution time of 1-2 h.

7. The method for easily preparing a ceramic membrane having a small pore size, a narrow pore size distribution, and high pollution resistance according to claim 2, characterized in that: The surfactant in step S1 is one of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, cetyltrimethylammonium bromide, sodium cetyl sulfate, and sodium octadecyl sulfate.

8. The method for easily preparing a ceramic membrane having a small pore size, a narrow pore size distribution, and high pollution resistance according to claim 2, characterized in that: The defoaming agent in step S1 is one of polyethylene glycol fatty alcohol ether, glycerol polyoxypropylene ether, polypropylene glycol, polydimethylsiloxane, and tributyl phosphate.

9. The method for easily preparing a ceramic membrane having a small pore size, a narrow pore size distribution, and high pollution resistance according to claim 2, characterized in that: The pre-set conditions for scraping the ceramic coating in step S2 are a scraping rate of 30 mm to 2 m / min. -1 The ambient temperature is 25–35℃, the ambient humidity is 20%–40%, and the film thickness is 100–500μm.

10. The product prepared by the method of claim 1 or 2.