A preparation method of a prussian blue-like inorganic fine separation membrane based on interface confinement principle

Abstract

A preparation method of a Prussian blue-like inorganic fine separation membrane based on interface confinement principle belongs to the technical field of inorganic membrane material preparation. The present application solves the problems of complicated preparation process, high cost, low separation precision, large permeation resistance and easy cracking in the calcination process of the existing inorganic membrane. The method comprises the following steps: one, porous ceramic substrate preparation; two, preparation of Prussian blue-like thin film. The present application is used for the preparation of Prussian blue-like inorganic fine separation membrane based on interface confinement principle.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of inorganic membrane material preparation. BACKGROUND

[0002] Inorganic membranes are membranes with separation function made of ceramic, metal, oxide and carbon materials, etc. Due to good mechanical strength, chemical stability and thermal stability, inorganic membranes show good stability, repeatability and long service life in practical engineering applications. Therefore, inorganic membranes are paid attention to in the fields of chemical industry, environmental protection, medical treatment and food processing, etc.

[0003] Most of the current inorganic membrane materials adopt asymmetric structure, which helps the membrane material to have good separation capacity while maintaining high permeability. Especially in the preparation process of fine inorganic membrane materials, the pore structure and thickness of the separation layer have a great influence on the overall performance of the membrane. However, the current inorganic membrane preparation process generally has problems such as complicated preparation process, high cost, etc. The separation precision of fine inorganic membrane materials is still low and the permeation resistance is large, and the inorganic membrane separation layer is prone to cracking during calcination, which leads to significant degradation of the membrane performance, which greatly limits the popularization and application of inorganic membrane materials. Therefore, developing a simple and mild preparation method of high-performance inorganic membrane separation layer is the key to simplifying the inorganic membrane preparation process, improving the performance of inorganic membranes and promoting the development and application of inorganic membrane technology. SUMMARY

[0004] The application aims to solve the problems of complicated preparation process, high cost, low separation precision and large permeation resistance in the current inorganic membrane preparation process, and further provides a preparation method of Prussian blue-like inorganic fine separation membrane based on interface confinement principle.

[0005] A preparation method of Prussian blue-like inorganic fine separation membrane based on interface confinement principle, which is carried out according to the following steps:

[0006] I. Preparation of porous ceramic substrate:

[0007] ①Polyether sulfone and polyvinylpyrrolidone are dissolved in N-methylpyrrolidone and ball milled, then Al2O3 powder and TiO2 powder are added and ball milled, and finally vacuum degassing and standing are carried out to obtain a casting solution;

[0008] ②The nano-TiO2 ethanol dispersion liquid and nano-Al2O3 ethanol dispersion liquid are mixed and ultrasonically dispersed, then added to anhydrous ethanol and continuously ultrasonically dispersed to obtain a dispersion liquid;

[0009] ③The casting solution is coated on the ceramic membrane substrate by spin coating, and after spin coating, it is immersed in ultrapure water and finally dried to obtain a ceramic membrane coated with the casting solution, and the ceramic membrane coated with the casting solution is sintered to obtain a sintered ceramic membrane;

[0010] (4) using a spin coating method, the dispersion liquid is coated on the surface of the sintered ceramic film and dried;

[0011] (5) repeating steps (1) to (4) three to six times, and finally calcining to obtain the coated porous ceramic substrate;

[0012] II. Preparation of Prussian Blue Analog Film

[0013] (1) Preparation of water phase solution for Prussian Blue Analog Film: potassium ferricyanide is dissolved in ultrapure water to obtain a potassium ferricyanide water phase solution;

[0014] (2) Preparation of oil phase solution for Prussian Blue Analog Film: acetylacetone salt is dissolved in n-hexane and ultrasonically treated in a water bath to obtain an acetylacetone salt oil phase solution;

[0015] (3) Using a rubber ring seal, the potassium ferricyanide water phase solution is poured onto the surface of the coated porous ceramic substrate for immersion treatment, and then dried to obtain a porous ceramic substrate treated with water phase;

[0016] (4) Using a rubber ring seal, the acetylacetone salt oil phase solution is poured onto the surface of the porous ceramic substrate treated with water phase to deposit uniformly, to obtain a porous ceramic substrate treated with water phase and oil phase;

[0017] (5) Drying the porous ceramic substrate treated with water phase and oil phase to obtain a Prussian Blue Analog inorganic fine separation film based on the principle of interface confinement.

[0018] The beneficial effects of the present application are:

[0019] (1) The present application uses an interfacial polymerization method to limit the crystallization and growth orientation of Prussian Blue Analog substances in the water-oil interface confinement space, and constructs a Prussian Blue Analog film preparation method on the surface of a porous ceramic. The method has mild conditions, flexible and simple operation, and the raw materials are relatively easy to obtain.

[0020] (2) The Prussian Blue Analog film prepared by the present application has a relatively thin and complete defect-free thickness, and the Prussian Blue Analog inorganic fine separation film has a complete and dense surface and is not prone to cracking. Compared with conventional methods for preparing fine ceramic separation membranes, the present application has higher permeation performance and better inorganic salt and dye separation effect, with a pure water flux of 290 L / h·m 2 bar or more, the rejection rate of divalent inorganic salt (MgSO4) can reach 20%, the rejection rate of Congo red dye can reach 95%, and the rejection rate of methyl blue dye can reach 88%, and the inorganic fine separation film has high stability and long service life.

[0021] The present application relates to a preparation method of a Prussian Blue Analog inorganic fine separation film based on the principle of interface confinement.

[0022] Drawings of the specification

[0023] Figure 1 Surface scanning electron micrograph of the Prussian blue analogue inorganic fine separation membrane prepared in Example 1;

[0024] Figure 2 Cross-sectional scanning electron micrograph of the Prussian blue analogue inorganic fine separation membrane prepared in Example 1;

[0025] Figure 3 XRD pattern of the Prussian blue analogue inorganic fine separation membrane prepared in Example 1;

[0026] Figure 4 Zeta potential of the ceramic membrane substrate and the Prussian blue analogue thin film in the Prussian blue analogue inorganic fine separation membrane prepared in Example 1;

[0027] Figure 5 Retention rate of inorganic salts and dyes of the Prussian blue analogue inorganic fine separation membrane prepared in Example 1 and the conventional fine ceramic membrane, a is the conventional fine ceramic membrane, b is the Prussian blue analogue inorganic fine separation membrane;

[0028] Figure 6 Pure water flux and retention rate of Congo red dye of the Prussian blue analogue inorganic fine separation membrane prepared in Example 1;

[0029] Figure 7 Pure water flux and retention rate of Congo red dye of the Prussian blue analogue inorganic fine separation membrane prepared in Example 2;

[0030] Figure 8 Pure water flux and retention rate of Congo red dye of the Prussian blue analogue inorganic fine separation membrane prepared in Example 3;

[0031] Figure 9 Pure water flux and retention rate of Congo red dye of the Prussian blue analogue inorganic fine separation membrane prepared in Example 4. DETAILED DESCRIPTION

[0032] Detailed implementation one: a preparation method of the Prussian blue analogue inorganic fine separation membrane based on the interface confinement principle, which is carried out according to the following steps:

[0033] I. Preparation of porous ceramic substrate:

[0034] ①Dissolve polyether sulfone and polyvinylpyrrolidone in N-methylpyrrolidone and ball mill, then add Al2O3 powder and TiO2 powder and ball mill, and finally vacuum degassing and standing to obtain a casting solution;

[0035] ②Mix the nano-TiO2 ethanol dispersion and nano-Al2O3 ethanol dispersion and ultrasonic dispersion, then add to anhydrous ethanol and continue ultrasonic dispersion to obtain a dispersion;

[0036] ③Using a spin coating method, the casting solution is coated on the ceramic membrane substrate, and after spin coating, it is immersed in ultrapure water, and finally dried to obtain a ceramic membrane coated with a casting solution. The ceramic membrane coated with the casting solution is sintered to obtain a sintered ceramic membrane;

[0037] ④Using a spin coating method, the dispersion liquid is coated on the surface of the sintered ceramic membrane and dried;

[0038] ⑤Repeat steps 1-4 three to six times, and finally calcine to obtain a coated porous ceramic substrate;

[0039] II. Preparation of Prussian Blue Analog Thin Film:

[0040] ①Preparation of water phase solution for Prussian Blue Analog Thin Film: Dissolve potassium ferricyanide in ultrapure water and stir to obtain a potassium ferricyanide water phase solution;

[0041] ②Preparation of oil phase solution for Prussian Blue Analog Thin Film: Dissolve acetylacetone salt in n-hexane and ultrasonic water bath to obtain an acetylacetone salt oil phase solution;

[0042] ③Using a rubber ring seal, pour the potassium ferricyanide water phase solution onto the surface of the coated porous ceramic substrate for immersion treatment, and then dry to obtain a porous ceramic substrate treated with water phase;

[0043] ④Using a rubber ring seal, pour the acetylacetone salt oil phase solution onto the surface of the porous ceramic substrate treated with water phase to deposit uniformly, to obtain a porous ceramic substrate treated with water phase and oil phase;

[0044] ⑤Dry the porous ceramic substrate treated with water phase and oil phase to obtain a Prussian Blue Analog Inorganic Fine Separation Membrane based on the principle of interface confinement.

[0045] Principle: The prior art Prussian blue-like crystals are usually grown in solution to form micron-sized bulk. In order to ensure that the interface between the oil phase solution and the aqueous phase solution is formed only on the surface of the porous ceramic substrate, the periphery of the porous substrate is sealed with a rubber ring, and only the surface is exposed during the reaction period. First, pour the aqueous phase solvent, and then pour the oil phase solution. The oil phase solution does not need to be dried during the oil phase solution treatment. Since the oil phase and the aqueous phase are not miscible, the oil phase forms an oil phase solution-porous substrate / aqueous phase solution interface on the surface of the porous substrate. Metal ions diffuse from the oil phase into the aqueous phase and form nanoscale Prussian blue-like crystal grains by coordinating with potassium ferricyanide. Since potassium ferricyanide and Prussian blue-like crystals are insoluble in the oil phase, the oil phase solution-porous substrate / aqueous phase solution interface greatly limits the growth of Prussian blue-like crystals, and a thin film of Prussian blue-like crystals is formed on the surface of the porous substrate, with a thickness of nanometers. This is completely different from the micron-sized granular Prussian blue-like crystals prepared by conventional methods. The Prussian blue-like film of the present embodiment has good adsorption and screening ability, and can have good separation effect on inorganic salts and dyes in water. In the present embodiment, the Prussian blue film is loaded on the porous ceramic substrate in a new way, and a Prussian blue-like inorganic fine separation membrane with high separation precision and high permeability is prepared.

[0046] The beneficial effects of the present embodiment are:

[0047] (1) The present embodiment utilizes the interface polymerization method to limit the crystallization and growth orientation of Prussian blue-like substances in the water-oil interface limited space, and constructs a preparation method of Prussian blue-like film on the surface of the porous ceramic. The method has mild conditions, flexible and simple operation mode, and raw materials are relatively easy to obtain.

[0048] (2) The Prussian blue-like film prepared by the present embodiment is thin and complete without defects, and the surface of the Prussian blue-like inorganic fine separation membrane is complete and dense and not easy to crack. Compared with the fine ceramic separation membrane prepared by the conventional method, the present embodiment has higher permeability and better inorganic salt and dye separation effect. The pure water flux is 290 L / h·m 2 above, the rejection rate of divalent inorganic salt (MgSO4) can reach 20%, the rejection rate of Congo red dye can reach 95%, and the rejection rate of methyl blue dye can reach 88%. The inorganic fine separation membrane has high stability and long service life.

[0049] Specific embodiment two: the embodiment is different from the specific embodiment one: in step one ①, polyether sulfone and polyvinyl pyrrolidone are dissolved in N-methyl pyrrolidone, under the condition of 300 rpm ~ 400 rpm, ball milling 2h ~ 3h, then adding Al2O3 powder and TiO2 powder, under the condition of 300 rpm ~ 400 rpm, ball milling 24h ~ 48h, ball milling vacuum degassing 30 min ~ 60 min, finally standing, get casting solution; The mass ratio of polyether sulfone and polyvinyl pyrrolidone is 1:(0.1 ~ 0.4); The mass ratio of polyether sulfone and N-methyl pyrrolidone is 1:(3.0 ~ 7.3); The mass ratio of polyether sulfone and Al2O3 powder is 1:(7.0 ~ 16.0); The mass ratio of polyether sulfone and TiO2 powder is 1:(0.3 ~ 2.0); The particle size of Al2O3 powder is 0.3 μm ~ 3.0 μm; The particle size of TiO2 powder is 0.1 μm ~ 5.0 μm. The others are the same as specific embodiment one.

[0050] Specific embodiment three: the embodiment is different from one of the specific embodiment one or two: in step one ②, nano TiO2 ethanol dispersion and nano Al2O3 ethanol dispersion are mixed, under the condition of 120 W ~ 240 W, ultrasonic dispersion 1h ~ 2h, then added to anhydrous ethanol, under the condition of 120 W ~ 240 W, continue ultrasonic dispersion 1h ~ 2h; The mass percentage of nano TiO2 in nano TiO2 ethanol dispersion is 10% ~ 20%, the particle size is 0.1 μm ~ 0.3 μm; The mass percentage of nano Al2O3 in nano Al2O3 ethanol dispersion is 10% ~ 20%, the particle size is 0.1 μm ~ 0.3 μm; The volume ratio of nano TiO2 ethanol dispersion and nano Al2O3 ethanol dispersion is 1:(3.5 ~ 5.7); The volume ratio of nano TiO2 ethanol dispersion and anhydrous ethanol is 1:(4.0 ~ 5.5). The others are the same as specific embodiment one or two.

[0051] Specific embodiment four: the embodiment is different from one of the specific embodiment one to three: in step one ③, the casting solution is coated on the ceramic membrane substrate by spin coating method, under the condition of 1500 rpm ~ 2500 rpm and coating amount of 1 mL / cm 2 ~ 3 mL / cm 2 , after spin coating, immerse in ultrapure water within 30 s ~ 60 s for 5h ~ 10h, finally dry at temperature of 40℃ ~ 60℃, get the ceramic membrane coated with casting solution, put the ceramic membrane coated with casting solution in the tube furnace at temperature of 1200℃ ~ 1400℃ for sintering 3h ~ 7h; The pore size of the ceramic membrane substrate is 0.2 μm ~ 0.5 μm. The others are the same as specific embodiment one to three.

[0052] Specific embodiment five: the difference between this embodiment and the first four embodiments is that: step one ④, the dispersion solution is coated on the surface of the sintered ceramic membrane by spin coating method under the conditions of 1500 rpm ~ 2000 rpm and 0.2 mL / cm 2 ~ 0.5 mL / cm 2 coating amount, and then dried at a temperature of 40 ℃ ~ 60 ℃ for 30 s ~ 120 s; step one ⑤, calcined in a muffle furnace at a temperature of 800 ℃ ~ 1000 ℃ for 2 h ~ 4 h. The others are the same as the first four embodiments.

[0053] Specific embodiment six: the difference between this embodiment and the first five embodiments is that: in step two ①, potassium ferricyanide is dissolved in ultrapure water, then stirred at a temperature of 20 ℃ ~ 30 ℃ and a speed of 350 rpm ~ 400 rpm for 1 h ~ 2 h to obtain a potassium ferricyanide aqueous solution; the concentration of potassium ferricyanide in the potassium ferricyanide aqueous solution is 2.5 mM ~ 4.4 mM. The others are the same as the first five embodiments.

[0054] Specific embodiment seven: the difference between this embodiment and the first six embodiments is that: in step two ②, acetylacetone salt is dissolved in n-hexane, and ultrasonic water bath is used at a temperature of 20 ℃ ~ 30 ℃ and a power of 120 W ~ 240 W for 20 min ~ 30 min to obtain an acetylacetone salt oil phase solution; the concentration of acetylacetone salt in the acetylacetone salt oil phase solution is 5 mM ~ 10 mM; the acetylacetone salt is acetylacetone iron, acetylacetone copper, acetylacetone cobalt or acetylacetone nickel; the concentration ratio of acetylacetone salt in the acetylacetone salt oil phase solution in step two ② to the concentration of potassium ferricyanide in the potassium ferricyanide aqueous solution in step two ① is 5: (2.0 ~ 3.3). The others are the same as the first six embodiments.

[0055] Specific embodiment eight: the difference between this embodiment and the first seven embodiments is that: in step two ③, the porous ceramic substrate after coating is dipped in the potassium ferricyanide aqueous solution by sealing with a rubber ring at 0.5 g / cm 2 ~ 1.5 g / cm 2 , and then the excess potassium ferricyanide aqueous solution is poured out, and the porous ceramic substrate after water phase treatment is obtained by air drying or nitrogen blowing drying at room temperature. The others are the same as the first seven embodiments.

[0056] Specific embodiment nine: the difference between this embodiment and the first eight embodiments is that: in step two ④, the porous ceramic substrate after coating is dipped in the potassium ferricyanide aqueous solution by sealing with a rubber ring at 1.0 g / cm 2 ~ 2.5 g / cm 2The acetylacetone salt oil phase solution is poured on the surface of the porous ceramic substrate treated by the water phase, and the deposition is shaken for 30-60 minutes at a shaking bed rotation frequency of 100-150 rpm to obtain the porous ceramic substrate treated by the water phase and the oil phase. The other aspects are the same as those in Embodiments 1-8.

[0057] Embodiment 10: Different from any one of Embodiments 1-9, the drying in step two (5) is specifically drying for 3-6 minutes at a temperature of 40-60°C. The other aspects are the same as those in Embodiments 1-9.

[0058] The beneficial effects of the present application are verified by the following examples:

[0059] Example 1:

[0060] A preparation method of a Prussian blue-like inorganic fine separation membrane based on the interface confinement principle, which is performed according to the following steps:

[0061] I. Preparation of a porous ceramic substrate:

[0062] ① 4.1 g of polyether sulfone (PES) and 0.5 g of polyvinylpyrrolidone (PVPK30) are dissolved in 15 g of N-methyl pyrrolidone (NMP), ball-milled at a rotation speed of 300 rpm for 2 hours, then 45 g of Al2O3 powder and 3.5 g of TiO2 powder are added, ball-milled at a rotation speed of 300 rpm for 24 hours, vacuum degassed for 30 minutes after ball-milling, and finally left to stand to obtain a casting solution;

[0063] The particle size of the Al2O3 powder is 0.3 μm; and the particle size of the TiO2 powder is 100 nm;

[0064] ② 2 mL of a nano-TiO2 ethanol dispersion liquid and 8 mL of a nano-Al2O3 ethanol dispersion liquid are mixed, ultrasonically dispersed at a power of 240 W for 1 hour, then added to 10 mL of anhydrous ethanol, and continuously ultrasonically dispersed at a power of 240 W for 1 hour to obtain a dispersion liquid;

[0065] The mass percentage of nano-TiO2 in the nano-TiO2 ethanol dispersion liquid is 20%, and the particle size is 100 nm; the mass percentage of nano-Al2O3 in the nano-Al2O3 ethanol dispersion liquid is 20%, and the particle size is 100 nm;

[0066] ③ A spin coating method is used to spin coat the dispersion liquid at a rotation speed of 2000 rpm and a coating amount of 2 mL / cm 2Under certain conditions, a casting solution was spin-coated onto a ceramic membrane substrate for 25 seconds. After spin-coating, the substrate was immersed in ultrapure water for 8 hours after 30 seconds. Finally, the substrate was dried at 40°C to obtain a ceramic membrane coated with the casting solution. The ceramic membrane coated with the casting solution was then placed in a tube furnace at 1300°C and sintered for 5 hours to obtain a sintered ceramic membrane.

[0067] The ceramic membrane substrate has a pore size of 0.3 μm and is made of alumina.

[0068] ④ Using spin coating, at a speed of 2000 rpm and a coating amount of 0.3 mL / cm 2 Under these conditions, a dispersion was spin-coated onto the surface of the sintered ceramic film for 25 seconds, and then dried at 60°C for 60 seconds.

[0069] ⑤ Repeat step 1④ 3 times, and finally calcine in a muffle furnace at 950℃ for 3 hours to obtain the coated porous ceramic substrate.

[0070] II. Preparation of Prussian Blue-like Thin Films:

[0071] ① Preparation of an aqueous solution for Prussian blue-like film preparation: Dissolve potassium ferricyanide in ultrapure water, and then stir for 1 hour at a temperature of 20℃~30℃ and a rotation speed of 350rpm to obtain an aqueous solution of potassium ferricyanide; the concentration of potassium ferricyanide in the aqueous solution of potassium ferricyanide is 3.2mM.

[0072] ② Preparation of the oil phase solution for Prussian blue-like film preparation: Acetylacetone salt is dissolved in n-hexane, and ultrasonicated in a water bath for 20 min at a temperature of 20℃~30℃ and a power of 240W to obtain an acetylacetone salt oil phase solution; the concentration of acetylacetone salt in the acetylacetone salt oil phase solution is 6.3mM; the acetylacetone salt is acetylacetone iron;

[0073] ③ Use a rubber ring for sealing, at 0.9g / cm 2 Potassium ferricyanide aqueous solution was poured onto the coated porous ceramic substrate and immersed for 30 minutes. Then, excess potassium ferricyanide aqueous solution was poured out and the substrate was dried at room temperature to obtain the porous ceramic substrate after aqueous treatment.

[0074] ④ Use a rubber ring for sealing, at 1.5g / cm 2 An acetylacetone salt oil phase solution was poured onto the surface of a porous ceramic substrate after aqueous phase treatment. The substrate was then shaken and deposited for 30 minutes at a shaking frequency of 150 rpm to obtain porous ceramic substrates after aqueous and oil phase treatment.

[0075] ⑤ The porous ceramic substrate after aqueous and oil phase treatment was dried at 60℃ for 5 min to obtain a Prussian blue-like inorganic fine separation membrane.

[0076] Example 2: The difference between this example and Example 1 is that in step one ①, 3.8 g of polyether sulfone (PES) and 0.5 g of polyvinylpyrrolidone (PVP K30) are dissolved in 11.6 g of N-methylpyrrolidone (NMP), and then 41.7 g of Al2O3 powder and 3.6 g of TiO2 powder are added, and ball milling is carried out at a rotation speed of 300 rpm for 24 h. After ball milling, vacuum degassing is carried out for 30 min, and finally standing is carried out to obtain a casting solution. In step two ②, the acetylacetone salt is copper acetylacetonate. The other steps are the same as in Example 1.

[0077] Example 3: The difference between this example and Example 1 is that in step one ①, 4.3 g of polyether sulfone (PES) and 1.5 g of polyvinylpyrrolidone (PVP K30) are dissolved in 15 g of N-methylpyrrolidone (NMP), and then 43.8 g of Al2O3 powder and 2.7 g of TiO2 powder are added, and ball milling is carried out at a rotation speed of 300 rpm for 24 h. After ball milling, vacuum degassing is carried out for 30 min, and finally standing is carried out to obtain a casting solution. In step two ②, the acetylacetone salt is cobalt acetylacetonate. The other steps are the same as in Example 1.

[0078] Example 4: The difference between this example and Example 1 is that in step one ①, 4.1 g of polyether sulfone (PES) and 1.2 g of polyvinylpyrrolidone (PVP K30) are dissolved in 18 g of N-methylpyrrolidone (NMP), and then 45 g of Al2O3 powder and 2.5 g of TiO2 powder are added, and ball milling is carried out at a rotation speed of 300 rpm for 24 h. After ball milling, vacuum degassing is carried out for 30 min, and finally standing is carried out to obtain a casting solution. In step two ②, the acetylacetone salt is nickel acetylacetonate. The other steps are the same as in Example 1.

[0079] Figure 1 The surface scanning electron microscope image of the Prussian blue analog inorganic fine separation membrane prepared in Example 1; as can be seen from the figure, the Prussian blue analog inorganic fine separation membrane prepared by the interface confinement principle has a complete and dense surface and is not easy to crack. In addition, since this method is similar to the interface polymerization method, substance diffusion and aggregation occur at the oil-water interface, and therefore the Turing structure formed in the interface polymerization will appear on the surface of the inorganic membrane.

[0080] Figure 2 The cross-sectional scanning electron microscope image of the Prussian blue analog inorganic fine separation membrane prepared in Example 1; as can be seen from the figure, due to the extremely narrow space limitation of the oil-water interface and the porous ceramic surface, the thickness of the Prussian blue analog layer prepared on the surface of the porous ceramic substrate by this method is very thin. As can be seen from the cross-sectional scanning electron microscope, the deposition layer on the surface is only 32.19 nm.

[0081] Figure 3 The XRD pattern of the Prussian blue analog inorganic fine separation membrane prepared in Example 1; from the figure, the characteristic peaks of the Prussian blue structure appear, and no other impurity peaks are observed, indicating that the purity of the generated Prussian blue analog is very high.

[0082] In order to study the reason why the Prussian blue analog film is tightly loaded on the surface of the ceramic membrane, the Zeta potential of the ceramic substrate surface and the Prussian blue analog film was tested. The ceramic substrate surface is the surface layer powder of the coated porous ceramic substrate prepared in step one 5 of Example 1, which is dispersed and then tested. The Prussian blue analog film is prepared under the condition of no substrate, and the molar ratio of acetylacetone salt in the acetylacetone salt oil phase solution to potassium ferricyanide in the potassium ferricyanide aqueous phase solution is 5:3. First, the potassium ferricyanide aqueous phase solution is added to the centrifuge tube, and then the acetylacetone salt oil phase solution is added along the inner wall of the centrifuge tube to form a Prussian blue analog substance after the oil phase-aqueous phase solution interface reacts. The Prussian blue analog substance is then sucked out with a pipette and dispersed for testing. Figure 4 The Zeta potential of the ceramic membrane substrate and the Prussian blue analog film in the Prussian blue analog inorganic fine separation membrane prepared in Example 1; from the figure, under neutral conditions (pH 7), the Zeta potential of the ceramic substrate surface is -23 mV, and the Zeta potential of the Prussian blue analog is -10.5 mV, which indicates that the Prussian blue analog film can be tightly combined on the surface of the porous ceramic substrate through electrostatic interaction.

[0083] 50 mL of 100 ppm Congo red dye, 50 mL of 100 ppm methyl blue dye, and 50 mL of 2 g / L MgSO4 solution were respectively passed through the ultrafiltration device to measure the absorbance of the raw water and the effluent dye and the conductivity of MgSO4 of Example 1 and the conventional fine ceramic membrane (TAMI 5kDa 47mm diameter); Figure 5 The rejection rate of inorganic salt and dye of the Prussian blue analog inorganic fine separation membrane prepared in Example 1 and the conventional fine ceramic membrane, a is the conventional fine ceramic membrane, and b is the Prussian blue analog inorganic fine separation membrane; from the figure, when treating inorganic salt and dye, the rejection rate of divalent inorganic salt (MgSO4) reaches 20%, the rejection rate of Congo red dye reaches 95%, and the rejection rate of methyl blue dye reaches 88%, while the conventional fine ceramic membrane has almost no rejection effect on divalent inorganic salt, the rejection rate of Congo red dye is only 52%, and the rejection rate of methyl blue dye is only 41%, which is increased by 43% and 47% respectively. Therefore, the Prussian blue analog inorganic fine separation membrane prepared by the application has better rejection accuracy than the conventional ceramic membrane.

[0084] 50 mL of 100 ppm Congo red dye and 50 mL of pure water were passed through the ultrafiltration device to measure the absorbance of the raw water and the effluent dye and the average mass difference of the pure water, and then the flux was calculated.Figure 6 Pure water flux and Congo red dye rejection rate of the Prussian blue analogue inorganic fine separation membrane prepared in Example 1; Figure 7 Pure water flux and Congo red dye rejection rate of the Prussian blue analogue inorganic fine separation membrane prepared in Example 2; Figure 8 Pure water flux and Congo red dye rejection rate of the Prussian blue analogue inorganic fine separation membrane prepared in Example 3; Figure 9 Pure water flux and Congo red dye rejection rate of the Prussian blue analogue inorganic fine separation membrane prepared in Example 4. The Congo red dye removal rates of the Prussian blue analogue inorganic fine separation membranes prepared in Examples 1 to 4 were 95%, 87%, 90% and 75% respectively in the first cycle, and 91%, 85%, 86% and 72% respectively in the fifth cycle, the pure water fluxes corresponding to the first cycle were 350 L / h·m 2 ·bar, 362 L / h·m 2 ·bar, 292 L / h·m 2 ·bar and 375 L / h·m 2 ·bar, the pure water fluxes corresponding to the fifth cycle were 353 L / h·m 2 ·bar, 365 L / h·m 2 ·bar, 296 L / h·m 2 ·bar and 380 L / h·m 2 ·bar. It can be seen that the rejection performance of the Prussian blue analogue inorganic fine separation membrane prepared by the interfacial deposition method to the Congo red dye and the pure water flux do not change significantly after five cycles (without cleaning between each cycle), thereby proving that the inorganic fine separation membrane prepared by the method has high stability and long service life. The dye rejection rate of Example 4 is lower, which is due to the large particle size of the nickel-iron Prussian blue thin film formed after interfacial deposition, the large pore between the particles, and thus the poor rejection rate of the dye and the larger flux than Examples 1 to 3.

Claims

1. A method for preparing a Prussian blue analogue inorganic fine separation membrane based on interface confinement principle, characterized in that It is carried out in the following steps: I. Preparation of porous ceramic substrate: ①Polyether sulfone and polyvinyl pyrrolidone are dissolved in N-methyl pyrrolidone by ball milling, then Al2O3 powder and TiO2 powder are added and ball milled, and finally vacuum degassing and standing are carried out to obtain a casting solution; ②The nano-TiO2 ethanol dispersion and nano-Al2O3 ethanol dispersion are mixed and ultrasonically dispersed, then added to anhydrous ethanol and ultrasonically dispersed to obtain a dispersion; ③The casting solution is coated on the ceramic membrane substrate by spin coating, then immersed in ultrapure water after spin coating, and finally dried to obtain a ceramic membrane coated with the casting solution, which is sintered to obtain a sintered ceramic membrane; ④The dispersion is coated on the surface of the sintered ceramic membrane by spin coating and dried; ⑤Steps 1-4 are repeated three to six times, and finally calcined to obtain a coated porous ceramic substrate; II. Preparation of Prussian blue analog film: ①Prepare the aqueous solution for preparing the Prussian blue analog film: dissolve potassium ferricyanide in ultrapure water and stir to obtain a potassium ferricyanide aqueous solution; ②Prepare the oil phase solution for preparing the Prussian blue analog film: dissolve acetylacetone salt in n-hexane and ultrasonically in a water bath to obtain an acetylacetone salt oil phase solution; ③Use a rubber ring to seal the potassium ferricyanide aqueous solution and pour it onto the surface of the coated porous ceramic substrate for immersion treatment, then dry to obtain a porous ceramic substrate treated with water phase; ④Use a rubber ring to seal the acetylacetone salt oil phase solution and pour it onto the surface of the porous ceramic substrate treated with water phase to deposit uniformly, to obtain a porous ceramic substrate treated with water phase and oil phase; ⑤Dry the porous ceramic substrate treated with water phase and oil phase to obtain a Prussian blue analog inorganic fine separation membrane based on the principle of interface confinement.

2. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that In step 1, polyether sulfone and polyvinyl pyrrolidone are dissolved in N-methyl pyrrolidone by ball milling at a speed of 300-400 rpm for 2-3 hours, then Al2O3 powder and TiO2 powder are added and ball milled at a speed of 300-400 rpm for 24-48 hours, then vacuum degassed for 30-60 minutes, and finally left to stand to obtain a casting solution; the mass ratio of polyether sulfone to polyvinyl pyrrolidone is 1:(0.1-0.4); the mass ratio of polyether sulfone to N-methyl pyrrolidone is 1:(3.0-7.3); the mass ratio of polyether sulfone to Al2O3 powder is 1:(7.0-16.0); the mass ratio of polyether sulfone to TiO2 powder is 1:(0.3-2.0); the particle size of Al2O3 powder is 0.3-3.0 μm; the particle size of TiO2 powder is 0.1-5.0 μm.

3. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that In step one ②, the nano-TiO2 ethanol dispersion liquid and the nano-Al2O3 ethanol dispersion liquid are mixed, ultrasonic dispersion is carried out under the condition that the power is 120W-240W for 1h-2h, and then added into anhydrous ethanol, and ultrasonic dispersion is continuously carried out under the condition that the power is 120W-240W for 1h-2h; the mass percentage of nano-TiO2 in the nano-TiO2 ethanol dispersion liquid is 10%-20%, and the particle size is 0.1μm-0.3μm; the mass percentage of nano-Al2O3 in the nano-Al2O3 ethanol dispersion liquid is 10%-20%, and the particle size is 0.1μm-0.3μm; the volume ratio of the nano-TiO2 ethanol dispersion liquid to the nano-Al2O3 ethanol dispersion liquid is 1:(3.5-5.7); the volume ratio of the nano-TiO2 ethanol dispersion liquid to anhydrous ethanol is 1:(4.0-5.5).

4. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that Step one ③ using spin coating method, the rotation speed is 1500rpm~2500rpm and the coating amount is 1mL / cm 2 ~3mL / cm 2 , after spin coating, immerse in ultrapure water within 30s~60s for 5h~10h, finally dry at the temperature of 40℃~60℃, get the ceramic membrane coated with casting solution, put the ceramic membrane coated with casting solution in the tube furnace at the temperature of 1200℃~1400℃ for 3h~7h; the pore size of the ceramic membrane substrate is 0.2μm~0.5μm.

5. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that Step 1-4: The dispersion solution was coated on the surface of the sintered ceramic membrane using a spin coating method at a rotation speed of 1500 rpm to 2000 rpm and a coating amount of 0.2 mL / cm to 0.5 mL / cm, and then dried at a temperature of 40°C to 60°C for 30 s to 120 s. 2 2 Step 1-4: The dispersion solution was coated on the surface of the sintered ceramic membrane using a spin coating method at a rotation speed of 1500 rpm to 2000 rpm and a coating amount of 0.2 mL / cm to 0.5 mL / cm, and then dried at a temperature of 40°C to 60°C for 30 s to 120 s. 2 2 Step 1-4: The dispersion solution was coated on the surface of the sintered ceramic membrane using a spin coating method at a rotation speed of 1500 rpm to 2000 rpm and a coating amount of 0.2 mL / cm to 0.5 mL / cm, and then dried at a 6. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that In step two ①, potassium ferricyanide is dissolved in ultrapure water, and then stirred under the condition that the temperature is 20℃-30℃ and the rotating speed is 350rpm-400rpm for 1h-2h to obtain a potassium ferricyanide aqueous solution; the concentration of potassium ferricyanide in the potassium ferricyanide aqueous solution is 2.5mM-4.4mM.

7. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that In step two ②, acetylacetone salt is dissolved in n-hexane, and water bath ultrasonic is carried out under the condition that the temperature is 20℃-30℃ and the power is 120W-240W for 20min-30min to obtain an acetylacetone salt oil phase solution; the concentration of acetylacetone salt in the acetylacetone salt oil phase solution is 5mM-10mM; the acetylacetone salt is acetylacetone iron, acetylacetone copper, acetylacetone cobalt or acetylacetone nickel; the concentration ratio of acetylacetone salt in the acetylacetone salt oil phase solution in step two ② to potassium ferricyanide in the potassium ferricyanide aqueous solution in step two ① is 5:(2.0-3.3).

8. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that Step two ③ use rubber ring seal, according to 0.5g / cm 2 ~1.5g / cm 2 The potassium ferricyanide aqueous solution is poured on the surface of the coated porous ceramic substrate for 30min~60min of immersion treatment, then the excess potassium ferricyanide aqueous solution is poured out, and the porous ceramic substrate is dried at room temperature or dried by blowing nitrogen, to obtain the porous ceramic substrate treated by the aqueous phase.

9. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that Step two (4) uses rubber ring sealing, according to 1.0g / cm 2 ~ 2.5g / cm 2 The acetylacetone salt oil phase solution is poured on the surface of the water phase treated porous ceramic substrate, and the deposition is shaken for 30min-60min under the condition that the rotation frequency of the shaking bed is 100rpm-150rpm, to obtain the water phase and oil phase treated porous ceramic substrate.

10. The method for preparing a Prussian blue analog inorganic fine separation membrane based on interface confinement principle according to claim 1, characterized in that In step two ⑤, the drying is carried out under the condition that the temperature is 40℃-60℃ for 3min-6min.

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