Alumina-based catalytic ceramic membrane loaded with high content of iron oxide, its preparation method and application

Abstract

This invention discloses an alumina-based catalytic ceramic membrane loaded with a high content of iron oxide, its preparation method, and its application, belonging to the technical field of inorganic functional ceramic microfiltration membranes and their preparation. This invention solves the problems of low catalyst loading limiting the catalytic activity of existing catalytic ceramic membranes, as well as the complex and costly preparation processes. In preparing the alumina-based ceramic membrane, this invention adds silica to generate a liquid phase during sintering to promote sintering, and adds the catalyst α-Fe₂O₃ to the ceramic powder before sintering. A one-step co-sintering method is used to prepare a ceramic membrane with catalytic function, simplifying the preparation process while increasing the α-Fe₂O₃ content on the surface and inside of the ceramic membrane, utilizing Fe… 3+ It activates the crystal lattice and promotes sintering. Furthermore, with the increase of α-Fe2O3 addition, small pores are expelled during sintering, pore walls shrink, large pores are generated, the pore size of the ceramic membrane gradually increases, and the permeation flux of the ceramic membrane is improved.

Description

Technical Field

[0001] This invention relates to an alumina-based catalytic ceramic membrane loaded with high iron oxide content, its preparation method and application, belonging to the field of inorganic functional ceramic microfiltration membrane and its preparation technology. Background Technology

[0002] Endocrine disruptors are substances that interfere with endocrine function. They have long half-lives, easily accumulate in organisms, and pose a serious threat to human health. Membrane technology, as an advanced water treatment technology, is used to remove organic matter from drinking water or wastewater. Ceramic membranes possess numerous technical advantages, including good mechanical properties, antifouling properties, hydrophilicity, acid and alkali resistance, chemical resistance, and long lifespan. In water treatment, low-pressure driven ceramic membranes have a molecular weight cutoff much higher than that of micropollutants, making physical filtration ineffective in removing pollutants. To overcome this key technological obstacle, developing functional ceramic membranes with catalytic properties for the removal and degradation of pollutants during filtration is of great significance.

[0003] Ozone oxidation technology utilizes both the oxidation and decomposition of ozone molecules to generate highly reactive free radicals, resulting in excellent pollutant removal. Furthermore, ozone oxidation technology is widely used in engineering projects due to its lack of secondary pollution. Heterogeneous catalysis promotes the decomposition of ozone molecules to generate highly oxidizing ·OH, improving oxidation efficiency. The catalyst is also easily recoverable, making it dominant in ozone catalytic oxidation for water treatment.

[0004] Currently, the main methods for preparing catalytic ceramic membranes include dip coating, magnetron sputtering, vacuum filtration, and hydrothermal / solvothermal synthesis. While these methods are technically mature, the preparation process is cumbersome, the catalyst can only be loaded onto the surface, and the loading is often less than 10%, resulting in limited catalytic effect and easy detachment under water erosion, which is detrimental to industrial production and application. Furthermore, existing ceramic membrane preparation processes typically require multiple high-temperature sintering operations, consuming significant energy and increasing production costs. Therefore, improving the catalyst loading on the membrane surface and inside, and rationally utilizing the sintering process in ceramic membrane preparation are key to improving the catalytic performance of ceramic membranes and reducing preparation costs. Summary of the Invention

[0005] This invention addresses the limitations of existing catalytic ceramic membranes, such as low catalyst loading restricting their catalytic activity, as well as the problems of complex preparation processes and high costs. It provides an alumina-based catalytic ceramic membrane loaded with high iron oxide content, its preparation method, and its applications.

[0006] The technical solution of the present invention:

[0007] One objective of this invention is to provide a method for preparing an alumina-based catalytic ceramic membrane loaded with a high iron oxide content, specifically comprising the following steps:

[0008] (1) Alumina, silica, iron oxide and water were ball-milled to obtain a powder dispersion;

[0009] (2) Add binder and pore-forming agent to the powder dispersion and perform secondary ball milling. After thorough mixing, dry and sieve to obtain pre-pressed powder.

[0010] (3) Place the pre-pressed powder in a mold and press it into shape to obtain a green body;

[0011] (4) The green body is sintered to obtain a catalytic ceramic membrane.

[0012] Further specified, in (1) the particle size of alumina is 150-1000 nm, the particle size of silicon dioxide is 50-500 nm, and the particle size of iron oxide is 30-500 nm.

[0013] Further specified, in (1) the molar ratio of alumina to silicon dioxide is 1:0.05 to 3, and the mass of iron oxide is 0.5 to 50% of the total mass of alumina and silicon dioxide.

[0014] Further specified, the ball milling time in (1) is 0.5 to 24 hours.

[0015] Further specifying, in (2), the binder is one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, methyl cellulose, and polyvinyl alcohol; the added mass of the binder is 0.5 to 50% of the total mass of alumina, silica and silicon dioxide.

[0016] Further specified, (2) the pore-forming agent is one or more of corn starch, nano carbon, yellow dextrin, cyclodextrin, calcium carbonate, and melamine; the added mass of the pore-forming agent is 0.5 to 50% of the total mass of alumina, silica and silicon dioxide.

[0017] Further specified, (2) the drying temperature is 40~100℃ and the time is 0.5~12h.

[0018] Further specifying, the sieve size in (2) is 40 to 400 mesh.

[0019] Further specified, the molding pressure in (3) is 2 to 60 MPa.

[0020] Further specified, (3) the thickness of the green blank is 0.5 to 2.5 mm.

[0021] Further specifying, the sintering conditions in (4) are as follows: the temperature is raised from room temperature to 500℃ at a rate of 0.5 to 10℃ / min, then raised to 800℃ at a rate of 0.5 to 15℃ / min, held for 0.5 to 5 hours, and finally raised to 900 to 1600℃ at a rate of 0.5 to 15℃ / min, held for 0.5 to 12 hours, and then cooled to room temperature at a rate of 2 to 10℃ / min after the holding period.

[0022] The second objective of this invention is to provide an alumina-based catalytic ceramic membrane loaded with high iron oxide content prepared by the above method.

[0023] The third objective of this invention is to provide an application of the above-mentioned alumina-based catalytic ceramic membrane loaded with high iron oxide content, specifically for catalytic ozone oxidation to remove organic pollutants from water.

[0024] Beneficial effects:

[0025] This invention promotes sintering by adding silica to generate a liquid phase during the sintering process, and by adding the catalyst α-Fe₂O₃ to the ceramic powder before sintering. A one-step co-sintering method is used to prepare a ceramic membrane with catalytic function, simplifying the preparation process while increasing the α-Fe₂O₃ content on the surface and inside the ceramic membrane. Furthermore, both α-Fe₂O₃ and Al₂O₃ are hexagonal close-packed crystals, and during sintering, Fe... 3+ The addition of α-Fe₂O₃ activates the crystal lattice and promotes sintering. Furthermore, with the increase of α-Fe₂O₃ content, small pores are expelled during sintering, pore walls shrink, and large pores are generated, gradually increasing the pore size of the ceramic membrane and improving its permeation flux. Compared with existing technologies, this application also has the following advantages:

[0026] (1) The catalytic ceramic membrane provided by this invention has a simple preparation process, low raw material price, and a catalyst loading of up to 50%. During the ozone catalytic oxidation process, the adsorption of ozone molecules by α-Fe2O3 is utilized, and there is electron transfer between Fe atoms and O atoms, which promotes the decomposition of ozone to produce ·OH and O2. ·- Free radicals enhance the mass transfer process of heterogeneous catalytic ozonation, strengthen the removal effect of low-pressure membranes on micropollutants, and maintain good catalytic function of the catalytic membrane under different water quality conditions.

[0027] (2) The catalytic ceramic membrane prepared by this invention has the characteristics of large pore size and high pure water flux. During high-flux operation, the removal rate of atrazine reaches over 80%. Taking a catalytic ceramic membrane with 50% α-Fe2O3 addition as an example, at 380 L·m⁻¹… -2 ·h -1 At the specified permeation flux, the removal rate of atrazine was 83.1%. Attached Figure Description

[0028] Figure 1 The XRD patterns of the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1 are shown in comparison.

[0029] Figure 2 The graph shows a comparison of the pure water flux of the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1.

[0030] Figure 3 The graph shows a comparison of the removal rates of atrazine by the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1 at an ozone concentration of 5 mg / L.

[0031] Figure 4 The pore size distribution of the catalytic ceramic membrane prepared in Comparative Example 1 is shown.

[0032] Figure 5 The pore size distribution diagram is shown for the catalytic ceramic membrane prepared in Example 1.

[0033] Figure 6 The pore size distribution diagram is shown for the catalytic ceramic membrane prepared in Example 2.

[0034] Figure 7 The pore size distribution diagram is shown for the catalytic ceramic membrane prepared in Example 3.

[0035] Figure 8 (a) and (b) are SEM images of the catalytic ceramic membranes prepared in Comparative Example 1 and Example 3, respectively;

[0036] Figure 9 Thermogravimetric curve of the catalytic ceramic membrane prepared in Example 3;

[0037] Figure 10 The image shows the degradation effect of the catalytic ceramic membrane prepared in Example 3 on the catalytic oxidation of atrazine in water under different ozone concentrations.

[0038] Figure 11 The image shows the superoxide radical detection results during the catalytic oxidation process of the catalytic ceramic membrane prepared in Example 3.

[0039] Figure 12 The image shows the detection results of hydroxyl radicals during the catalytic oxidation process of the catalytic ceramic membrane prepared in Example 3. Detailed Implementation

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0041] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0042] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0043] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, all materials, reagents, methods, and instruments used are conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art. Furthermore, all solid and liquid reagents used are of analytical grade.

[0044] Example 1

[0045] The process for preparing the catalytic ceramic membrane in this embodiment is as follows:

[0046] (1) Add 150ml of water to the ball mill jar, add 5g of alumina, 0.375g of iron oxide and 2.5g of silicon dioxide to the ball mill jar, mix thoroughly for 12h to obtain a uniform powder dispersion;

[0047] (2) Add 0.05g polyvinyl alcohol and 2.3g corn starch to the dispersion, mix for 12h, and then place the mixed slurry in a vacuum drying oven at 60℃ to dry and pass it through a 200-mesh sieve;

[0048] (3) Place the dried powder in a stainless steel mold and press it into a green body under a pressure of 40MPa;

[0049] (4) Place the ceramic membrane green body in a tube furnace, adjust the heating program, heat to 200℃ at a heating rate of 1.0℃ / min, and hold for 1h; then heat to 800℃ at a heating rate of 1.5℃ / min and hold for 2h; finally heat to 1200℃ at a heating rate of 2℃ / min, sinter for 5h, and maintain a cooling rate of 2.0℃ / min until the temperature drops to room temperature to obtain the catalytic ceramic membrane.

[0050] Example 2

[0051] The process for preparing the catalytic ceramic membrane in this embodiment is as follows:

[0052] (1) Add 150ml of water to the ball mill jar, and add 7.1g of alumina, 1.815g of iron oxide and 5g of silicon dioxide to the ball mill jar. Mix thoroughly for 12 hours to obtain a uniform powder dispersion.

[0053] (2) Add 0.05g polyvinyl alcohol and 4g corn starch to the dispersion, mix for 24h, and then place the mixed slurry in a vacuum drying oven at 60℃ to dry and pass it through a 200-mesh sieve.

[0054] (3) Place the dried powder in a stainless steel mold and press it into a ceramic film green body under a pressure of 50MPa.

[0055] (4) Place the ceramic membrane green body in a tube furnace, adjust the heating program, heat to 200℃ at a heating rate of 3.0℃ / min, and hold for 0.5h; then heat to 800℃ at a heating rate of 3.0℃ / min and hold for 0.5h; finally heat to 1300℃ at a heating rate of 3.0℃ / min, sinter for 5h, and maintain a cooling rate of 5.0℃ / min until the temperature drops to room temperature to obtain the catalytic ceramic membrane.

[0056] Example 3

[0057] (1) Add 150ml of water to the ball mill jar, add 3g of alumina, 1.75g ​​of iron oxide and 1.5g of silicon dioxide to the ball mill jar, mix thoroughly for 12h to obtain a uniform powder dispersion;

[0058] (2) Add 0.02g polyvinyl alcohol and 2g corn starch to the dispersion, mix for 24h, and then place the mixed slurry in a vacuum drying oven at 60℃ to dry and pass it through a 200-mesh sieve;

[0059] (3) Place the dried powder in a stainless steel mold and press it into a ceramic film green body under a pressure of 40MPa;

[0060] (4) Place the ceramic membrane green body in a tube furnace, adjust the heating program, heat to 200℃ at a heating rate of 1.5℃ / min, and hold for 0.5h; then heat to 800℃ at a heating rate of 1.5℃ / min and hold for 0.5h; finally heat to 1200℃ at a heating rate of 1.5℃ / min, sinter for 5h, and maintain a cooling rate of 5.0℃ / min until it reaches room temperature to obtain the catalytic ceramic membrane, named 50-FeAl.

[0061] Comparative Example 1

[0062] (1) Add 150ml of water to the ball mill jar, add 3g of alumina and 1.5g of silica to the ball mill jar, mix thoroughly for 12h to obtain a uniform powder dispersion;

[0063] (2) Add 0.02g polyvinyl alcohol and 2g corn starch to the dispersion, mix for 24h, and then dry the slurry in a vacuum drying oven at 60℃ and pass it through a 200-mesh sieve.

[0064] (3) Place the dried powder in a stainless steel mold and press it into a ceramic film green body under a pressure of 40MPa;

[0065] (4) Place the ceramic membrane green body in a tube furnace, adjust the heating program, heat to 200℃ at a heating rate of 1.5℃ / min, and hold for 0.5h; then heat to 800℃ at a heating rate of 1.5℃ / min and hold for 0.5h; finally heat to 1200℃ at a heating rate of 1.5℃ / min, sinter for 5h, and keep the cooling rate at 5.0℃ / min to cool to room temperature to obtain the catalytic ceramic membrane, named O-FeAl.

[0066] Example of effect

[0067] (1) The XRD patterns of the catalytic ceramic films prepared in Examples 1-3 and Comparative Example 1 are shown in the figure. Figure 1 As shown, by Figure 1 It can be seen that the characteristic peaks corresponding to α-Fe2O3 (104), (110) and (113) appear at 33.2°, 35.7° and 43.5° in Examples 1 to 3, indicating that α-Fe2O3 crystals were successfully added to the ceramic film in a single-phase form.

[0068] (2) The pure water flux of the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1 was tested using an ultrafiltration cup under dead-end filtration. The results are as follows: Figure 2 As shown, by Figure 2 It can be seen that the pure water flux of the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1 is 979.26 L·m⁻¹, respectively. -2 ·h -1 ·bar -1 1105.09 L·m -2 ·h -1 ·bar -1 1615.97 L·m -2 ·h -1 ·bar -1 and 745.62 L·m -2 ·h -1 ·bar -1 .

[0069] (3) The catalytic degradation performance of the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1 was characterized. The specific test method was as follows: saturated O3 water and water were pumped into a dead-end filter at a volume ratio of 4:1 using a peristaltic pump. Samples were taken periodically, and excess Na2S2O3 was quickly added to the effluent to terminate the reaction. The test results showed that, under the condition of 5 mg / L ozone, the removal rates of atrazine by the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1 were 58.63%, 65.3%, 86.2%, and 32.1%, respectively.

[0070] (4) The pore size distribution of the catalytic ceramic membranes prepared in Examples 1-3 and Comparative Example 1 was tested, and the results are as follows: Figures 4-7 As shown in the figure, the pore size of the comparative example is 162.4 nm. In Example 1, adding 5% α-Fe₂O₃ reduced the pore size to 156.8 nm. This is mainly because the addition of α-Fe₂O₃ blocked the membrane pores, leading to a reduction in pore size. In Examples 2 and 3, adding 15% and 50% α-Fe₂O₃, respectively, increased the pore size to 195.5 nm and 281.9 nm, respectively. This is mainly because Fe₂O₃ can promote sintering at high temperatures and lower the sintering temperature.

[0071] (5) The microstructure of the catalytic ceramic films prepared in Comparative Example 1 and Example 3 was characterized, and the results are as follows: Figure 8 As shown in (a) and (b), the surface pores of the membranes in Comparative Example 1 and Example 3 are caused by the combustion of the pore-forming agent. Compared with Comparative Example 1, the surface morphology of the ceramic membrane prepared in Example 3 did not change significantly, but a large number of white particles were present, which were the added α-Fe2O3 catalyst.

[0072] (6) The thermogravimetric curve of the catalytic ceramic membrane prepared in Example 3 is shown in Figure 3. Figure 9 As shown, by Figure 9 It can be seen that within the temperature range of 0–100℃, the mass loss is 3%, mainly due to the evaporation of water molecules within the ceramic membrane. Between 300 and 500℃, the mass loss of the ceramic membrane is 15.1%, primarily due to the vigorous combustion of the pore-forming agent, resulting in a rapid decrease in mass. Above 500℃, the mass change is relatively low, as the crystals undergo a phase transition, releasing heat.

[0073] (7) The catalytic ceramic membrane prepared in Example 3 was tested to catalyze the degradation effect of atrazine in water by ozone oxidation under different ozone concentrations. At a water temperature of 25°C, saturated O3 water and 500 μg / L atrazine solution were fed into the dead-end filter using a peristaltic pump at volume ratios of 20:1, 6:1, 4:1, and 2:1. The flux of the catalytic process was 380 L·m -2 ·h -1 ·bar -1 The test results are as follows: Figure 10 As shown, by Figure 10 It can be seen that the removal rate of atrazine increases with increasing ozone concentration. 5 mg / L is the optimal ozone concentration, achieving a removal rate of 81.7% for atrazine.

[0074] (8) The superoxide radicals and hydroxyl radicals of the catalytic ceramic membranes prepared in Example 3 and Comparative Example 1 were compared during the catalytic oxidation process. The results are as follows: Figure 11 and 12 As shown in the figure, during the catalytic filtration process, Example 3 can effectively catalyze the generation of superoxide radicals and hydroxyl radicals from ozone molecules. No radical generation can be detected when ozone is added alone or when using Comparative Example 1.

[0075] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for preparing an alumina-based catalytic ceramic membrane loaded with high iron oxide content, characterized in that, include: Step (1) Alumina, silica, iron oxide and water are ball-milled to obtain a powder dispersion; The alumina has a particle size of 150~1000nm, the silica has a particle size of 50~500nm, and the iron oxide has a particle size of 30~500nm; the molar ratio of alumina to silica is 1:0.05~3, and the mass of iron oxide is 50% of the total mass of alumina and silica; Step (2) Add binder and pore-forming agent to the powder dispersion and perform secondary ball milling. After thorough mixing, dry and sieve to obtain pre-pressed powder. Step (3) Place the pre-pressed powder in a mold and press it into shape to obtain a green body; Step (4) involves sintering the green body to obtain a catalytic ceramic membrane for catalytic ozone oxidation to remove organic pollutants from water.

2. The preparation method according to claim 1, characterized in that, The ball milling time in step (1) is 0.5~24h.

3. The preparation method according to claim 1, characterized in that, In step (2), the binder is one or more of carboxymethyl cellulose, sodium carboxymethyl cellulose, methyl cellulose, and polyvinyl alcohol; the added mass of the binder is 0.5 to 50% of the total mass of alumina, silica and iron oxide.

4. The preparation method according to claim 1, characterized in that, In step (2), the pore-forming agent is one or more of corn starch, nano carbon, yellow dextrin, cyclodextrin, calcium carbonate, and melamine; the added mass of the pore-forming agent is 0.5 to 50% of the total mass of alumina, silicon dioxide, and iron oxide.

5. The preparation method according to claim 1, characterized in that, In step (3), the thickness of the green blank is 0.5~2.5mm.

6. The preparation method according to claim 1, characterized in that, The sintering conditions in step (4) are as follows: the temperature is raised from room temperature to 500℃ at a rate of 0.5~10℃ / min, then raised to 800℃ at a rate of 0.5~15℃ / min, held for 0.5~5h, and finally raised to 900~1600℃ at a rate of 0.5~15℃ / min, held for 0.5~12h, and then lowered to room temperature at a rate of 2~10℃ / min after the holding period.

7. An alumina-based catalytic ceramic membrane loaded with high iron oxide content prepared by the method of any one of claims 1 to 6.

8. The application of the alumina-based catalytic ceramic membrane loaded with high iron oxide content as described in claim 7, characterized in that, It is used to catalyze ozone oxidation to remove organic pollutants from water.

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