A kind of AlOOH loaded mullite porous ceramic and its preparation method and application

Abstract

The present invention relates to a porous mullite ceramic loaded with AlOOH, a preparation method thereof, and an application thereof, belonging to the field of ceramic technology, and solving the problems of high cost and limited adsorption effect of existing adsorbents. The preparation method comprises: step 1: preparing a gelling agent; step 2: injecting the gelling agent obtained in step 1 into a mullite fiber felt, soaking the mullite fiber felt in a sol, causing the sol to gel in the mullite fiber felt, and then obtaining the mullite porous ceramic through a drying and sintering process; step 3: preparing an acidic Al solution; step 4: mixing the mullite porous ceramic obtained in step 2 with the acidic Al solution obtained in step 3, performing hydrothermal synthesis, ultrasonic cleaning, and drying to obtain the AlOOH-loaded mullite porous ceramic. The AlOOH-loaded mullite porous ceramic of the present invention has high compressive strength and has both filtration and adsorption properties.

Description

Technical Field

[0001] The present invention relates to the technical field of inorganic non-metallic materials, and in particular to an AlOOH-loaded mullite porous ceramic, a preparation method thereof, and applications thereof. Background Art

[0002] Porous ceramics, with their numerous pores, offer a range of advantages, including heat resistance, corrosion resistance, large specific surface area, high strength, and stable physical and chemical properties. They are widely used in the steel, nonferrous metals, petrochemical, military, and aerospace industries. These advantages guarantee their promising application prospects in wastewater treatment. Mullite, the only stable compound in the Al2O3-SiO2 binary system at normal pressure, possesses high strength, a high melting point, low thermal conductivity, a low coefficient of thermal expansion, and excellent corrosion resistance, making porous ceramic materials widely applicable.

[0003] Dyes are widely used in many industries, including papermaking, printing, plastics, and textiles. Based on the ionic state of the dye molecules in aqueous solution, dyes are generally classified as organic anionic dyes, cationic dyes, and nonionic dyes. Toxic dyes pose a significant threat to the aquatic environment, even causing disturbances to aquatic life and causing cancer.

[0004] Currently, known dye removal methods include adsorption, photolysis, and advanced oxidation. Traditional adsorbents such as activated carbon and zeolite are expensive and have limited adsorption effects. Photolysis often uses ultraviolet irradiation, which consumes a lot of energy, and incomplete photolysis can easily produce toxic metabolites, causing secondary pollution to the environment. Advanced oxidation has high oxidation efficiency and good removal effect, and can degrade pollutants into carbon dioxide and water. However, advanced oxidation requires high voltage, which increases operating costs. Therefore, developing an efficient, environmentally friendly, cheap and convenient adsorption, filtration, and recycling method that can be used to remove dye wastewater to reduce the content of polluting and harmful dyes is a key topic of concern in today's environmental protection industry. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a mullite porous ceramic loaded with AlOOH and its preparation method and application, which is used to solve one of the problems of existing adsorbents (such as activated carbon, zeolite, etc.) such as high cost, limited adsorption effect, and difficult recovery.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] The present invention provides a method for preparing AlOOH-loaded mullite porous ceramics, the preparation method comprising:

[0008] Step 1: preparing a gel;

[0009] Step 2: injecting the gelling agent obtained in step 1 into the mullite fiber felt, soaking the mullite fiber felt in the sol, so that the sol is gelled in the mullite fiber felt, and then obtaining the mullite porous ceramic through drying and sintering processes;

[0010] Step 3: preparing an acidic Al solution;

[0011] Step 4: The mullite porous ceramic obtained in step 2 is mixed with the acidic Al solution obtained in step 3, and subjected to hydrothermal synthesis, ultrasonic cleaning, and drying to obtain the AlOOH-loaded mullite porous ceramic.

[0012] Furthermore, step 1 includes:

[0013] S11. Prepare a sodium salt solution, add a catalyst, and obtain a gelling agent.

[0014] Furthermore, in S11, the sodium salt is one or more of sodium citrate, sodium tungstate, sodium alginate, sodium molybdate, sodium silicate, sodium acetate, sodium borate, sodium carbonate, sodium sulfate or sodium bicarbonate; preferably, the sodium salt is one or more of sodium molybdate, sodium silicate, sodium tungstate and sodium alginate.

[0015] Furthermore, in S11, the catalyst is one or more of aluminum fluoride, lanthanum oxide, cobalt oxide, molybdenum oxide or ammonium molybdate.

[0016] Furthermore, in S11, the mass ratio of sodium salt to catalyst is (3-4.5): (1-2).

[0017] Furthermore, in step 2, the mass ratio of sodium salt to mullite fiber felt is (3-4.5): (6-7).

[0018] Furthermore, step 3 includes:

[0019] S31, respectively preparing a NaOH solution and an ammonia solution, and mixing the NaOH solution and the ammonia solution to obtain an alkaline precipitant;

[0020] S32. Prepare an aluminum nitrate solution, and use the alkaline precipitant obtained in S31 to adjust the pH of the aluminum nitrate solution to 2.8-4.5 to obtain an acidic Al solution.

[0021] Furthermore, in step 4, the temperature of the hydrothermal synthesis is 180-250° C., and the time of the hydrothermal synthesis is 1-24 h.

[0022] The present invention also provides an AlOOH-loaded mullite porous ceramic, which is prepared by adopting the above-mentioned preparation method.

[0023] The present invention also provides an application of AlOOH-loaded mullite porous ceramics, wherein the AlOOH-loaded mullite porous ceramics are used for filtering and adsorbing negatively charged dyes in wastewater.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] (1) In the preparation method of the AlOOH-loaded mullite porous ceramic provided by the present invention, a sol-gel method is first adopted to obtain a uniformly structured mullite porous ceramic, which has a high specific surface area and provides the possibility of loading AlOOH; and due to the improvement of structural uniformity, the mechanical properties of the mullite porous ceramic are also improved to a certain extent; then, mullite whiskers are grown by high-temperature calcination to obtain a structure with a large specific surface area and rich pores; the AlOOH-loaded mullite porous ceramic is obtained by hydrothermal synthesis, AlOOH is densely distributed between the surface of the mullite whiskers and the gaps, and overlaps to form nanopores in the mullite whisker skeleton, and AlOOH grows outward in a needle-tip cluster, so that the AlOOH-loaded mullite porous ceramic of the present invention has a high compressive strength and has both filtration and adsorption properties.

[0026] (2) The compressive strength of the AlOOH-loaded mullite porous ceramic of the present invention is above 0.28 MPa, which is relatively high. The aspect ratio of the mullite whiskers is 0.1 to 100 (e.g., 1.5 to 80), the porosity is 40% to 90% (e.g., 50% to 80%), and the bulk density is 0.38 to 1.1 g / cm 3 The AlOOH-loaded mullite porous ceramics of the present invention can be particularly used for filtering and adsorbing negatively charged dyes in wastewater.

[0027] (3) The AlOOH-loaded mullite porous ceramic of the present invention has a certain strength. Combined with microstructural observation and pore size distribution analysis, as AlOOH increases, the pore size in the material decreases significantly, and smaller nanopores are formed in the mullite whisker skeleton, thereby further improving the compressive strength of the ceramic. Moreover, with more AlOOH loaded, the adsorption efficiency is greatly improved. Therefore, when using it for wastewater treatment, it can be directly used as part of a filtration and adsorption device. The wastewater can be directly poured onto the AlOOH-loaded mullite porous ceramic to complete filtration and adsorption.

[0028] (4) The preparation method of the present invention has simple process, low cost and wide source of medicines.

[0029] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages will become apparent from the description or be understood through practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the contents pointed out in the embodiments of the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0031] Figure 1 This is an optical image of the mullite porous ceramic prepared by the present invention;

[0032] Figure 2a This is one of the scanning electron microscope characterization images of the mullite porous ceramic prepared in the present invention;

[0033] Figure 2b This is the second scanning electron microscope characterization image of the mullite porous ceramic prepared in the present invention;

[0034] Figure 3a This is one of the scanning electron microscope characterization images of the AlOOH-loaded mullite porous ceramics prepared in the present invention;

[0035] Figure 3b This is the second scanning electron microscope characterization image of the AlOOH-loaded mullite porous ceramic prepared in the present invention;

[0036] Figure 4 This is a diagram showing the adsorption effect of Congo red (CR) on the AlOOH-loaded mullite porous ceramics of the present invention;

[0037] Figure 5 Schematic diagram of the structure of the filtration adsorption device.

[0038] Reference numerals

[0039] 1-Separatory funnel, 2-Funnel, 3-Adsorption filter block, 4-Erlenmeyer flask. DETAILED DESCRIPTION

[0040] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0041] The present invention provides a method for preparing AlOOH (aluminum oxyhydroxide) loaded mullite porous ceramics, comprising:

[0042] Step 1: preparing a gel;

[0043] Step 2: injecting the gelling agent obtained in step 1 into the mullite fiber felt, soaking the mullite fiber felt in the sol, so that the sol is gelled in the mullite fiber felt, and then obtaining the mullite porous ceramic through drying and sintering processes;

[0044] Step 3: preparing an acidic Al solution;

[0045] Step 4: The mullite porous ceramic obtained in step 2 is mixed with the acidic Al solution obtained in step 3, and subjected to hydrothermal synthesis, ultrasonic cleaning, and drying to obtain the AlOOH-loaded mullite porous ceramic.

[0046] Specifically, step 1 includes the following steps:

[0047] S11. Prepare a sodium salt solution, add a catalyst, and obtain a gelling agent.

[0048] Specifically, in S11, the sodium salt is one or more of sodium citrate, sodium tungstate, sodium alginate, sodium molybdate, sodium silicate, sodium acetate, sodium borate, sodium carbonate, sodium sulfate or sodium bicarbonate; preferably, the sodium salt is one or more of sodium molybdate, sodium silicate, sodium tungstate and sodium alginate.

[0049] Specifically, in S11, the catalyst is one or more of aluminum fluoride, lanthanum oxide, cobalt oxide, molybdenum oxide or ammonium molybdate; the preferred catalyst is aluminum fluoride or ammonium molybdate.

[0050] Specifically, considering that in S11, the mass ratio of sodium salt to catalyst is too high, the gelation rate is fast, and the catalytic effect is not obvious, resulting in insufficient whisker synthesis, coarse whiskers, and small aspect ratio; the mass ratio of sodium salt to catalyst is too low, the gelation rate is slow, and the radial growth of whiskers is more significant than the axial growth, thus causing the whiskers to become thinner and the aspect ratio to increase; therefore, the mass ratio of sodium salt to catalyst in S11 is controlled to be (3~4.5):(1~2).

[0051] Specifically, in step 2, if the mullite fiber felt is too high in mass, the whisker growth space is limited, resulting in mutual obstruction and difficulty in growth; if the mullite fiber felt is too low in mass, the whisker growth space is too large and gelation is excessive. Therefore, the mass ratio of sodium salt to mullite fiber felt is controlled to be (3-4.5):(6-7).

[0052] Specifically, in step 2, the sol is an aluminum silicate sol with a mass concentration of 30% to 40%.

[0053] Specifically, in step 2, considering that the mass ratio of sol to mullite fiber felt is too high, gelation is impossible, and too low, gelation is excessive, the mass ratio of sol to mullite fiber felt is controlled to be (4-6):(1-2).

[0054] Specifically, in step 2, the drying temperature is 40-80°C.

[0055] Specifically, in step 2, if the sintering temperature is too high, the whisker growth rate will be significantly accelerated, the whisker length will not change much, but it will become significantly thicker, thus reducing the aspect ratio and the whisker conversion efficiency. If the sintering temperature is too low, the whisker growth rate will be slow, the gas-solid reaction will proceed slowly and incompletely, and the aspect ratio of the synthesized whiskers will be small. Therefore, the sintering temperature is controlled to 1100-1500°C.

[0056] Specifically, in the above preparation method, a mullite fiber felt composite gel material with a certain flexibility is used to make it have a certain compressive deformation resistance, and then mullite whiskers are grown by high-temperature calcination to obtain a structure with a large specific surface area and rich pores; therefore, the mullite porous ceramic obtained in step 2 has the advantages of low volume density, low specific heat capacity, low thermal conductivity, good thermal shock resistance, etc., and the high porosity, fine pores and mullite whiskers make the material have low thermal conductivity and high specific surface area. The prepared porous ceramic has a special three-dimensional network structure, thereby improving the compressive strength of the ceramic.

[0057] Specifically, step 3 includes the following steps:

[0058] S31, respectively preparing a NaOH solution and an ammonia solution, and mixing the NaOH solution and the ammonia solution to obtain an alkaline precipitant;

[0059] S32. Prepare an aluminum nitrate solution, and use the alkaline precipitant obtained in S31 to adjust the pH of the aluminum nitrate solution to 2.6 to 4.5 (e.g., 2.8 to 4.5) to obtain an acidic Al solution.

[0060] Specifically, in S32, the alkaline precipitant in S31 can be used to hydrolyze the inorganic salt into free aluminum ions to provide hydroxide ions.

[0061] Specifically, in step 4, if the mass ratio of the porous mullite ceramic to the acidic Al solution is too high, sufficient bundled (needle-tip clustered) AlOOH structures cannot be formed or are less likely to form. Therefore, the mass ratio of the porous mullite ceramic to the acidic Al solution is controlled to be (1-2):(14-15).

[0062] Specifically, in step 4, if the hydrothermal synthesis temperature is too high, the activity of the formed aluminum oxyhydroxide will be reduced, or aluminum oxyhydroxide may not be formed; if the hydrothermal synthesis temperature is too low, aluminum oxyhydroxide may not be formed or may be less. If the hydrothermal synthesis time is too long, the aluminum oxyhydroxide structure may be destroyed; if the hydrothermal synthesis time is too short, the reaction will be incomplete, resulting in little or no aluminum oxyhydroxide being formed. Therefore, the hydrothermal synthesis temperature is controlled to 180-250°C, and the hydrothermal synthesis time is controlled to 1-24 hours.

[0063] Specifically, in step 4, the ultrasonic cleaning time is 1 to 60 minutes.

[0064] Specifically, in step 4, if the drying temperature is too high, the aluminum oxyhydroxide will tend to aggregate excessively; if the temperature is too low, the drying time will be too long. Excessive drying time can lead to partial agglomeration of the aluminum oxyhydroxide structure; too short a drying time can prevent the removal of free water contained in the resulting aluminum oxyhydroxide. Therefore, the drying temperature is controlled between 40 and 80°C, and the drying time is controlled between 5 and 24 hours.

[0065] The invention provides an AlOOH-loaded mullite porous ceramic, which is prepared by adopting the above-mentioned preparation method.

[0066] Specifically, in the AlOOH-loaded mullite porous ceramic of the present invention, AlOOH is densely distributed between the surface of the mullite whiskers and the gaps, overlapping to form nanopores in the mullite whisker skeleton, and AlOOH grows outward in the shape of needle-tip clusters.

[0067] Specifically, in the AlOOH-loaded mullite porous ceramic of the present invention, the aspect ratio of the mullite whiskers is 0.1 to 100 (e.g., 1.5 to 80), the porosity is 40% to 90% (e.g., 50% to 80%), and the bulk density is 0.38 to 1.1 g / cm 3 .

[0068] Specifically, the AlOOH-loaded mullite porous ceramic of the present invention exhibits considerable strength and high adsorption efficiency. AlOOH is grown on mullite whiskers through hydrothermal synthesis, resulting in the porous mullite ceramic exhibiting both filtration and adsorption properties. Furthermore, the presence of the whiskers provides a support for the growth of AlOOH, thereby improving the adsorption time, adsorption efficiency, and reusability of the AlOOH.

[0069] Specifically, the compressive strength of the AlOOH-loaded mullite porous ceramic is greater than 0.28 MPa, for example, 0.3 to 1.1 MPa.

[0070] The AlOOH-loaded mullite porous ceramics of the present invention can be particularly used for filtering and adsorbing negatively charged dyes in wastewater. For example, the AlOOH-loaded mullite porous ceramics of the present invention are used to efficiently remove Congo red dye from wastewater, with a removal rate of more than 80%, for example, 80% to 99.2%.

[0071] Specifically, the AlOOH-loaded mullite porous ceramic of the present invention has a certain strength. Combined with microstructural observation and pore size distribution analysis, it is found that with the increase of AlOOH, the pore size in the material is significantly reduced, and smaller nanopores are formed in the mullite whisker skeleton, thereby further improving the compressive strength of the ceramic. Moreover, with more AlOOH loaded, the adsorption efficiency is greatly improved. Therefore, when using it for wastewater treatment, it can be directly used as part of a filtration and adsorption device. The wastewater can be directly poured through the AlOOH-loaded mullite porous ceramic to complete the filtration and adsorption.

[0072] Specifically, the AlOOH-loaded mullite porous ceramics of the present invention can be used for wastewater treatment. Figure 5 The filtration and adsorption device shown includes a conical flask 4, a funnel 2, and a separatory funnel 1, which are assembled from bottom to top. An adsorption filter block 3 is placed in the funnel 2. The adsorption filter block 3 is made of the AlOOH-loaded mullite porous ceramic of the present invention.

[0073] Specifically, the used AlOOH-loaded mullite porous ceramic is immersed in an aqueous solution and hydrothermally heated again to remove the adsorbed Congo red dye. After hydrothermal treatment at 180-250°C, Congo red is decomposed at high temperature, and AlOOH is regenerated through a hydrothermal reaction. After ultrasonic cleaning and drying, the adsorbent can be reused repeatedly, and the operation is simple.

[0074] Compared with the prior art, the preparation method of the AlOOH-loaded mullite porous ceramic of the present invention first adopts a sol-gel method to obtain a structurally uniform mullite porous ceramic, and the mullite porous ceramic has a high specific surface area, which provides the possibility of loading AlOOH; and due to the improvement of structural uniformity, the mechanical properties of the mullite porous ceramic are also improved to a certain extent; then, mullite whiskers are grown by high-temperature calcination to obtain a structure with a large specific surface area and abundant pores; and the AlOOH-loaded mullite porous ceramic is obtained by a hydrothermal synthesis method, wherein AlOOH is densely distributed on the surface and between the gaps of the mullite whiskers, overlaps to form nanopores in the mullite whisker skeleton, and AlOOH grows outward in a needle-tip cluster shape, so that the AlOOH-loaded mullite porous ceramic of the present invention has high compressive strength and has both filtration and adsorption properties.

[0075] The AlOOH-loaded mullite porous ceramic of the present invention has a compressive strength of 0.28 MPa or more (e.g., 0.3-1.1 MPa), a relatively high compressive strength, an aspect ratio of the mullite whiskers of 0.1-100 (e.g., 1.5-80), a porosity of 40%-90% (e.g., 50%-80%), and a bulk density of 0.38-1.1 g / cm 3The AlOOH-loaded mullite porous ceramics of the present invention can be particularly used for filtering and adsorbing negatively charged dyes in wastewater.

[0076] The AlOOH-loaded mullite porous ceramic of the present invention has a certain strength. Combined with microstructural observation and pore size distribution analysis, it is found that with the increase of AlOOH, the pore size in the material is significantly reduced, and smaller nanopores are formed in the mullite whisker skeleton, thereby further improving the compressive strength of the ceramic. Moreover, with more AlOOH loaded, the adsorption efficiency is greatly improved. Therefore, when using it for wastewater treatment, it can be directly used as part of a filtration and adsorption device. The wastewater can be directly poured through the AlOOH-loaded mullite porous ceramic to complete the filtration and adsorption.

[0077] The preparation method of the invention has simple process, low cost and wide source of raw materials.

[0078] The present invention will be described in detail below with reference to specific examples. Five parallel samples are prepared in each of the specific examples and comparative examples.

[0079] Example 1

[0080] This embodiment provides a method for preparing AlOOH-loaded mullite porous ceramics, comprising the following steps:

[0081] Mullite fiber felt with uniform thickness was selected as the matrix, and a 0.2 mol / L sodium alginate solution and aluminum fluoride as the catalyst were prepared. The fibers were combined with each other at a mass ratio of sodium salt: catalyst: mullite fiber felt = 3.2:1.3:6.5. The fibers were then immersed in aluminum silica sol (the mass ratio of sol to mullite fiber felt was 5:1) for one day to gel. The fibers were then oven-dried at 60°C and sintered at 1300°C to obtain the mullite porous ceramics.

[0082] A NaOH solution and an ammonia solution are prepared separately, and the two alkaline solutions are mixed to obtain an alkaline precipitant. The pH of the aluminum nitrate solution is adjusted to 4 using the alkaline precipitant. The acidic Al solution with adjusted pH and the mullite porous ceramic are placed in a reactor and mixed. The mixture is hydrothermally synthesized at 220°C for 5 hours, and dried to obtain the AlOOH-loaded mullite porous ceramic. The mass ratio of the mullite porous ceramic to the acidic Al solution is 1:15.

[0083] Figure 1 This is an optical image of the mullite porous ceramic prepared in this embodiment; Figure 2a 、 Figure 2b This is a scanning electron microscope image of the mullite porous ceramic prepared in this example; Figure 3a 、 Figure 3bThis is a scanning electron microscope characterization image of the AlOOH-loaded mullite porous ceramic prepared in this example; combined with microstructural observation and pore size distribution analysis, aluminum oxide hydroxide is densely distributed between the surface and gaps of the mullite whiskers, and smaller nanopores are formed by overlapping in the mullite whisker skeleton, and aluminum oxide hydroxide appears to grow outward in needle-like clusters.

[0084] The compressive strength of the AlOOH-loaded mullite porous ceramic of this embodiment is 0.51-0.6 MPa, the aspect ratio of the mullite whiskers is 1.5-3, the porosity is 70%-80%, and the bulk density is 0.92-1.1 g / cm 3 .

[0085] use Figure 5 The filtration and adsorption device shown in the figure was used to perform adsorption filtration on 10 ml of a 100 mg / L aqueous solution of Congo red. Spectrophotometric sampling was used for detection. Calculations showed that the AlOOH-loaded mullite porous ceramic of this embodiment had a Congo red removal rate of 80% to 87%. The adsorption effect on Congo red (CR) is shown in FIG. Figure 4 shown. Figure 4 In the figure, the left side is an aqueous solution with a Congo red concentration of 100 mg / L, and the right side is an aqueous solution after Congo red is removed from water using the AlOOH-loaded mullite porous ceramic of this embodiment.

[0086] Example 2

[0087] This embodiment provides a method for preparing AlOOH-loaded mullite porous ceramics, comprising the following steps:

[0088] Mullite fiber felt with uniform thickness was selected as the matrix, and a 0.2 mol / L sodium tungstate solution and aluminum fluoride as the catalyst were prepared. The fibers were combined with each other at a mass ratio of sodium salt: catalyst: mullite fiber felt = 4:1.3:6.5. The fibers were then immersed in aluminum silica sol (the mass ratio of sol to mullite fiber felt was 5:1) for one day to gel. The fibers were then dried in an oven at 70°C and sintered at 1400°C to obtain the mullite porous ceramics.

[0089] A NaOH solution and an ammonia solution are prepared separately, and the two alkaline solutions are mixed to obtain an alkaline precipitant. The pH of the aluminum nitrate solution is adjusted to 3.8 using the alkaline precipitant. The acidic Al solution with adjusted pH and the mullite porous ceramic are placed in a reactor and mixed. The mixture is hydrothermally synthesized at 200°C for 3 hours, and the AlOOH-loaded mullite porous ceramic is obtained after drying and adsorption filtration. The mass ratio of the mullite porous ceramic to the acidic Al solution is 1:15.

[0090] In this embodiment, in the AlOOH-loaded mullite porous ceramic, aluminum oxyhydroxide is densely distributed between the surface and gaps of the mullite whiskers, forming smaller nanopores in the mullite whisker skeleton, and the aluminum oxyhydroxide grows outward in a needle-like cluster. The compressive strength of the AlOOH-loaded mullite porous ceramic of this embodiment is 0.42 to 0.51 MPa, the aspect ratio of the mullite whiskers is 3 to 10, the porosity is 65% to 76%, and the bulk density is 0.38 to 0.46 g / cm 3 .

[0091] use Figure 5 The filtration and adsorption device shown in the figure performs adsorption filtration on 10 ml of an aqueous solution with a Congo red concentration of 100 mg / L, and adopts spectrophotometric sampling and detection. After calculation, the AlOOH-loaded mullite porous ceramic of this embodiment has a Congo red removal rate of 84% to 92% in water.

[0092] Example 3

[0093] This embodiment provides a method for preparing AlOOH-loaded mullite porous ceramics, comprising the following steps:

[0094] Mullite fiber felt with uniform thickness was selected as the matrix, and a 0.2 mol / L sodium silicate solution was prepared. The catalyst was aluminum fluoride. The fibers were combined with each other in a mass ratio of sodium salt: catalyst: mullite fiber felt = 4.2:1.4:6.2. The fibers were immersed in aluminum silicate sol (the mass ratio of sol to mullite fiber felt was 5:1) for one day to gel. The fibers were then dried in an oven at 60°C and calcined at 1350°C to obtain mullite porous ceramics.

[0095] A NaOH solution and an ammonia solution are prepared separately, and the two alkaline solutions are mixed to obtain an alkaline precipitant, which is used to adjust the pH of the aluminum nitrate solution to 4. The acidic Al solution with adjusted pH and the mullite porous ceramic are placed in a reactor and mixed, and hydrothermally synthesized at 220°C for 4 hours. The AlOOH-loaded mullite porous ceramic is obtained after drying and adsorption filtration. The mass ratio of the mullite porous ceramic to the acidic Al solution is 1:15.

[0096] In this embodiment, in the AlOOH-loaded mullite porous ceramic, aluminum oxyhydroxide is densely distributed between the surface and gaps of the mullite whiskers, forming smaller nanopores in the mullite whisker skeleton, and the aluminum oxyhydroxide grows outward in needle-like clusters. The compressive strength of the AlOOH-loaded mullite porous ceramic of this embodiment is 0.8 to 1.1 MPa, the aspect ratio of the mullite whiskers is 20 to 80, the porosity is 50% to 69%, and the bulk density is 0.45 to 0.52 g / cm 3 .

[0097] use Figure 5The filtration and adsorption device shown in the figure performs adsorption filtration on 10 ml of an aqueous solution with a Congo red concentration of 100 mg / L, and adopts spectrophotometric sampling and detection. After calculation, the AlOOH-loaded mullite porous ceramic of this embodiment has a Congo red removal rate of 95% to 99% in water.

[0098] Comparative Example 1

[0099] This comparative example provides a method for preparing a porous mullite ceramic. The preparation method comprises:

[0100] A mullite fiber felt with uniform thickness was selected as the matrix. A 0.2 mol / L sodium alginate solution was prepared and the fibers were bonded together at a mass ratio of sodium salt to mullite fiber felt of 3.2:6.5. The fibers were then immersed in an alumina-silica sol (the mass ratio of sol to mullite fiber felt was 5:1) for one day to gel. The fibers were then oven-dried at 60°C and sintered at 1300°C to obtain a mullite porous ceramic without whiskers.

[0101] A NaOH solution and an ammonia solution are prepared separately, and the two alkaline solutions are mixed to obtain an alkaline precipitant. The pH of the aluminum nitrate solution is adjusted to 4.4 using the alkaline precipitant. The acidic Al solution with adjusted pH and the mullite porous ceramic are placed in a reactor and mixed. The mixture is hydrothermally synthesized at 220°C for 0.5 hours, and dried to obtain the AlOOH-loaded mullite porous ceramic. The mass ratio of the mullite porous ceramic to the acidic Al solution is 1:15.

[0102] The compressive strength of the mullite porous ceramic obtained in this comparative example is 0.35-0.40 MPa, the aspect ratio of the mullite whiskers is 0, the porosity is 76%-85%, and the bulk density is 0.72-0.84 g / cm 3 It was used to remove Congo red from water by adsorption. The adsorption conditions and detection methods were the same as those in Example 1. The results showed that the removal rate of Congo red from water by the mullite porous ceramic in this comparative example was 44% to 56%.

[0103] Comparative Example 2

[0104] In this comparative example, mullite fiber felt with uniform thickness was selected as the matrix, and a 0.2 mol / L sodium tungstate solution was prepared. The catalyst was aluminum fluoride. The matrix was combined with each other in a mass ratio of sodium salt: catalyst: mullite fiber felt = 4:0.01:6.2. The matrix was immersed in aluminum silica sol (the mass ratio of sol to mullite fiber felt was 5:1) for one day to gel it, dried in an oven at 60°C, and calcined at 1300°C to obtain a mullite porous ceramic.

[0105] A NaOH solution was prepared to obtain an alkaline precipitant, and the pH value of the aluminum nitrate solution was adjusted to 2.6 using the alkaline precipitant. The acidic Al solution with adjusted pH value and the mullite porous ceramic were added into a reactor and mixed. The mixture was hydrothermally synthesized at 180° C. for 0.5 hour, and dried to obtain the AlOOH-loaded mullite porous ceramic. The mass ratio of the mullite porous ceramic to the acidic Al solution was 1:15.

[0106] In this comparative example, the compressive strength of the mullite porous ceramic is 0.28-0.36 MPa, the mass ratio of the sodium salt to the catalyst is too low, the gelation rate is slow, the aspect ratio of the mullite whiskers is 0.5-3, the porosity is 66%-83%, and the bulk density is 0.34-0.42 g / cm 3 , resulting in a decrease in specific surface area and the amount of loaded aluminum oxyhydroxide, which in turn leads to a decrease in Congo red removal rate.

[0107] use Figure 5 The filtration and adsorption device shown was used to perform adsorption filtration on 10 ml of an aqueous solution with a Congo red concentration of 100 mg / L. Spectrophotometric sampling was used for detection. Calculation showed that the AlOOH-loaded mullite porous ceramic in this comparative example had a Congo red removal rate of 35% to 46% in water.

[0108] Comparative Example 3

[0109] This comparative example provides a method for preparing a porous mullite ceramic without AlOOH loading, comprising the following steps:

[0110] Mullite fiber felt with uniform thickness was selected as the matrix, and a 0.2 mol / L sodium silicate solution was prepared. The catalyst was aluminum fluoride. The fibers were combined with each other in a mass ratio of sodium salt: catalyst: mullite fiber felt = 1:0.6:6.2. The fibers were immersed in aluminum silicate sol (the mass ratio of sol to mullite fiber felt was 5:1) for one day to gel. The fibers were then dried in an oven at 60°C and calcined at 1350°C to obtain mullite porous ceramics.

[0111] In this embodiment, the compressive strength of the mullite porous ceramic is 0.62-0.73 MPa, the aspect ratio of the mullite whiskers is 6-25, the porosity is 71%-83%, and the bulk density is 0.32-0.44 g / cm 3 .

[0112] use Figure 5 The filtration and adsorption device shown was used to perform adsorption filtration on 10 ml of an aqueous solution with a Congo red concentration of 100 mg / L. Samples were taken and tested using spectrophotometry. Calculations showed that the removal rate of Congo red in water by the mullite porous ceramic without AlOOH loading in this comparative example was 31% to 39%.

[0113] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing AlOOH-loaded mullite porous ceramics, characterized in that: The preparation method comprises: Step 1: preparing a gel; Step 2: injecting the gelling agent obtained in step 1 into the mullite fiber felt, soaking the mullite fiber felt in the sol, so that the sol is gelled in the mullite fiber felt, and then obtaining the mullite porous ceramic through drying and sintering processes; Step 3: preparing an acidic Al solution; Step 4: mixing the mullite porous ceramic obtained in step 2 with the acidic Al solution obtained in step 3, performing hydrothermal synthesis, ultrasonic cleaning, and drying to obtain the AlOOH-loaded mullite porous ceramic; The step 1 comprises: S11, prepare a sodium salt solution, add a catalyst, and obtain a gelling agent; the sodium salt is one or more of sodium citrate, sodium tungstate, sodium alginate, sodium molybdate, sodium silicate, sodium acetate, sodium borate, sodium carbonate, sodium sulfate or sodium bicarbonate, and the catalyst is one or more of aluminum fluoride, lanthanum oxide, cobalt oxide, molybdenum oxide or ammonium molybdate; In said S11, the mass ratio of sodium salt to catalyst is 3-4.5:1-2; The step 3 comprises: S31, respectively preparing a NaOH solution and an ammonia solution, and mixing the NaOH solution and the ammonia solution to obtain an alkaline precipitant; S32, preparing an aluminum nitrate solution, adjusting the pH of the aluminum nitrate solution to 2.8-4.5 using the basic precipitant obtained in S31 to obtain an acidic Al solution; In step 4, the temperature of the hydrothermal synthesis is 180-250° C., and the time of the hydrothermal synthesis is 1-24 hours.

2. The preparation method according to claim 1, characterized in that In the above-mentioned S11, the sodium salt is one or more of sodium molybdate, sodium silicate, sodium tungstate and sodium alginate.

3. The preparation method according to claim 1, characterized in that In the S11, the mass ratio of the sodium salt to the catalyst is 3.2-4.5:1-2.

4. The preparation method according to claim 1, characterized in that In the step 2, the mass ratio of the sodium salt to the mullite fiber felt is 3-4.5:6-7.

5. The preparation method according to claim 1, characterized in that In step 4, the temperature of the hydrothermal synthesis is 200-250° C., and the time of the hydrothermal synthesis is 3-24 hours.

6. A porous mullite ceramic loaded with AlOOH, characterized in that: The AlOOH-loaded mullite porous ceramic is prepared by the preparation method according to any one of claims 1 to 5.

7. An application of AlOOH-loaded mullite porous ceramics, characterized in that: The AlOOH-loaded mullite porous ceramic according to claim 6 is used for filtering and adsorbing negatively charged dyes in wastewater.

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