Activated alumina ball, preparation method and application of activated alumina ball in sewage treatment

Abstract

The invention relates to an activated alumina ball, a preparation method and application of the activated alumina ball in sewage treatment, and relates to the technical field of alumina balls. The activated aluminum oxide ball comprises a ceramic matrix, an activated aluminum oxide layer and a hydrophobic layer which are sequentially arranged from inside to outside, the preparation process comprises the steps of ceramic matrix preparation, intermediate product preparation, vapor deposition of the hydrophobic layer and post-treatment. The silicon dioxide hydrophobic layer is additionally arranged on the outer layer of the prepared activated aluminum oxide ball, direct contact between a water phase and a chemical medium and active components is isolated, the structural protection stability is enhanced, and the prepared activated aluminum oxide ball has a good industrial application prospect in the field of sewage treatment.

Description

Technical Field

[0001] This invention relates to the field of alumina ball technology, and in particular to an activated alumina ball, its preparation method, and its application in wastewater treatment. Background Technology

[0002] Activated alumina spheres, as a porous and highly dispersible solid material, are widely used in chemical reaction catalysts, catalyst supports, and pollutant adsorption in water treatment due to their large specific surface area, excellent adsorption performance, good thermal stability, and mechanical strength. In the field of wastewater treatment, activated alumina spheres can effectively adsorb various organic pollutants in water and have excellent properties such as being non-toxic and odorless, insoluble in water or ethanol, and retaining their original shape after absorbing water. Therefore, they have become an indispensable functional material in wastewater treatment and purification processes.

[0003] While traditional activated alumina balls exhibit certain advantages in pollutant adsorption, they still face significant limitations in practical applications. Traditional activated alumina balls primarily rely on physical adsorption to capture pollutants in water. Once adsorption reaches saturation, their adsorption capacity drops sharply, requiring complex regeneration processes such as heating and solvent soaking to restore adsorption performance. This adsorption-regeneration cycle is not only cumbersome and increases treatment costs, but it also forces interruptions in water treatment, severely impacting the efficiency of continuous pollutant treatment and thus limiting their widespread application in wastewater treatment.

[0004] To address the aforementioned issues, Chinese invention patent application CN108940253A, published on December 7, 2018, provides a method for preparing activated alumina balls for water treatment. The specific steps of this method are as follows: First, raw materials such as ethanol, zinc acetate, and aluminum isopropoxide are heated, evaporated, and concentrated to obtain a stable aluminum-zinc mixture. Second, activated alumina balls pretreated with phosphoric acid are subjected to a hydrothermal reaction with the aluminum-zinc mixture. After the reaction, the mixture is filtered and washed. Finally, the final product is obtained through drying, high-temperature calcination, and cooling. The activated alumina balls prepared using this method have an Al-Zn-O surface-bonded coating on their surface, which not only removes pollutants from water through adsorption but also degrades adsorbed organic pollutants through photocatalytic reaction, thus possessing continuous adsorption capacity.

[0005] However, technicians discovered that the Al-Zn-O coating on the surface of the activated alumina spheres in the above solution is directly exposed to the water environment. When in long-term contact with the water phase, it is easily affected by factors such as water phase erosion and chemical media, resulting in the loss of active components such as Zn, thereby reducing the adsorption-photocatalytic performance of the material and shortening its service life. Summary of the Invention

[0006] To address the problem that in existing activated alumina balls for water treatment, the active components, such as zinc oxide, are directly exposed to the aquatic environment and are susceptible to corrosion by the aqueous phase and loss due to chemical media, thus reducing the lifespan of the activated alumina balls, this invention provides an activated alumina ball, a preparation method, and its application in wastewater treatment. The invention employs a hydrophobic silica protective film covering the outer surface of the activated alumina ball. This effectively isolates the active components, such as zinc oxide, from direct corrosion by water, preventing loss of active components and significantly improving the material's aqueous phase stability. Furthermore, it ensures that the hydrophobic properties do not hinder adsorption and catalytic degradation reactions, ultimately guaranteeing the material's long-term stable water treatment performance.

[0007] In a first aspect, the present invention provides an activated alumina ball, which adopts the following technical solution: An activated alumina ball comprises a ceramic matrix, an activated alumina layer, and a hydrophobic layer arranged sequentially from the inside out; wherein the mass ratio of the ceramic matrix, the activated alumina layer, and the hydrophobic layer is 85-92:7-14:0.1-0.5. The ceramic matrix is ​​made by sintering raw materials; the sintering raw materials include clay. The activated alumina layer is loaded with a composite active component; the composite active component includes zinc oxide and magnesium oxide, wherein the mass ratio of zinc oxide to magnesium oxide is 1 to 2:1; the total mass of the composite active component accounts for 4.0 to 6.0 wt% of the mass of the activated alumina layer. The hydrophobic layer is a silicon dioxide protective film.

[0008] By adopting the above technical solution, the outer layer of silica hydrophobic layer acts as a physical barrier, effectively isolating the aqueous phase, dissolved acidic and alkaline substances and other chemical media from direct contact with the composite active components in the activated alumina layer. This prevents the loss of zinc oxide and magnesium oxide due to dissolution, hydrolysis or chemical reactions, and improves the long-term stability of the activated alumina balls in complex aquatic environments. At the same time, the thickness of the hydrophobic layer is controlled at 6±3nm, which, while ensuring the integrity of the protection, does not hinder the diffusion of pollutants in the water to the surface of the activated alumina layer and composite active components, ensuring the normal progress of adsorption and catalytic degradation reactions.

[0009] The ceramic matrix uses clay as the sintering raw material, ensuring the basic mechanical strength and structural stability of the activated alumina spheres, thus providing a reliable carrier for the loading of the activated alumina layer. The composite active components of zinc oxide and magnesium oxide loaded on the activated alumina layer play a synergistic role in catalytically degrading water pollutants, improving the removal efficiency of pollutants. In addition, the silica protective film of the hydrophobic layer has good interfacial compatibility with the activated alumina layer, forming a stable interlayer bond, further improving the durability of the overall structure, extending its service life, and ensuring stable water treatment performance.

[0010] Optionally, the sintering raw material further includes activated alumina, wherein the mass ratio of activated alumina to clay is 1-3:9-17.

[0011] By adopting the above technical solution, activated alumina possesses a high specific surface area and excellent adsorption performance. When compounded with clay as a sintering raw material, it significantly increases the specific surface area of ​​the ceramic matrix, enhances the adsorption and binding capacity of the matrix to the activated alumina layer, prevents the activated alumina layer from detaching during use, and improves the stability of interlayer bonding. On the other hand, the activated alumina introduced into the matrix can form a synergistic adsorption with the surface activated alumina layer, enhancing the initial adsorption capacity of pollutants in water, reducing the catalytic load of the surface composite active components, and further improving the overall water treatment efficiency.

[0012] Optionally, the sintering raw materials further include a composite silane precursor encapsulated in urea-formaldehyde resin microcapsules and ammonium bicarbonate; the microcapsule wall material of the composite silane precursor encapsulated in urea-formaldehyde resin microcapsules is coated with methyltriethoxysilane, wherein the methyltriethoxysilane accounts for 1-3 wt% of the microcapsule wall material. The composite silane precursor encapsulated in urea-formaldehyde resin microcapsules comprises 3-5 wt% of the clay mass, and the ammonium bicarbonate comprises 2-3 wt% of the clay mass. The composite silane precursor comprises tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane-modified organomontmorillonite, wherein the mass ratio of tetraethyl orthosilicate to γ-glycidoxypropyltrimethoxysilane-modified organomontmorillonite in the composite silane precursor is 3 to 5:1.

[0013] By adopting the above technical solution, adding composite silane precursors and ammonium bicarbonate to the sintering raw materials mainly improves the rationality of the pore structure of the ceramic matrix and the interfacial bonding force between the matrix and the activated alumina layer. The γ-glycidyl etheroxypropyltrimethoxysilane modified organomontmorillonite in the composite silane precursor introduces active functional groups such as epoxy and amino groups, enhancing the chemical bonding with hydroxyl groups on the surface of clay and activated alumina, thereby improving the compactness and structural stability of the matrix. Tetraethyl orthosilicate undergoes a hydrolysis-condensation reaction during sintering to form a silica network structure, further optimizing the pore size distribution of the matrix. At the same time, ammonium bicarbonate decomposes during sintering to produce CO2 and NH3 gases, forming uniformly distributed micropores in the matrix, significantly improving the porosity of the ceramic matrix and providing sufficient channels for pollutant diffusion and contact between active components and pollutants.

[0014] In addition, the composite silane precursor is encapsulated in urea-formaldehyde resin microcapsules and coated with methyltriethoxysilane as the wall material, which enables the slow release of the composite silane precursor: avoiding its rapid reaction in the early stage of sintering that would cause the pore structure to collapse. At the same time, methyltriethoxysilane enhances the compatibility between the microcapsules and the matrix, further improving the stability of the matrix.

[0015] Optionally, the composite active component further includes cerium dioxide, wherein the mass ratio of cerium dioxide, zinc oxide, and magnesium oxide is 0.06–0.12:1–2:1.

[0016] By adopting the above technical solution, cerium dioxide is introduced into the composite active component to improve catalytic performance and resistance to deactivation; cerium dioxide has unique redox properties: Ce 3+ With Ce 4+ There is a reversible process between them, which acts as an electron transfer medium in the catalytic reaction, promotes electron transfer on the surfaces of zinc oxide and magnesium oxide, reduces the activation energy of pollutant degradation, and significantly improves the oxidation and degradation efficiency of recalcitrant organic pollutants in water. At the same time, cerium dioxide has a strong oxygen storage and release capacity, which dynamically regulates the oxygen concentration in the reaction system. When carbon deposits or pollutants are adsorbed on the surface of the active components, cerium dioxide releases active oxygen to oxidize and decompose the carbon deposits, alleviate the deactivation of the active components, and extend the catalytic life of the active components.

[0017] In addition, cerium dioxide forms a solid solution structure with zinc oxide and magnesium oxide, which further improves the dispersibility of active components, reduces particle agglomeration of active components, and increases the number of active sites. Overall, the addition of cerium dioxide significantly improves the catalytic performance and anti-fouling ability of activated alumina balls, further expanding the application range of activated alumina balls.

[0018] Optionally, the activated alumina sphere further includes an Al2O3 transition layer, which is disposed between the activated alumina layer and the hydrophobic layer; wherein the mass ratio of the ceramic substrate, the activated alumina layer, the Al2O3 transition layer and the hydrophobic layer is: 85~92:7~14:0.05~0.15:0.1~0.5.

[0019] By adopting the above technical solution, an Al2O3 transition layer is added, which has the same main crystalline phase as the active alumina layer, significantly reducing the interfacial energy and improving the interlayer bonding force. At the same time, Al2O3 and the silica of the hydrophobic layer form Si-O-Al chemical bonds through hydroxyl condensation reaction, achieving chemical bonding and further enhancing the bonding stability between the hydrophobic layer and the transition layer, thus preventing the hydrophobic layer from peeling off from both physical and chemical dimensions.

[0020] In addition, the prepared Al2O3 transition layer ensures that pollutants in the water can diffuse smoothly through the transition layer to the active alumina layer without hindering the catalytic reaction. On the other hand, the Al2O3 transition layer can fill the small defects on the surface of the active alumina layer, such as pinholes and depressions, so that the hydrophobic layer can cover its surface more evenly, improve the integrity of hydrophobic protection, and avoid local damage to the hydrophobic layer caused by defects on the surface of the active alumina layer, which would lead to the loss of active components.

[0021] Optionally, the Al2O3 transition layer is prepared as follows: Atomic layer deposition reaction was carried out on a ceramic substrate containing an active alumina layer. The vacuum was evacuated to a pressure ≤1 Pa and the temperature was raised to 150 °C. Trimethylaluminum was used as the aluminum source precursor and deionized water was used as the oxygen source precursor. The mixture was alternately introduced into the atomic layer deposition reaction chamber and the deposition was carried out in cycles of 20 to 30 times to deposit an Al2O3 transition layer on the surface of the active alumina layer.

[0022] By adopting the above technical solution, an atomic layer deposition (ALD) technique is used to prepare the transition layer. First, the ceramic substrate containing the active alumina layer is evacuated to a pressure ≤1Pa and heated to 150℃ to effectively remove moisture and adsorbed impurities from the substrate surface, providing a clean and active deposition surface for ALD. Trimethylaluminum and deionized water undergo orderly chemical adsorption and reaction on the substrate surface to form a single atomic layer deposition, which in turn forms a continuous and dense Al2O3 transition layer, further improving the overall stability of the active alumina spheres.

[0023] Optionally, in the method for preparing the Al2O3 transition layer, during the 10th to 15th atomic layer deposition cycles, an amino-terminated polysiloxane, accounting for 1 to 2 wt% of the mass of trimethylaluminum, is added; nano-TiO2 is loaded on the surface of the amino-terminated polysiloxane; and the nano-TiO2 accounts for 5 to 8 wt% of the mass fraction of the amino-terminated polysiloxane. The preparation method of the amino-terminated polysiloxane surface loaded with nano-TiO2 is as follows: Amino-terminated polysiloxane was dispersed in deionized water to form a suspension. Tetrabutyl titanate, a precursor of TiO2, was added, along with 1–3 wt% diethanolamine. The suspension was then subjected to a hydrothermal reaction at 80–90 °C for 2–4 h. After the reaction, the mixture was centrifuged, washed with deionized water until the pH reached 7.0 ± 0.1, and dried at 120 °C for 2 h to obtain amino-terminated polysiloxane microspheres with uniformly loaded nano-TiO2 on their surface. By adopting the above technical solution, amino-terminated polysiloxane loaded with nano-TiO2 is added during the preparation of the transition layer, giving the transition layer a dual function of interface enhancement and catalysis. The nano-TiO2 loaded on the surface of the amino-terminated polysiloxane has photocatalytic properties, absorbing visible or ultraviolet light to generate hydroxyl radicals, thereby rapidly degrading recalcitrant organic pollutants in water. At the same time, the nano-TiO2 works synergistically with other composite active components in the activated alumina layer to improve the degradation efficiency of pollutants through electron transfer, further enhancing the water treatment effect.

[0024] In addition, amino-terminated polysiloxanes have good flexibility and compatibility, which enhances the toughness of the transition layer, alleviates the internal stress of the activated alumina balls caused by temperature changes or water impact during use, avoids film cracking, and further improves the overall structural stability. During the 10th to 15th deposition cycles, the transition layer has formed a preliminary dense structure, which allows the added amino-terminated polysiloxanes to be uniformly dispersed in the transition layer. This ensures that the density of the transition layer is not affected, and that the nano-TiO2 is fully exposed to exert its catalytic effect.

[0025] Secondly, the present invention provides a method for preparing activated alumina spheres, which adopts the following technical solution: A method for preparing activated alumina spheres includes the following steps: S1: Preparation of ceramic matrix: Add the sintering raw materials to deionized water and ball mill to mix them to obtain a uniform slurry; spray granulate the slurry to obtain a spherical green body; sinter the spherical green body and cool it to room temperature to obtain the ceramic matrix; S2: Preparation of intermediate products: Preparation of activated alumina sol: Boehmite was dissolved in nitric acid solution and stirred until a homogeneous sol was formed; Coating: The ceramic substrate is immersed in activated alumina sol, removed and dried to obtain an activated alumina layer; Composite active component loading: Weigh zinc nitrate and magnesium nitrate, dissolve them in deionized water, and prepare a mixed solution with a total metal ion concentration of 0.5-1.0 mol / L; immerse the ceramic substrate coated with the active alumina layer in the mixed solution, sonicate, add ammonia to adjust the pH to 8-9, and let it stand to precipitate; take out the precipitated substrate, rinse the surface with deionized water, dry it, and keep it at 400-450℃ for 3 hours to obtain the active alumina layer loaded with composite active components; Preparation of Al2O3 transition layer: An Al2O3 transition layer is coated on the surface of an active alumina layer loaded with composite active components; S3: Vapor deposition of the hydrophobic layer: Preparation for vapor deposition: Dry the obtained active alumina layer loaded with composite active components; after sealing the deposition furnace, evacuate to a pressure ≤10Pa and purge with argon gas for 30min; Silane monomer evaporation and deposition: Methyltriethoxysilane is heated and evaporated, and the evaporated silane monomer is carried into the deposition furnace with argon gas; Post-treatment: After deposition, the substrate is allowed to cool naturally to room temperature, forming a 6±3 nm thick hydrophobic silica layer on the surface of the preform. S4: Finished product processing: After the hydrophobic layer is deposited, the activated alumina balls are taken out and the unreacted silane monomers remaining on the surface are purged with argon gas to obtain the finished activated alumina balls.

[0026] By adopting the above technical solutions, ball milling ensures that raw materials such as clay are evenly dispersed, avoiding raw material agglomeration that leads to uneven matrix properties; spray granulation produces spherical green bodies with uniform particle size, ensuring the sphericity and particle size consistency of the product and improving the uniformity of hydraulic distribution in the sewage treatment process; sintering improves the mechanical strength and structural stability of the matrix.

[0027] In the intermediate product preparation stage, a uniform activated alumina sol is first prepared and then uniformly coated to ensure consistent coating thickness. Ultrasonic treatment during the loading of the composite active components promotes the diffusion of zinc nitrate and magnesium nitrate solutions into the pores of the activated alumina layer, ensuring uniform loading of the active components inside and outside the pores. Ammonia water is used to adjust the pH to 8-9 to allow metal ions to fully precipitate on the surface of the activated alumina layer, preventing the loss of active components. Calcination at 400-450℃ converts the metal hydroxides into oxides with high catalytic activity, such as zinc oxide and magnesium oxide, ensuring the catalytic performance of the active components.

[0028] In the hydrophobic layer vapor deposition step, the deposition furnace is first evacuated and purged with argon gas to remove oxygen and impurities inside the furnace, preventing the oxidation of silane monomers and removing residual moisture and impurities from the surface of the activated alumina layer. Methyltriethoxysilane enhances the adhesion between the film layer and the transition layer. The evaporated silane monomers are carried into the deposition furnace with the argon gas to achieve uniform deposition. In the post-processing step, argon gas is further purged to remove unreacted silane monomers from the surface, preventing residual impurities from affecting the hydrophobic properties and water treatment effect.

[0029] Overall, the above preparation method solves the problems of unstable product performance and large batch-to-batch differences, ensuring batch consistency and performance reliability of activated alumina balls.

[0030] Optionally, in the step of preparing the ceramic matrix, the sintering method is as follows: first, heat the temperature to 550-650℃ at 5℃ / min and hold for 0.5-1.5h; then heat the temperature to 1100-1200℃ at 3℃ / min and hold for 2-3h.

[0031] By adopting the above technical solution and using a segmented heating sintering method, the first stage of rapid heating allows the moisture and organic impurities in the green body to be fully decomposed and volatilized, achieving degreasing and avoiding the rapid volatilization of impurities during subsequent high-temperature sintering, which could lead to porosity, cracks, or deformation in the green body. The second stage of heating is at a slower rate, which is the grain growth and densification stage. The slower heating rate promotes the slow and uniform growth of grains in the green body, avoiding excessively large grains that could damage the pore structure. At the same time, it ensures that the green body is fully densified, improving the mechanical strength and structural stability of the matrix.

[0032] Thirdly, this invention provides an application of activated alumina balls in wastewater treatment, employing the following technical solution: The application steps of the activated alumina balls in wastewater treatment are as follows: Activated alumina balls are packed into the wastewater treatment reactor, with a packing volume of 30-50% of the effective volume of the reactor. The wastewater to be treated is introduced into the reactor after pretreatment by bar filtration and sedimentation tank. At the same time, ozone is introduced in the form of microbubbles through an aeration device, and the wastewater retention time is controlled to be 30-60 minutes. After the reaction, the wastewater is settled in a sedimentation tank and then filtered by activated carbon to obtain effluent that meets the standards.

[0033] By adopting the above technical solutions, the filling volume is limited to 30-50% of the effective volume of the reactor to ensure sufficient contact between the activated alumina balls and the wastewater, while ensuring that the wastewater has reasonable flow resistance. Secondly, a pretreatment process is set up, in which the wastewater to be treated is introduced into the reactor after being pretreated by bar filtration and sedimentation tank to remove large particulate impurities in the wastewater and avoid impurities clogging the pores of the activated alumina balls, affecting their adsorption and catalytic performance. Thirdly, ozone is introduced in the form of microbubbles through an aeration device. The composite active components in the activated alumina balls act as a catalyst for ozone catalytic decomposition, promoting the generation of hydroxyl radicals with strong oxidizing properties. Hydroxyl radicals rapidly degrade recalcitrant organic pollutants. Subsequent sedimentation tank sedimentation and activated carbon filtration further remove the flocs and residual pollutants generated by the reaction, ensuring that the effluent water quality meets the standards.

[0034] In summary, the present invention has at least one of the following beneficial technical effects: 1. By covering the active alumina layer with a hydrophobic silica layer, a dual physical and chemical protective barrier is formed, isolating the aqueous phase and chemical media from direct contact with the active components, thus fundamentally solving the problem of active component loss and enhancing structural protection stability; an additional transition layer is added and atomic layer deposition technology is used to prevent peeling from the hydrophobic layer; amino-terminated polysiloxane loaded with nano-TiO2 is introduced into the transition layer, which ensures the integrity of the protection while not hindering the diffusion of pollutants, significantly improving the long-term structural stability of the product in complex aquatic environments.

[0035] 2. By introducing activated alumina into the sintering raw materials, the specific surface area and surface roughness of the matrix are increased, enhancing the bonding force with the activated alumina layer; the addition of composite silane precursors and ammonium bicarbonate increases the porosity and density of the matrix, providing a high-quality carrier for pollutant diffusion and active component loading; segmented heating sintering ensures uniform grain growth in the green body, laying a reliable carrier foundation for the stable loading and performance of subsequent functional layers.

[0036] 3. By utilizing the redox properties of cerium dioxide in the composite active component, electron transfer is promoted and the activation energy of the reaction is reduced, thereby improving the degradation efficiency of recalcitrant pollutants; its oxygen storage and release capabilities alleviate carbon poisoning at active sites, extend catalytic life, and broaden its application range in high-concentration recalcitrant wastewater.

[0037] 4. By adopting the preparation process of the present invention, the uniformity and controllability of each layer structure are ensured, guaranteeing the consistency of product performance and the feasibility of industrial scale-up. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to the embodiments.

[0039] Unless otherwise specified, the experimental methods used in the embodiments of this application are conventional methods, and the materials used are commercially available unless otherwise specified.

[0040] Example 1: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0041] 1. An activated alumina ball, comprising a ceramic substrate, an activated alumina layer, and a hydrophobic layer arranged sequentially from the inside to the outside; wherein the mass ratio of the ceramic substrate, the activated alumina layer, and the hydrophobic layer is 92:7:0.5; The ceramic matrix is ​​made by sintering raw materials; the sintering raw materials are clay. The activated alumina layer is loaded with a composite active component; the composite active component includes zinc oxide and magnesium oxide, wherein the mass ratio of zinc oxide to magnesium oxide is 1.5:1; the total mass of the composite active component accounts for 5.0 wt% of the mass of the activated alumina layer. The hydrophobic layer is a silicon dioxide protective film with a thickness of 6±3nm.

[0042] 2. The preparation method of activated alumina balls includes the following steps: S1: Preparation of ceramic matrix: S11: Ingredient mixing: Add the sintering raw materials to deionized water at a mass ratio of 1:1.5 and ball mill for 3 hours to obtain a uniform slurry; S12: Granulation and molding: Spray granulation of slurry, controlling the inlet air temperature to 200℃, the outlet air temperature to 80℃, and the feeding speed to 5mL / min, to obtain spherical green bodies; S13: Sintering and solidification: The spherical blank is sintered using the following sintering method: First, the temperature is increased to 450℃ at a rate of 5℃ / min and held for 1.5h to remove the binder; then, the temperature is increased to 1150℃ at a rate of 5℃ / min and held for 2.5h to complete sintering; after sintering, the furnace is cooled to room temperature to obtain the ceramic matrix. S2: Preparation of intermediate products: S21: Preparation of activated alumina sol: Boehmite was dissolved in a 5% (w / w) nitric acid solution, and the (w / w) mass fraction of boehmite in the final sol was controlled to be 12%. The mixture was stirred at 80℃ for 2 hours to form a uniform sol. S22: Coating: Immerse the ceramic substrate in the activated alumina sol for 10 minutes, then remove and dry at 120°C for 2 hours to obtain the activated alumina layer. S23: Loading of composite active components: Weigh zinc nitrate and magnesium nitrate, dissolve them in deionized water, and prepare a mixed solution with a total metal ion concentration of 0.75 mol / L; immerse the ceramic substrate coated with an active alumina layer into the mixed solution, sonicate it for 30 min at a power of 200 W and a frequency of 40 kHz, slowly add ammonia water to adjust the pH to 8.5, and let it stand to precipitate for 2 h; take out the substrate after precipitation, rinse the surface with deionized water until there are no impurities, dry it at 120℃ for 4 h, and keep it at 420℃ for 3 h to obtain an active alumina layer loaded with composite active components; S3: Vapor deposition of the hydrophobic layer: S31: Preparation for vapor deposition: Dry the above intermediate product at 150°C for 2 hours; then seal the deposition furnace, evacuate to a pressure of 8Pa, and purge with argon gas for 30 minutes at a flow rate of 20mL / min. S32: Silane monomer evaporation and deposition: Methyltriethoxysilane was heated to 150℃ and evaporated at a constant temperature for 35 min. The evaporated silane monomer was carried into the deposition furnace with argon gas. The carrier gas flow rate was 15 mL / min, the deposition temperature was 200℃, and the deposition time was 2 h. S33: Post-treatment: After deposition, the substrate is allowed to cool naturally to room temperature to form a 6±3nm thick hydrophobic silica layer on the surface of the preform. S4: Finished product processing: Take out the activated alumina balls after the hydrophobic layer is deposited, place them in a purging device, and purge the surface with argon gas at room temperature to remove any remaining unreacted silane monomers. The purging flow rate is 30 mL / min and the purging time is 15 min to obtain the finished activated alumina balls.

[0043] The following parameters are specified: ① Clay purity ≥ 95%, particle size 250 ± 50 mesh; ② Ceramic matrix diameter 5.60 ± 2.80 μm; ③ Activated alumina can be either θ-type or γ-type activated alumina. In this embodiment, γ-type activated alumina is selected, and the specific surface area of ​​the γ-type activated alumina used is ≥ 200 m² / g. 2 / g.

[0044] 3. Application of activated alumina balls in wastewater treatment: Activated alumina balls were packed into the wastewater treatment reactor, filling 40% of the reactor's effective volume. The wastewater to be treated was filtered through a grid with a pore size of 3±2mm and sent to a horizontal flow sedimentation tank for pretreatment. The hydraulic retention time in the sedimentation tank was 2 hours. Then, the wastewater was introduced into the reactor by a lift pump at a volumetric flow rate of 1.5 m3 / h. At the same time, ozone was introduced into the reactor in the form of microbubbles through a bottom aeration device. The bubble particle size was 75±25μm, the aeration intensity was 2.5 m3 / (m3・h), the ozone purity was ≥90%, and the wastewater retention time was controlled at 45 minutes. After the reaction, the wastewater was settled in a sedimentation tank for 1 hour and then filtered through a granular activated carbon filter column with an activated carbon particle size of 3±1mm to finally obtain effluent that meets the standards.

[0045] 4. Detection Indicators The main tests include COD removal rate, ozone utilization rate, and recycling performance degradation rate.

[0046] COD removal rate (%): Reflects the adsorption-catalytic degradation ability of alumina balls for organic pollutants in wastewater. According to GB / T11914-1989 Determination of Chemical Oxygen Demand in Water - Dichromate Method, the detection method is to take wastewater samples before and after treatment, determine the COD value by dichromate titration and calculate the removal rate. Ozone utilization rate (%): reflects the efficiency of ozone activation and decomposition catalyzed by alumina balls. According to "HJ504-2009 Determination of ozone in water quality - Sodium indigo disulfonate spectrophotometric method", the detection method is to measure the ozone concentration in the inlet and outlet air and calculate the ratio of ozone consumption to dosage. Cyclic performance decay rate (%): This reflects the performance stability of alumina balls after multiple wastewater treatment cycles. The test method is to continuously use alumina balls for 50 wastewater treatment cycles, measure the COD removal rate at the first and 50th cycles, calculate the performance decay range, and convert it into the decay rate per 50 cycles. The decay rate is (first removal rate - 50th removal rate) / first removal rate × 100%.

[0047] The recalcitrant organic industrial wastewater used in the experiment was a complex pollutant containing phenols and dyes, with a phenol concentration of 50±2 mg / L and a methylene blue concentration of 20±5 mg / L. The initial COD concentration, detected by the dichromate method, was 180 mg / L, and the pH value was 6.8.

[0048] Example 2: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0049] An activated alumina sphere comprises a ceramic matrix, an activated alumina layer, and a hydrophobic layer arranged sequentially from the inside out; wherein the mass ratio of the ceramic matrix, the activated alumina layer, and the hydrophobic layer is 85:14:0.1. Everything else is exactly the same as in Example 1.

[0050] Example 3: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0051] An activated alumina sphere comprises a ceramic substrate, an activated alumina layer, and a hydrophobic layer arranged sequentially from the inside out; wherein the mass ratio of the ceramic substrate, the activated alumina layer, and the hydrophobic layer is 88.5:10.5:0.3. Everything else is exactly the same as in Example 1.

[0052] The activated alumina balls prepared in Examples 1-3 were applied to wastewater treatment, and the test results are shown in Table 1: Table 1. Detection results of Examples 1-3 Testing items Example 1 Example 2 Example 3 COD removal rate (%) 86.2 87.5 86.8 Ozone utilization rate (%) 78.5 76.3 77.4 Performance degradation rate (%) after repeated use 8.8 9.2 8.5 Based on the test data from Examples 1-3, it can be seen that Example 1 has the highest proportion of hydrophobic layer, resulting in the best ozone adsorption and activation efficiency. However, the low proportion of activated alumina layer leads to a slightly lower COD removal rate. Example 2 has the highest proportion of activated alumina layer and sufficient catalytic sites, resulting in the best COD removal rate. However, the excessively thick activated alumina layer hinders ozone conduction, resulting in the lowest ozone utilization rate and the highest attenuation rate among the three examples. Example 3 has a balanced ratio, taking into account catalytic sites, efficient ozone activation, and good interlayer stability, with the most balanced overall performance across the three indicators.

[0053] Example 4: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0054] The sintering raw materials are activated alumina and clay, wherein the mass ratio of activated alumina to clay is 2:13. Everything else is the same as in Example 3.

[0055] Example 5: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0056] In this embodiment, the sintering raw materials are activated alumina, clay, a composite silane precursor encapsulated in urea-formaldehyde resin microcapsules, and ammonium bicarbonate; the composite silane precursor encapsulated in urea-formaldehyde resin microcapsules accounts for 4 wt% of the clay mass, and the ammonium bicarbonate accounts for 2.5 wt% of the clay mass. The microcapsule wall material of the composite silane precursor encapsulated in urea-formaldehyde resin microcapsules is coated with methyltriethoxysilane, wherein the methyltriethoxysilane accounts for 2 wt% of the microcapsule wall material. The composite silane precursor comprises tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane-modified organomontmorillonite, wherein the mass ratio of tetraethyl orthosilicate to γ-glycidoxypropyltrimethoxysilane-modified organomontmorillonite in the composite silane precursor is 4:1. a. The preparation method of the composite silane precursor is as follows: sodium-based organomontmorillonite is added to anhydrous ethanol and mixed to form a uniform suspension. γ-glycidoxypropyltrimethoxysilane, accounting for 12 wt% of the mass of organomontmorillonite, is added, the temperature is raised to 58°C, and ultrasonic stirring is continued for 2.0 h to obtain γ-glycidoxypropyltrimethoxysilane-modified organomontmorillonite with a grafting rate of 35%. Tetraethyl orthosilicate was added to the above suspension, and the temperature was maintained at 58°C. The mixture was then ultrasonically stirred for 1.5 hours. It was then evaporated at a rotary evaporation temperature of 50°C, a vacuum degree of -0.085 MPa, and a rotation speed of 90 r / min until no liquid distilled out. The mixture was then placed in a vacuum drying oven and dried at 85°C and a vacuum degree of -0.095 MPa for 3 hours. After cooling to room temperature, the mixture was ground through a 200-mesh sieve to obtain the composite silane precursor. The interlayer spacing of the sodium-based organomontmorillonite is 2.0 ± 0.2 nm; b. The preparation method of the composite silane precursor encapsulated in urea-formaldehyde resin microcapsules is as follows: 1) Preparation of urea-formaldehyde resin prepolymer: Mix urea and formaldehyde at a molar ratio of 1:1.75, add deionized water and stir to dissolve, adjust the pH to 8.5 with 10% sodium hydroxide solution, heat to 72℃ and stir for 60 min, cool to room temperature and add deionized water to dilute, and obtain a urea-formaldehyde resin prepolymer solution with a mass concentration of 45wt%. 2) Preparation of composite silane precursor dispersion: The composite silane precursor was added to anhydrous ethanol and ultrasonically dispersed for 20 min at a power of 300W and a frequency of 40kHz to prepare a composite silane precursor dispersion with a mass concentration of 15wt%. 3) Microcapsule coating: Deionized water was placed in a reaction vessel, polyvinyl alcohol was added, and the mixture was stirred at 300 rpm and 30°C to dissolve it, so that the mass fraction of polyvinyl alcohol was 0.8 wt%, resulting in a homogeneous aqueous phase. The composite silane precursor dispersion was added to the aqueous phase, and the volume ratio of the composite silane precursor dispersion to the aqueous phase was controlled at 1:8. The mixture was emulsified at 1200 rpm for 30 min. The pH of the emulsion was adjusted to 3.5 with a 10 wt% hydrochloric acid solution. Urea-formaldehyde resin prepolymer solution was added according to the mass of urea-formaldehyde resin prepolymer being 1.2 times the mass of the composite silane precursor. The mixture was heated to 48°C and kept at that temperature for 2.5 h to complete the polymerization and coating. 4) Microcapsule separation and purification: After the reaction was completed, the mixture was cooled to room temperature, centrifuged at 6000 rpm for 10 min, washed 3 times with deionized water, washed once with anhydrous ethanol, and dried at 80℃ for 4 h to obtain the composite silane precursor encapsulated in urea-formaldehyde resin microcapsules. 5) Coating with methyltriethoxysilane for wall material: Mix anhydrous ethanol and deionized water at a volume ratio of 95:5, add methyltriethoxysilane to prepare a coating solution with a mass concentration of 5wt%, and stir for 30 min to hydrolyze; add the microcapsules obtained in step 4 to the coating solution at a solid-liquid ratio of 1:20 (g / mL), and immerse at 40℃ for 40 min while stirring at 300 rpm; after immersion coating, centrifuge and dry at 105℃ for 2 h to allow the silane to hydrolyze, crosslink and solidify, thus obtaining the final product.

[0057] Everything else is the same as in Example 4.

[0058] Example 6: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0059] In this embodiment, the composite active components are zinc oxide, magnesium oxide and cerium dioxide, wherein the mass ratio of cerium dioxide, zinc oxide and magnesium oxide is 0.10:1.5:1; In the preparation steps of activated alumina balls: S23: Loading of composite active components: Weigh zinc nitrate, magnesium nitrate and cerium nitrate according to the mass ratio, dissolve the three nitrates in deionized water, stir until dissolved, and prepare a mixed solution with a total metal ion concentration of 0.75 mol / L. Everything else is the same as in Example 5.

[0060] The activated alumina balls prepared in Examples 4-6 were applied to wastewater treatment, and the test results are shown in Table 2: Table 2 Detection results of Examples 4-6 Testing items Example 4 Example 5 Example 6 COD removal rate (%) 88.0 89.8 90.5 Ozone utilization rate (%) 79.2 81.5 84.5 Performance degradation rate (%) after repeated use 7.9 6.3 5.8 By comparing Example 4 with Example 3, it can be seen that adding activated alumina to the sintering raw material increases the bonding ability between the activated alumina layer and the substrate, and at the same time improves the exposure of catalytic sites. Therefore, the COD removal rate and ozone utilization rate are improved. Meanwhile, the optimization of the pore structure reduces the interlayer stress during recycling and the recycling performance decay rate is reduced.

[0061] By comparing Example 5 with Example 4, it can be seen that the ammonium bicarbonate decomposes and creates pores during sintering, further increasing the porosity of the matrix. The composite silane precursor encapsulated in urea-formaldehyde resin microcapsules achieves the slow release of the composite silane precursor, strengthens the binding force between the active component and the carrier, and significantly improves the ozone activation efficiency and COD removal rate under the dual effect. Furthermore, the enhanced component stability leads to a decrease in the decay rate.

[0062] By comparing Example 6 with Example 5, it can be seen that the addition of cerium dioxide to the composite active component can promote the generation of hydroxyl radicals as a co-catalyst, enhance the ozone catalytic degradation efficiency, and optimize the electron transfer efficiency of the active component. Therefore, the COD removal rate is improved, the ozone utilization rate is improved, and the decay rate is reduced.

[0063] Example 7: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0064] In this embodiment, an activated alumina sphere comprises a ceramic substrate, an activated alumina layer, an Al2O3 transition layer, and a hydrophobic layer arranged sequentially from the inside out; wherein the mass ratio of the ceramic substrate, the activated alumina layer, the Al2O3 transition layer, and the hydrophobic layer is 88.5:10.5:0.1:0.3; and the thickness of the Al2O3 transition layer is 2.5±0.5 nm. In the preparation method of activated alumina balls: An Al2O3 transition layer preparation step is added after the S23 composite active component loading step and before the S3 step. The Al2O3 transition layer preparation steps are as follows: Aluminum isopropoxide was dissolved in a mixture of anhydrous ethanol and deionized water at a volume ratio of 4:1. The pH was adjusted to 3.5 by adding 5 wt% nitric acid solution. The mixture was stirred at 80°C for 1.5 h to obtain an Al2O3 sol with a mass concentration of 8 wt%. The sol was then allowed to stand and cool to room temperature for later use. An active alumina substrate loaded with composite active components was immersed in the sol for 5 min. After immersion, the substrate was dried at 120°C for 1 h and then calcined at 450°C for 2 h to form an Al2O3 transition layer. Then proceed with the S3 step: vapor deposition of the hydrophobic layer. Preparation for vapor deposition: The intermediate product containing the Al2O3 transition layer was dried at 150°C for 2 hours; then the deposition furnace was sealed, the vacuum was drawn to a pressure of 8 Pa, and argon gas was introduced to purge for 30 min at a flow rate of 20 mL / min. Everything else is the same as in Example 6.

[0065] Example 8: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0066] In this embodiment, in the preparation method of activated alumina balls: An Al2O3 transition layer preparation step is added after the S23 composite active component loading step and before the S3 step. The Al2O3 transition layer preparation steps are as follows: The ceramic substrate loaded with the composite active components in S23 was placed in the atomic layer deposition reaction chamber. After the chamber was closed, the vacuum system was started and the chamber pressure was stabilized at 0.8 Pa. The temperature was raised to 150℃ and held for 30 min. Trimethylaluminum was used as the aluminum source precursor and deionized water was used as the oxygen source precursor. Deposition was carried out using an alternating pulse injection method: the aluminum source precursor was injected for 10 s at a time, followed by argon purging for 20 s; the oxygen source precursor was injected for 10 s at a time, followed by argon purging for 20 s again, completing one deposition cycle. The above cycle was repeated for 20 to 30 deposition cycles. After deposition, the chamber was kept under vacuum and the substrate was removed after cooling to room temperature to obtain an intermediate product containing an Al2O3 transition layer. Everything else is the same as in Example 7.

[0067] Example 9: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0068] In this embodiment, the preparation steps of the Al2O3 transition layer in the preparation method of activated alumina spheres are as follows: During the 12th cycle, 1.5 wt% of amino-terminated polysiloxane (based on the mass of trimethylaluminum) was introduced simultaneously with the aluminum source precursor pulse during the 3rd second of the pulse introduction. It was delivered via a micro-pulse pump and mixed with trimethylaluminum before being introduced into the reaction chamber for 7 seconds, synchronizing with the aluminum source introduction time. Subsequently, argon purging was performed for 20 seconds according to standard parameters, followed by oxygen source introduction and purging, completing the 12th cycle.

[0069] The amino-terminated polysiloxane is surface-loaded with nano-TiO2; the nano-TiO2 accounts for 6.5 wt% of the amino-terminated polysiloxane. The preparation method of the amino-terminated polysiloxane surface loaded with nano-TiO2 is as follows: Amino-terminated polysiloxane was dispersed in deionized water to form a suspension with a mass concentration of 2 wt%. Tetrabutyl titanate, a precursor of TiO2, was added, along with diethanolamine at a mass of 2 wt% of tetrabutyl titanate. The suspension was subjected to a hydrothermal reaction at 85 °C for 3 h. After the reaction, the mixture was centrifuged at 8000 r / min for 15 min, washed with deionized water until the pH value reached 7.0 ± 0.1, and dried at 120 °C for 2 h to obtain amino-terminated polysiloxane microspheres with uniformly loaded nano-TiO2 on the surface, which were then set aside for later use. The amino content in the amino-terminated polysiloxane is 1.0 ± 0.2 mmol / g. The preparation method of the amino-terminated polysiloxane is as follows: Amino-terminated polydimethylsilane was mixed with anhydrous toluene at a solid-liquid ratio of 1:5 (g / mL). After stirring and dissolving, the mixture was heated to 80°C. Under nitrogen protection, γ-aminopropyltriethoxysilane (KH-550) was added, with the mass ratio of KH-550 to amino-terminated polydimethylsilane controlled at 1:8. After the addition was complete, the mixture was kept at this temperature for 3 hours. Then, 0.5 wt% of dibutyltin dilaurate was added, and the mixture was heated to 100°C and reacted for another 2 hours. After cooling to room temperature, the mixture was washed twice with anhydrous ethanol, centrifuged at 5000 rpm for 8 minutes, and dried under vacuum at 80°C for 3 hours to obtain amino-terminated polysiloxane. Everything else is the same as in Example 8.

[0070] Example 10: This example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0071] In this embodiment, in the method for preparing activated alumina balls, In the S1 step of preparing the ceramic matrix, the sintering method is as follows: first, the temperature is raised to 550-650℃ at 5℃ / min and held for 0.5-1.5h; then the temperature is raised to 1100-1200℃ at 3℃ / min and held for 2-3h. Everything else is the same as in Example 9.

[0072] The activated alumina balls prepared in Examples 7-10 were applied to wastewater treatment, and the test results are shown in Table 3: Table 3 Detection results of Examples 7-10 Testing items Example 7 Example 8 Example 9 Example 10 COD removal rate (%) 90.6 91.2 91.8 91.8 Ozone utilization rate (%) 84.6 85.8 86.5 86.7 Performance degradation rate (%) after repeated use 5.0 4.3 4.0 4.0 By comparing Example 7 with Example 6, it can be seen that adding the Al2O3 transition layer can fill the interface defects between the active alumina layer and the hydrophobic layer, enhance the interlayer adhesion, and reduce the loss of active components during recycling, thus reducing the decay rate. However, the transition layer has no significant effect on catalytic activity.

[0073] By comparing Example 8 with Example 7, it can be seen that the transition layer preparation method has been improved and optimized, thereby forming a denser and more uniform nanoscale Al2O3 film layer. This not only more efficiently prevents the loss of active components, but also reduces the obstruction of catalytic sites and promotes the contact between ozone and active components. Therefore, all three indicators are improved.

[0074] By comparing Example 9 with Example 8, it can be seen that the amino-terminated polysiloxane in the transition layer is loaded with nano-TiO2. The TiO2 further catalyzes the existing active components and further increases the amount of hydroxyl radicals generated. The amino-terminated polysiloxane enhances the bonding force between the transition layer and the hydrophobic layer. Therefore, all indicators are improved accordingly.

[0075] By comparing Example 10 with Example 9, it can be seen that adjusting the sintering process further makes the ceramic matrix grain growth more uniform, improves structural stability, reduces matrix damage during recycling, indirectly optimizes ozone conduction efficiency, improves ozone utilization, and keeps COD removal rate and decay rate unchanged.

[0076] Comparative Example 1: This comparative example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0077] In this comparative example, the active alumina spheres do not include a hydrophobic layer; An activated alumina ball comprises a ceramic matrix and an activated alumina layer arranged sequentially from the inside out; wherein the mass ratio of the ceramic matrix to the activated alumina layer is 88.5:10.5. Everything else is the same as in Example 3.

[0078] Comparative Example 2: This comparative example discloses an activated alumina ball, its preparation method, and its application in wastewater treatment.

[0079] In this comparative example, the ratio of the composite active components was adjusted, with the mass ratio of zinc oxide to magnesium oxide being 3:1; other aspects were the same as in Example 3.

[0080] The activated alumina balls prepared in Comparative Examples 1-2 were applied to wastewater treatment, and the test results are shown in Table 4. Table 4. Test results of Comparative Examples 1-2 Testing items Comparative Example 1 Comparative Example 2 COD removal rate (%) 75.8 81.1 Ozone utilization rate (%) 68.2 70.6 Performance degradation rate (%) after repeated use 22.5 11.3 By comparing Comparative Example 1 and Example 3, it can be seen that without a hydrophobic layer, water cannot prevent the erosion of the active components. During recycling, a large amount of active components are lost, the catalytic sites are continuously reduced, and ozone is easily released directly. Therefore, the COD removal rate and ozone utilization rate both decrease. The absence of a hydrophobic layer also exacerbates the damage to the interlayer interface. Cyclic stress causes the active alumina layer to fall off, which greatly increases the rate of performance degradation during recycling.

[0081] By comparing Comparative Example 2 and Example 3, the change in the ratio of the composite active components caused agglomeration during the crystallization process, which reduced the effective exposure of catalytic sites, decreased the efficiency of ozone activation and pollutant degradation, and reduced both COD removal rate and ozone utilization rate. The agglomerated active components had weak bonding with the activated alumina layer, and even with the protection of a hydrophobic layer, local detachment would still occur during recycling, which would increase the attenuation rate.

[0082] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. An activated alumina ball, characterized in that, It includes a ceramic matrix, an active alumina layer, and a hydrophobic layer arranged sequentially from the inside out; wherein the mass ratio of the ceramic matrix, the active alumina layer, and the hydrophobic layer is 85~92:7~14:0.1~0.

5. The ceramic matrix is ​​made by sintering raw materials; the sintering raw materials include clay. The activated alumina layer is loaded with a composite active component; the composite active component includes zinc oxide and magnesium oxide, wherein the mass ratio of zinc oxide to magnesium oxide is 1 to 2:1; the total mass of the composite active component accounts for 4.0 to 6.0 wt% of the mass of the activated alumina layer. The hydrophobic layer is a silicon dioxide protective film.

2. The activated alumina spheres according to claim 1, characterized in that, The sintering raw materials also include activated alumina, wherein the mass ratio of activated alumina to clay is 1-3:9-17.

3. The activated alumina spheres according to claim 1, characterized in that, The sintering raw materials also include a composite silane precursor encapsulated in urea-formaldehyde resin microcapsules and ammonium bicarbonate; the microcapsule wall material of the composite silane precursor encapsulated in urea-formaldehyde resin microcapsules is coated with methyltriethoxysilane, wherein the methyltriethoxysilane accounts for 1-3 wt% of the microcapsule wall material. The composite silane precursor encapsulated in urea-formaldehyde resin microcapsules comprises 3-5 wt% of the clay mass, and the ammonium bicarbonate comprises 2-3 wt% of the clay mass. The composite silane precursor comprises tetraethyl orthosilicate and γ-glycidoxypropyltrimethoxysilane-modified organomontmorillonite, wherein the mass ratio of tetraethyl orthosilicate to γ-glycidoxypropyltrimethoxysilane-modified organomontmorillonite in the composite silane precursor is 3 to 5:

1.

4. The activated alumina spheres according to claim 1, characterized in that, The composite active component also includes cerium dioxide, wherein the mass ratio of cerium dioxide, zinc oxide, and magnesium oxide is 0.06–0.12:1–2:

1.

5. The activated alumina spheres according to claim 1, characterized in that, It also includes an Al2O3 transition layer, which is disposed between the active alumina layer and the hydrophobic layer; wherein the mass ratio of the ceramic substrate, the active alumina layer, the Al2O3 transition layer and the hydrophobic layer is: 85~92:7~14:0.05~0.15:0.1~0.

5.

6. The activated alumina spheres according to claim 5, characterized in that, The Al2O3 transition layer is prepared as follows: Atomic layer deposition reaction was carried out on a ceramic substrate containing an active alumina layer. The vacuum was evacuated to a pressure ≤1 Pa and the temperature was raised to 150 °C. Trimethylaluminum was used as the aluminum source precursor and deionized water was used as the oxygen source precursor. The mixture was alternately introduced into the atomic layer deposition reaction chamber and the deposition was carried out in cycles of 20 to 30 times to deposit an Al2O3 transition layer on the surface of the active alumina layer.

7. The activated alumina spheres according to claim 6, characterized in that, In the preparation method of the Al2O3 transition layer, during the 10th to 15th atomic layer deposition cycles, an amino-terminated polysiloxane, accounting for 1 to 2 wt% of the mass of trimethylaluminum, is added; nano-TiO2 is loaded on the surface of the amino-terminated polysiloxane; the nano-TiO2 accounts for 5 to 8 wt% of the mass fraction of the amino-terminated polysiloxane. The preparation method of the amino-terminated polysiloxane surface loaded with nano-TiO2 is as follows: Amino-terminated polysiloxane was dispersed in deionized water to form a suspension. Tetrabutyl titanate, a precursor of TiO2, was added, along with diethanolamine accounting for 1–3 wt% of the mass of tetrabutyl titanate. The suspension was subjected to a hydrothermal reaction at 80–90 °C for 2–4 h. After the reaction, the suspension was centrifuged, washed with deionized water until the pH value reached 7.0 ± 0.1, and dried at 120 °C for 2 h to obtain amino-terminated polysiloxane microspheres with uniformly loaded nano-TiO2 on the surface.

8. A method for preparing the activated alumina spheres according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Preparation of ceramic matrix: Add the sintering raw materials to deionized water and ball mill to mix them to obtain a uniform slurry; spray granulate the slurry to obtain a spherical green body; sinter the spherical green body and cool it to room temperature to obtain the ceramic matrix; S2: Preparation of intermediate products: Preparation of activated alumina sol: Boehmite was dissolved in nitric acid solution and stirred until a homogeneous sol was formed; Coating: The ceramic substrate is immersed in activated alumina sol, removed and dried to obtain an activated alumina layer; Composite active component loading: Weigh zinc nitrate and magnesium nitrate, dissolve them in deionized water, and prepare a mixed solution with a total metal ion concentration of 0.5-1.0 mol / L; immerse the ceramic substrate coated with the active alumina layer in the mixed solution, sonicate, add ammonia to adjust the pH to 8-9, and let it stand to precipitate; take out the precipitated substrate, rinse the surface with deionized water, dry it, and keep it at 400-450℃ for 3 hours to obtain the active alumina layer loaded with composite active components; Preparation of Al2O3 transition layer: An Al2O3 transition layer is coated on the surface of an active alumina layer loaded with composite active components; S3: Vapor deposition of the hydrophobic layer: Preparation for vapor deposition: Dry the obtained intermediate product; seal the deposition furnace and evacuate to a pressure ≤10Pa, then purge with argon gas for 30min; Silane monomer evaporation and deposition: Methyltriethoxysilane is heated and evaporated, and the evaporated silane monomer is carried into the deposition furnace with argon gas; Post-treatment: After deposition, the substrate is allowed to cool naturally to room temperature, forming a 6±3 nm thick hydrophobic silica layer on the surface of the preform. S4: Finished product processing: After the hydrophobic layer is deposited, the activated alumina balls are taken out and the unreacted silane monomers remaining on the surface are purged with argon gas to obtain the finished activated alumina balls.

9. The method for preparing activated alumina spheres according to claim 8, characterized in that, In the step of preparing the ceramic matrix, the sintering method is as follows: first, the temperature is raised to 550-650℃ at 5℃ / min and held for 0.5-1.5h; then the temperature is raised to 1100-1200℃ at 3℃ / min and held for 2-3h.

10. The application of an activated alumina ball according to any one of claims 1-7, or an activated alumina ball prepared by the preparation method according to claim 8 or 9, in wastewater treatment, characterized in that, The application steps of the activated alumina balls in wastewater treatment are as follows: Activated alumina balls are packed into the wastewater treatment reactor, with a packing volume of 30-50% of the effective volume of the reactor. The wastewater to be treated is introduced into the reactor after pretreatment by bar filtration and sedimentation tank. At the same time, ozone is introduced in the form of microbubbles through an aeration device, and the wastewater retention time is controlled to be 30-60 minutes. After the reaction, the wastewater is settled in a sedimentation tank and then filtered by activated carbon to obtain effluent that meets the standards.