Biomimetic silicification enhanced catalysts, methods of making and using the same

Abstract

A biomimetic silicification-enhanced catalyst and its preparation method are disclosed. The preparation method includes the following steps: S1: Urea, iron salt, and copper salt are added to a first solvent to obtain a mixed solution; S2: The mixed solution undergoes a hydrothermal reflux reaction to obtain particle units; S3: The particle units undergo a silicification reaction with ammonia and a silica precursor to obtain a catalyst. The catalyst prepared by this method can not only reduce its band gap by copper doping to utilize visible light as a reaction light source and reduce reaction conditions, but also inhibit the aggregation of catalyst particles by utilizing the mesoporous silica layer on the surface, expose more reaction sites, and limit the heat loss of the internal particle units, thereby increasing the reaction temperature. This can effectively improve the organic matter treatment effect of the catalyst. It adsorbs and degrades dyes in wastewater through two modes: electrostatic attraction and catalytic decomposition of hydrogen peroxide to generate strong oxidizing free radicals.

Description

Technical Field

[0001] This invention relates to the field of composite materials, specifically to biomimetic silicification reinforced catalysts, their preparation methods, and applications. Background Technology

[0002] In recent years, high-concentration organic wastewater has posed a threat to water environmental protection. Traditional biological treatment methods are inadequate for treating substances with poor biodegradability and relative molecular masses ranging from several thousand to tens of thousands. Advanced oxidation processes (AOPs) can generate free radicals with strong oxidizing capabilities. Under reaction conditions such as high temperature and pressure, electricity, sound, light irradiation, and catalysts, they can oxidize large, recalcitrant organic molecules into low-toxicity or non-toxic small molecules. AOPs can completely mineralize or decompose most organic matter and have great potential in treating organic matter in wastewater generated from industrial production and urban life.

[0003] Among them, the photo-Fenton reaction is one of the powerful and economical AOPs for degrading organic matter through hydroxyl radicals and / or superoxide radicals. However, traditional heterogeneous photo-Fenton catalysts have a wide band gap, which places certain requirements on the wavelength of the reaction light source, making it impossible to directly use sunlight as the reaction light source, resulting in relatively harsh reaction conditions. In addition, due to the nanoscale size of the catalyst particles, they are prone to agglomeration during the reaction under the influence of electrostatic and van der Waals forces, significantly reducing the reaction sites and leading to poor reaction results. Summary of the Invention

[0004] One objective of this invention is to provide a method for preparing a biomimetic silicification-enhanced catalyst. The biomimetic silicification-enhanced catalyst prepared by this method has a narrower band gap, thereby enabling the use of visible light as a reaction light source. At the same time, the biomimetic silicification-enhanced catalyst can utilize the externally formed silica layer to suppress the agglomeration of catalyst particles, thereby effectively improving the organic matter treatment effect of the catalyst. Moreover, this preparation method has a short reaction path, mild reaction conditions, and low energy consumption, which is conducive to the large-scale production of the catalyst.

[0005] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0006] A method for preparing a biomimetic silicification-enhanced catalyst, characterized by comprising the following steps:

[0007] S1: Urea, iron salt, and copper salt are added to the first solvent to obtain a mixed solution;

[0008] S2: The mixture solution is subjected to a hydrothermal reflux reaction to obtain particle units;

[0009] S3: The particle unit is reacted with ammonia and silicon dioxide precursor to produce a catalyst.

[0010] In this technical solution, urea, iron salt, and copper salt are added to a first solvent and thoroughly mixed to obtain a mixed solution. The mixed solution can then be directly subjected to a hydrothermal reflux reaction to obtain copper-doped iron hydroxyl oxide particle units, which are then silicided to obtain a particulate catalyst. Alternatively, the substrate can be immersed in the mixed solution to undergo a hydrothermal reflux reaction to generate copper-doped iron hydroxyl oxide particle units in situ on the substrate, which are then silicided to obtain a catalyst with a substrate.

[0011] In this technical solution, copper-doped iron hydroxyl oxide is prepared by hydrothermal reflux reaction of a mixed solution containing urea, iron salt, and copper salt. It can self-assemble into nanoflowers with a three-dimensional structure, thus having a larger specific surface area. This allows it to effectively adsorb organic matter and provide more catalytic reaction sites. At the same time, as a commonly used photo-Fenton catalyst, iron hydroxyl oxide can effectively reduce its band gap after being doped with copper ions. This enables it to catalyze the decomposition of hydrogen peroxide under visible light irradiation to generate strong oxidizing free radicals to degrade organic dyes in wastewater, thereby improving the catalytic performance of the catalyst.

[0012] In one or more embodiments, the first solvent is a mixed solvent of deionized water and anhydrous ethanol in a certain volume ratio. In some preferred embodiments, the volume ratio of deionized water to anhydrous ethanol in the first solvent is 4:1. In one or more embodiments, after the hydrothermal reflux reaction, the solid can be collected by centrifugation, washed with deionized water and anhydrous ethanol, and dried to obtain copper-doped iron hydroxyl oxide powder. In one or more embodiments, after the hydrothermal reflux reaction, a catalyst with a substrate can also be obtained by washing a copper-doped iron hydroxyl oxide substrate with water and then drying it.

[0013] In some preferred embodiments, the iron salt is ferrous sulfate heptahydrate, ferric nitrate nonahydrate, or ferrous nitrate nonahydrate; the copper salt is copper sulfate pentahydrate or copper nitrate trihydrate; and the silicon dioxide precursor is tetraethoxysilane or tetramethoxysilane.

[0014] In this technical solution, a silanization reaction is carried out between particle units and ammonia water and a silica precursor. The silica precursor, after hydrolysis, carries a negative charge and can electrostatically attract and bind to the positively charged iron hydroxyl oxide. Simultaneously, during the formation of the mesoporous silica layer, some silica precursor molecules react with the hydroxyl groups on the surface of the iron hydroxyl oxide, resulting in chemical bonds between the interior and exterior of the catalyst. Ultimately, a mesoporous silica layer is formed on the surface of the particle units through the silanization reaction, thus obtaining a catalyst with particle units inside and a mesoporous silica layer outside.

[0015] In this technical solution, the thickness of the mesoporous silica layer of the catalyst is on the nanometer scale, which does not significantly affect optical transparency and mass exchange. Therefore, the catalyst can still effectively utilize the energy of incident light for catalytic reaction. The mesoporous silica layer can increase the surface potential of the catalyst, thereby effectively inhibiting the aggregation of catalyst nanoparticles and exposing more reaction sites. At the same time, the mesoporous silica layer also has heat insulation and infrared shielding effects, which can limit the heat loss of internal particle units, further increase the reaction temperature, and thus improve the catalytic reaction efficiency.

[0016] Therefore, the catalyst prepared by the above method can not only reduce its band gap by doping with copper to utilize visible light as a reaction source and lower reaction conditions, but also utilize the mesoporous silica layer on the surface to inhibit catalyst particle aggregation, expose more reaction sites, and limit the heat loss of internal particle units, thereby increasing the reaction temperature. This effectively improves the catalyst's organic matter treatment efficiency, adsorbing and degrading dyes in wastewater through both electrostatic attraction and the generation of strong oxidizing free radicals from the catalytic decomposition of hydrogen peroxide. Furthermore, the above preparation method is simple, low in cost and energy consumption, operates under mild conditions, and does not require demanding or expensive equipment, making it suitable for large-scale production.

[0017] In a preferred embodiment of the present invention, for the preparation of particulate catalyst, in step S3, the particle unit is dispersed in a second solvent, and after adding ammonia and silica precursor, it reacts to obtain silanized particle unit. The silanized particle unit is then etched with hot water to obtain particulate catalyst.

[0018] In this technical solution, after obtaining particle units through a hydrothermal reflux reaction, the particle units are dispersed in a second solvent. In one or more embodiments, the second solvent is a mixed solvent of deionized water and anhydrous ethanol in a certain volume ratio. Subsequently, ammonia and a silica precursor, such as tetraethoxysilane, are added under continuous stirring to carry out a silanization reaction. After the reaction is completed, the particles are collected by centrifugation and washed with deionized water and anhydrous ethanol to obtain silanized particle units. Next, the silanized particle units are transferred to a flask for hot water etching. After cooling to room temperature, they are collected by centrifugation and washed with deionized water, and finally dried to obtain particulate catalyst.

[0019] In another preferred embodiment of the present invention, for the preparation of the catalyst with a substrate, in step S2, the substrate is immersed in the mixed solution and subjected to a hydrothermal reflux reaction to obtain a substrate loaded with particle units; in step S3, ammonia water, silica precursor and substrate loaded with particle units are placed together in a desiccator and reacted under negative pressure to obtain the catalyst with a substrate.

[0020] In this technical solution, the substrate can be a two-dimensional substrate, such as a filter membrane, or a three-dimensional substrate, such as a sponge.

[0021] For a two-dimensional substrate, taking a filter membrane as an example, in step S2, the filter membrane is immersed in a mixed solution for a hydrothermal reflux reaction. After the reaction, the filter membrane is removed, rinsed with water, and dried to obtain a filter membrane loaded with copper-doped iron hydroxide. Then, in step S3, the silica precursor and ammonia are placed in open containers, and then placed together with the copper-doped iron hydroxide filter membrane in a desiccator. A vacuum pump is used to create a negative pressure environment for the reaction, and the reaction is carried out at a constant temperature in an oven for 18–36 hours under negative pressure. After the reaction, a silicified mineralized composite catalyst film is obtained. In this technical solution, the silica precursor readily volatilizes under negative pressure and heating conditions with ammonia. Under alkaline conditions, the silica precursor hydrolyzes and condenses on the surface of the copper-doped iron hydroxide to form a mesoporous silica layer.

[0022] Similarly, for a three-dimensional substrate, taking a sponge as an example, in step S2, the sponge is immersed in the mixed solution for a hydrothermal reflux reaction. After the reaction, the sponge is removed, rinsed with water, and freeze-dried to obtain a sponge loaded with copper-doped iron hydroxide. Then, in step S3, the silica precursor and ammonia are placed in open containers, and then placed together with the copper-doped iron hydroxide sponge in a desiccator. A vacuum pump is used to create a negative pressure environment for the reaction, and the reaction is carried out at a constant temperature in an oven for 18–36 hours under negative pressure. After the reaction, a silicified mineralized composite film catalyst sponge is obtained. Likewise, the vapor-deposited silica layer itself is not closed but porous, therefore etching to form pores is unnecessary.

[0023] In some preferred embodiments, the sponge is a chitosan sponge, and the preparation method of the chitosan sponge includes the following steps: adding chitosan powder to an acetic acid solution and stirring thoroughly in a constant temperature water bath to completely dissolve it, thereby obtaining a chitosan solution; pouring the chitosan solution into a mold and freezing it, then transferring the frozen sample to a freeze dryer for drying and shaping; preparing a NaOH solution, removing the freeze-dried solid from the mold, immersing it in the NaOH solution for 10 hours, and then rinsing it repeatedly with deionized water until the material is neutral; freezing the obtained sponge again, and then freeze-drying it to obtain the chitosan sponge.

[0024] The substrate-based catalyst prepared by the above method is beneficial for catalyst use and recycling. The iron ions in the catalyst particle units can chelate with various organic groups such as hydroxyl and amino groups. Therefore, iron hydroxy oxide can not only self-assemble into flower-like nanoparticles in solution, but also mineralize in situ on the surface of a two-dimensional or three-dimensional substrate. At the same time, the mesoporous silica layer on the outside of the catalyst can effectively inhibit the catalyst from falling off the substrate surface, maintaining the stability and long-term effectiveness of the wastewater treatment process.

[0025] Further, the molar ratio of iron ions in the iron salt to copper ions in the copper salt is 9–19. For the particle unit, the incorporated copper ions will replace the positions of iron ions in the iron hydroxide lattice. Since the radius of copper ions is larger than that of iron ions, the incorporation of copper ions will cause the unit cell of iron hydroxide to expand. In this technical solution, by adjusting the molar ratio of iron ions to copper ions to 9–19, an appropriate amount of copper ions is incorporated into the particle unit. This promotes a more dispersed distribution of hydroxyl and oxygen vacancies on the surface of the particle unit after the unit cell expands. This makes the silica layer formed by the polymerization of silica precursor and particle surface groups more susceptible to etching to produce a porous structure. The distribution of the porous structure is more uniform, which improves the heat insulation and infrared shielding effect of the mesoporous silica layer, better restricts the heat loss of the internal particle unit, and the more uniformly distributed porous structure also helps to expose reaction sites, further improving the catalytic performance of the catalyst. Furthermore, appropriate copper ion doping can increase the surface potential of the flower-like particle units, enhance the electrostatic attraction between them and the silicon dioxide precursor, and make the bond between the internal particle units and the external mesoporous shell more compact.

[0026] Furthermore, the volume ratio of the silica precursor to the mass of the particle unit is 6.25:1 to 18.75:1. This ratio affects the catalytic degradation efficiency of organic matter by the prepared catalyst. If the proportion of silica precursor is low, some iron hydroxyl oxide particles will not be silanized or will be incompletely silanized within the same reaction time, leading to particle aggregation. Particles on the membrane or sponge surface will easily detach due to the lack of a mesoporous silica layer, resulting in reduced stability. If the proportion of silica precursor is high, the external silanization layer of the particle unit will be too thick, making it difficult for the copper-doped iron hydroxyl oxide to contact the external reaction solution, inhibiting the particle-catalyzed decomposition of hydrogen peroxide. Additionally, if the proportion of silica precursor is too high, excess silica precursor will spontaneously aggregate into silica spheres instead of forming a silica layer on the particle surface. Therefore, in this technical solution, the ratio of the volume of the silica precursor to the mass of the particle unit is 6.25:1 to 18.75:1, which can improve the stability of the catalyst, inhibit its agglomeration, and better form a mesoporous silica layer, thereby improving the catalytic performance of the catalyst.

[0027] Another objective of this invention is to provide a particulate catalyst prepared using the aforementioned biomimetic silicification-enhanced catalyst preparation method. This particulate catalyst comprises particle units, wherein the particle units are copper-doped iron hydroxyl oxide, and the surface of the particle units is covered with a mesoporous silica layer. This catalyst can use visible light as a reaction light source, is not prone to aggregation during the reaction, and its multi-level hierarchical micro / nano structure improves the catalyst's dispersibility, stability, and photothermal effect, significantly enhancing wastewater treatment capacity.

[0028] Another objective of this invention is to provide a substrate-based catalyst prepared using the aforementioned biomimetic silicification-enhanced catalyst preparation method. This substrate-based catalyst includes a substrate on which particle units are attached. The particle units are copper-doped iron hydroxyl oxide, and the surface of the particle units is covered with a mesoporous silica layer, which is capable of connecting to the substrate. This type of catalyst not only utilizes the chelation effect between iron ions and organic groups in the particle units to fix the catalytic system on the substrate, but also utilizes the external mesoporous silica layer to strengthen the connection with the substrate, preventing the particle units from detaching during use. Furthermore, the mesoporous silica layer provides the substrate with richer micro / nano structures, further improving the hydrophilicity of the substrate material and enabling it to adapt to more complex wastewater systems.

[0029] Another object of the present invention is to provide an application of any of the aforementioned biomimetic silicification enhanced catalysts, specifically, the biomimetic silicification enhanced catalyst is used to adsorb organic dyes in solution and catalyze the decomposition of hydrogen peroxide under visible light irradiation to generate strong oxidizing free radicals to degrade organic dyes in wastewater.

[0030] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0031] 1. The catalyst provided by this invention can not only reduce its band gap by copper doping to utilize visible light as a reaction light source and reduce reaction conditions, but also use the mesoporous silica layer on the surface to inhibit the agglomeration of catalyst particles, expose more reaction sites, and limit the heat loss of internal particle units, thereby increasing the reaction temperature. This can effectively improve the organic matter treatment effect of the catalyst. It adsorbs and degrades dyes in wastewater through two methods: electrostatic attraction and catalytic decomposition of hydrogen peroxide to generate strong oxidizing free radicals.

[0032] 2. By adjusting the molar ratio of iron ions to copper ions, this invention makes the silicon dioxide layer more easily etched to form a porous structure, and the distribution of the porous structure is more uniform. This improves the heat insulation and infrared shielding effect of the mesoporous silicon dioxide layer, better restricts the heat loss of the internal particle units, and the more uniformly distributed porous structure is also conducive to exposing reaction sites, further improving the catalytic performance of the catalyst. In addition, the appropriate amount of copper ion doping can increase the surface potential of the flower-like particle units, enhance the electrostatic attraction between them and the silicon dioxide precursor, and make the bonding between the internal particle units and the external mesoporous shell layer tighter.

[0033] 3. In this invention, the volume ratio of the silica precursor to the mass of the particle unit is 6.25:1 to 18.75:1, which can improve the stability of the catalyst, inhibit its agglomeration, and better form a mesoporous silica layer, thereby improving the catalytic performance of the catalyst.

[0034] 4. The preparation method provided by this invention is simple, low in cost and energy consumption, and operates under mild conditions. It does not require demanding and expensive equipment, which is conducive to large-scale production.

[0035] 5. The substrate-based catalyst prepared by this invention is beneficial for the use and recycling of the catalyst. The iron ions in the particle units of the catalyst can chelate with various organic groups such as hydroxyl and amino groups. Therefore, iron hydroxy oxide can not only self-assemble into flower-like nanoparticles in solution, but also mineralize in situ on the surface of a two-dimensional or three-dimensional substrate. At the same time, the mesoporous silica layer on the outside of the catalyst can effectively inhibit the catalyst from falling off the substrate surface, maintaining the stability and long-term effectiveness of the wastewater treatment process. Attached Figure Description

[0036] The accompanying drawings, which are included to provide a further understanding of embodiments of the invention and form part of this application, do not constitute a limitation thereof. In the drawings:

[0037] Figure 1 This is a flowchart illustrating the preparation method of the particulate catalyst in a specific embodiment of the present invention;

[0038] Figure 2 This is a flowchart illustrating a method for preparing a substrate with a catalyst according to a specific embodiment of the present invention.

[0039] Figure 3 This is a scanning electron microscope image of flower-like nanoparticles of copper-doped iron hydroxide powder prepared in a specific embodiment of the present invention.

[0040] Figure 4 This is a scanning electron microscope image of the flower-like nanoparticles of the particulate catalyst prepared in a specific embodiment of the present invention.

[0041] Figure 5This is a comparison diagram of the effects of granular catalyst C2 and copper-doped iron hydroxide powder P1 on the catalytic degradation of methylene blue dye in wastewater in a specific embodiment of the present invention;

[0042] Figure 6 These are scanning electron microscope images of the catalyst film before and after C9 mineralization in a specific embodiment of the present invention;

[0043] Figure 7 This is a comparison diagram of the catalytic degradation effect of methylene blue dye by catalyst film C9 and unmineralized cellulose acetate filter membrane in a specific embodiment of the present invention;

[0044] Figure 8 The image shows the adsorption and removal effect of methylene blue dye by catalyst sponge C10 and unsilicified mineralized chitosan sponge of the same volume in a specific embodiment of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of this invention are only for explaining this invention and are not intended to limit this invention.

[0046] All raw materials used in this invention are not particularly limited in their source; they can be purchased commercially or prepared using conventional methods well-known to those skilled in the art. The purity of all raw materials used in this invention is not particularly limited; however, analytical grade or purity requirements conventional in the field of composite materials are preferred. All raw materials used in this invention have designations and abbreviations that are conventional in the art, and each designation and abbreviation is clearly defined within its relevant application. Those skilled in the art can obtain these materials from commercial sources or prepare them using conventional methods based on the designation, abbreviation, and corresponding application.

[0047] The present invention does not impose any particular restrictions on the expression of the substituents, and all expressions are well known to those skilled in the art. Based on common sense, those skilled in the art can correctly understand their meaning according to their expression.

[0048] I. Preparation of Biomimetic Silicification Enhanced Catalysts

[0049]

Example 1

[0050] 2.64 g of ferrous sulfate heptahydrate was dissolved in a mixture of 80 ml of deionized water and 20 ml of anhydrous ethanol. Then, 600 mg of urea and 124.8 mg of copper sulfate pentahydrate were added sequentially and mixed thoroughly to form a homogeneous solution. The solution was transferred to a three-necked flask and refluxed at 90 °C for 6 h. The solution was then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol, and dried to obtain copper-doped iron hydroxyl oxide powder P1. A scanning electron microscope image of copper-doped iron hydroxyl oxide powder P1 is shown below. Figure 3 As shown.

[0051] 40 mg of copper-doped iron hydroxyl oxide powder P1 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 250 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 h. The silicide catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silicide catalyst particles were re-ultrasonically dispersed in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 h. The silicide was then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C1.

[0052]

Example 2

[0053] 40 mg of copper-doped iron hydroxyl oxide powder P1 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 500 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 hour. The silanized catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silanized catalyst particles were re-ultrasonically dispersed in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 hours. The particles were then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C2. A high-magnification transmission electron microscope image of particulate catalyst C2 is shown below. Figure 4 As shown.

[0054]

Example 3

[0055] 40 mg of copper-doped iron hydroxyl oxide powder P1 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 750 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 h. The silicide catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silicide catalyst particles were re-ultrasonically dispersed in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 h. The silicide catalyst particles were then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C3.

[0056]

Example 4

[0057] 2.5 g of ferrous sulfate heptahydrate was dissolved in a mixture of 80 ml of deionized water and 20 ml of anhydrous ethanol. Then, 600 mg of urea and 249.6 mg of copper sulfate pentahydrate were added sequentially and mixed thoroughly to form a homogeneous solution. The solution was transferred to a three-necked flask and refluxed at 90 °C for 6 h. The solution was then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. After drying, copper-doped iron hydroxide powder P2 was obtained.

[0058] 40 mg of copper-doped iron hydroxyl oxide powder P2 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 250 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 h. The silicide catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silicide catalyst particles were re-ultrasonically dispersed in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 h. The silicide was then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C4.

[0059]

Example 5

[0060] 40 mg of copper-doped iron hydroxyl oxide powder P2 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 750 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 h. The silicide catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silicide catalyst particles were re-ultrasonically dispersed in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 h. The silicide catalyst particles were then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C5.

[0061]

Example 6

[0062] 2.72 g of ferrous sulfate heptahydrate was dissolved in a mixture of 80 ml of deionized water and 20 ml of anhydrous ethanol. Then, 600 mg of urea and 49.9 mg of copper sulfate pentahydrate were added sequentially and mixed thoroughly to form a homogeneous solution. The solution was transferred to a three-necked flask and refluxed at 90 °C for 6 h. The solution was then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. After drying, copper-doped iron hydroxide powder P3 was obtained.

[0063] 40 mg of copper-doped iron hydroxyl oxide powder P3 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 500 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 h. The silicide catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silicide catalyst particles were re-ultrasonically dispersed in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 h. The silicide particles were then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C6.

[0064]

Example 7

[0065] 2.57 g of ferrous sulfate heptahydrate was dissolved in a mixture of 80 ml of deionized water and 20 ml of anhydrous ethanol. Then, 600 mg of urea and 187.2 mg of copper sulfate pentahydrate were added sequentially and mixed thoroughly to form a homogeneous solution. The solution was transferred to a three-necked flask and refluxed at 90 °C for 6 h. The solution was then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. After drying, copper-doped iron hydroxide powder P4 was obtained.

[0066] 40 mg of copper-doped iron hydroxyl oxide powder P4 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 1500 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 h. The silicide catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silicide catalyst particles were re-dispersed ultrasonically in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 h. The silicide was then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C7.

[0067]

Example 8

[0068] 40 mg of copper-doped iron hydroxyl oxide powder P4 was added to a mixed solution of 15 ml deionized water and 80 ml anhydrous ethanol. After ultrasonic dispersion for 15 minutes, 1 ml of 28 wt% ammonia and 125 μl of tetraethoxysilane were added sequentially under continuous stirring, and the reaction was carried out at room temperature for 1 hour. The silicide catalyst particles were then collected by centrifugation and washed at least four times with deionized water and anhydrous ethanol. The obtained silicide catalyst particles were re-ultrasonically dispersed in 100 ml of deionized water. The dispersion was transferred to a flask and etched with hot water at 95 °C for 2 hours. The etched dispersion was then collected by centrifugation and washed twice with deionized water, and dried to obtain mesoporous silica-reinforced particulate catalyst C8.

[0069]

Example 9

[0070] 1.32 g of ferrous sulfate heptahydrate was dissolved in a mixed solution of 160 ml of deionized water and 40 ml of anhydrous ethanol. Then, 300 mg of urea and 62.4 mg of copper sulfate pentahydrate were added sequentially and mixed thoroughly to form a homogeneous solution. The solution was then transferred to a three-necked flask and a 50 mm diameter filter membrane was immersed in the solution. The mixture was refluxed at 90 °C for 6 h to obtain a mineralized membrane.

[0071] The mineralized membrane was removed, rinsed with water, and dried in a 60°C oven. 1 ml of 28 wt% ammonia and 1 ml of tetraethoxysilane were placed in two open containers, and the two containers and the dried mineralized membrane were placed together in a vacuum desiccator. The air inside the desiccator was extracted using a vacuum pump, and then the desiccator was placed in a 30°C oven for constant temperature reaction for 24 h to obtain the siliconized enhanced catalyst film C9.

[0072] Figure 6 The images are scanning electron microscope images of the catalyst film before and after C9 mineralization.

[0073]

Example 10

[0074] Add 500 mg of chitosan powder to 50 ml of 2 wt% acetic acid solution and stir thoroughly in a 37°C constant temperature water bath until completely dissolved to obtain a chitosan solution. Pour the chitosan solution into a mold and place it in a freezer at -4°C and -20°C for 24 h respectively. Transfer the frozen sample to a freeze dryer for drying and shaping. Prepare a 2.5 wt% NaOH solution (anhydrous ethanol: deionized water = 1:1), remove the freeze-dried solid from the mold, soak it in the NaOH solution for 10 h, and then rinse it several times with deionized water until the material is neutral. Place the obtained sponge in a freezer at -20°C again to freeze, and then transfer it to a freeze dryer for drying and shaping to obtain a chitosan sponge.

[0075] 1.32 g of ferrous sulfate heptahydrate was dissolved in a mixed solution of 160 ml deionized water and 40 ml anhydrous ethanol. Then, 300 mg of urea and 62.4 mg of copper sulfate pentahydrate were added sequentially and mixed thoroughly to form a homogeneous solution. The solution was transferred to a three-necked flask and the chitosan sponge was immersed in the solution. The mixture was refluxed at 90 °C for 6 h to obtain a mineralized sponge. The mineralized sponge was removed, rinsed with water, and then frozen in a -20 °C freezer. Finally, it was transferred to a freeze dryer to dry and shape, thus obtaining the mineralized chitosan sponge.

[0076] 1 ml of 28 wt% ammonia and 1 ml of tetraethoxysilane were placed in two open containers respectively. The two containers, together with the dried mineralized chitosan sponge, were placed in a vacuum desiccator. The air inside the desiccator was extracted using a vacuum pump. Then, the desiccator was placed in a 30°C oven for constant temperature reaction for 24 h to obtain catalyst sponge C10.

[0077] II. Performance Tests of Biomimetic Siliconized Enhanced Catalysts

[0078]

Example 11

[0079] This embodiment provides an experimental testing method for the catalytic degradation performance of granular catalysts in treating wastewater containing methylene blue dye. The steps are as follows:

[0080] Add 5 mg of copper-doped iron hydroxyl oxide powder P1 or granular catalyst C2 to 10 ml of a 10 mg / L methylene blue solution (pH 3.5). Stir for 30 minutes in the dark to reach adsorption equilibrium. Centrifuge 500 μl of the mixture. Add hydrogen peroxide solution to the remaining mixture and place it under xenon lamp illumination at a wavelength of 400–800 nm to carry out the catalytic degradation reaction. Centrifuge 500 μl of the mixture every 15 minutes. Measure the absorbance of the supernatant at 664 nm using a microplate reader. Calculate the concentration of methylene blue in the supernatant using the absorbance and compare it with the initial concentration of methylene blue solution to calculate the catalytic degradation efficiency.

[0081] like Figure 5 As shown, both copper-doped iron hydroxyl oxide powder P1 (FeCu5) and particulate catalyst C2 (FeCu5@SiO2) can catalyze degradation. Comparing C2 and P1 in the examples reveals that the adsorption effect and catalytic degradation rate of dyes by the silanized C2 particles are significantly better than those of P1. This demonstrates that the external mesoporous silica layer can enhance the adsorption effect and catalytic degradation efficiency of the catalyst particles on dyes by inhibiting nanoparticle aggregation, enhancing photothermal effects, and increasing particle surface potential.

[0082]

Example 12

[0083] Table 1 shows the degradation rates of methylene blue dye (MB) under the experimental conditions of Example 11, with particulate catalysts C1 to C8 and copper-doped iron hydroxyl oxide powder P1, after 30 minutes of light irradiation.

[0084] Table 1:

[0085]

[0086] Table 1 shows that all particulate catalysts can catalyze the decomposition of hydrogen peroxide and the degradation of methylene blue dye in solution under xenon lamp irradiation. After 30 minutes of irradiation, catalysts C1-C5 almost completely degraded the methylene blue dye. However, catalyst C6, with its lower copper doping, had a lower dye degradation rate. When catalyst C7 was silanized, excessive TEOS addition not only resulted in the waste of some precursor molecules but also caused an excessively thick silica layer on the particle surface, obscuring the internal reaction sites. Conversely, when catalyst C8 was silanized, insufficient precursor addition led to incomplete silica layer coverage on the particle surface, making the particles prone to aggregation in solution. Therefore, both catalysts resulted in incomplete dye degradation.

[0087]

Example 13

[0088] This embodiment provides an experimental method for testing the catalytic degradation performance of a siliconized enhanced catalyst mineralization membrane in treating wastewater containing methylene blue dye. The steps are as follows:

[0089] The area is 10cm 2 A mineralized C9 (FeCu5@SiO2) catalyst membrane or an unmineralized cellulose acetate (CA) membrane of the same area was immersed in a 5 mg / L methylene blue solution and allowed to stand in the dark for 30 minutes to reach adsorption equilibrium. 200 μl of the solution was then collected. Hydrogen peroxide solution was added to the remaining mixture, and the mixture was placed under xenon lamp illumination for catalytic degradation at a wavelength of 400–800 nm. 200 μl of the solution was collected every 15 minutes. The absorbance of the collected solutions was measured at 664 nm using a microplate reader. The concentration of methylene blue in the solution was calculated using the absorbance, and the catalytic degradation efficiency was calculated by comparing it with the initial concentration of methylene blue in the solution.

[0090] like Figure 7 As shown, the catalyst membrane exhibits superior adsorption and catalytic degradation effects compared to the unmineralized cellulose acetate membrane. This is because the thermal insulation and infrared shielding properties of the mesoporous silica layer in the catalyst membrane enhance its ability to catalyze the decomposition of hydrogen peroxide by strengthening the photothermal effect of copper-doped iron hydroxyl oxide. Simultaneously, the negatively charged silica promotes the binding of positively charged methylene blue molecules and improves the hydrophilicity of the mineralized membrane. In contrast, the degradation of methylene blue in the solution of the unmineralized cellulose acetate membrane primarily originates from the decomposition of hydrogen peroxide under light irradiation.

[0091]

Example 14

[0092] This embodiment provides an experimental method for detecting the adsorption performance of a catalyst sponge in treating wastewater containing methylene blue dye, the steps of which are as follows:

[0093] A 15*15*15mm silanized reinforced catalyst sponge (C10) and an equal volume of unsilanized mineralized chitosan sponge were immersed in methylene blue solutions of 10 mg / L, 20 mg / L, 30 mg / L, or 40 mg / L. After the sponges reached adsorption equilibrium, they were removed from the solution. The sponges were squeezed to expel the solution, and 200 μl of the extruded liquid was collected. The absorbance of the extracted solution at 664 nm was measured using a microplate reader. The concentration of methylene blue in the solution was calculated using the absorbance, and the adsorption removal efficiency was calculated by comparing it with the initial methylene blue solution concentration.

[0094] like Figure 8 As shown, the adsorption and removal efficiency of methylene blue dye by the catalyst sponge C10 (CS-FeCu5@SiO2) is significantly better than that of the unmineralized chitosan sponge (CS). The sponge surface, after mineralization and silicification with copper-doped iron hydroxyl oxide, exhibits a richer micro-nano structure, significantly increasing the material's specific surface area and hydrophilicity. Furthermore, the negatively charged silica layer and the positively charged methylene blue dye molecules attract each other via electrostatic forces, further enhancing the sponge's adsorption and removal efficiency.

[0095] The terms "first," "second," etc., used in this article (e.g., first solvent, second solvent, etc.) are merely for the purpose of clarity in describing the corresponding components and are not intended to restrict any order or emphasize any importance.

[0096] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a biomimetic silicification-enhanced catalyst, characterized in that, Includes the following steps: S1: Urea, iron salt, and copper salt are added to the first solvent to obtain a mixed solution, wherein the molar ratio of iron ions in the iron salt to copper ions in the copper salt is 9~19; S2: The mixture solution is subjected to a hydrothermal reflux reaction to obtain particle units; S3: The particle unit is reacted with ammonia and silica precursor to form a catalyst, wherein the volume ratio of the silica precursor to the mass of the particle unit is 6.25:1 to 18.75:

1. The silica precursor is tetraethoxysilane or tetramethoxysilane.

2. The method for preparing the biomimetic silicification-enhanced catalyst according to claim 1, characterized in that, In step S3, the particle unit is dispersed in a second solvent, and after adding ammonia and silicon dioxide precursor, it reacts to obtain silanized particle units. The silanized particle units are then etched with hot water to obtain a particulate catalyst.

3. The method for preparing the biomimetic silicification enhanced catalyst according to claim 1, characterized in that, In step S2, the substrate is immersed in the mixture solution and subjected to a hydrothermal reflux reaction to obtain a substrate loaded with particle units. In step S3, the separately contained ammonia water, silica precursor and substrate loaded with particle units are placed together in a desiccator and reacted under negative pressure to obtain a catalyst with substrate.

4. The method for preparing the biomimetic silicification enhanced catalyst according to claim 3, characterized in that, The substrate is a filter membrane or a sponge.

5. The method for preparing the biomimetic silicification-enhanced catalyst according to any one of claims 1 to 4, characterized in that, The iron salt is ferrous sulfate heptahydrate, ferric nitrate nonahydrate, or ferrous nitrate nonahydrate, and the copper salt is copper sulfate pentahydrate or copper nitrate trihydrate.

6. A biomimetic silicification-enhanced catalyst, characterized in that, The biomimetic silicification enhanced catalyst is prepared by any one of the preparation methods described in claims 1 to 5, wherein the biomimetic silicification enhanced catalyst comprises particle units, wherein the particle units are copper-doped iron hydroxyoxide, and the surface of the particle units is covered with a mesoporous silica layer.

7. The application of biomimetic silicification enhanced catalysts, characterized in that, The biomimetic silicification enhanced catalyst of claim 6 is used to adsorb organic dyes in solution and catalyze the decomposition of hydrogen peroxide under visible light irradiation to generate strong oxidizing free radicals to degrade organic dyes in wastewater.

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