Load-type defluorination composite material, preparation method and application thereof

Abstract

The application provides a supported fluorine removal composite material, a preparation method and application thereof. The preparation method comprises the following steps: first aging of a metal source, an alcohol, a catalyst and water to obtain a metal sol; impregnating the metal sol on a carrier by using an impregnation-drawing method to obtain an impregnated carrier; standing treatment of the impregnated carrier to obtain a gelled carrier; second aging of the gelled carrier to obtain a supported precursor; and calcination treatment of the supported precursor to obtain the supported fluorine removal composite material. By controlling uniform impregnation of the active metal oxide precursor on the carrier, optimizing the gelation process and calcination fixation, the obtained supported fluorine removal composite material has excellent characteristics such as high adsorption capacity, fast adsorption rate, wide pH applicability, good mechanical strength and renewable and repeated use.

Description

Technical Field

[0001] This invention relates to the field of environmental functional materials, and more specifically, to a supported fluoride-removing composite material, its preparation method, and its application. Background Technology

[0002] Fluorine, a common trace element found in natural water bodies, is beneficial to dental health when consumed in moderation. However, excessive fluoride intake can cause health problems, and in severe cases, even affect nerve development and bone health. Therefore, developing efficient, economical, and long-lasting fluoride removal technologies has become a hot research topic in the global water treatment field.

[0003] Currently, defluoridation technologies mainly encompass adsorption, chemical precipitation, electrodialysis, reverse osmosis, and ion exchange. Among these, adsorption is widely used due to its simplicity and relatively low cost, making it particularly suitable for decentralized or small-scale water treatment systems. Traditional defluoridation adsorbents include activated alumina, bone char, hydroxyapatite, and zeolite. While these materials can effectively remove fluoride ions to some extent, they suffer from several technical bottlenecks and limitations, including but not limited to limited adsorption capacity, slow adsorption rate, narrow pH range, low mechanical strength, easy pulverization, and poor regenerability.

[0004] Activated alumina (AA), a common defluoridation adsorbent, performs well under acidic conditions, but its adsorption capacity drops sharply in neutral or alkaline environments. Furthermore, it is prone to pulverization during use, leading to difficulties in solid-liquid separation and limiting its application in practical water treatment projects. Bone char, while possessing some defluoridation capacity, suffers from a complex adsorption mechanism and demanding regeneration conditions, making economical industrial-scale reuse difficult. Hydroxyapatite (HAP) has a high theoretical adsorption capacity, but its practical application is limited by preparation costs and the actual saturation adsorption capacity for fluoride ions. It also easily dissolves during water treatment, leading to secondary fluoride pollution. Zeolite, while having some affinity for fluoride ions, has adsorption performance constrained by its internal pores. It also experiences rapid saturation in high-fluoride environments, resulting in short regeneration cycles and high long-term operating costs. In recent years, the rise of nanomaterials has brought new hope to the water treatment field. Metal oxides, due to their extremely high affinity for fluoride ions and large theoretical adsorption capacity, have become a research hotspot. However, directly using these metal oxides at the nanoscale faces engineering challenges such as difficulties in solid-liquid separation, easy agglomeration leading to a decrease in specific surface area, and increased operating pressure drop. Furthermore, in some cases, these nanomaterials are not stable enough and may release metal ions during water treatment, causing secondary pollution.

[0005] To overcome the aforementioned problems, researchers have attempted various methods to load metal oxides onto supports with good mechanical strength and high specific surface area to prepare composite defluorination materials. Commonly used methods include impregnation, precipitation, and spray drying. While impregnation and precipitation can achieve metal oxide loading, they often result in uneven distribution of the active components on the support surface, weak binding forces, and easy detachment during use. Furthermore, the loading capacity is limited by the pore structure and surface properties of the support, making it difficult to achieve optimal adsorption performance. Spray drying requires sophisticated equipment, is relatively expensive, and is prone to pore collapse during the drying process, affecting the material's pore structure and adsorption efficiency.

[0006] Furthermore, traditional loading methods struggle to precisely control the dispersion and loading of active components during preparation, directly impacting the final material's defluorination efficiency. This is particularly challenging for composite adsorbent materials containing multiple metal oxides, where achieving effective loading of these oxides without compromising the material's structure and properties remains a significant hurdle.

[0007] Therefore, how to provide a new method for preparing a supported defluorination composite material so that the obtained defluorination material can exhibit high fluoride ion saturation adsorption capacity in a wide pH range and a wide fluoride ion range, thereby achieving effective adsorption and removal of fluoride ions in fluoride-containing water bodies, is one of the important technical problems that need to be solved in this field. Summary of the Invention

[0008] The main objective of this invention is to provide a supported fluoride removal composite material, its preparation method, and its application, in order to solve the problem that existing fluoride removal materials are difficult to exhibit high fluoride ion saturation adsorption capacity over a wide pH range and a wide fluoride ion range.

[0009] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a supported fluoride-removing composite material, comprising: step S1, wherein a metal source, an alcohol, a catalyst, and water are subjected to a first aging process to obtain a metal sol; step S2, wherein the metal sol is impregnated onto a carrier using an impregnation-coating method to obtain an impregnated carrier; step S3, wherein the impregnated carrier is subjected to a static treatment to obtain a gelled carrier; the gelled carrier is subjected to a second aging process to obtain a supported precursor; step S4, wherein the supported precursor is subjected to a calcination treatment to obtain a supported fluoride-removing composite material; wherein the metal source is selected from one or more of cerium, zirconium, aluminum, titanium, iron, and lanthanum sources; and the weight ratio of the metal source in step S1 to the carrier in step S2 is 1:(1~5).

[0010] Further, in step S1, the molar ratio of the metal source, water, and catalyst is 1:(6~12):(0.2~0.8); and / or, the solid-liquid ratio of the metal source to the alcohol is (3~10) g:50 mL; and / or, the first aging time is 12h~48h, and the first aging is carried out at 25±2℃; and / or, the alcohol is selected from one or more of ethanol, isopropanol, and n-butanol; the catalyst is selected from one or more of nitric acid, hydrochloric acid, and ammonia water; preferably, the metal source is selected from one or more of cerium nitrate hexahydrate, aluminum isopropoxide, zirconium oxynitrate, tetrabutyl titanate, and lanthanum nitrate.

[0011] Further, step S1 includes: step S1-1, preparing a metal alkoxide by mixing a metal source with an alcohol, and preparing a catalyst solution by mixing a catalyst with water; step S1-2, adding the catalyst solution dropwise to the metal alkoxide at a rate of 0.1 mL / min to 0.5 mL / min under stirring conditions, and then stirring for 1 h to 3 h after the addition is complete, followed by a first aging process to obtain a metal sol.

[0012] Further, in step S2, the carrier is selected from one or more of porous ceramics, activated alumina, and silica gel particles; and / or, the particle size of the carrier is 1 mm to 2 mm; and / or, the impregnation-lifting process includes alternating impregnation and lifting, with each impregnation lasting 40 ± 10 min and alternating the process 1 to 5 times; before impregnation, step S2 also includes activating the carrier, and the activation treatment includes: immersing the carrier in an acid solution with a concentration of 0.1 ± 0.05 mol / L for 3 h to 5 h, preferably, the acid solution is selected from one or more of HNO3 solution, HCl solution, and H2SO4 solution.

[0013] Further, in step S3, the settling time is 18±3h; and / or, the second aging time is 24±5h, and the second aging is carried out in an organic solvent; preferably, the settling is carried out at a temperature of 25±2℃ and a humidity of 65±5%RH; and / or, the organic solvent is selected from one or more of ethanol, isopropanol and acetone; and / or, during the second aging process, the organic solvent is replaced at least twice.

[0014] Furthermore, in step S4, the heating rate of the calcination treatment is 1℃ / min~5℃ / min, the holding temperature is 300℃~600℃, and the holding time is 2h~6h.

[0015] A second aspect of the present invention provides a supported fluoride removal composite material, which is prepared by the above-described method for preparing the supported fluoride removal composite material.

[0016] A third aspect of the present invention provides an application of the above-mentioned supported defluorination composite material as a defluorinating agent in the field of water treatment.

[0017] Further, the supported defluoridation composite material is placed in a fluoride-containing water body and subjected to shaking treatment to adsorb fluoride ions in the fluoride-containing water body, thereby obtaining defluoridated water body and waste defluoridation material; preferably, the fluoride ion concentration of the fluoride-containing water body is 30.5 mg / L~800 mg / L, more preferably 30.5 mg / L~200 mg / L; and / or, the solid-liquid ratio of the supported defluoridation composite material to the fluoride-containing water body is (0.1 g~0.5 g):100 mL; and / or, the pH value of the fluoride-containing water body is 1~8; and / or, the shaking treatment time is 120±30 min, more preferably the shaking treatment is carried out at 25±2℃.

[0018] Furthermore, the above application also includes the step of regenerating the waste defluorination material to obtain regenerated defluorination material; preferably, the regeneration process includes: immersing the waste defluorination material in an alkaline solution with a mass concentration of 0.1% to 1.0% for a soaking time of 4±1 hours to obtain the regenerated defluorination material; more preferably, the alkaline solution is selected from one or more of NaOH solution, KOH solution, LiOH solution and (NH4)OH solution.

[0019] By applying the technical solution of this invention, based on the sol-gel method, and through controlling the uniform impregnation of the active metal oxide precursor on the support, optimizing the gelation process, and calcining fixation, the active components are highly dispersed and firmly bonded to the support. The resulting supported fluoride removal composite material exhibits excellent properties such as high adsorption capacity, fast adsorption rate, wide pH applicability, good mechanical strength, and recyclability. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0021] Figure 1 This is a graph showing the adsorption capacity of the supported fluoride removal composite material obtained in Example 2 of the present invention in fluoride-containing water at different pH values.

[0022] Figure 2 The diagram shows the adsorption capacity of the defluorination materials obtained in Example 1 and Comparative Example 2 of this invention in fluoride-containing water bodies with different initial concentrations of fluoride ions. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0024] As described in the background art, existing defluorination materials suffer from the problem of failing to exhibit high fluoride ion saturation adsorption capacity over a wide pH range and a wide fluoride ion range. To address this technical problem, a first aspect of the present invention provides a method for preparing a supported defluorination composite material, comprising: step S1, a metal source, an alcohol, a catalyst, and water undergoing a first aging process to obtain a metal sol; step S2, impregnating a support with the metal sol using an impregnation-coating method to obtain an impregnated support; step S3, subjecting the impregnated support to a static treatment to obtain a gelled support; subjecting the gelled support to a second aging process to obtain a supported precursor; and step S4, subjecting the supported precursor to calcination treatment to obtain a supported defluorination composite material; wherein the metal source is selected from one or more of cerium, zirconium, aluminum, titanium, iron, and lanthanum sources; and the weight ratio of the metal source in step S1 to the support in step S2 is 1:(1~5).

[0025] This invention utilizes a sol-gel method to load metal oxides onto a support, specifically including key steps such as initial aging of a metal source, alcohol, catalyst, and water, impregnation-lifting, gelation, and calcination. Specifically, the sol-gel process begins with the dissolution of a metal alkoxide (i.e., a mixture of the metal source and alcohol) in a solvent, forming a homogeneous solution. At this point, the metal ions are highly dispersed. After the metal alkoxide dissolves, the addition of water and a catalyst triggers its hydrolysis reaction, forming a highly reactive metal hydroxyl alkenylate. This process essentially transforms the metal oxide into a form more readily reacting with the support surface. The metal hydroxyl alkenylate then undergoes a condensation reaction, forming a three-dimensional network gel, a process typically occurring slowly at room temperature. Gelation not only promotes the uniform distribution of the active component on the support but also enhances the binding force between the active component and the support through the formation of the gel network. This process occurs at the molecular scale, ensuring the uniform distribution of the final metal oxide on the support. This is difficult to achieve with traditional impregnation methods, which often result in the accumulation of the active component on the support surface, leading to insufficient utilization of the internal pores. After aging, the gelled carrier is transformed into a solid material through calcination. During calcination, organic components are removed, and metal hydroxyl alkynes are converted into metal oxides. Simultaneously, calcination further promotes the formation of chemical bonds between the metal oxides and the carrier, enhancing the material's mechanical strength and ensuring its durability and stability in practical water treatment applications.

[0026] In summary, the preparation method provided by this invention has the following technical effects:

[0027] Firstly, high dispersibility and high loading capacity: The above sol-gel process is carried out at the molecular level, which allows the active oxide precursor metal source to penetrate uniformly into the micropores and mesopores of the carrier. After calcination, it forms nanoscale active sites and is highly dispersed, avoiding agglomeration and greatly increasing the effective specific surface area and loading capacity.

[0028] Secondly, the binding is strong: During the gelation process, the precursor of the active component (such as hydroxyl compounds) forms strong chemical bonds (MO-Si or MO-Al bonds) with the hydroxyl groups on the surface of the carrier, making the active component and the carrier very tightly bound. It is not easy to fall off or be lost during use, and there is no secondary pollution.

[0029] Thirdly, excellent comprehensive performance: The defluorination composite material prepared by the above method perfectly combines the advantages of high adsorption capacity of nano-active oxides and good mechanical strength of the carrier. It has the characteristics of large adsorption capacity, fast adsorption rate, wide pH range, high mechanical strength, friction resistance, and suitability for continuous operation of packed fixed beds.

[0030] Fourth, it has strong designability: by changing the type and proportion of the above metal sources, single or composite oxide active components can be prepared and their surface properties can be controlled; and by controlling the concentration of the formed metal sol and the number of dip-pull cycles, the loading of active components can be precisely controlled.

[0031] Fifth, renewability: The material can be efficiently regenerated after adsorption saturation, restoring its adsorption capacity, with a long service life and low operating cost.

[0032] In step S1, the preferred molar ratio of metal source, water, and catalyst is 1:(6~12):(0.2~0.8). Since the hydrolysis reaction of metal alkoxides is an exothermic process, an improper ratio of water to catalyst may lead to an excessively fast or slow reaction, affecting the stability of the sol and the performance of the final material. Therefore, by optimizing the above molar ratio range, the reaction rate and extent can be better controlled, promoting the formation of metal hydroxyalkoxides. The subsequent polycondensation reaction can then proceed at a lower water and catalyst ratio, which is beneficial for forming a tighter three-dimensional network structure, enhancing the bonding force between the metal oxide and the support, and ultimately strengthening the defluorination performance of the resulting composite material. Furthermore, to obtain a more fully dissolved metal alkoxide, the preferred solid-liquid ratio of metal source to alcohol is (3~10) g:50 mL.

[0033] Furthermore, during the first aging process, the preferred aging time is 12h to 48h, and the first aging is carried out at 25±2℃. During the first aging process, the metal hydroxyl alkyd gradually condenses to form a gel network. By optimizing the above-mentioned aging time and temperature conditions, the metal ions can participate more fully in the hydrolysis and condensation reactions, forming a more uniform and stable gel network, which is beneficial for subsequent gelation and calcination treatments, resulting in a composite material with higher fluoride ion adsorption performance and stability.

[0034] In practical applications, the alcohol can be selected from one or more of ethanol, isopropanol, and n-butanol; the catalyst can be selected from one or more of nitric acid, hydrochloric acid, and ammonia; and the metal source is further selected from one or more of cerium nitrate hexahydrate, aluminum isopropoxide, zirconium oxynitrate, tetrabutyl titanate, and lanthanum nitrate.

[0035] Furthermore, to promote more uniform hydrolysis of metal ions and improve the controllability of the polycondensation process, thereby forming a uniformly dispersed metal sol at the molecular scale, step S1 preferably includes: step S1-1, preparing a metal alkoxide with a metal source and an alcohol, and preparing a catalyst solution with a catalyst and water; step S1-2, adding the catalyst solution dropwise to the metal alkoxide at a rate of 0.1 mL / min to 0.5 mL / min under stirring conditions, followed by stirring for 1 h to 3 h, and then performing a first aging process to obtain the metal sol. In the above preferred embodiment, the preferred dropwise rate can further control the rate of hydrolysis reaction, reducing premature gel formation or structural inhomogeneity caused by excessively vigorous local reactions. The optimized stirring time after the dropwise addition further promotes more thorough mixing and uniform hydrolysis of the components, ultimately resulting in a more efficient and uniformly loaded metal oxide, and improving the fluoride ion adsorption of the resulting composite material.

[0036] In several typical embodiments, in preferred step S2: the carrier is selected from one or more of porous ceramics, activated alumina, and silica gel particles; and / or, the particle size of the carrier is 1 mm to 2 mm; and / or, the immersion-lifting process includes alternating immersion and lifting, with each immersion lasting 40 ± 10 min and alternating 1 to 5 times; before immersion, step S2 further includes activating the carrier, which includes immersing the carrier in an acid solution with a concentration of 0.1 ± 0.05 mol / L for 3 to 5 hours. In the above preferred embodiments, the activation treatment (acid washing) of the carrier can not only remove contaminants from the carrier surface and increase the number of surface hydroxyl groups, which is more conducive to the subsequent loading of metal oxides. Further optimization of the immersion-lifting process can promote more uniform adhesion of the metal sol to the inner and outer surfaces of the carrier, and more significantly avoid the problems of uneven surface coverage and insufficient pore utilization that are prone to occur in traditional immersion methods. By optimizing the number of immersions and soaking time, the loading of active components can be more precisely adjusted, thereby improving the material's defluorination efficiency and further enhancing its stability in dynamic water treatment environments. In practical applications, the acid solution used for activation treatment can be selected from one or more of HNO3 solution, HCl solution, and H2SO4 solution.

[0037] Furthermore, in step S3, the preferred settling time is 18±3 hours to facilitate the complete hydrolysis of the metal alkoxide, forming a more stable three-dimensional gel network, and providing sufficient space for the gel to grow uniformly on the carrier surface and within the pores. More preferably, the settling process is carried out at a temperature of 25±2℃ and a humidity of 65±5%RH, which allows the condensation reaction of the metal hydroxyl alkyd to proceed more smoothly and also better promotes its transition to the gel state, preventing premature solidification or evaporation. This ultimately results in a gelled carrier with a more uniform pore distribution, and consequently, a supported fluoride removal composite material with stronger adsorption capacity.

[0038] Building upon the above, the gel network structure is further improved by immersing the gelled carrier in an organic solvent during the second aging stage, promoting the transition from gel to dry gel and reducing the possibility of pore collapse during drying. Therefore, the second aging time is preferably 24±5 hours, and the second aging is carried out in an organic solvent. This allows the gel network to mature more fully in the organic solvent, forming a more compact dry gel with abundant pores, thus resulting in a composite material with higher mechanical strength and superior adsorption performance during subsequent calcination. In practical applications, the organic solvent can be selected from one or more of ethanol, isopropanol, and acetone. During the second aging process, to significantly reduce the moisture content in the pores and further reduce the risk of pore deformation during drying, thereby improving the mechanical strength and stability of the final defluorinated composite material, this step preferably includes at least two replacements of the organic solvent.

[0039] Furthermore, in step S4, the preferred heating rate for the calcination treatment is 1℃ / min to 5℃ / min, the holding temperature is 300℃ to 600℃, and the holding time is 2h to 6h. The optimized heating rate allows the internal structure of the material more time to adapt to temperature changes, thereby more effectively reducing stress concentration and structural defects. The synergistic optimization of the holding temperature and holding time promotes more complete decomposition of the metal hydroxyl alkyd into metal oxides, while better preserving the structure of the carrier material, ultimately forming a supported composite material with a more stable structure, higher dispersion of active components, and more significant fluorine adsorption.

[0040] A second aspect of this invention provides a supported defluorination composite material, which is prepared by the method described above. The resulting supported defluorination composite material exhibits high mechanical strength, excellent defluorination performance, and a wide applicable pH range. It should be noted that due to the complex structural formation and compositional changes during the preparation process, and the limitations of the field of nanomaterials and existing testing and characterization methods, a comprehensive quantitative characterization of the complex microstructure of the obtained composite material is difficult. However, performance test results have already shown that the supported defluorination composite material obtained by this invention possesses superior defluorination capabilities.

[0041] A third aspect of the present invention provides an application of the above-mentioned supported defluoridation composite material as a defluorinating agent in the field of water treatment. Because the obtained supported defluoridation composite material exhibits a more uniform distribution of active components and a tighter bond with the carrier, and especially demonstrates excellent defluoridation function over a wider pH range and a wider fluoride ion concentration range, it is particularly suitable for deep defluorination of drinking water and industrial wastewater.

[0042] In practical applications, the supported defluoridation composite material is placed in fluoride-containing water and subjected to agitation to adsorb fluoride ions, resulting in defluorinated water and waste defluoridation material. In this process, the preferred fluoride ion concentration in the fluoride-containing water is 30.5 mg / L to 800 mg / L, more preferably 30.5 mg / L to 200 mg / L. This indicates that the supported defluoridation composite material exhibits flexibility and effectiveness in treating water with low to high concentrations of fluoride. A preferred solid-liquid ratio of the supported defluoridation composite material to the fluoride-containing water is (0.1 g to 0.5 g): 100 mL, which ensures sufficient contact between the composite material and the fluoride-containing water, further enhancing adsorption efficiency. The pH value of the fluoride-containing water is 1 to 8, meaning the composite material has stronger pH adaptability and can work stably under different water quality conditions, avoiding the problem of traditional defluoridating agents failing at specific pH values. The preferred oscillation treatment time is 120±30 min, and more preferably it is carried out at 25±2℃, which can enable the composite material to remove fluoride ions from the water more quickly and effectively, and achieve a deeper purification effect.

[0043] Furthermore, in order to achieve effective material regeneration, thereby extending its service life and ultimately reducing water treatment costs, the above applications also include the step of regenerating waste defluorination materials to obtain regenerated defluorination materials.

[0044] In several typical embodiments, the regeneration process preferably includes immersing the waste defluorination material in an alkaline solution with a mass concentration of 0.1% to 1.0% for 4 ± 1 hours to obtain regenerated defluorination material. During this process, fluoride ions are removed from the adsorbed material through alkaline immersion, restoring its defluorination activity. Because fluoride ions are more easily released from adsorption sites on the material surface in an alkaline environment, they dissolve and are released into the solution, allowing the composite material to be reused. Optimal immersion time and volume further promote more complete desorption of fluoride ions and reduce potential damage to the material structure from excessively long immersion times. Specifically, the alkaline solution can be selected from one or more of NaOH solution, KOH solution, LiOH solution, and (NH4)OH solution.

[0045] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0046] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0047] Example 1

[0048] A method for preparing a supported fluoride removal composite material:

[0049] Before preparing the supported fluoride removal composite material, the carrier was first activated: silica gel particles with a particle size of 1~2 mm were soaked in 0.1 mol / L HNO3 solution for 4 hours, then rinsed repeatedly with deionized water until the pH of the effluent was neutral, and dried at 110℃ to obtain the activated carrier.

[0050] (1-1) Weigh 10g of cerium nitrate hexahydrate (Ce(NO3)3·6H2O) and dissolve it in 50mL of anhydrous ethanol to obtain a metal alkoxide (the solid-liquid ratio of the metal source to the alcohol is 10g:50mL). In another beaker, mix 3mL of deionized water with 0.5mL of concentrated nitric acid (mass concentration of 68%, used as a catalyst).

[0051] (1-2) Under magnetic stirring, the above water-acid mixture (i.e., catalyst solution) was slowly added dropwise to the above cerium nitrate ethanol solution (i.e., metal alkoxide) at a rate of 0.2 mL / min. After the addition was complete, stirring was continued for 2 hours. Then, the mixture was sealed and aged at room temperature (25±2℃) for 24 hours to obtain cerium sol. The molar ratio of metal source, water and catalyst was 23:166:12 (which, after conversion, is 1:7.22:0.52).

[0052] (2) Immerse 10g of activated pretreated silica particles (the weight ratio of the metal source to the silica particles in step (1-1) above is 1:1) into the above cerium sol for 40 minutes, remove them with tweezers to complete one impregnation-lifting process, and obtain the impregnated carrier.

[0053] (3) The obtained impregnated carrier was placed in a fume hood (25°C, RH~65%) for 18 hours to complete gelation and obtain a gelled carrier. The gelled carrier was soaked in anhydrous ethanol for 24 hours and aged, with the ethanol being replaced twice during the period. Then it was dried at 80°C for 12 hours.

[0054] (4) Finally, the dried sample is placed in a muffle furnace and heated to 500°C at 2°C / min. The temperature is maintained for 4 hours and then naturally cooled to obtain the final product, cerium oxide@silicone, which is a supported fluorine removal composite material.

[0055] Application of the obtained supported defluoridation composite material as a defluorinating agent in fluoride-containing water: Simulated fluoride-containing water (pH=5±0.2) with different initial fluoride ion concentrations was prepared. 0.1g of the prepared material was placed in 100mL of each water sample (solid-liquid ratio 0.1g:100mL), and the mixture was shaken at 25℃. Samples were taken periodically, filtered, and the fluoride ion concentration was measured.

[0056] The results show that the material obtained in this example reaches adsorption equilibrium within 120 minutes, and the maximum saturated adsorption capacity can reach 35 mg F. - / g, higher than commercially available cerium oxide (~34mg F) under the same conditions. - / g).

[0057] The resulting adsorbed waste material can be effectively regenerated after soaking in a 1% NaOH solution for 4 hours.

[0058] Example 2

[0059] A method for preparing a supported fluoride removal composite material:

[0060] The difference between this embodiment and embodiment 1 lies only in steps (1-1), (1-2), and (4), specifically:

[0061] (1-1) Weigh 4g of aluminum isopropoxide (Al(OCH(CH3)2)3) and dissolve it in 50mL of isopropanol to obtain a metal alkoxide (the solid-liquid ratio of the metal source to the alcohol is 4g:50mL). In another beaker, mix 4mL of deionized water with 0.3mL of ammonia water (as a catalyst).

[0062] (1-2) Under magnetic stirring, the above water-acid mixture (i.e., catalyst solution) was slowly added dropwise to the above metal alkoxide at a rate of 0.2 mL / min. After the addition was complete, stirring was continued for 3 hours. Then, the mixture was sealed and aged at room temperature (25±2℃) for 36 hours to obtain a metal sol. The molar ratio of metal source, water and catalyst was 19.6:222:7.8 (which, after conversion, is 1:11.33:0.40).

[0063] Steps (2) and (3) are consistent with those in Example 1. At this time, the weight ratio of the metal source to the carrier in step (1-1) above is 1:2.5.

[0064] In step (4), the heat preservation temperature is changed to 450℃, while the heat preservation time remains unchanged.

[0065] Application of the obtained supported defluoridation composite material as a defluorinating agent in fluoride-containing water: The concentration of fluoride ions in the fluoride-containing water to be adsorbed was changed to 100 mg / L, and tests were carried out simultaneously in eight fluoride-containing water bodies with pH values ​​of 1 to 8. The specific steps are as described in Example 1.

[0066] The adsorption capacity diagram of the supported fluoride removal composite material obtained in this embodiment at different initial pH values ​​is shown below. Figure 1 .

[0067] Example 3

[0068] A method for preparing a supported fluoride removal composite material:

[0069] The only difference between this embodiment and Embodiment 1 is that in steps (1-1) and (1-2), the concentration of the catalyst solution and the total amount of drops are changed so that the molar ratio of the metal source, water and catalyst is changed to 1:5:1.

[0070] Example 4

[0071] A method for preparing a supported fluoride removal composite material:

[0072] The only difference between this embodiment and Embodiment 1 is that in steps (1-1) and (1-2), the concentration of the catalyst solution and the total amount of drops are changed so that the molar ratio of the metal source, water and catalyst is changed to 1:15:0.1.

[0073] Example 5

[0074] A method for preparing a supported fluoride removal composite material:

[0075] The only difference between this embodiment and Example 1 is that in step (1-2), the dropping rate of the catalyst solution is changed to 0.8 mL / min, and stirring is continued for 5 hours after the dropping is completed.

[0076] Example 6

[0077] A method for preparing a supported fluoride removal composite material:

[0078] The only difference between this embodiment and Example 1 is that in step (1-2), the dropping rate of the catalyst solution is changed to 0.05 mL / min, and stirring is continued for 0.5 hours after the dropping is completed.

[0079] Example 7

[0080] A method for preparing a supported fluoride removal composite material:

[0081] The only difference between this embodiment and Embodiment 1 is that in step (1-2), the temperature of the first aging is changed to 10°C and the time is changed to 60h.

[0082] Example 8

[0083] A method for preparing a supported fluoride removal composite material:

[0084] The only difference between this embodiment and Embodiment 1 is that in step (1-2), the temperature of the first aging is changed to 30°C and the time is changed to 10 hours.

[0085] Example 9

[0086] A method for preparing a supported fluoride removal composite material:

[0087] The only difference between this embodiment and Embodiment 1 is that the carrier was not activated before the experiment began.

[0088] Example 10

[0089] A method for preparing a supported fluoride removal composite material:

[0090] The only difference between this embodiment and Embodiment 1 is that, before starting the experiment, the concentration of the acid solution used for activation treatment was changed to 0.01 mol / L, and the activation time was changed to 8 hours.

[0091] Example 11

[0092] A method for preparing a supported fluoride removal composite material:

[0093] The only difference between this embodiment and Example 1 is that the concentration of the acid solution used for activation treatment was changed to 0.2 mol / L and the activation time was changed to 2 h before the experiment began.

[0094] Example 12

[0095] A method for preparing a supported fluoride removal composite material:

[0096] The only difference between this embodiment and embodiment 1 is that in step (3), the settling time is changed to 25 hours.

[0097] Example 13

[0098] A method for preparing a supported fluoride removal composite material:

[0099] The only difference between this embodiment and embodiment 1 is that in step (3), the settling time is changed to 12 hours.

[0100] Example 14

[0101] A method for preparing a supported fluoride removal composite material:

[0102] The only difference between this embodiment and embodiment 1 is that in step (3), the second aging time is changed to 10 hours.

[0103] Example 15

[0104] A method for preparing a supported fluoride removal composite material:

[0105] The only difference between this embodiment and embodiment 1 is that in step (4), the calcination conditions are changed to: heating to 250°C at 0.5°C / min and holding for 8 hours.

[0106] Example 16

[0107] A method for preparing a supported fluoride removal composite material:

[0108] The only difference between this embodiment and embodiment 1 is that in step (4), the calcination conditions are changed to: heating to 700°C at 6°C / min and holding for 1 hour.

[0109] Comparative Example 1

[0110] A method for preparing a fluoride removal material:

[0111] The only difference between this comparative example and Example 1 is that the activated and pretreated silica gel was directly immersed in a 0.5 mol / L cerium nitrate aqueous solution for 4 hours, then dried at 110°C and calcined at 500°C for 4 hours.

[0112] The application of the obtained defluoridating material as a defluorinating agent in fluoride-containing water bodies was carried out in accordance with Example 1.

[0113] In the adsorption experiment, the fluoride removal material sample obtained in the comparative example showed a slight shedding of cerium ions.

[0114] Comparative Example 2

[0115] This comparative example directly used commercial cerium oxide (manufacturer's model: Maclean cerium oxide, high purity 99.99%, CAS: 1306-38-3) as the sample for the obtained defluorination material.

[0116] The application of the obtained defluoridating material as a defluorinating agent in fluoride-containing water bodies was carried out in accordance with Example 1.

[0117] Furthermore, the defluoridation effects of the defluoridation materials obtained in Example 1 and Comparative Example 2 were tested in fluoride-containing water bodies with different initial concentrations of fluoride ions. The test results are shown in the figure below. Figure 2 .from Figure 2 As can be seen from the results, based on the defluorination experiment at low initial fluoride ion concentrations (30.5 mg / L~200 mg / L), the adsorption capacity of the cerium oxide@silica gel supported defluorination composite material obtained in Example 1 is significantly higher than that of commercial cerium oxide.

[0118] Comparative Example 3

[0119] A method for preparing a fluoride removal material:

[0120] The only difference between this comparative example and Example 1 is that the activated pretreated silica particles in step (2) are changed from 10g to 5g, so that the weight ratio of the metal source to it in step (1-1) is changed to 2:1.

[0121] Comparative Example 4

[0122] A method for preparing a fluoride removal material:

[0123] The only difference between this comparative example and Example 1 is that the activated pretreated silica particles in step (2) are changed from 10g to 60g, so that the weight ratio of the metal source to it in step (1-1) is changed to 1:6.

[0124] In each embodiment and comparative example, the test method for the saturated adsorption capacity of the composite material was as follows: Samples were taken and filtered periodically, and the fluoride ion concentration was measured until the fluoride ion concentration no longer changed. The saturated adsorption capacity of the fluoride ion was then obtained, and the results are shown in Table 1. Meanwhile, the fluoride ion concentrations in the water before and after adsorption in each embodiment and comparative example are also shown in Table 1.

[0125] Table 1

[0126]

[0127] As can be seen from the above description, the embodiments of the present invention target supported defluoridation materials. Based on the sol-gel method, by controlling the uniform impregnation of the active metal oxide precursor on the carrier, optimizing the gelation process, and calcining fixation, the active components are highly dispersed and firmly bonded to the carrier. The resulting supported defluoridation composite material exhibits a more uniform distribution of active components and a tighter bond with the carrier. In particular, it demonstrates excellent defluoridation function over a wider pH range and fluoride ion concentration range, making it especially suitable for deep defluoridation of drinking water and industrial wastewater.

[0128] Specifically, in each embodiment:

[0129] Comparing Examples 3 and 4 with Example 1, it can be seen that by optimizing the molar ratio of metal source, water, and catalyst, the reaction rate and extent can be better adjusted, promoting the formation of metal hydroxyl alkyd. The subsequent polycondensation reaction can then proceed at a lower water and catalyst ratio, which is beneficial for forming a tighter three-dimensional network structure, enhancing the bonding force between the metal oxide and the support, and ultimately strengthening the defluorination performance of the resulting composite material.

[0130] Comparing Examples 5 and 6 with Example 1, it can be seen that by optimizing the dropwise addition conditions of the catalyst solution, the rate of hydrolysis reaction can be further controlled, reducing premature gel formation or structural inhomogeneity caused by excessively intense local reactions; at the same time, it can further promote more thorough mixing and uniform hydrolysis of each component, ultimately obtaining a more efficient and uniformly loaded metal oxide, and enhancing the fluoride ion adsorption of the resulting composite material.

[0131] Comparing Examples 7 and 8 with Example 1, it can be seen that by optimizing the conditions of the first aging, metal ions can participate more fully in the hydrolysis and condensation reactions, forming a more uniform and stable gel network, which is beneficial to subsequent gelation and calcination treatments, and obtaining a composite material with higher fluoride ion adsorption performance and stability.

[0132] Comparing Examples 9 to 11 with Example 1, it can be seen that by optimizing the activation treatment and further optimizing the relevant conditions of the activation treatment, it is possible to remove contaminants from the surface of the carrier and increase the number of surface hydroxyl groups, which is more conducive to the subsequent loading of metal oxides.

[0133] Comparing Examples 12 and 13 with Example 1, it can be seen that by optimizing the standing time in step S3, the metal alkoxide can be fully hydrolyzed to form a more stable three-dimensional gel network, and there is enough space to allow the gel to grow uniformly on the surface of the carrier and in the pores, ultimately forming a gelled carrier with more uniform pore distribution, and thus obtaining a loaded fluoride removal composite material with stronger adsorption capacity.

[0134] Comparing Example 14 with Example 1, it can be seen that by optimizing the conditions for the second aging, the gel network can be made to mature more fully in the organic solvent, forming a dry gel with a more compact structure and rich pore structure, thereby forming a composite material with higher mechanical strength and better adsorption performance in the subsequent calcination process.

[0135] Comparing Examples 15 and 16 with Example 1, it can be seen that by optimizing the calcination conditions, the internal structure of the material can be given more time to adapt to temperature changes, thereby more effectively reducing stress concentration and structural defects. At the same time, it can also promote the more complete decomposition of metal hydroxyl alkyd into metal oxides, while the structure of the carrier material can be better maintained, ultimately forming a supported composite material with a more stable structure, a more highly dispersed active component, and a more significant fluorine adsorption effect.

[0136] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such terms can be used interchangeably where appropriate so that the embodiments of this application described herein can be implemented, for example, in a sequence other than those described herein.

[0137] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. 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 supported fluoride removal composite material, characterized in that, include: Step S1: The metal source, alcohol, catalyst and water are aged for the first time to obtain a metal sol; Step S2: The metal sol is impregnated onto the carrier using an impregnation-lifting method to obtain an impregnated carrier. Step S3: The impregnated carrier is subjected to a static treatment to obtain a gelled carrier; the gelled carrier is subjected to a second aging process to obtain a supported precursor. Step S4: The supported precursor is calcined to obtain the supported defluorination composite material. The metal source is selected from one or more of cerium source, zirconium source, aluminum source, titanium source, iron source and lanthanum source; The weight ratio of the metal source in step S1 to the carrier in step S2 is 1:(1~5).

2. The method for preparing the supported fluoride-removing composite material according to claim 1, characterized in that, In step S1 The molar ratio of the metal source, the water, and the catalyst is 1:(6~12):(0.2~0.8); and / or, The solid-liquid ratio of the metal source to the alcohol is (3~10) g: 50 mL; and / or, The first aging period is 12h~48h, and the first aging is carried out at 25±2℃; and / or, The alcohols are selected from one or more of ethanol, isopropanol, and n-butanol; The catalyst is selected from one or more of nitric acid, hydrochloric acid, and ammonia water; Preferably, the metal source is selected from one or more of cerium nitrate hexahydrate, aluminum isopropoxide, zirconium oxynitrate, tetrabutyl titanate, and lanthanum nitrate.

3. The method for preparing the supported fluoride-removing composite material according to claim 2, characterized in that, Step S1 includes: Step S1-1: Prepare a metal alkoxide by mixing the metal source with the alcohol, and prepare a catalyst solution by mixing the catalyst with the water; In step S1-2, under stirring conditions, the catalyst solution is added dropwise to the metal alkoxide at a dropping rate of 0.1 mL / min to 0.5 mL / min. After the addition is complete, the mixture is stirred for 1 h to 3 h, and then the first aging process is carried out to obtain the metal sol.

4. The method for preparing the supported fluoride-removing composite material according to any one of claims 1 to 3, characterized in that, In step S2 The carrier is selected from one or more of porous ceramics, activated alumina, and silica gel particles; and / or, The particle size of the carrier is 1 mm to 2 mm; and / or, The soaking-lifting process includes alternating soaking and lifting, with each soaking lasting 40±10 minutes and the alternation being performed 1 to 5 times. Prior to the impregnation, step S2 further includes activating the carrier, wherein the activation treatment comprises: immersing the carrier in an acid solution with a concentration of 0.1 ± 0.05 mol / L for 3 to 5 hours. Preferably, the acid solution is selected from one or more of HNO3 solution, HCl solution and H2SO4 solution.

5. The method for preparing the supported fluoride-removing composite material according to any one of claims 1 to 4, characterized in that, In step S3 The settling time is 18±3 hours; and / or, The second aging time is 24±5h, and the second aging is carried out in an organic solvent; Preferably, the settling process is carried out at a temperature of 25±2℃ and a humidity of 65±5%RH. And / or, the organic solvent is selected from one or more of ethanol, isopropanol, and acetone; And / or, during the second aging process, the organic solvent may be replaced at least twice.

6. The method for preparing the supported fluoride-removing composite material according to any one of claims 1 to 5, characterized in that, In step S4, the heating rate of the calcination treatment is 1℃ / min to 5℃ / min, the holding temperature is 300℃ to 600℃, and the holding time is 2h to 6h.

7. A supported fluoride removal composite material, characterized in that, The supported fluoride removal composite material is prepared by the method for preparing the supported fluoride removal composite material according to any one of claims 1 to 6.

8. The application of the supported defluorination composite material according to claim 7 as a defluorinating agent in the field of water treatment.

9. The application according to claim 8, characterized in that, The loaded defluorination composite material is placed in a fluoride-containing water body and subjected to oscillation treatment to adsorb fluoride ions in the fluoride-containing water body, thereby obtaining defluorinated water body and waste defluorination material; Preferably, the fluoride ion concentration of the fluoride-containing water is 30.5 mg / L to 800 mg / L, more preferably 30.5 mg / L to 200 mg / L; And / or, the solid-liquid ratio of the supported defluorination composite material to the fluoride-containing water is (0.1g~0.5g):100mL; And / or, the pH value of the fluoride-containing water body is 1 to 8; And / or, the oscillation treatment time is 120±30 min, more preferably the oscillation treatment is performed at 25±2℃.

10. The application according to claim 9, characterized in that, The application also includes the step of regenerating the waste defluorination material to obtain recycled defluorination material; Preferably, the regeneration process includes: immersing the waste defluorination material in an alkaline solution with a mass concentration of 0.1% to 1.0% for a soaking time of 4 ± 1 h to obtain the regenerated defluorination material; More preferably, the alkaline solution is selected from one or more of NaOH solution, KOH solution, LiOH solution and (NH4)OH solution.

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