Ag-tiO2 modified biomass rare earth tailing photocatalytic material, preparation method and application thereof

Abstract

The application provides a preparation method and application of an Ag-TiO2 modified modified biomass rare earth tailing photocatalytic material, which can use SBA-15, TiO2, AgNO3 and melamine as raw materials, and prepare the modified photocatalyst through a thermal condensation polymerization method and an impregnation method. The preparation method of the catalytic material comprises the following steps: adding melamine and SBA-15 template into deionized water and mixing, then adding hydrochloric acid and anhydrous ethanol in sequence, stirring and centrifuging, washing the precipitate and roasting to obtain a g-C3N4 carrier; mixing carbonized biomass powder and rare earth tailing powder with water, using the dispersed rare earth tailing powder to obtain a first suspension, granulating and roasting; dissolving the g-C3N4 carrier, AgNO3 and TiO2 in anhydrous ethanol, ultrasonic dispersing to obtain a second suspension, standing, vacuum drying to obtain an Ag-TiO2 / g-C3N4 material; adding the Ag-TiO2 / g-C3N4 material and the doped biomass rare earth tailing carrier into anhydrous ethanol and deionized water, uniformly mixing, ultrasonic dispersing to obtain a third suspension, standing, vacuum drying and temperature rising calcining.

Description

Technical Field

[0001] This invention relates to the field of indoor air purification, and more specifically, to an Ag-TiO2 modified biomass rare earth tailings photocatalytic material, its preparation method, and its application. Background Technology

[0002] As people's demands for material well-being increase, related industries such as home decoration, vehicles, food, and clothing have developed rapidly, bringing many conveniences to people's lives. However, rapid economic development inevitably comes at the cost of environmental pollution. In particular, fine particulate pollution in my country's air has become increasingly serious in recent years, and most VOCs, one of the sources of pollution, come from building materials, vehicle exhaust emissions, and industrial production processes.

[0003] Formaldehyde, a common VOC (volatile organic compounds) air pollutant, is a colorless gas with a pungent odor at room temperature. As a chronically toxic chemical, it causes varying degrees of discomfort in humans at low to medium concentrations, and increases with concentrations exceeding 30 mg / m³. -3 It can directly cause death. Furthermore, prolonged exposure to formaldehyde can induce mutations in various genes in the human body, leading to cancerous changes in human cells. Therefore, formaldehyde can cause serious and even irreversible damage to the human body, both directly and indirectly. Against this backdrop, research on the treatment of formaldehyde in the atmosphere is of great significance for improving people's quality of life and protecting their health.

[0004] Currently, there are four main methods for formaldehyde treatment: physical technology, chemical technology, biotechnology, and a combination of multiple technologies. Physical technologies include absorption, adsorption, condensation, and membrane separation, which work by using physical methods such as changing temperature and pressure, or employing selective adsorbents and selectively permeable membranes to enrich and separate formaldehyde. Chemical technologies include direct combustion, catalytic combustion, metal catalysts, and photocatalytic degradation, which work by rapidly converting formaldehyde in the air into low-toxicity or non-toxic substances through chemical reactions, thus achieving harmless treatment. Biotechnology includes plant-based methods, microbial methods, and enzyme catalysis, which utilize the body's own ability to decompose formaldehyde. The combination of multiple technologies involves combining the advantages of different methods to achieve the best formaldehyde treatment effect.

[0005] The formaldehyde content in the atmosphere is relatively low. In recent years, the highest formaldehyde concentration in areas with developed energy extraction industries has been 17.40 × 10¹⁵ molec·cm⁻¹. -2 For such low concentrations of formaldehyde, adsorption and photocatalytic oxidation are two relatively economical and effective treatment technologies. Photocatalytic oxidation, as a hot research area in formaldehyde treatment technology, demonstrates significant advantages in energy conservation and environmental protection due to its simple operation, low energy consumption, and lack of secondary pollution.

[0006] Photocatalysis is a photochemical reaction based on redox mechanisms. The redox mechanism mainly involves the photocatalyst absorbing light energy when exposed to light, undergoing electron transitions, and generating electron-hole pairs. These pairs directly oxidize or reduce pollutants adsorbed on the surface, or oxidize adsorbed hydroxyl radicals (OH-) on the surface to generate highly oxidizing hydroxyl radicals (OH), thus oxidizing the pollutants.

[0007] There are many types of photocatalysts with a wide range of applications, such as metal oxides, transition metal semiconductor compounds, and organic photocatalysts. For the treatment of formaldehyde in the atmosphere, transition metal semiconductor compound catalysts are currently the most widely researched and applied photocatalysts due to their advantages such as strong catalytic activity, non-toxicity, good chemical stability, and low cost. Summary of the Invention

[0008] The purpose of this invention is to provide a modified biomass rare earth tailings photocatalytic material modified with Ag-TiO2, which can be used for air purification, especially indoor air purification, so that indoor air can meet the requirements of excellent air quality standards.

[0009] Another objective of this invention is to provide a method for preparing Ag-TiO2 modified biomass rare earth tailings photocatalytic material, which can be prepared by using template agent SBA-15, TiO2, AgNO3, and melamine as raw materials through thermal shrinkage polymerization and impregnation methods.

[0010] The embodiments of the present invention are implemented as follows:

[0011] A method for preparing Ag-TiO2-modified biomass rare earth tailings photocatalytic material, the method comprising the following steps:

[0012] To generate the g-C3N4 support, melamine and SBA-15 template agent were added to deionized water and mixed. Then hydrochloric acid and anhydrous ethanol were added sequentially and stirred. The lower layer precipitate was collected by centrifugation, washed, and calcined to obtain the g-C3N4 support.

[0013] To generate a rare earth tailings carrier doped with biomass, carbonized biomass powder and rare earth tailings powder are mixed with water, and the rare earth tailings powder is dispersed by ultrasonication to obtain a first suspension. The first suspension is dried, granulated, calcined, and cooled to obtain a rare earth tailings carrier doped with biomass.

[0014] To generate Ag-TiO2 / g-C3N4 material, g-C3N4 support, AgNO3 and TiO2 were dissolved in anhydrous ethanol, ultrasonically dispersed to obtain a second suspension, and then allowed to stand and vacuum dried to obtain Ag-TiO2 / g-C3N4 material.

[0015] A modified biomass rare earth tailings photocatalytic material modified with Ag-TiO2 was generated by uniformly mixing Ag-TiO2 / g-C3N4 material and biomass-doped rare earth tailings carrier with anhydrous ethanol and deionized water, followed by ultrasonic dispersion to obtain a third suspension. After standing and vacuum drying, gray solid particles were obtained. The gray solid particles were then calcined to obtain the modified biomass rare earth tailings photocatalytic material modified with Ag-TiO2.

[0016] In a preferred embodiment of the present invention, the specific method for generating the above-mentioned g-C3N4 carrier is as follows:

[0017] Melamine and SBA-15 template agent in a ratio of 6:1 were added to deionized water and mixed evenly to obtain a white suspension.

[0018] Add hydrochloric acid and a trace amount of anhydrous ethanol to the white suspension, and stir rapidly with a magnetic stirrer for 5 minutes to obtain a white viscous liquid.

[0019] The white viscous liquid was centrifuged to separate the solids. The lower precipitate was removed and washed repeatedly by centrifugation with anhydrous ethanol and deionized water until a semi-transparent semi-solid was formed.

[0020] The semi-solid was placed in a semi-enclosed porcelain crucible and calcined to obtain a white flocculent powder g-C3N4 support.

[0021] In a preferred embodiment of the present invention, the specific method for generating the above-mentioned rare earth tailings carrier doped with biomass includes:

[0022] To prepare carbonized biomass powder, straw-type biomass is carbonized at 400℃ in an oxygen-deficient environment and then pulverized to 100-150 mesh for later use.

[0023] 100-150 mesh carbonized biomass powder and rare earth tailings powder are mixed with water at a mass ratio of 1:5, and the solid-liquid ratio is 1:50-60.

[0024] The rare earth tailings powder was dispersed using ultrasound at 30-50 kHz and 50 W / L to form the first suspension.

[0025] The first suspension was dried in a 40℃ drying oven for 2 hours and then granulated.

[0026] The material is then placed in a tubular furnace and roasted at 500-550℃ for 2 hours, and then cooled to obtain a rare earth tailings carrier doped with biomass.

[0027] In a preferred embodiment of the present invention, the above-mentioned straw-based biomass includes wheat straw and corn stalks.

[0028] In a preferred embodiment of the present invention, the specific method for generating the above-mentioned Ag-TiO2 / g-C3N4 material includes:

[0029] The g-C3N4 support was dissolved in anhydrous ethanol to obtain the g-C3N4 sample;

[0030] TiO2 and AgNO3 with a TiO2 / Ag doping molar ratio of 1:3 were uniformly mixed to obtain an Ag-TiO2 mixture;

[0031] The g-C3N4 sample and Ag-TiO2 mixture with a mass ratio of 5:1 were stirred until AgNO3 was completely dissolved, and then sonicated for 30 min to obtain a second suspension.

[0032] The second suspension was sealed and allowed to stand. The second suspension was then placed in a vacuum oven and dried at 80°C to obtain Ag-TiO2 / g-C3N4 material.

[0033] In a preferred embodiment of the present invention, the method for generating the Ag-TiO2-modified biomass rare earth tailings photocatalytic material includes:

[0034] A certain proportion of Ag-TiO2 and g-C3N4 materials were added to a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 4:1 and mixed evenly.

[0035] Add rare earth tailings carrier doped with biomass, with the mass ratio of Ag-TiO2 / g-C3N4 material to rare earth tailings carrier doped with biomass being 1:10-20, and stir for 10 min;

[0036] The third suspension was obtained by sonication for 30 minutes.

[0037] The third suspension was sealed and allowed to stand for 24 hours. The third suspension was then placed in a vacuum oven and dried at 80°C to obtain gray solid particles.

[0038] The material was heated to 500-520℃ in a muffle furnace at a heating rate of 5℃ / min and then calcined for 4 hours to obtain Ag-TiO2 modified biomass rare earth tailings photocatalytic material.

[0039] In a preferred embodiment of the present invention, the muffle furnace is heated to 500°C at a heating rate of 5°C / min.

[0040] In a preferred embodiment of the present invention, the mass ratio of the Ag-TiO2 and g-C3N4 materials is 1:4-5; the mass ratio of the Ag-TiO2 / g-C3N4 materials and the rare earth tailings carrier doped with biomass is 1:20.

[0041] This invention also provides an Ag-TiO2 modified biomass rare earth tailings photocatalytic material, prepared by any of the above preparation methods.

[0042] This invention also provides an application of Ag-TiO2 modified biomass rare earth tailings photocatalytic material, including its application in air purification.

[0043] The beneficial effects of the embodiments of the present invention are:

[0044] The photocatalytic material for air purification obtained through the embodiments of the present invention is prepared by using melamine-doped SBA-15 template agent to form a g-C3N4 support. This results in a more regular template structure on the support, which is an ordered tubular structure with a corrugated surface, increased specific surface area, and fine grooves (see the SEM and EDS images of the g-C3N4 support in Figure 1). This provides an effective site for loading AgNO3 and TiO2, while increasing the contact area between organic pollutants in the atmosphere and the active components in the catalyst, thereby enhancing the degradation effect of organic pollutants in the atmosphere.

[0045] Rare earth tailings carriers doped with biomass release carbon dioxide during roasting, altering the crystal structure of the tailings minerals and increasing porosity. Rare earth tailings do not contain radioactive elements, and when mixed with biomass and roasted together, they form a regular carrier, providing a site for loading Ag-TiO2 / g-C3N4 materials. At the same time, the activity of metal elements can also promote electron transitions through light irradiation, generating electron-hole pairs, which directly oxidize pollutants adsorbed on the surface, improving air purification efficiency. Attached Figure Description

[0046] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating the preparation process of photocatalytic materials according to an embodiment of the present invention.

[0048] Figure 2 The graph shows the degradation effect of formaldehyde on different doping ratios in Embodiment S2 of the present invention.

[0049] Figure 3 The graph shows the degradation effect of different loading amounts on formaldehyde in the atmosphere according to embodiments of the present invention.

[0050] Figure 4 The figures show the effects of different catalysts and dosages on formaldehyde degradation in embodiments of the present invention.

[0051] Figure 5This is a graph showing the effect of reaction time on formaldehyde degradation in an embodiment of the present invention;

[0052] Figure 6 and 7 The images shown are SEM and EDS spectra of the g-C3N4 carrier in this embodiment of the invention.

[0053] Figure 8 This is a SEM image of a rare earth tailings carrier doped with biomass, according to an embodiment of the present invention.

[0054] Figure 9 and 10 The images shown are SEM images and EDS spectra of the Ag-TiO2 / g-C3N4 material in the embodiments of the present invention.

[0055] Figure 11 This is a diagram of the experimental setup according to an embodiment of the present invention. Detailed Implementation

[0056] The present invention will now be described in detail with respect to various exemplary embodiments. This detailed description should not be regarded as a limitation of the invention, but should be understood as a more detailed description of certain aspects, features and embodiments of the invention.

[0057] It should be understood that the terminology used in this invention is merely for describing particular specific embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included within the scope of this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0058] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0059] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other specific embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0060] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0061] First Embodiment

[0062] This embodiment provides a method for preparing Ag-TiO2-modified biomass rare earth tailings photocatalytic material. This modified photocatalytic material is used for air purification, especially for the purification of materials with high VOC content. For details, please refer to [link to relevant documentation]. Figure 1 The preparation method of this photocatalytic material includes the following steps:

[0063] S1: Generation of g-C3N4 vector:

[0064] Weigh melamine and SBA-15 template agent at a mass ratio of 6:1 and place them in a 500ml beaker. Add a certain amount of deionized water and stir until a uniform white suspension is formed. Adjust the pH with hydrochloric acid, then add a trace amount of anhydrous ethanol. Place the beaker on a magnetic stirrer and stir rapidly for 5 minutes to obtain a white viscous liquid. Centrifuge to separate the solid, take the lower precipitate, and wash it repeatedly with anhydrous ethanol and deionized water until a translucent semi-solid is formed (centrifugation speed 4000 r / min, 5 min). Place it in a semi-enclosed porcelain crucible and calcine (heating rate 5℃ / min) to obtain a white flocculent powder, labeled as g-C3N4 carrier for later use.

[0065] The SEM and EDS images of the g-C3N4 vector are shown in the appendix. Figure 6 , 7 The g-C3N4 template structure prepared using the template agent SBA-15 is relatively regular, with an ordered tubular structure and a corrugated surface, increasing the specific surface area and containing fine grooves. This provides an effective site for loading AgNO3 and TiO2, while increasing the contact area between atmospheric organic pollutants and the active components in the catalyst, thus enhancing the degradation effect of atmospheric organic pollutants.

[0066] S2: Rare earth tailings carrier for generating biomass doped with biomass:

[0067] Biomass such as wheat straw and corn stalks were carbonized at 400℃ under oxygen-deficient conditions and then pulverized to 100-150 mesh to obtain carbonized biomass powder. 100-150 mesh rare earth tailings powder from Mianning Yak Ping was selected as the rare earth tailings powder. The mixing ratio of carbonized biomass powder to rare earth tailings powder was 1:5. An appropriate amount of water was added, resulting in a solid-liquid ratio of 1:50-60. The rare earth tailings powder was dispersed using ultrasound at 30-50 kHz and 50 W / L to form a first suspension. This suspension was dried in a 40℃ drying oven for 2 hours and then granulated. In this embodiment, the granules were extruded into cylindrical shapes with a diameter of 3 mm and a length of 5 mm using an extruder. These granules were then calcined in a tube furnace at 550℃ for 2 hours, cooled, and removed, and recorded as the formed rare earth tailings carrier doped with biomass.

[0068] Please refer to the SEM image of the rare earth tailings carrier doped with biomass. Figure 8 The biochar formed by the rare earth tailings biomass carrier varies in pore size and surface area depending on the temperature during roasting. The main rare earth carrier mineral in the rare earth tailings is bastnaesite, with fluorite, barite, celestite, aluminosilicate minerals, and quartz as the main minerals, and a small amount of iron oxides. During roasting, carbon dioxide is released, which changes the crystal form of the tailings minerals and increases the porosity.

[0069] S3: Generation of Ag-TiO2 / g-C3N4 material:

[0070] The g-C3N4 support sample prepared in S1 was weighed and dissolved in anhydrous ethanol. A certain amount of AgNO3 and TiO2 were added, with a TiO2 / Ag doping molar ratio of 1:3, and the mixture was homogeneously mixed to obtain an Ag-TiO2 mixture. The mass ratio of the g-C3N4 sample to the Ag-TiO2 mixture was 5:1. After stirring until the AgNO3 was completely dissolved, the mixture was sonicated for 30 minutes to form a homogeneous white second suspension, which was then sealed and allowed to stand for 24 hours. The beaker was then removed and placed in a vacuum oven at 80°C for vacuum drying to obtain a gray powder, i.e., the Ag-TiO2 / g-C3N4 material.

[0071] The SEM and EDS images of the Ag-TiO2 / g-C3N4 material are shown in [reference 1]. Figure 9 , 10 Rare earth tailings do not contain radioactive elements. When mixed with biomass and calcined, they form a regular carrier, providing a site for loading Ag-TiO2 / g-C3N4 materials. At the same time, the activity of the metal elements can also promote electron transitions through light irradiation, generating electron-hole pairs, which can directly oxidize pollutants adsorbed on the surface, thereby improving the efficiency of air purification.

[0072] S4: Generation of Ag-TiO2 modified biomass rare earth tailings photocatalytic materials:

[0073] The Ag-TiO2 / g-C3N4 material prepared by S3 was added to a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 4:1 and mixed evenly.

[0074] Add the rare earth tailings carrier doped with biomass prepared by S2 to the solution. The optimal mass ratio of Ag-TiO2 / g-C3N4 material to rare earth tailings carrier doped with biomass is 1:20. Then stir for 10 min to mix evenly.

[0075] After ultrasonication for 30 minutes, the mixture was sealed and allowed to stand for 24 hours. The beaker was then removed and placed in a vacuum oven at 80°C for vacuum drying to obtain gray solid particles. These particles were then heated in a muffle furnace to 500°C at a heating rate of 5°C / min and calcined for 4 hours to obtain white particles, which were labeled as modified biomass rare earth tailings photocatalytic material modified with Ag-TiO2 particles.

[0076] By loading Ag-TiO2 / g-C3N4 onto a calcined biomass rare earth tailings photocatalyst carrier, not only is the mechanical strength of the photocatalytic material carrier improved, but the addition of Ag-TiO2 modification also enhances the separation of photogenerated carriers during photocatalysis, reducing the recombination rate of photogenerated electrons and holes. This allows for the successful decomposition of pollutants in a shorter time. The pollutants can be oxidized and degraded into CO2 and H2O, which are non-toxic to humans. The material is recyclable and has a long catalytic duration. It overcomes the problems of poor visible light response, low quantum efficiency, difficult recycling, and easy secondary pollution caused by using TiO2 alone, thus safeguarding ecological security.

[0077] The key technical features of this embodiment are described in detail below with reference to experiments, but the embodiments of the present invention include, but are not limited to, these features.

[0078] According to the Indoor Air Quality Standard (GB / T18883-2022), indoor air purification should be carried out when the formaldehyde content in indoor air exceeds 0.08 mg / m3 on average over 1 hour.

[0079] Based on this, the experimental setup is as follows: Figure 11 As shown, it includes a local heater, a reactor, and a circulating pump connected in a closed loop via pipelines. Formaldehyde solution is added to the local heater to simulate a 15m³ flow rate. 2 The indoor air formaldehyde concentration in a closed space; in this embodiment, VOCs concentration is characterized by formaldehyde concentration.

[0080] The reactor is connected to a photocatalytic space tube, within which granular Ag-TiO2-modified biomass rare earth tailings photocatalytic material is placed. An adjustable ultraviolet lamp is installed on the ring side of the photocatalytic space tube, and this adjustable ultraviolet lamp is fixedly installed on the reactor tube wall and at the center. The photocatalytic material can move within the reaction lamp tube due to airflow, forming a fluidized bed. The degree of fluidization of the photocatalytic material is adjusted by regulating the power of the air pump according to the VOCs concentration in the air. The change in the initial indoor formaldehyde concentration is detected before and after the experiment using a calibrated VOCs detector.

[0081] Experiment 1: The effect of different baking temperatures on formaldehyde degradation in S2

[0082] Specifically, the initial indoor formaldehyde concentration was 0.16 mg / m³, the reaction time was 20 min, and the amount of photocatalyst material added was 500 g. The loading ratio of Ag-TiO₂ to g-C₃N₄ was selected as 1:5, and the molar ratio of TiO₂ / Ag doping was 1:3.

[0083] For the effects of different calcination temperatures on the preparation of biomass-doped rare earth tailings carriers on the degradation of formaldehyde in the atmosphere by the final Ag-TiO2-modified biomass rare earth tailings photocatalytic material, please refer to [link to relevant documentation]. Figure 1 .like Figure 2 As shown, the formaldehyde degradation rate reaches an inflection point at 530℃, and decreases when the temperature exceeds 530℃. Therefore, the preferred baking temperature for S4 in this embodiment is 530℃.

[0084] Experiment 2: The effect of different doping ratios in S2 on formaldehyde degradation

[0085] Similarly, assuming the initial formaldehyde concentration, reaction time, and amount of photocatalyst remain constant. From Figure 2 It can be seen that rare earth tailings-based carriers with different biochar ratios also affect the formaldehyde degradation rate in indoor air. This is because the biomass doping amount is too small (1:6), resulting in fewer pores in the carrier after calcination, insufficient loading of Ag-TiO2 / g-C3N4 material, limiting the probability and activity range of formaldehyde in the air contacting the catalyst, which is not conducive to the degradation of formaldehyde. At the same time, the high density of the rare earth tailings-based carrier reduces the boiling degree of the catalytic material.

[0086] Excessive biomass doping (1:4) makes the biomass rare earth tailings carrier prone to collapse during roasting, and its formaldehyde degradation effect is also slightly weaker than that of photocatalysts with a doping ratio of 1:5.

[0087] When a rare earth tailings-based carrier with a biochar doping ratio of 1:5 is roasted at 500℃, the formaldehyde degradation rate in indoor air reaches approximately 70%. However, the formaldehyde degradation rate decreases after roasting temperatures exceed 530℃. This is because low roasting temperatures of the biomass-doped rare earth tailings carrier hinder the decomposition of biochar, resulting in incomplete decomposition and an irregular carrier structure. This prevents Ag-TiO2 / g-C3N4 from being effectively and uniformly dispersed on the granular biomass-doped rare earth tailings carrier, limiting the catalyst's active range for formaldehyde contact and hindering its degradation. Conversely, excessively high roasting temperatures cause partial collapse of the biomass-doped rare earth tailings carrier structure, reducing its specific surface area and photocatalytic performance. Therefore, the regularity of the microstructure of the biomass-doped rare earth tailings carrier significantly affects the probability of the loaded metal oxide contacting organic pollutants and its catalytic oxidation effect at different roasting temperatures.

[0088] Experiment 3: The effect of different loading amounts on the degradation of formaldehyde in the atmosphere

[0089] from Figure 3 As can be seen, the air purification efficiency of the photocatalyst prepared by loading Ag-TiO2 / g-C3N4 materials with different mass ratios of Ag-TiO2 mixtures onto the g-C3N4 support via impregnation method is affected to some extent.

[0090] When the mass ratio of Ag-TiO2 loaded in g-C3N4 is 5:1, and the mass ratio of the prepared TiO2 / g-C3N4 material to the rare earth tailings-based carrier doped with biochar is 1:20, the degradation efficiency of formaldehyde in the air reaches 72.57%.

[0091] Considering both formaldehyde removal rate and material cost, this embodiment selects a photocatalyst with the optimal g-C3N4-loaded Ag-TiO2 mass ratio of 5:1 and a TiO2 / g-C3N4 material to a rare earth tailings-based carrier doped with biochar loading mass ratio of 1:20.

[0092] Experiment 4: Effects of different catalysts and dosages on formaldehyde degradation

[0093] Under strong ultraviolet light, with an initial formaldehyde concentration of 0.16 g·m⁻³ and a reaction time of 20 min, the degradation effects of different dosages of Ag-TiO₂-modified biomass rare earth tailings photocatalytic materials, and the loading of different materials (Ag, Ag-TiO₂, g-C₃N₄, Ag / g-C₃N₄, TiO₂ / g-C₃N₄, Ag-TiO₂ / g-C₃N₄) onto rare earth tailings-based carriers doped with biochar on the formaldehyde-degrading effects in the air are investigated. Please refer to [link to relevant documentation]. Figure 4 .

[0094] from Figure 4It can be seen that the degradation capacity of formaldehyde in the air by loading different materials Ag, Ag-TiO2, and Ag-TiO2 / g-C3N4 onto rare earth tailings-based carriers doped with biochar is Ag <TiO2<g-C3N4<Ag / g-C3N4<TiO2 / g-C3N4<Ag-TiO2 / g-C3N4。

[0095] The g-C3N4 support exhibits stronger formaldehyde degradation capabilities compared to other catalysts because the doping of nano-element Ag greatly enhances the separation and mobility of photogenerated electrons and holes, thereby improving photocatalytic efficiency.

[0096] The Ag-TiO2 / g-C3N4 photocatalyst exhibits the strongest formaldehyde degradation capability because Ag doping reduces the band gap of TiO2 and enhances its visible light absorption. At the same time, the addition of Ag inhibits the crystal growth of g-C3N4, increases the specific surface area and the separation rate of photogenerated electrons and holes, thereby improving the photocatalytic efficiency.

[0097] Experiment 5: Effect of reaction time on formaldehyde degradation

[0098] When a strong ultraviolet light source is applied, the initial formaldehyde concentration is 0.16 g·m³. -3 The effects of adding 500g of Ag-TiO2-modified biomass rare earth tailings photocatalytic materials with different particle sizes on the degradation of formaldehyde in the air are as follows: Figure 5 .Depend on Figure 5 It can be seen that the formaldehyde degradation rate in the air increases with the reaction time, and the formaldehyde degradation efficiency reaches 96% when the reaction time is 1 hour.

[0099] In summary, this embodiment uses template agent SBA-15, TiO2, AgNO3, and melamine as raw materials to prepare Ag-based photocatalysts via thermal shrinkage polymerization and impregnation methods. Formaldehyde degradation simulation was conducted in a self-made simulated photocatalytic experimental chamber. Analysis of the preparation conditions for the Ag-based photocatalysts revealed that the modified biomass rare earth tailings photocatalytic material prepared by this method for atmospheric purification, modified with Ag-TiO2, and loaded with Ag-TiO2 / g-C3N4 on a calcined biomass rare earth tailings photocatalyst support, not only improves the mechanical strength of the photocatalytic material support but also enhances the separation of photogenerated carriers during photocatalysis by adding Ag-TiO2 modification, reducing the recombination rate of photogenerated electrons and holes. This allows for successful decomposition of pollutants in a shorter time. Pollutants can be oxidized and degraded into CO2 and H2O, which are non-toxic to humans. The materials are recyclable and have a long catalytic duration. This method overcomes the problems of poor visible light response, low quantum efficiency, difficult recycling, and easy secondary pollution caused by using TiO2 alone, thus maintaining ecological safety.

[0100] This specification describes examples of embodiments of the invention, but does not imply that these embodiments illustrate or describe all possible forms of the invention. It should be understood that the embodiments in the specification can be implemented in various alternative forms. The drawings are not necessarily drawn to scale; some features may be enlarged or reduced to show details of specific components. The specific structural and functional details disclosed should not be construed as limiting, but merely as a representative basis for teaching those skilled in the art to implement the invention in various forms. Those skilled in the art will understand that multiple features illustrated and described with reference to any of the drawings can be combined with features illustrated in one or more other drawings to form embodiments not explicitly illustrated or described. The illustrated combinations of features provide representative embodiments for typical applications. However, various combinations and variations of features consistent with the teachings of the invention may be used as needed for specific applications or implementations.

[0101] 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 Ag-TiO2-modified biomass rare earth tailings photocatalytic material, characterized in that, The preparation method of the catalytic material includes the following steps: To generate the g-C3N4 support, melamine and SBA-15 template agent were added to deionized water and mixed. Then hydrochloric acid and anhydrous ethanol were added sequentially and stirred. The lower layer precipitate was collected by centrifugation, washed, and calcined to obtain the g-C3N4 support. To generate a rare earth tailings carrier doped with biomass, carbonized biomass powder and rare earth tailings powder are mixed with water at a mass ratio of 1:

5. The rare earth tailings powder is then dispersed using ultrasound to obtain a first suspension. The first suspension is dried, granulated, calcined, and cooled to obtain the rare earth tailings carrier doped with biomass. To generate Ag-TiO2 / g-C3N4 material, the g-C3N4 support, AgNO3 and TiO2 were dissolved in anhydrous ethanol, ultrasonically dispersed to obtain a second suspension, and then allowed to stand and vacuum dried to obtain Ag-TiO2 / g-C3N4 material. To generate Ag-TiO2-modified biomass rare earth tailings photocatalytic material, the Ag-TiO2 / g-C3N4 material and the biomass-doped rare earth tailings carrier were added to anhydrous ethanol and deionized water and mixed evenly. After ultrasonic dispersion, a third suspension was obtained. After standing and vacuum drying, gray solid particles were obtained. The gray solid particles were then calcined to obtain Ag-TiO2-modified biomass rare earth tailings photocatalytic material.

2. The preparation method of the Ag-TiO2 modified biomass rare earth tailings photocatalytic material according to claim 1, characterized in that, The specific method for generating the g-C3N4 carrier is as follows: Melamine and SBA-15 template agent in a ratio of 6:1 were added to deionized water and mixed evenly to obtain a white suspension. Add hydrochloric acid and a trace amount of anhydrous ethanol to the white suspension, and stir rapidly with a magnetic stirrer for 5 minutes to obtain a white viscous liquid. The white viscous liquid was centrifuged to separate the solids, and the lower precipitate was removed and washed repeatedly by centrifugation with anhydrous ethanol and deionized water until a semi-transparent semi-solid was formed. The semi-solid was placed in a semi-enclosed porcelain crucible and calcined to obtain a white flocculent powder g-C3N4 carrier.

3. The preparation method of the Ag-TiO2 modified biomass rare earth tailings photocatalytic material according to claim 1, characterized in that, Specific methods for generating rare earth tailings carriers doped with biomass include: To prepare carbonized biomass powder, straw-type biomass is carbonized at 400℃ in an oxygen-deficient environment and then pulverized to 100-150 mesh for later use. 100-150 mesh carbonized biomass powder and rare earth tailings powder are mixed with water at a mass ratio of 1:5, and the solid-liquid ratio is 1:50-60. The rare earth tailings powder was dispersed using ultrasound at 30-50 kHz and 50 W / L to form the first suspension. The first suspension was dried in a 40°C drying oven for 2 hours and then granulated. The material is then placed in a tubular furnace and roasted at 500-550℃ for 2 hours, and then cooled to obtain a rare earth tailings carrier doped with biomass.

4. The preparation method of the Ag-TiO2 modified biomass rare earth tailings photocatalytic material according to claim 3, characterized in that, The straw-based biomass refers to wheat straw and corn stalks.

5. The preparation method of the Ag-TiO2 modified biomass rare earth tailings photocatalytic material according to claim 1, characterized in that, The method for generating the Ag-TiO2-modified biomass rare earth tailings photocatalytic material includes: A certain proportion of the Ag-TiO2 / g-C3N4 material was added to a mixed solution of anhydrous ethanol and deionized water with a volume ratio of 4:1 and mixed evenly. Add the rare earth tailings carrier doped with biomass, wherein the mass ratio of the Ag-TiO2 / g-C3N4 material to the rare earth tailings carrier doped with biomass is 1:10-20, and stir for 10 min; The third suspension was obtained by sonication for 30 minutes. The third suspension was sealed and allowed to stand for 24 hours. The third suspension was then placed in a vacuum oven and dried at 80°C to obtain gray solid particles. The material was heated to 500-520℃ in a muffle furnace at a heating rate of 5℃ / min and then calcined for 4 hours to obtain Ag-TiO2 modified biomass rare earth tailings photocatalytic material.

6. The preparation method of the Ag-TiO2 modified biomass rare earth tailings photocatalytic material according to claim 5, characterized in that, The muffle furnace heats the material to 500°C at a rate of 5°C / min.

7. The preparation method of the Ag-TiO2 modified biomass rare earth tailings photocatalytic material according to claim 5, characterized in that, The mass ratio of Ag-TiO2 to g-C3N4 material is 1:4-5; the mass ratio of Ag-TiO2 / g-C3N4 material to the rare earth tailings carrier doped with biomass is 1:

20.

8. A photocatalytic material made from Ag-TiO2-modified biomass rare earth tailings, characterized in that, It is prepared by the preparation method described in any one of claims 1-7.

9. The application of an Ag-TiO2-modified biomass rare earth tailings photocatalytic material, characterized in that, Application of the Ag-TiO2 modified biomass rare earth tailings photocatalytic material as described in claim 8 in air purification.

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