A bio-based platinum adsorbent material and its preparation method

Abstract

This invention discloses a bio-based platinum adsorbent material and its preparation method, relating to the field of metal adsorbent technology. The bio-based platinum adsorbent material of this invention comprises modified nitrogen-doped carbon spheres, persimmon powder coated on the outer surface of the modified nitrogen-doped carbon spheres, and urea-formaldehyde resin adhering the modified nitrogen-doped carbon spheres and persimmon powder together; the modified nitrogen-doped carbon spheres are glycine-modified nitrogen-doped carbon spheres; the nitrogen-doped carbon spheres are obtained by hydrothermal activation and high-temperature carbonization using the biomass material *Gastrodia elata* as a nitrogen and carbon source; the bio-based platinum adsorbent material prepared by this invention exhibits good platinum adsorption performance.

Description

Technical Field

[0001] This invention relates to the field of metal adsorbent technology, specifically to a bio-based platinum adsorbent material and its preparation method. Background Technology

[0002] With increasing attention being paid to environmental issues, the development of efficient and environmentally friendly adsorbents for the recovery of precious metal ions has become a research hotspot. Traditional adsorbent materials, such as activated carbon, while exhibiting excellent adsorption performance, are typically accompanied by high energy consumption and dependence on specific raw materials during their production process.

[0003] To address these issues, researchers have begun to focus on renewable biomass resources in hopes of finding greener and lower-cost solutions. These biomass sources are widespread, including agricultural waste, forestry byproducts, and various plant extracts. They not only provide abundant raw materials but also reduce carbon footprints and promote the development of a circular economy during the conversion into adsorbent materials.

[0004] Technicians paid particular attention to the unique advantages of Gastrodia elata as a carbon and nitrogen source. As a common traditional Chinese medicine, Gastrodia elata is rich in various organic components, which can form nitrogen-doped carbon spheres with high specific surface area and abundant pore structure during pyrolysis. The introduction of nitrogen gives this material higher surface chemical activity, thus significantly enhancing its adsorption capacity for heavy metal ions such as platinum. In addition, the use of Gastrodia elata avoids the high energy consumption problems that may occur in the preparation of traditional adsorption materials, which is in line with the principles of green chemistry.

[0005] Furthermore, persimmon powder has proven to be an ideal choice for preparing high-performance adsorbent materials. Persimmons contain a large amount of tannic acid and other polyphenolic compounds, which can be transformed into materials with excellent adsorption properties under appropriate conditions. Tannic acid is a natural polymer with the ability to bind to metal ions, thus showing great potential in treating wastewater containing heavy metals. Utilizing persimmon powder to prepare adsorbent materials not only effectively utilizes agricultural waste but also provides a new approach to solving the problem of poor dispersibility in water.

[0006] However, despite the excellent properties of both Gastrodia elata and persimmon powder, their dispersibility in water and adsorption effect on platinum ions still have certain limitations when used. To solve this problem, this invention prepares a bio-based platinum adsorbent material. Summary of the Invention

[0007] The purpose of this invention is to provide a bio-based platinum adsorbent material and its preparation method, so as to solve the problems existing in the prior art.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0009] A bio-based platinum adsorbent material includes modified nitrogen-doped carbon spheres, persimmon powder coated on the outer surface of the modified nitrogen-doped carbon spheres, and urea-formaldehyde resin adhering the modified nitrogen-doped carbon spheres and persimmon powder together; the modified nitrogen-doped carbon spheres are glycine-modified nitrogen-doped carbon spheres; the nitrogen-doped carbon spheres are obtained by hydrothermal treatment, activation, and high-temperature carbonization of nitrogen source and carbon source.

[0010] Furthermore, the free formaldehyde content in the urea-formaldehyde resin is 1~2wt%.

[0011] Furthermore, the activation is performed using zinc chloride.

[0012] Furthermore, the nitrogen and carbon sources are derived from the biomass material Gastrodia elata.

[0013] This invention also provides a method for preparing a bio-based platinum adsorbent material, characterized by comprising the following preparation steps:

[0014] (1) A layer of urea-formaldehyde resin is coated on the outer surface of the modified nitrogen-doped carbon spheres to obtain nitrogen-doped carbon spheres with one-time coating;

[0015] (2) Coat the surface of the nitrogen-doped carbon spheres with a layer of persimmon powder to obtain nitrogen-doped carbon spheres with a second coating;

[0016] (3) Disperse the nitrogen-doped carbon spheres that have been coated twice in distilled water with a solid-liquid ratio of 1:9~11. After adding concentrated hydrochloric acid, heat the mixture to 40~60℃ and stir for 100~125 min. Then filter the mixture and wash it with distilled water 2~4 times. Finally, dry it in a forced-air drying oven at 50℃ for 24 h to obtain the bio-based platinum adsorbent material.

[0017] Furthermore, the preparation method of the modified nitrogen-doped carbon spheres is as follows: nitrogen-doped carbon spheres are dispersed in glycine aqueous solution, then concentrated sulfuric acid is added, the temperature is raised to 60~70℃, kept at the temperature, stirred at 100~200rpm for 7~9h, then allowed to stand for 4h, filtered, repeatedly washed with deionized water until neutral, and dried to obtain modified nitrogen-doped carbon spheres.

[0018] Furthermore, the concentration of the glycine aqueous solution is 2% to 6%; the mass ratio of the nitrogen-doped carbon spheres to glycine is 3:2 to 10; and the mass of the concentrated sulfuric acid is 0.6 to 0.8 times that of the nitrogen-doped carbon spheres.

[0019] Furthermore, the preparation method of the nitrogen-doped carbon spheres is as follows: the biomass material Gastrodia elata is washed, dried, and pulverized with deionized water, and then added to a high-pressure reactor with 80-120 times the mass of deionized water. The reaction is carried out at the first reaction temperature for 23-25 ​​hours, and then naturally cooled to room temperature. After centrifugation, washing, and vacuum drying, powder is obtained. The powder is then activated with zinc chloride, heated to the carbonization temperature under nitrogen protection, and carbonized. After natural cooling to room temperature, the powder is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. After vacuum drying, nitrogen-doped carbon spheres are obtained.

[0020] Furthermore, the step of activating the powder with zinc chloride is as follows: the powder is added to a 19-21% zinc chloride solution at 9-11 times its weight of Gastrodia elata and soaked for 23-25 ​​hours.

[0021] Furthermore, the first reaction temperature is 178~182℃; the carbonization temperature is 795~805℃.

[0022] Furthermore, the concentration of the concentrated hydrochloric acid is 36-38%.

[0023] Furthermore, the mass of the concentrated hydrochloric acid is 0.015 to 0.25 times that of the persimmon powder.

[0024] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0025] The bio-based platinum adsorbent material prepared by this invention includes modified nitrogen-doped carbon spheres, persimmon powder coated on the outer surface of the modified nitrogen-doped carbon spheres, and urea-formaldehyde resin adhering the modified nitrogen-doped carbon spheres and persimmon powder together; the modified nitrogen-doped carbon spheres are glycine-modified nitrogen-doped carbon spheres; the nitrogen-doped carbon spheres are obtained by hydrothermal activation and high-temperature carbonization using biomass material Gastrodia elata as nitrogen and carbon source.

[0026] First, nitrogen-doped carbon spheres were prepared by hydrothermal activation and high-temperature carbonization using Gastrodia elata, a biomass material, as the nitrogen and carbon source. Glycine was then used to modify the nitrogen-doped carbon spheres. Since Gastrodia elata is abundant, readily available, and inexpensive, it was chosen as the primary source for preparing nitrogen-doped carbon spheres. The resulting nitrogen-doped carbon spheres are reticulated and have numerous nanopores, exhibiting good adsorption properties. Furthermore, glycine modification was used to introduce amino groups onto the carbon spheres, which increased both the adsorption capacity of the nitrogen-doped carbon spheres for platinum and their adhesion to urea-formaldehyde resin.

[0027] Secondly, urea-formaldehyde resin can be used to firmly bond modified nitrogen-doped carbon spheres and persimmon powder together. Persimmon powder is rich in tannins, which have a good adsorption effect on platinum metal ions. Moreover, they are widely available, environmentally friendly, and have a good adsorption effect. When combined with modified nitrogen-doped carbon spheres, the prepared bio-based platinum adsorbent material has a better platinum adsorption effect.

[0028] Finally, urea-formaldehyde resin and persimmon powder were sequentially coated onto the surface of modified nitrogen-doped carbon spheres and mixed under concentrated hydrochloric acid conditions. Glycine on the surface of the modified nitrogen-doped carbon spheres, free formaldehyde in the urea-formaldehyde resin, and tannins in the persimmon powder underwent the Mannich reaction to form amphoteric tannins. Under acidic conditions, the amphoteric tannins exist in the form of salts and have excellent solubility. This caused changes in the functional groups such as hydroxyl and carboxyl groups on the surface of persimmon phenol. The introduced amino groups, together with the hydroxyl and carboxyl groups, adsorbed platinum ions through ion exchange or coordination, further enhancing the platinum adsorption effect of the bio-based platinum adsorbent material. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The test methods for various indicators of the bio-based platinum adsorbent material prepared in the following embodiments are as follows:

[0031] Platinum adsorption effect: 50 parts by mass of bio-based platinum adsorbent material were added to 500 parts by mass of chloroplatinic acid solution with a concentration of 30 mg / L, the pH was adjusted to 1, and the mixture was kept at 70℃ and shaken for 12 h. After filtration, the filtrate was collected, and the concentration of platinum metal ions in the filtrate was determined by atomic absorption spectrophotometer. Platinum adsorption rate = (30 - concentration of platinum metal ions in filtrate) * 100% / 30.

[0032] Example 1

[0033] A method for preparing a bio-based platinum adsorbent material includes the following preparation steps:

[0034] (1) A layer of urea-formaldehyde resin is coated on the outer surface of the modified nitrogen-doped carbon spheres to obtain nitrogen-doped carbon spheres with one-time coating;

[0035] (2) Coat the surface of the nitrogen-doped carbon spheres with a layer of persimmon powder to obtain nitrogen-doped carbon spheres with a second coating;

[0036] (3) Disperse the nitrogen-doped carbon spheres that have been coated twice in distilled water at a solid-liquid ratio of 1:9. Add 36% concentrated hydrochloric acid and heat to 40°C and stir for 100 min. After solid-liquid separation, washing and drying, the bio-based platinum adsorbent material is obtained. The mass of concentrated hydrochloric acid is 0.015 times that of persimmon powder.

[0037] The modified nitrogen-doped carbon spheres are prepared as follows: nitrogen-doped carbon spheres are dispersed in an aqueous solution of glycine, then concentrated sulfuric acid is added, the temperature is raised to 60°C, kept at the temperature, stirred at 100 rpm for 7 hours, allowed to stand for 4 hours, filtered, repeatedly washed with deionized water until neutral, and dried to obtain modified nitrogen-doped carbon spheres.

[0038] The concentration of the glycine aqueous solution is 2%; the mass ratio of the nitrogen-doped carbon spheres to glycine is 3:2; and the mass of the concentrated sulfuric acid is 0.6 times that of the nitrogen-doped carbon spheres.

[0039] The preparation method of the nitrogen-doped carbon spheres is as follows: The biomass material *Gastrodia elata* is washed with deionized water, dried at 49°C to a moisture content of 8%, and then pulverized into powder with a particle size of 140 mesh. This powder is then added to a high-pressure reactor with 80 times the mass of the *Gastrodia elata* in deionized water, and the reaction is maintained at 178°C for 23 hours. Afterward, the mixture is naturally cooled to room temperature, centrifuged, and washed with deionized water and anhydrous ethanol until the solution is colorless. After vacuum drying, the mixture is then immersed in a 19% zinc chloride solution (9 times the mass of the *Gastrodia elata*) at room temperature for 23 hours. Under nitrogen protection, the temperature is raised to 795°C and held. After natural cooling to room temperature, the mixture is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. Finally, after vacuum drying, nitrogen-doped carbon spheres are obtained.

[0040] Example 2

[0041] A method for preparing a bio-based platinum adsorbent material includes the following preparation steps:

[0042] (1) A layer of urea-formaldehyde resin is coated on the outer surface of the modified nitrogen-doped carbon spheres to obtain nitrogen-doped carbon spheres with one-time coating;

[0043] (2) Coat the surface of the nitrogen-doped carbon spheres with a layer of persimmon powder to obtain nitrogen-doped carbon spheres with a second coating;

[0044] (3) Disperse the nitrogen-doped carbon spheres that have been coated twice in distilled water at a solid-liquid ratio of 1:10. After adding 36% concentrated hydrochloric acid, heat the mixture to 50°C and stir for 110 min. After solid-liquid separation, washing and drying, the bio-based platinum adsorbent material is obtained. The mass of the concentrated hydrochloric acid is 0.02 times that of the persimmon powder.

[0045] The modified nitrogen-doped carbon spheres are prepared as follows: nitrogen-doped carbon spheres are dispersed in an aqueous solution of glycine, then concentrated sulfuric acid is added, the temperature is raised to 65°C, kept at the temperature, stirred at 150 rpm for 8 hours, allowed to stand for 4 hours, filtered, repeatedly washed with deionized water until neutral, and dried to obtain modified nitrogen-doped carbon spheres.

[0046] The concentration of the glycine aqueous solution is 4%; the mass ratio of the nitrogen-doped carbon spheres to glycine is 3:6; and the mass of the concentrated sulfuric acid is 0.7 times that of the nitrogen-doped carbon spheres.

[0047] The preparation method of the nitrogen-doped carbon spheres is as follows: The biomass material *Gastrodia elata* is washed with deionized water, dried at 50°C until the moisture content is 10%, then pulverized into powder with a particle size of 150 mesh. This powder is then added to a high-pressure reactor with 100 times the mass of the *Gastrodia elata* in deionized water. The reaction is maintained at 180°C for 24 hours, then naturally cooled to room temperature, centrifuged, and washed with deionized water and anhydrous ethanol until the solution is colorless. After vacuum drying, the solution is immersed in a 20% zinc chloride solution (10 times the mass of the *Gastrodia elata*) at room temperature for 24 hours. Under nitrogen protection, the temperature is raised to 800°C and held, then naturally cooled to room temperature. The solution is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. After vacuum drying, nitrogen-doped carbon spheres are obtained.

[0048] Example 3

[0049] A method for preparing a bio-based platinum adsorbent material includes the following preparation steps:

[0050] (1) A layer of urea-formaldehyde resin is coated on the outer surface of the modified nitrogen-doped carbon spheres to obtain nitrogen-doped carbon spheres with one-time coating;

[0051] (2) Coat the surface of the nitrogen-doped carbon spheres with a layer of persimmon powder to obtain nitrogen-doped carbon spheres with a second coating;

[0052] (3) Disperse the nitrogen-doped carbon spheres that have been coated twice in distilled water with a solid-liquid ratio of 1:11. After adding 38% concentrated hydrochloric acid, heat the mixture to 60°C and stir for 125 min. After solid-liquid separation, washing and drying, the bio-based platinum adsorbent material is obtained. The mass of the concentrated hydrochloric acid is 0.025 times that of the persimmon powder.

[0053] The modified nitrogen-doped carbon spheres are prepared as follows: nitrogen-doped carbon spheres are dispersed in an aqueous solution of glycine, then concentrated sulfuric acid is added, the temperature is raised to 70°C, kept at the temperature, stirred at 200 rpm for 9 hours, allowed to stand for 4 hours, filtered, repeatedly washed with deionized water until neutral, and dried to obtain modified nitrogen-doped carbon spheres.

[0054] The concentration of the glycine aqueous solution is 6%; the mass ratio of the nitrogen-doped carbon spheres to glycine is 3:10; and the mass of the concentrated sulfuric acid is 0.8 times that of the nitrogen-doped carbon spheres.

[0055] The preparation method of the nitrogen-doped carbon spheres is as follows: The biomass material *Gastrodia elata* is washed with deionized water, dried at 52°C until the moisture content is 12%, then pulverized into powder with a particle size of 160 mesh. This powder is then added to a high-pressure reactor with 120 times the mass of the *Gastrodia elata* in deionized water. The reaction is maintained at 182°C for 25 hours, then naturally cooled to room temperature, centrifuged, and washed with deionized water and anhydrous ethanol until the solution is colorless. After vacuum drying, the solution is immersed in a 21% zinc chloride solution (11 times the mass of the *Gastrodia elata*) at room temperature for 25 hours. The temperature is then raised to 805°C under nitrogen protection and held. After natural cooling to room temperature, the solution is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. Finally, after vacuum drying, nitrogen-doped carbon spheres are obtained.

[0056] Comparative Example 1

[0057] A method for preparing a bio-based platinum adsorbent material includes the following preparation steps:

[0058] (1) A layer of urea-formaldehyde resin is coated on the outer surface of the nitrogen-doped carbon sphere to obtain a nitrogen-doped carbon sphere with one-time coating;

[0059] (2) Coat the surface of the nitrogen-doped carbon spheres with a layer of persimmon powder to obtain nitrogen-doped carbon spheres with a second coating;

[0060] (3) Disperse the nitrogen-doped carbon spheres that have been coated twice in distilled water at a solid-liquid ratio of 1:10. After adding 36% concentrated hydrochloric acid, heat the mixture to 50°C and stir for 110 min. After solid-liquid separation, washing and drying, the bio-based platinum adsorbent material is obtained. The mass of the concentrated hydrochloric acid is 0.02 times that of the persimmon powder.

[0061] The preparation method of the nitrogen-doped carbon spheres is as follows: The biomass material *Gastrodia elata* is washed with deionized water, dried at 50°C until the moisture content is 10%, then pulverized into powder with a particle size of 150 mesh. This powder is then added to a high-pressure reactor with 100 times the mass of the *Gastrodia elata* in deionized water. The reaction is maintained at 180°C for 24 hours, then naturally cooled to room temperature, centrifuged, and washed with deionized water and anhydrous ethanol until the solution is colorless. After vacuum drying, the solution is immersed in a 20% zinc chloride solution (10 times the mass of the *Gastrodia elata*) at room temperature for 24 hours. Under nitrogen protection, the temperature is raised to 800°C and held, then naturally cooled to room temperature. The solution is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. After vacuum drying, nitrogen-doped carbon spheres are obtained.

[0062] Comparative Example 2

[0063] A method for preparing a bio-based platinum adsorbent material includes the following preparation steps:

[0064] (1) A layer of persimmon powder is coated on the outer surface of the modified nitrogen-doped carbon sphere to obtain a nitrogen-doped carbon sphere with one coating.

[0065] (2) Disperse the nitrogen-doped carbon spheres that were once coated in distilled water with a solid-liquid ratio of 1:10. After adding 36% concentrated hydrochloric acid, heat the mixture to 50°C and stir for 110 min. After solid-liquid separation, washing and drying, the bio-based platinum adsorbent material is obtained. The mass of the concentrated hydrochloric acid is 0.02 times that of the persimmon powder.

[0066] The modified nitrogen-doped carbon spheres are prepared as follows: nitrogen-doped carbon spheres are dispersed in an aqueous solution of glycine, then concentrated sulfuric acid is added, the temperature is raised to 65°C, kept at the temperature, stirred at 150 rpm for 8 hours, allowed to stand for 4 hours, filtered, repeatedly washed with deionized water until neutral, and dried to obtain modified nitrogen-doped carbon spheres.

[0067] The concentration of the glycine aqueous solution is 4%; the mass ratio of the nitrogen-doped carbon spheres to glycine is 3:6; and the mass of the concentrated sulfuric acid is 0.7 times that of the nitrogen-doped carbon spheres.

[0068] The preparation method of the nitrogen-doped carbon spheres is as follows: The biomass material *Gastrodia elata* is washed with deionized water, dried at 50°C until the moisture content is 10%, then pulverized into powder with a particle size of 150 mesh. This powder is then added to a high-pressure reactor with 100 times the mass of the *Gastrodia elata* in deionized water. The reaction is maintained at 180°C for 24 hours, then naturally cooled to room temperature, centrifuged, and washed with deionized water and anhydrous ethanol until the solution is colorless. After vacuum drying, the solution is immersed in a 20% zinc chloride solution (10 times the mass of the *Gastrodia elata*) at room temperature for 24 hours. Under nitrogen protection, the temperature is raised to 800°C and held, then naturally cooled to room temperature. The solution is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. After vacuum drying, nitrogen-doped carbon spheres are obtained.

[0069] Comparative Example 3

[0070] Nitrogen-doped carbon spheres were used as bio-based platinum adsorbents.

[0071] Comparative Example 4

[0072] The modified nitrogen-doped carbon spheres obtained by the same modification method as in Example 1 were used as the bio-based platinum adsorbent material.

[0073] Comparative Example 5

[0074] Persimmon powder was used as a bio-based platinum adsorbent.

[0075] Comparative Example 6

[0076] A method for preparing a bio-based platinum adsorbent material includes the following preparation steps:

[0077] (1) A layer of urea-formaldehyde resin is coated on the outer surface of the modified nitrogen-doped carbon spheres to obtain nitrogen-doped carbon spheres with one-time coating;

[0078] (2) A layer of persimmon powder was coated on the surface of a nitrogen-doped carbon sphere to obtain a bio-based platinum adsorbent material.

[0079] The modified nitrogen-doped carbon spheres are prepared as follows: nitrogen-doped carbon spheres are dispersed in an aqueous solution of glycine, then concentrated sulfuric acid is added, the temperature is raised to 65°C, kept at the temperature, stirred at 150 rpm for 8 hours, allowed to stand for 4 hours, filtered, repeatedly washed with deionized water until neutral, and dried to obtain modified nitrogen-doped carbon spheres.

[0080] The concentration of the glycine aqueous solution is 4%; the mass ratio of the nitrogen-doped carbon spheres to glycine is 3:6; and the mass of the concentrated sulfuric acid is 0.7 times that of the nitrogen-doped carbon spheres.

[0081] The preparation method of the nitrogen-doped carbon spheres is as follows: The biomass material *Gastrodia elata* is washed with deionized water, dried at 50°C until the moisture content is 10%, then pulverized into powder with a particle size of 150 mesh. This powder is then added to a high-pressure reactor with 100 times the mass of the *Gastrodia elata* in deionized water. The reaction is maintained at 180°C for 24 hours, then naturally cooled to room temperature, centrifuged, and washed with deionized water and anhydrous ethanol until the solution is colorless. After vacuum drying, the solution is immersed in a 20% zinc chloride solution (10 times the mass of the *Gastrodia elata*) at room temperature for 24 hours. Under nitrogen protection, the temperature is raised to 800°C and held, then naturally cooled to room temperature. The solution is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. After vacuum drying, nitrogen-doped carbon spheres are obtained.

[0082] Example of effect

[0083] Table 1 below shows the performance analysis results of the bio-based platinum adsorbent materials of Examples 1-3 and Comparative Examples 1-6 of the present invention.

[0084] Table 1

[0085]

[0086] A comparison of the experimental data from Examples 1-3 and Comparative Examples 1-6 in Table 1 reveals that the bio-based platinum adsorbents prepared in each example exhibit better platinum adsorption performance compared to those prepared in the comparative examples. Analysis indicates that this is because the use of glycine-modified nitrogen-doped carbon spheres, introducing amino groups and other functional groups onto the carbon spheres, increases both the platinum adsorption capacity of the nitrogen-doped carbon spheres and the adhesion between the modified nitrogen-doped carbon spheres and urea-formaldehyde resin. Furthermore, the urea-formaldehyde resin can firmly bond the modified nitrogen-doped carbon spheres and persimmon powder together. The free formaldehyde in the urea-formaldehyde resin can undergo a Mannich reaction with the glycine on the surface of the modified nitrogen-doped carbon spheres and the tannins in the persimmon powder, increasing the dispersion of the bio-based platinum adsorbent in water, thus improving its platinum adsorption performance. Moreover, by relying on… In this first step, urea-formaldehyde resin and persimmon powder were coated onto the surface of modified nitrogen-doped carbon spheres to prepare a bio-based platinum adsorbent material. The mixture was then reacted under concentrated hydrochloric acid conditions to form amphoteric tannins. Under acidic conditions, the amphoteric tannins exist in a salt state, exhibiting excellent solubility, which enhances the dispersion of the bio-based platinum adsorbent material in water. Furthermore, the hydroxyl and carboxyl groups on the surface of the persimmon powder underwent changes, with the introduced amino groups adsorbing platinum ions through ion exchange or coordination with the hydroxyl and carboxyl groups, further enhancing the platinum adsorption effect of the bio-based platinum adsorbent material. The resulting bio-based platinum adsorbent material exhibited significantly better platinum adsorption performance.

[0087] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A bio-based platinum adsorbent material, characterized in that, The product comprises modified nitrogen-doped carbon spheres, persimmon powder coated on the outer surface of the modified nitrogen-doped carbon spheres, and urea-formaldehyde resin adhering the modified nitrogen-doped carbon spheres and persimmon powder together; the modified nitrogen-doped carbon spheres are nitrogen-doped carbon spheres modified with glycine; the nitrogen-doped carbon spheres are obtained by hydrothermal treatment, activation, and high-temperature carbonization of nitrogen and carbon sources; the nitrogen and carbon sources are derived from the biomass material Gastrodia elata; the free formaldehyde content in the urea-formaldehyde resin is 1-2 wt%. The preparation method of the bio-based platinum adsorbent material includes the following preparation steps: (1) A layer of urea-formaldehyde resin is coated on the outer surface of the modified nitrogen-doped carbon spheres to obtain nitrogen-doped carbon spheres with one-time coating; (2) Coat the surface of the nitrogen-doped carbon spheres with a layer of persimmon powder to obtain nitrogen-doped carbon spheres with a second coating; (3) Disperse the nitrogen-doped carbon spheres that have been coated twice in distilled water with a solid-liquid ratio of 1:9~11. After adding concentrated hydrochloric acid, heat the mixture to 40~60℃ and stir for 100~125 min. After solid-liquid separation, washing and drying, the bio-based platinum adsorbent material is obtained. The modified nitrogen-doped carbon spheres are prepared as follows: nitrogen-doped carbon spheres are dispersed in glycine aqueous solution, then concentrated sulfuric acid is added, the temperature is raised to 60~70℃, kept at the temperature, stirred at 100~200rpm for 7~9h, then allowed to stand, filtered, repeatedly washed with deionized water until neutral, and dried to obtain modified nitrogen-doped carbon spheres.

2. The bio-based platinum adsorbent material according to claim 1, characterized in that, The activation is performed using zinc chloride.

3. The bio-based platinum adsorbent material according to claim 1, characterized in that, The concentration of the glycine aqueous solution is 2% to 6%; the mass ratio of the nitrogen-doped carbon spheres to glycine is 3:2 to 10; and the mass of the concentrated sulfuric acid is 0.6 to 0.8 times that of the nitrogen-doped carbon spheres.

4. The bio-based platinum adsorbent material according to claim 1, characterized in that, The preparation method of the nitrogen-doped carbon spheres is as follows: the biomass material Gastrodia elata is washed, dried and pulverized with deionized water, and then added to a high-pressure reactor with 80 to 120 times the weight of the Gastrodia elata in deionized water. The reaction is carried out at the first reaction temperature for 23 to 25 hours. After that, it is naturally cooled to room temperature, centrifuged, washed and vacuum dried to obtain powder. The powder is then activated with zinc chloride, heated to the carbonization temperature under nitrogen protection and carbonized. After naturally cooling to room temperature, it is repeatedly centrifuged and washed with hydrochloric acid and deionized water to remove residual metal impurities. After vacuum drying, nitrogen-doped carbon spheres are obtained.

5. The bio-based platinum adsorbent material according to claim 4, characterized in that, The activation step of the powder with zinc chloride is as follows: the powder is added to a 19-21% zinc chloride solution at 9-11 times the weight of Gastrodia elata and soaked for 23-25 ​​hours.

6. The bio-based platinum adsorbent material according to claim 4, characterized in that, The first reaction temperature is 178~182℃; the carbonization temperature is 795~805℃.

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