Mesoporous carbon material for precious metal recovery and preparation method and application thereof

Abstract

The application discloses a kind of mesoporous carbon materials for precious metal recovery and preparation method and application, belong to precious metal adsorption material technical field. Including the following steps: S1, after being treated, rape straw is crushed and sieved, then add water, hydrothermal reaction is carried out at 240~280 DEG C, after reaction, freeze-thaw cycle is carried out to obtain precursor, active agent is added to precursor, pyrolysis is obtained under the atmosphere of protective gas at 600~800 DEG C;S2, after etching, active material is added in chloroform and ultrasonic, then add 3-mercapto propyl trimethoxysilane and phosphorus thiocyanate, hydrothermal reaction is carried out at 160~180 DEG C to obtain mesoporous carbon material.The application adopts freeze-thaw cycle after hydrothermal reaction, adds active agent to carry out pore modification to micropore, improves pore distribution uniformity and specific surface area, increases mesoporous pore, so that mesoporous carbon is more easily contacted with metal ion solution inside, improves the adsorption capacity and stability of mesoporous carbon.

Description

Technical Field

[0001] This invention relates to the field of precious metal adsorption materials technology, and more specifically to a mesoporous carbon material for precious metal recovery, its preparation method, and its application. Background Technology

[0002] Gold, silver, and the six platinum group elements (palladium, osmium, iridium, rhodium, platinum, and ruthenium) are collectively known as precious metals. Precious metals possess unique physicochemical properties such as high melting points, good electrical conductivity and catalytic performance, and chemical inertness in complex environments, leading to their widespread application in chemical, aerospace, electronics, and medical fields. Precious metal resources are scarce and expensive. In contrast, secondary resources contain significantly higher amounts of precious metals. These secondary resources primarily originate from waste catalysts in industries such as electronic waste, printed circuit boards, and wastewater from jewelry processing. Therefore, from the perspective of resource conservation and environmental protection, the recycling and utilization of secondary precious metal resources is of great significance.

[0003] Currently, commonly used methods for recycling precious metals include ion exchange, extraction, chemical precipitation, electrolysis, and adsorption. Ion exchange technology does not require complex operating procedures and has high separation efficiency, but it suffers from long separation cycles, limited load capacity, and high costs. Extraction has short extraction cycles, simple processes, high selectivity, low cost, and low pollution, but back-extraction time is long and efficiency is low. Chemical precipitation and electrolysis methods easily cause precious metals to mix with other products, making it difficult to separate impurities. Compared with the above methods, adsorption is an ideal green extraction technology. It uses the porous structure and specific functional groups of adsorbent materials to adsorb metal ions from aqueous solutions, offering advantages such as large adsorption capacity, high efficiency, good selectivity, short adsorption time, and reusability. Currently used adsorbents are mainly divided into carbon materials and organic polymer materials.

[0004] Carbon materials have a porous structure and various active functional groups (such as carboxyl and hydroxyl groups), thus exhibiting a strong affinity for precious metals and are used to recover precious metals from industrial wastewater. However, porous carbon materials have a small specific surface area and insufficient adsorption capacity. To improve the adsorption capacity of carbon materials for precious metals, existing technologies often employ direct carbonization or activators to expand the pores and enhance the adsorption capacity of porous carbon materials. Then, functional groups are introduced through chemical modification to improve the adsorption performance for precious metals. However, mesoporous carbon materials have a small specific surface area, uneven pore distribution, insufficient stability, and insufficient adsorption capacity. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a mesoporous carbon material for precious metal recovery, its preparation method, and its application. This invention employs a hydrothermal reaction followed by freeze-thaw cycles, pyrolysis with an activator, and simple methods to modify the micropores, introducing mesoporous channels to improve pore distribution uniformity and specific surface area. Etching further enhances the active sites of the mesoporous carbon, increasing the size of the mesoporous channels and facilitating contact between the mesoporous carbon and metal ion solutions. The introduction of P=S and -SH enables quantitative adsorption of precious metal ions or separation between ions, improving the adsorption selectivity, stability, and repeatability of the mesoporous carbon.

[0006] The first objective of this invention is to provide a method for preparing mesoporous carbon materials for precious metal recycling, comprising the following steps:

[0007] S1. After the treated rapeseed straw is crushed and passed through a 100-mesh sieve, water is added and hydrothermal reaction is carried out at 240-280℃. After the reaction is completed, freeze-thaw cycles are carried out 3-5 times to obtain the precursor. After grinding and sieving, an activator is added to the precursor. The precursor is pyrolyzed at 600-800℃ under a protective gas atmosphere. After washing until neutral, it is dried to obtain the activated product.

[0008] S2. After etching the activated material obtained in S1, filter and wash it until neutral, then add it to chloroform and sonicate it. Then add 3-mercaptopropyltrimethoxysilane and trichlorophosphorus, and perform a hydrothermal reaction at 160-180℃. After the reaction is completed, wash it with water until the filtrate is neutral, and then dry it to obtain mesoporous carbon material.

[0009] Preferably, in S1, the rapeseed straw is treated by soaking and washing the rapeseed straw in water and then drying it at 100-120°C for 8-12 hours.

[0010] Preferably, in S1, the mass ratio of rapeseed straw to water is 3:6 to 8, the hydrothermal reaction time is 4 to 6 hours, and the freeze-thaw temperature is -18°C.

[0011] Preferably, in S1, the mass ratio of the precursor to the activator is 1:2 to 4, and the activator is a mixture of phosphoric acid and potassium nitrate, wherein the mass ratio of phosphoric acid to potassium nitrate is 1:0.3 to 0.8.

[0012] Preferably, in S1, the pyrolysis time is 3 to 5 hours, and the protective gas is nitrogen.

[0013] Preferably, in S2, the etching involves placing the activator in a 1-3% potassium permanganate solution and refluxing it at 60-80°C for 3-4 hours, with the mass-to-volume ratio of the activator to the potassium permanganate solution being 1g:10-20mL; and the mass-to-volume ratio of the activator to chloroform being 1g:5-8mL.

[0014] Preferably, in S2, the mass-to-volume ratio of the activator, trichlorophosphine, and 3-mercaptopropyltrimethoxysilane is 1 g: 0.5–1 g: 8–10 mL.

[0015] Preferably, in S2, the hydrothermal reaction time is 3-5 hours, and the washing method is to first wash with 0.5-5 mol / L hydrochloric acid and then wash with deionized water.

[0016] A second objective of this invention is to provide a mesoporous carbon material prepared by the above-described preparation method.

[0017] A third objective of this invention is to provide the application of the aforementioned mesoporous carbon materials in the recovery of precious metals from wastewater.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) This invention modifies the micropores by performing a hydrothermal reaction followed by freeze-thaw cycles and using an activator. By using freeze-thaw cycles and pyrolysis of the activator, the micropores are expanded to introduce mesoporous channels, thereby improving the uniformity of channel distribution and specific surface area, and enhancing the adsorption capacity of mesoporous carbon. Then, by etching with potassium permanganate solution, the mesoporous channels of the mesoporous carbon are oxidized and dissolved, increasing the pore size of the activated carbon and enhancing the active sites of the mesoporous carbon. By introducing P=S and -SH through trichlorophosphorus and 3-mercaptopropyltrimethoxysilane, quantitative adsorption of noble metal ions or mutual separation between ions is achieved, thereby improving the adsorption selectivity, stability and repeatability of mesoporous carbon.

[0020] (2) This invention modifies rapeseed straw to prepare high-performance mesoporous carbon. The raw materials are inexpensive and readily available. Multiple methods were used to modify the rapeseed straw, successfully preparing mesoporous carbon materials with super-strong adsorption performance for heavy metal ions. The potassium nitrate adjuvant in the activator improved the oxidation and pore-forming performance of the phosphoric acid activator, enhancing the activation and pore-forming effect of the activator. Simultaneously, K... + The secondary pore-forming effect promotes the expansion of the pore size of activated carbon. Trichlorophosphorus and 3-mercaptopropyltrimethoxysilane increase the S and P content of mesoporous carbon. Through the chemical reaction between P=S and -SH with the metal to be adsorbed, the metal is captured efficiently. It has the advantages of high adsorption capacity and good stability, and improves the adsorption capacity of gold ions, platinum ions, etc. Attached Figure Description

[0021] Figure 1 The adsorption capacity of mesoporous carbon materials for platinum ions at different times in Example 1 and Comparative Examples 1-5 of this invention;

[0022] Figure 2 The adsorption amounts of gold ions by mesoporous carbon materials at different times are shown in Example 1 and Comparative Examples 1-5 of the present invention. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0025] Example 1

[0026] A method for preparing mesoporous carbon materials for precious metal recycling includes the following steps:

[0027] S1. After soaking and washing rapeseed straw in water, dry it at 120℃ for 8-12 hours, crush it and pass it through a 100-mesh sieve. Take 10g of the treated rapeseed straw and add it to 80mL of deionized water. Place it in a reaction vessel and hydrothermally react at 260℃ for 4 hours. After the reaction is completed, filter it and freeze it in a -18℃ refrigerator for 5 hours. Then take it out and thaw it at room temperature. Repeat this freeze-thaw cycle 4 times to obtain the precursor. Dry the precursor at 60℃ for 4 hours, grind it and pass it through a 50-mesh sieve. Then add 20g of a mixture of phosphoric acid and potassium nitrate (the mass ratio of phosphoric acid and potassium nitrate is 1:0.5). Place the mixture in a muffle furnace and pyrolyze it at 800℃ for 3 hours under a nitrogen atmosphere. The heating rate of the pyrolysis is 5℃ / min. After pyrolysis, wash it with deionized water until neutral and dry it at 80℃ to constant weight to obtain the activated product.

[0028] S2. Take 10g of the activated material, add 100mL of 2% potassium permanganate solution, and reflux in an 80℃ water bath for 3h. After reflux, dry at 80℃ for 5h, then add 60mL of chloroform and sonicate at 60℃ for 2h. Then add 5g of trichlorophosphine and 80mL of 3-mercaptopropyltrimethoxysilane, place in a reaction vessel, and hydrothermally react at 160℃ for 3h. After the reaction, wash with 0.5-5mol / L hydrochloric acid, then wash with deionized water until neutral, and dry at 80℃ to constant weight to obtain mesoporous carbon material.

[0029] Example 2

[0030] A method for preparing mesoporous carbon materials for precious metal recycling includes the following steps:

[0031] S1. After soaking and washing rapeseed straw in water, dry it at 120℃ for 10h, crush it and pass it through a 100-mesh sieve. Take 10g of the treated rapeseed straw and add it to 80mL of deionized water. Place it in a reaction vessel and hydrothermally react at 260℃ for 4h. After the reaction is completed, filter it and freeze it in a -18℃ refrigerator for 5h. Then take it out and thaw it at room temperature. Repeat this freeze-thaw cycle 4 times to obtain the precursor. Dry the precursor at 60℃ for 4h, grind it and pass it through a 50-mesh sieve. Then add 20g of a mixture of phosphoric acid and potassium nitrate (the mass ratio of phosphoric acid and potassium nitrate is 1:0.5). Place the mixture in a muffle furnace and pyrolyze it at 800℃ for 3h under a nitrogen atmosphere. The heating rate of the pyrolysis is 5℃ / min. After pyrolysis, wash it with deionized water until neutral and dry it at 80℃ to constant weight to obtain the activated product.

[0032] S2. Take 10g of the activated material, add 100mL of 2% potassium permanganate solution, and reflux in an 80℃ water bath for 3h. After reflux, dry at 80℃ for 5h, then add 60mL of chloroform and sonicate at 60℃ for 2h. Then add 5g of trichlorophosphine and 80mL of 3-mercaptopropyltrimethoxysilane, place in a reaction vessel, and hydrothermally react at 160℃ for 3h. After the reaction, wash with 0.5-5mol / L hydrochloric acid, then wash with deionized water until neutral, and dry at 80℃ to constant weight to obtain mesoporous carbon material.

[0033] Example 3

[0034] A method for preparing mesoporous carbon materials for precious metal recycling includes the following steps:

[0035] S1. After soaking and washing rapeseed straw in water, dry it at 100-120℃ for 8-12 hours, crush it and pass it through a 100-mesh sieve. Take 10g of the treated rapeseed straw and add it to 80mL of deionized water. Place it in a reaction vessel and hydrothermally react at 260℃ for 4 hours. After the reaction is completed, filter it and freeze it in a -18℃ refrigerator for 5 hours. Then take it out and thaw it at room temperature. Repeat this freeze-thaw cycle 4 times to obtain the precursor. Dry the precursor at 60℃ for 4 hours, grind it and pass it through a 50-mesh sieve. Then add 20g of a mixture of phosphoric acid and potassium nitrate (the mass ratio of phosphoric acid and potassium nitrate is 1:0.5). Place the mixture in a muffle furnace and pyrolyze it at 800℃ for 3 hours under a nitrogen atmosphere. The heating rate of the pyrolysis is 5℃ / min. After pyrolysis, wash it with deionized water until neutral and dry it at 80℃ to constant weight to obtain the activated product.

[0036] S2. Take 10g of the activated material, add 100mL of 2% potassium permanganate solution, and reflux in an 80℃ water bath for 3h. After reflux, dry at 80℃ for 5h, then add 60mL of chloroform and sonicate at 60℃ for 2h. Then add 5g of trichlorophosphine and 80mL of 3-mercaptopropyltrimethoxysilane, place in a reaction vessel, and hydrothermally react at 160℃ for 3h. After the reaction, wash with 0.5-5mol / L hydrochloric acid, then wash with deionized water until neutral, and dry at 80℃ to constant weight to obtain mesoporous carbon material.

[0037] Example 4

[0038] A method for preparing mesoporous carbon materials for precious metal recycling includes the following steps:

[0039] S1. After soaking and washing rapeseed straw in water, dry it at 100-120℃ for 8-12 hours, crush it and pass it through a 100-mesh sieve. Take 10g of the treated rapeseed straw and add it to 80mL of deionized water. Place it in a reaction vessel and hydrothermally react at 260℃ for 4 hours. After the reaction is completed, filter it and freeze it in a -18℃ refrigerator for 5 hours. Then take it out and thaw it at room temperature. Repeat this freeze-thaw cycle 4 times to obtain the precursor. Dry the precursor at 60℃ for 4 hours, grind it and pass it through a 50-mesh sieve. Then add 20g of a mixture of phosphoric acid and potassium nitrate (the mass ratio of phosphoric acid and potassium nitrate is 1:0.5). Place the mixture in a muffle furnace and pyrolyze it at 800℃ for 3 hours under a nitrogen atmosphere. The heating rate of the pyrolysis is 5℃ / min. After pyrolysis, wash it with deionized water until neutral and dry it at 80℃ to constant weight to obtain the activated product.

[0040] S2. Take 10g of the activated material, add 100mL of 2% potassium permanganate solution, and reflux in an 80℃ water bath for 3h. After reflux, dry at 80℃ for 5h, then add 60mL of chloroform and sonicate at 60℃ for 2h. Then add 5g of trichlorophosphine and 80mL of 3-mercaptopropyltrimethoxysilane, place in a reaction vessel, and hydrothermally react at 160℃ for 3h. After the reaction, wash with 0.5-5mol / L hydrochloric acid, then wash with deionized water until neutral, and dry at 80℃ to constant weight to obtain mesoporous carbon material.

[0041] Comparative Example 1

[0042] A method for preparing mesoporous carbon materials includes the following steps:

[0043] S1. After soaking and washing the rapeseed straw in water, dry it at 100-120℃ for 8-12 hours, crush it and pass it through a 100-mesh sieve. Take 10g of the treated rapeseed straw and add it to 80mL of deionized water. Place it in a reaction vessel and hydrothermally react at 260℃ for 4 hours. After the reaction is completed, filter it and freeze it in a -18℃ refrigerator for 5 hours. Then take it out and thaw it at room temperature. Repeat this freeze-thaw cycle 4 times to obtain the precursor. Dry it at 80℃ to constant weight to obtain the activated product.

[0044] S2. Take 10g of the activated material, add 100mL of 2% potassium permanganate solution, and reflux in an 80℃ water bath for 3h. After reflux, dry at 80℃ for 5h, then add 60mL of chloroform and sonicate at 60℃ for 2h. Then add 5g of trichlorophosphine and 80mL of 3-mercaptopropyltrimethoxysilane, place in a reaction vessel, and hydrothermally react at 160℃ for 3h. After the reaction, wash with 0.5-5mol / L hydrochloric acid, then wash with deionized water until neutral, and dry at 80℃ to constant weight to obtain mesoporous carbon material.

[0045] Comparative Example 2

[0046] A method for preparing mesoporous carbon materials includes the following steps:

[0047] S1. After soaking and washing rapeseed straw in water, dry it at 100-120℃ for 8-12 hours, crush it and pass it through a 100-mesh sieve. Take 10g of the treated rapeseed straw and add it to 80mL of deionized water. Place it in a reaction vessel and hydrothermally react at 260℃ for 4 hours. After the reaction is completed, filter it and freeze it in a -18℃ refrigerator for 5 hours. Then take it out and thaw it at room temperature. Repeat this freeze-thaw cycle 4 times to obtain the precursor. Dry the precursor at 60℃ for 4 hours, grind it and pass it through a 50-mesh sieve. Then add 20g of phosphoric acid. Place the mixture in a muffle furnace and pyrolyze it at 800℃ for 3 hours under a nitrogen atmosphere. The pyrolysis heating rate is 5℃ / min. After pyrolysis, wash it with deionized water until neutral and dry it at 80℃ to constant weight to obtain the activated product.

[0048] S2. Take 10g of the activated material, add 100mL of 2% potassium permanganate solution, and reflux in an 80℃ water bath for 3h. After reflux, dry at 80℃ for 5h, then add 60mL of chloroform and sonicate at 60℃ for 2h. Then add 5g of trichlorophosphine and 80mL of 3-mercaptopropyltrimethoxysilane, place in a reaction vessel, and hydrothermally react at 160℃ for 3h. After the reaction, wash with 0.5-5mol / L hydrochloric acid, then wash with deionized water until neutral, and dry at 80℃ to constant weight to obtain mesoporous carbon material.

[0049] Comparative Example 3

[0050] A method for preparing mesoporous carbon materials includes the following steps:

[0051] S1. Take 10g of treated rapeseed straw and add 20g of a mixture of phosphoric acid and potassium nitrate (the mass ratio of phosphoric acid to potassium nitrate is 1:0.5). Place the mixture in a muffle furnace and pyrolyze it at 800℃ for 3h under a nitrogen atmosphere. The pyrolysis heating rate is 5℃ / min. After pyrolysis, wash with deionized water until neutral and dry at 80℃ to constant weight to obtain the activated product.

[0052] S2. Take 10g of the activated material, add 100mL of 2% potassium permanganate solution, and reflux in an 80℃ water bath for 3h. After reflux, dry at 80℃ for 5h, then add 60mL of chloroform and sonicate at 60℃ for 2h. Then add 5g of trichlorophosphine and 80mL of 3-mercaptopropyltrimethoxysilane, place in a reaction vessel, and hydrothermally react at 160℃ for 3h. After the reaction, wash with 0.5-5mol / L hydrochloric acid, then wash with deionized water until neutral, and dry at 80℃ to constant weight to obtain mesoporous carbon material.

[0053] Comparative Example 4

[0054] A method for preparing mesoporous carbon materials includes the following steps:

[0055] S1. After soaking and washing rapeseed straw in water, dry it at 100-120℃ for 8-12 hours, crush it and pass it through a 100-mesh sieve. Take 10g of the treated rapeseed straw and add it to 80mL of deionized water. Place it in a reaction vessel and hydrothermally react at 260℃ for 4 hours. After the reaction, filter it and freeze it in a -18℃ refrigerator for 5 hours. Then take it out and thaw it at room temperature. Repeat this freeze-thaw cycle 4 times to obtain the precursor. Dry the precursor at 60℃ for 4 hours, grind it and pass it through a 50-mesh sieve. Then add 20g of a mixture of phosphoric acid and potassium nitrate (the mass ratio of phosphoric acid to potassium nitrate is 1:0.5). Place the mixture in a muffle furnace and pyrolyze it at 800℃ for 3 hours under a nitrogen atmosphere. The pyrolysis heating rate is 5℃ / min. After pyrolysis, wash it with deionized water until neutral and dry it at 80℃ to constant weight to obtain mesoporous carbon material.

[0056] Comparative Example 5

[0057] A method for preparing mesoporous carbon materials is basically the same as in Example 1, except that trichlorophosphorus is not added in S2.

[0058] Mesoporous carbon materials prepared in Examples 1-3 and Comparative Examples 1-5

[0059] Table 1. Pore structure properties and sulfur content of mesoporous carbon materials

[0060]

[0061]

[0062] As shown in Table 1, the BET pore structure properties of Examples 1-3 and Comparative Examples 1-5 were calculated using the BET method. The specific surface area of ​​the mesoporous carbon materials prepared in Examples 1-3 ranged from 838 to 912 m². 2 The pore volume and pore size are between 5.8-6.3 nm. Compared with the mesoporous carbon materials obtained without activating agents (e.g., Comparative Example 1), with phosphoric acid as the only activating agent (e.g., Comparative Example 2), and with direct activation by activating agents (e.g., Comparative Example 3), the pore structure and specific surface area of ​​the mesoporous carbon materials prepared in Examples 1-3 are significantly increased. Activation by activating agents after freeze-thaw cycles has a significant impact on the active sites of the mesoporous carbon materials. For example, the sulfur content of Comparative Examples 1-3 is significantly reduced, indicating that the introduction of P=S and -SH on the mesoporous carbon is reduced. The mesoporous carbon that was not etched, such as Comparative Example 4, also has a reduced pore structure and specific surface area compared to Example 1, indicating that potassium permanganate has an oxidizing and dissolving effect on the mesoporous carbon, increasing the pore size of the activated carbon and improving the active sites of the mesoporous carbon.

[0063] To determine the performance of the prepared composite material in adsorbing noble metals, noble metal ion adsorption experiments were conducted using the mesoporous carbon materials prepared in Example 1 and Comparative Examples 1-5.

[0064] The mesoporous carbon materials prepared in Examples 1-3 and Comparative Examples 1-5 were applied to study the adsorption behavior of platinum ions in water: a platinum ion solution with a concentration of 100 mg / L and pH 2-3 was prepared, and the above-mentioned mesoporous carbon materials were added as adsorbents at a feed ratio of 80 mg / 20 mL (i.e., 80 mg of the above-mentioned mesoporous carbon materials were added to every 20 mL of platinum ion solution). The solution was shaken at 20 °C and 250 rpm for 3 h. After solid-liquid separation, the supernatant was collected, and the concentration of residual palladium ions was detected by atomic absorption spectrometry (AAS) at 20 °C and pH 2-3. The results are shown in Table 2.

[0065] Table 2 Adsorption performance of mesoporous carbon materials for platinum ions

[0066]

[0067]

[0068] The mesoporous carbon materials prepared in Examples 1-3 and Comparative Examples 1-5 were used to study the adsorption behavior of precious metal gold ions in water: a gold ion solution with a concentration of 100 mg / L and pH 2-3 was prepared, and the above mesoporous carbon materials were added as adsorbents at a feed ratio of 80 mg / 20 mL (i.e., 80 mg of the above mesoporous carbon materials were added to every 20 mL of gold ion solution). The solution was shaken for 3 h at 20 °C and 250 rpm. After solid-liquid separation, the supernatant was collected, and the concentration of residual gold ions was detected by atomic absorption spectrometry (AAS) (at 20 °C and pH 2-3). The results are shown in Table 3.

[0069] Table 3 Adsorption performance of mesoporous carbon materials for gold ions

[0070]

[0071] As shown in Tables 2-3, the mesoporous carbon materials prepared in Examples 1-3 exhibit super-strong adsorption performance for platinum and gold ions, with adsorption rates exceeding 99% and 97%, respectively. However, in Comparative Example 1, the adsorption performance of the mesoporous carbon material without activation was significantly reduced. In Comparative Example 2, where the activator was only phosphoric acid, the adsorption performance was much improved compared to Comparative Example 1. This demonstrates that the activator plays a crucial role in the pore size of mesoporous carbon. Potassium nitrate enhances the oxidative pore-forming performance of phosphoric acid activator, thus strengthening the activating pore-forming effect. Simultaneously, K... + The secondary pore-forming effect promotes the expansion of activated carbon pore size, increasing the adsorption capacity of mesoporous carbon.

[0072] When activators are directly used, such as in Comparative Example 3, the adsorption performance of the mesoporous carbon material is reduced compared to Comparative Examples 1-2. This indicates that hydrothermal reaction and freeze-thaw cycle play a key role in the pyrolysis of the activator. Micropores are formed through hydrothermal reaction, and freeze-thaw cycle can cause water molecules to destroy the structure of straw cell walls. The volume of micropores changes during the freeze-thaw cycle, allowing the activator to enter the interior of the mesoporous carbon and expand the pores, thereby improving the uniformity of pore distribution and specific surface area, and enhancing the adsorption capacity of the mesoporous carbon.

[0073] Compared to Comparative Examples 4 and 5, Examples 1-3 increased the S and P content of the mesoporous carbon. Through the chemical reaction between P=S and -SH with the metal to be adsorbed, the metal was captured efficiently. It has the advantages of high adsorption capacity and good stability, and improves the adsorption capacity for gold ions, platinum ions, etc.

[0074] Figure 1 The figures represent the amount of platinum ions adsorbed by mesoporous carbon materials at different times in Examples 1 and 1-5 of this invention. Figure 1As shown, the mesoporous carbon material exhibits a high adsorption rate for platinum ions within 120 min. However, after 120 min, due to the decrease in the active sites and adsorption capacity of the mesoporous carbon material, the adsorption rate gradually becomes moderate, reaching its maximum adsorption capacity at 180 min. At 180 min, the platinum ion adsorption capacity of Example 1 reaches 1243.4 mg / g.

[0075] Figure 2 The adsorption amounts of gold ions by mesoporous carbon materials in Examples 1 and 1-5 of this invention at different times are shown. Figure 2 As shown, the mesoporous carbon material exhibits a high adsorption rate for gold ions within 150 min. However, after 150 min, due to the decrease in the active sites and adsorption capacity of the mesoporous carbon material, the adsorption rate gradually becomes moderate, reaching its maximum adsorption capacity at 180 min. At 180 min, the adsorption capacity of gold ions in Example 1 reaches 1233.5 mg / g.

[0076] In summary, this invention modifies the micropores through hydrothermal reaction, followed by freeze-thaw cycles and activator treatment. The freeze-thaw cycles and pyrolysis of the activator expand the micropores, introducing mesoporous channels and improving pore uniformity and specific surface area, thereby enhancing the adsorption capacity of the mesoporous carbon. Further etching with potassium permanganate solution oxidizes and dissolves the mesoporous channels, increasing the activated carbon pore size and enhancing its active sites. The introduction of P=S and -SH through trichlorophosphine and 3-mercaptopropyltrimethoxysilane allows for chemical reactions between P=S and -SH and the target metal, achieving highly efficient metal capture. This invention offers advantages such as high adsorption capacity and good stability, and improves the adsorption capacity for gold ions, platinum ions, and other similar metals.

[0077] It should be noted that when numerical ranges are mentioned in the claims of this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as those in the embodiments, preferred embodiments and their effects are described to avoid redundancy. However, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of this invention.

[0078] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the invention.

[0079] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing mesoporous carbon materials for precious metal recycling, characterized in that, Includes the following steps: S1. After processing, rapeseed straw is crushed and passed through a 100-mesh sieve. Water is added, and the mixture undergoes a hydrothermal reaction at 260℃. After the reaction, four freeze-thaw cycles are performed to obtain a precursor. The precursor is then ground, sieved, and an activator is added. The precursor is then pyrolyzed at 600-800℃ under a protective gas atmosphere. After washing until neutral, the product is dried to obtain the activated product. The mass ratio of the precursor to the activator is 1:2-4. The activator is a mixture of phosphoric acid and potassium nitrate, and the mass ratio of phosphoric acid to potassium nitrate is 1:0.3-0.

8. The freeze-thaw temperature is -18℃. The mass ratio of rapeseed straw to water is 3:6-8. The hydrothermal reaction time is 4-6 hours. S2. After etching the activated material obtained in S1, filter and wash until neutral, then add it to chloroform and sonicate. Then add 3-mercaptopropyltrimethoxysilane and trichlorophosphorus, and perform a hydrothermal reaction at 160-180℃. After the reaction is completed, wash with water until the filtrate is neutral, and then dry to obtain mesoporous carbon material. The etching is performed by placing the activated material in a 1-3% potassium permanganate solution and refluxing at 60-80℃ for 3-4 hours. The mass-volume ratio of the activated material to the potassium permanganate solution is 1g:10-20mL. The mass-volume ratio of the activated material to chloroform is 1g:5-8mL. The mass-volume ratio of the activated material, trichlorophosphorus, and 3-mercaptopropyltrimethoxysilane is 1g:0.5-1g:8-10mL. In S2, the hydrothermal reaction time is 3-5 hours, and the washing method is to first wash with 0.5-5 mol / L hydrochloric acid and then wash with deionized water.

2. The method for preparing mesoporous carbon materials for precious metal recycling according to claim 1, characterized in that, In S1, the rapeseed straw is treated by soaking and washing it in water, and then drying it at 100-120℃ for 8-12 hours.

3. The method for preparing mesoporous carbon materials for precious metal recycling according to claim 1, characterized in that, In S1, the pyrolysis time is 3-5 hours, and the protective gas is nitrogen.

4. A mesoporous carbon material prepared by the preparation method according to any one of claims 1-3.

5. The application of the mesoporous carbon material according to claim 4 in the recovery of precious metals from wastewater.

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