Activated carbon modification method and application thereof

Abstract

The invention discloses an activated carbon modification method which comprises the following steps: activating activated carbon through plasma, and then performing graft modification by using 3-amino-5-sulfydryl-1, 2, 4-triazole (AMT) to obtain the activated carbon. The method aims at solving the problems that in an existing modification process, the grafting rate is low, the adsorption performance is poor, and pores are prone to being damaged, and the method is suitable for continuous treatment of the m-phenylenediamine (MPD) oxidation color development aqueous solution. According to the process, the AMT grafting rate of the modified activated carbon is 1.0-1.2 mmol / g, the specific surface area is 950-1100 m < 2 > / g, the pore volume ratio of activated mesopores is increased to 43%, the decolorization rate is greatly increased, the saturated adsorption period of the activated carbon is prolonged, and the solution can be kept basically colorless within 120 hours by using 0.5 wt% of activated carbon under a static adsorption condition.

Description

Technical Field

[0001] This invention belongs to the field of activated carbon modification and separation purification technology, specifically relating to a plasma grafting modification method for 3-amino-5-mercapto-1,2,4-triazole (AMT) and its use as a decolorizing agent, especially in the decolorization of m-phenylenediamine. Background Technology

[0002] As is well known, m-phenylenediamine produces a small amount of byproducts during storage or use. These byproducts are mainly formed by the oxidation of m-phenylenediamine upon contact with air. The oxidation products are primarily quinone imines or azo compounds. These oxidation products further polymerize to form large colored molecules (such as phenazine polymers). These byproducts themselves are colored, and over time, the color of the accumulated byproduct solution changes continuously, gradually changing from an initial pale yellow to yellowish-brown or reddish-brown. The accumulation of these byproducts affects the overall color of the raw material, impacting its commercial value or the quality of downstream products. Currently, m-phenylenediamine is a major raw material for reverse osmosis membranes both domestically and internationally. During use, the color of the raw material solution gradually deepens with increasing time, and the higher the concentration, the faster the color change. From an industrial perspective, nitrogen sealing is used to slow down the oxidation rate, but the effect is not significant. Quality control can only be achieved through periodic replacement of the raw material.

[0003] Activated carbon is a porous adsorbent material with a highly developed pore structure and a large specific surface area. It is mainly composed of carbon (87%–97%), and its raw materials include carbon-containing materials such as wood, coconut shells, and coal, produced through high-temperature carbonization and activation processes. Its adsorption performance stems from the synergistic effect of physical adsorption (van der Waals forces) and chemical adsorption (surface functional group interactions). Its microporous (<2nm) and mesoporous (2–50nm) structures can efficiently capture organic matter, heavy metals, and gas molecules. The pore structure of activated carbon depends on the raw materials and activation process. Wood / coconut shell activated carbon has a high proportion of micropores (70%–90%), while coal-based activated carbon has a slightly higher proportion of mesopores and macropores (micropores account for 50%–80%). The specific surface area and pore volume of most activated carbons are mainly contributed by micropores; therefore, the adsorption performance of activated carbon is primarily dominated by micropores, but mesopores and macropores play a supporting role in mass transfer and specific adsorption processes.

[0004] Since activated carbon was first used in gas masks in the early 20th century, its applications have expanded to water treatment (COD and pigment removal), air purification (VOCs adsorption), medicine (antidote), food industry (decolorization and deodorization), and energy storage (supercapacitors). In recent years, through surface modification (such as loading nanomaterials) and pore size control, its selectivity and regeneration capacity have been significantly improved, making it a key material for environmental remediation and chemical separation. The global market size is projected to exceed US$10 billion by 2025. Its green adsorption properties align with the needs of sustainable development, and research focuses on low-cost preparation and recycling technologies.

[0005] Currently, the main methods for preparing mesoporous activated carbon include using silica, silicates, polymers, etc., as templates, or using carbon dioxide or water vapor as pore-directing agents to prepare mesoporous carbon under high-temperature conditions. For example, Chinese patent document CN 102125865 A describes a method for preparing mesoporous carbon using mesoporous silica SBA-15 as a template and sucrose as a carbon source at 600-900℃; Chinese patent document CN104140090A discloses a method for preparing a hydrophilic ordered mesoporous carbon material, which uses SBA-15 mesoporous molecular sieve as a mother template and generates ordered mesoporous carbon material TSC-1 by high-temperature carbonization of its internal P123 copolymer template agent. In addition, Chinese patent document CN 102616778 A proposes a method for preparing mesoporous activated carbon by microwave heating and regenerating waste coal-based activated carbon. This method includes continuous heating and holding, followed by activation by introducing water vapor or carbon dioxide, ultimately obtaining mesoporous activated carbon. However, these methods have some significant drawbacks, such as large amounts of template agent, high cost, low yield, complex process, high preparation temperature, and the need to consume large amounts of highly corrosive acid to remove the template.

[0006] Patent CN 102674343A discloses a method for producing activated carbon. This method involves adding polyphosphates, activated silica, and other binders to raw materials such as coal powder, followed by kneading, extrusion, drying, and activation to obtain the finished product. This method uses a binder composed of several compounds instead of coal tar, avoiding the serious pollution caused by using coal tar as a binder and saving a large amount of expensive coal tar, thus reducing production costs. The resulting activated carbon has high strength, low dust content, and strong adsorption capacity, making it suitable for water treatment, deodorization, decolorization, catalyst support, removal of CO2 and N2 gases in pressure swing adsorption, gas phase adsorption, solvent recovery, and carbon catalysts. Although this patent avoids the pollution caused by using coal tar as a binder, its product yield is low, and the resulting activated carbon is not mesoporous activated carbon.

[0007] Traditional impregnation methods (such as CN103752269A) introduce amine compounds (such as ethylenediamine) through physical adsorption. While this can enhance surface polarity, functional groups are easily detached (adsorption capacity decreases by more than 40% after 5 cycles) and micropores are severely clogged (specific surface area decreases by up to 30%). Metal-organic framework (MOF) composite technology (such as CN113908809B) enhances adsorption specificity through in-situ synthesis of MOFs, but MOF precursors are expensive, and solvothermal synthesis requires high temperature and pressure (120-180℃, 3-5MPa), resulting in high energy consumption and stringent equipment requirements. Direct plasma modification (such as CN104549153A) can activate the surface to generate oxygen-containing functional groups (such as -COOH), but it lacks targeted adsorption sites, with an adsorption capacity of only 80-100 mg / g for m-phenylenediamine (MPD) oxides, and the oxygen-containing functional groups are easily decomposed in acidic or alkaline environments. In addition, CN116253448A uses activated carbon and copper salt coordination polymerization to treat MPD wastewater. Although it can remove some pollutants, the residual copper ions (>0.5mg / L) require additional Fenton oxidation treatment, which makes the process more complicated and increases the cost by more than 20%.

[0008] Therefore, it is necessary to develop a new environmentally friendly, efficient and low-cost method for preparing activated carbon to solve the problems of serious pollution, low product yield and non-mesoporous activated carbon in the existing technology. At the same time, it is also necessary to optimize the m-phenylenediamine decolorization technology to overcome the shortcomings of the existing methods, such as unstable modification, by-product generation, low yield, high cost and difficulty in industrialization, so as to meet the needs of a wider range of industrial applications. Summary of the Invention

[0009] The purpose of this invention is to provide a method for modifying activated carbon by grafting activated carbon with 3-amino-5-mercapto-1,2,4-triazole (AMT) at low temperature plasma. Compared with traditional modification techniques, this invention presents multiple core advantages in terms of adsorption performance, structural protection, environmental friendliness, and adaptability: 1) Significantly improved grafting stability and adsorption efficiency; 2) Protection of pore structure and optimization of mass transfer efficiency; 3) Synergistic effect of multiple functional groups and enhanced selectivity; 4) Balancing environmental protection and economic efficiency.

[0010] Another objective of this invention is to provide the use of the modified activated carbon as a decolorizing agent, particularly addressing the color change problem that occurs during the industrial application of m-phenylenediamine. When the modified activated carbon is used for the decolorization of m-phenylenediamine, the amino (-NH2), mercapto (-SH), and triazole rings of AMT are completely preserved through plasma grafting. These rings can form hydrogen bonds with the -C=O group of MPD oxide and coordinate bonds with the -N=N- group, respectively, significantly improving the decolorization efficiency. Simultaneously, the mesopores (5-20 nm) formed during the AMT grafting process, together with the micropores, constitute a "gradient pore structure," reducing the diffusion resistance of MPD oxide and improving the mass transfer efficiency compared to a single microporous structure. This solves the pore blockage problem caused by traditional polymer coating and improves the physical adsorption efficiency.

[0011] The process of this invention can effectively decolorize amines through synergistic adsorption of "porous physical interception + thiol coordination + amino hydrogen bonding". The solvent can be recovered and the plasma treatment produces no waste. It has high efficiency, long-term stability and industrial value, meets the requirements of green process, and provides an innovative solution for the decolorization treatment of easily oxidized amine compounds.

[0012] To achieve the above-mentioned objectives, the technical solution of the present invention is as follows:

[0013] A method for modifying activated carbon includes the following steps: activating activated carbon with plasma and then grafting it with 3-amino-5-mercapto-1,2,4-triazole (AMT).

[0014] As a preferred embodiment, the activated carbon modification method further includes a pretreatment step:

[0015] (1) After drying or air-drying the activated carbon raw material, crush it and pass it through a 12-40 mesh sieve to obtain activated carbon raw material granules.

[0016] (2) Place the activated carbon raw material particles in an acid solution and stir to pickle and dissolve the inorganic ash. After removing them, wash them until neutral and then vacuum dry them to remove residual moisture.

[0017] As a preferred embodiment, the plasma activation step includes:

[0018] (3) Spread activated carbon evenly on the quartz sample stage of the plasma reactor, close the reactor and evacuate, and introduce inert gas to maintain stable pressure.

[0019] (4) Turn on the radio frequency power supply, set the power to activate the activated carbon, turn off the power supply after the treatment is completed, continue to pass inert gas, and cool naturally to room temperature to obtain activated activated carbon, which is denoted as AC-·.

[0020] As a preferred embodiment, the grafting modification involves adding AC-· to an AMT solution and stirring to obtain modified activated carbon;

[0021] (5) Prepare the AMT grafting solution and stir magnetically until completely dissolved;

[0022] (6) Quickly transfer the activated carbon AC-· to the grafting solution, seal the container, and stir the reaction magnetically at room temperature.

[0023] As a preferred embodiment, it also includes post-processing and purification steps: washing and drying, preferably,

[0024] (7) Separate the modified activated carbon by vacuum filtration, wash with anhydrous ethanol and deionized water, and filter until the filtrate is clear;

[0025] (8) The washed activated carbon was vacuum dried to obtain AMT-modified activated carbon, denoted as AC-AMT.

[0026] In this invention, the activated carbon raw material in step (1) is one or more of coal-based activated carbon, coconut shell activated carbon, wood-based activated carbon, etc., preferably, the activated carbon is coal-based activated carbon.

[0027] In this invention, in step (1), after drying or air drying, the moisture content of the activated carbon is 3 to 10 wt%. Preferably, the moisture content of the activated carbon should be 3 to 6 wt%, including but not limited to 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, 8 wt%, 8.5 wt%, 9 wt%, 9.5 wt%, or any combination thereof.

[0028] In this invention, the acid solution mentioned in step (2) is one or more of phosphoric acid, hydrochloric acid, nitric acid, and oxalic acid, preferably hydrochloric acid.

[0029] In this invention, the solid-liquid ratio in step (2) is 1:4 to 8, preferably 1:5 to 7, including but not limited to 1:4.5, 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8 or any combination thereof.

[0030] In this invention, the concentration of the pickling solution in step (2) is 0.05-0.2 mol / L, preferably 0.1-0.15 mol / L.

[0031] In this invention, the pickling time in step (2) is 10 to 60 minutes, preferably 20 to 50 minutes; including but not limited to 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or any combination thereof.

[0032] In this invention, the water content of the activated carbon after vacuum drying in step (2) is 3 to 8 wt%, preferably 4 to 7 wt%, including but not limited to 3.5 wt%, 4.0 wt%, 4.5 wt%, 5.0 wt%, 5.5 wt%, 6 wt%, 6.5 wt%, 7 wt%, 7.5 wt%, or any combination thereof.

[0033] In this invention, the vacuum pressure of the container in step (3) is 5 to 30 Pa. Preferably, the pressure inside the container should be 15 to 25 Pa and remain stable, including but not limited to 8 Pa, 10 Pa, 12 Pa, 15 Pa, 17 Pa, 20 Pa, 22 Pa, 25 Pa or any combination thereof.

[0034] In this invention, the inert gas mentioned in step (3) is argon, and the argon flow rate is 10 to 30 sccm. Preferably, the argon flow rate should be 10 to 20 sccm, including but not limited to 12 sccm, 15 sccm, 17 sccm, 20 sccm, 22 sccm, 25 sccm, 27 sccm or any combination thereof.

[0035] In this invention, the power of the radio frequency power supply mentioned in step (4) is 80 to 200W. Preferably, the power of the radio frequency power supply should be 100 to 150W, including but not limited to 85W, 90W, 95W, 100W, 105W, 110W, 115W, 120W, 125W, 130W, 135W, 140W, 145W, 155W, 160W, 170W, 180W, 190W, 195W, or any combination thereof.

[0036] In this invention, the activation time in step (4) is 5 to 30 minutes, preferably 8 to 20 minutes, including but not limited to 6 minutes, 7 minutes, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 21 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, 29 minutes or any combination thereof.

[0037] In this invention, the concentration of the AMT grafting solution in step (5) is 5 to 20 mg / mL. Preferably, the concentration of the AMT grafting solution should be 10 to 15 mg / mL, including but not limited to 6 mg / mL, 8 mg / mL, 10 mg / mL, 12 mg / mL, 14 mg / mL, 16 mg / mL, 18 mg / mL or any combination thereof.

[0038] In this invention, the solvent of the AMT grafting solution in step (5) is ethanol, methanol, or N,N'-dimethylformamide, preferably ethanol.

[0039] In this invention, the reaction time of AMT and activated carbon in step (6) is 1 to 5 hours, preferably 2 to 4 hours, including but not limited to 1.5 hours, 1.8 hours, 2.5 hours, 3 hours, 3.5 hours, 3.8 hours, 4.5 hours or any combination thereof.

[0040] In this invention, the volume ratio of ethanol to deionized water in step (7) is 1:2 to 4, preferably 1:2.5 to 3.5.

[0041] In this invention, the vacuum drying temperature in step (8) is 40 to 80°C. Preferably, the vacuum drying temperature should be 50 to 70°C, including but not limited to 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or any combination thereof.

[0042] In this invention, the vacuum drying time in step (6) is 4 to 10 hours, preferably, the reaction time should be 6 to 9 hours, including but not limited to 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours or any combination thereof.

[0043] As one specific implementation method, an activated carbon modification method includes the following steps:

[0044] Preprocessing:

[0045] (1) After drying or air-drying the activated carbon raw material, crush it and pass it through a 12-40 mesh sieve to obtain activated carbon raw material granules.

[0046] (2) Place activated carbon in a 0.1 mol / L hydrochloric acid solution at a solid-liquid ratio of 1:5 (g / mL) and stir for 30 minutes to dissolve the inorganic ash. After removing the solution, wash it with deionized water until the pH of the filtrate is 6-7. Then, vacuum dry it at 60℃ for 12 hours to remove residual moisture.

[0047] Plasma activation:

[0048] (3) Spread the pretreated activated carbon evenly on the quartz sample stage of the plasma reactor, close the reactor, evacuate to a pressure of 15 Pa, introduce argon gas (flow rate 20 sccm), and maintain the pressure at 15-20 Pa.

[0049] (4) Turn on the radio frequency power supply, set the power to 120W, and the processing time to 8 minutes. After the processing is completed, turn off the power supply, continue to pass argon gas for 5 minutes, and let it cool naturally to room temperature to obtain activated carbon (denoted as AC-·).

[0050] AMT covalent grafting:

[0051] (5) Prepare an AMT grafting solution with a concentration of 10 mg / mL and stir magnetically until completely dissolved;

[0052] (6) Quickly transfer the activated AC-· to the grafting solution, seal the container, and magnetically stir at room temperature (25℃) for 3 hours (200 rpm).

[0053] Post-processing and purification:

[0054] (7) Separate the modified activated carbon by vacuum filtration, wash it three times with 30 mL of anhydrous ethanol; wash it once with deionized water (to remove residual ethanol), and filter until the filtrate is clear.

[0055] (8) The washed activated carbon was transferred to a vacuum drying oven and dried at 50°C for 6 hours to obtain AMT-modified activated carbon (referred to as AC-AMT).

[0056] The modified activated carbon of this invention is used for decolorizing aqueous solutions of m-phenylenediamine, but is not limited to m-phenylenediamine, including aniline or homologues of phenylenediamine. AMT-grafted modified activated carbon is used for the treatment of raw materials or wastewater containing chromogenic substances oxidized by m-phenylenediamine (MPD), and can efficiently adsorb and remove chromogenic pollutants such as quinones, azo dyes, and phenazines. Furthermore, due to the multiple adsorption sites formed by amino (-NH2), mercapto (-SH), and triazole rings on its surface, it can also be used for decolorizing raw materials or wastewater containing other polar-conjugated organic pollutants (such as azo dyes and quinone dyes), as well as for Cu-containing... 2 +、Hg 2 For the treatment of wastewater containing heavy metal ions, the selective adsorption capacity of heavy metal ions is 3-4 times higher than that of unmodified activated carbon, and it has strong resistance to interference from coexisting ions. In addition, it has application potential in the removal of trace organic pollutants (such as trace phenols and pesticide residues) in drinking water. It combines high-efficiency adsorption performance with environmental sustainability and is suitable for water treatment scenarios of different scales.

[0057] The beneficial effects of this invention are as follows:

[0058] The plasma gas activation modification scheme uses inert gas as the gas source and assists in the covalent grafting of 3-amino-5-mercapto-1,2,4-triazole (AMT) onto activated carbon. Compared with traditional modification technologies, it exhibits multiple core advantages in adsorption performance, structural protection, environmental friendliness, and compatibility: Firstly, grafting stability and adsorption efficiency are significantly improved. Traditional impregnation methods rely on physical adsorption, resulting in a functional group detachment rate exceeding 40%. In contrast, this scheme generates carbon free radicals by bombarding the activated carbon surface with inert gas plasma, forming CN covalent bonds with the amino groups of AMT with a bond energy of up to 305 kJ / mol. Under this process, the AMT grafting rate of modified activated carbon is 1.0-1.2 mmol / g, far exceeding the combined performance of direct plasma oxidation modification and MOF composite modification. Secondly, pore structure protection and mass transfer efficiency are optimized. Traditional modification methods such as nitric acid oxidation and high-temperature calcination easily erode the micropores of activated carbon (micropore loss rate exceeds 10%). This solution, however, employs low-temperature treatment with a certain radio frequency power, combined with inert argon gas to avoid oxidation side reactions, maintaining the specific surface area of ​​the modified activated carbon at 950-1100 m². 2 / g, with a mesoporous pore volume ratio exceeding 43% through plasma gas activation, the decolorization rate is significantly improved, extending the saturated adsorption cycle of activated carbon. Under static adsorption conditions, using 0.5wt% activated carbon can keep the solution colorless for 120 hours. Simultaneously, the mesopores (5-20nm) formed during AMT grafting and the micropores constitute a "gradient pore" structure, reducing the diffusion resistance of MPD oxide by 40% and increasing mass transfer efficiency by 2 times compared to a single microporous structure. This solves the pore blockage problem caused by traditional polymer coatings, improving physical adsorption efficiency. Thirdly, multi-functional group synergy and enhanced selectivity. The amino (-NH2), mercapto (-SH), and triazole rings of AMT are completely preserved through plasma grafting, forming hydrogen bonds with -C=O of MPD oxide, coordination bonds with -N=N-, and π-π stacking with conjugated benzene rings, respectively. This triple effect synergistically improves adsorption selectivity by 60% compared to single amino modification, avoiding the poor adaptability of traditional modifications to the treated solution. Fourthly, it balances environmental protection and economy. Plasma treatment produces no waste, meets green process requirements, and eliminates the need for high-temperature, high-pressure equipment, resulting in lower energy consumption compared to solvothermal synthesis. This simple and easily scaled-up process can be extended to treat various easily oxidized amine compounds. Through innovative designs involving adsorption-antioxidant synergy, physicochemical synergy, and structure-function synergy, it provides an efficient, long-cycle, and low-cost solution for the oxidative color development of m-phenylenediamine, demonstrating significant industrial application value and social benefits. Attached Figure Description

[0059] Figure 1 This is a pore size distribution diagram of the activated carbon prepared in Example 1.

[0060] Figure 2 The activated carbon adsorption-desorption isotherm obtained in Example 1

[0061] Figure 3 This is the logarithmic distribution curve of pore volume and pore size of the activated carbon prepared by the BJH method in Example 1.

[0062] Figure 4 This is the infrared spectrum of the activated carbon prepared in Example 1. Detailed Implementation

[0063] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.

[0064] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0065] Main raw material sources

[0066]

[0067]

[0068] Main testing methods

[0069]

[0070] Grafting rate calculation method:

[0071]

[0072] Where C1 and C0 are the elemental contents of the modified and blank samples, respectively, N is the number of atoms of the element in the structural unit, and M is the molecular mass.

[0073] Example 1

[0074] 100g of naturally dried coal-based activated carbon granules were crushed in a mortar, passed through a 12-40 mesh sieve, and then placed in 500mL of 0.1mol / L hydrochloric acid aqueous solution and stirred for 30 minutes for pretreatment. After washing with deionized water until neutral, the carbon was filtered and vacuum dried at 60℃ for 12 hours. The pretreated activated carbon was placed in a plasma gas reactor, evacuated to a pressure of 15Pa, and argon gas was introduced at a flow rate of 20sccm. The radio frequency power supply was turned on and set to 120W for 8 minutes. After treatment, the power supply was turned off and argon gas was continued to be introduced for 5 minutes, followed by natural cooling. A 10mg / mL AMT ethanol solution was prepared, and the activated carbon was transferred to the grafting solution. The container was sealed and stirred at room temperature for 3 hours. The carbon was washed three times with 30mL of anhydrous ethanol and then washed with 270mL of deionized water until no ethanol residue was found. The carbon was transferred to a vacuum drying oven and dried at 50℃ for 6 hours until constant weight was obtained to obtain AMT modified activated carbon 1 (AC-AMT-1).

[0075] 100 ml of a 5% m-phenylenediamine aqueous solution was prepared in a transparent glass bottle, and 0.5 g of the prepared modified activated carbon 1 was added. A static adsorption experiment was conducted to test its purification effect. The main focus was on the adsorption effect of the modified activated carbon on m-phenylenediamine oxides. The experimental temperature was 20–25 °C. The adsorption effect of the activated carbon on m-phenylenediamine oxides was determined by visual observation and colorimetric testing. Specific experimental data are shown in Table 1.

[0076] As shown in the figure Figure 1 This is a pore size distribution diagram of the activated carbon prepared in Example 1. The area of ​​mesopores in the 2-10nm range exceeds 20%, indicating a large saturated adsorption capacity for m-phenylenediamine oxide. Figure 2 and Figure 3 These are the adsorption-desorption isotherms of the activated carbon prepared in Example 1, and the logarithmic distribution curves of pore volume and pore size obtained by the BJH method. Figure 2 The non-overlapping of adsorption and desorption curves (hysteresis loop) is direct evidence of the existence of mesopores. Figure 3 The obvious peaks at 2nm and 4nm indicate that the pore size distribution of this activated carbon is mainly micropores and mesopores, combining the high adsorption capacity of micropores with the mass transfer advantages of mesopores, and has a strong adsorption effect on m-phenylenediamine oxide. Figure 4 The image shows the infrared spectrum of the activated carbon prepared in Example 1. The presence of amino, thiol, and heterocyclic skeletons was confirmed by the characteristic peaks in each region.

[0077] Example 2

[0078] 100g of naturally dried coal-based activated carbon granules were crushed in a mortar, passed through a 12-40 mesh sieve, and then placed in 500mL of 0.1mol / L nitric acid aqueous solution and stirred for 30 minutes for pretreatment. After washing with deionized water until neutral, the carbon was filtered and vacuum dried at 60℃ for 12 hours. The pretreated activated carbon was placed in a plasma gas reactor, evacuated to a pressure of 15Pa, and argon gas was introduced at a flow rate of 20sccm. The radio frequency power supply was turned on and set to 80W for 8 minutes. After treatment, the power supply was turned off and argon gas was continued to be introduced for 5 minutes, followed by natural cooling. A 5mg / mL AMT ethanol solution was prepared, and the activated carbon was transferred to the grafting solution. The container was sealed and stirred at room temperature for 3 hours. The carbon was washed three times with 30mL of anhydrous ethanol and then washed with 270mL of deionized water until no ethanol residue was found. The carbon was transferred to a vacuum drying oven and dried at 50℃ for 6 hours until constant weight was obtained to obtain AMT modified activated carbon 2 (AC-AMT-2).

[0079] 100 ml of a 5% m-phenylenediamine aqueous solution was prepared in a transparent glass bottle, and 0.5 g of the prepared activated carbon 2 was added. A static adsorption experiment was conducted to test its purification effect. The main focus was on the adsorption effect of the modified activated carbon on m-phenylenediamine oxides. The experimental temperature was 20–25 °C. The adsorption effect of the activated carbon on m-phenylenediamine oxides was determined by visual observation and colorimetric testing. Specific experimental data are shown in Table 1.

[0080] Example 3

[0081] 100g of naturally dried coconut shell activated carbon granules were crushed in a mortar, passed through a 12-40 mesh sieve, and then placed in 500mL of 0.15mol / L phosphoric acid aqueous solution and stirred for 30 minutes for pretreatment. After washing with deionized water until neutral, the carbon was filtered and vacuum dried at 60℃ for 12 hours. The pretreated activated carbon was placed in a plasma gas reactor, evacuated to a pressure of 15Pa, and argon gas was introduced at a flow rate of 30sccm. The radio frequency power supply was turned on and set to 200W for 8 minutes. After treatment, the power supply was turned off and argon gas was continued to be introduced for 5 minutes, followed by natural cooling. A 20mg / mL AMT ethanol solution was prepared, and the activated carbon was transferred to the grafting solution. The container was sealed and stirred at room temperature for 4 hours. The carbon was washed three times with 30mL of anhydrous ethanol and then washed with 270mL of deionized water until no ethanol residue was found. The carbon was transferred to a vacuum drying oven and dried at 50℃ for 6 hours until constant weight was obtained to obtain AMT modified activated carbon 3 (AC-AMT-3).

[0082] 100 ml of a 5% m-phenylenediamine aqueous solution was prepared in a transparent glass bottle, and 0.5 g of the prepared activated carbon 3 was added. A static adsorption experiment was conducted to test its purification effect. The main focus was on the adsorption effect of the modified activated carbon on m-phenylenediamine oxides. The experimental temperature was 20–25 °C. The adsorption effect of activated carbon on m-phenylenediamine oxides was determined by visual observation and colorimetric testing. Specific experimental data are shown in Table 1.

[0083] Comparative Example 1

[0084] Compared with Example 1, the only difference is the grafting solution. The grafting solution was replaced with thiourea, and after the reaction was completed, thiourea-modified activated carbon 4 (AC-S-4) was obtained.

[0085] A 100ml solution of 5% m-phenylenediamine was prepared in a transparent glass bottle, and 0.5g of the prepared activated carbon 4 was added. A static adsorption experiment was conducted to test its purification effect. The main focus was on the adsorption effect of the modified activated carbon on m-phenylenediamine oxides. The experimental temperature was 20–25℃. The adsorption effect of activated carbon on m-phenylenediamine oxides was determined by visual observation and colorimetric testing. Specific experimental data are shown in Table 1.

[0086] Comparative Example 2

[0087] Compared with Example 1, the only difference is that there is no plasma activation step, and AMT modified activated carbon 5 (AC-AMT-5) is obtained after the reaction.

[0088] 100 ml of a 5% m-phenylenediamine aqueous solution was prepared in a transparent glass bottle, and 0.5 g of the prepared activated carbon 5 was added. A static adsorption experiment was conducted to test its purification effect. The main focus was on the adsorption effect of the modified activated carbon on m-phenylenediamine oxides. The experimental temperature was 20–25 °C. The adsorption effect of the activated carbon on m-phenylenediamine oxides was determined by visual observation and colorimetric testing. Specific experimental data are shown in Table 1.

[0089] Table 1

[0090]

Claims

1. A method for modifying activated carbon, characterized in that: The process includes the following steps: activated carbon is activated by plasma and then grafted with 3-amino-5-mercapto-1,2,4-triazole (AMT) to obtain the product.

2. The method according to claim 1, characterized in that: It also includes a preprocessing step: (1) After drying or air-drying the activated carbon raw material, crush it and pass it through a 12-40 mesh sieve to obtain activated carbon raw material granules. (2) Place the activated carbon raw material particles in an acid solution and stir to acid wash, dissolve the inorganic ash, take them out and wash until neutral, and vacuum dry to remove residual moisture.

3. The method according to claim 1 or 2, characterized in that: The plasma activation step includes: (3) Spread activated carbon evenly on the quartz sample stage of the plasma reactor, close the reactor and evacuate, and introduce inert gas to maintain stable pressure. (4) Turn on the radio frequency power supply, set the power to activate the activated carbon, turn off the power supply after the treatment is completed, continue to pass inert gas, and cool naturally to room temperature to obtain activated activated carbon, which is denoted as AC-·.

4. The method according to any one of claims 1-3, characterized in that: The grafting modification involves adding AC-· to an AMT solution and stirring to obtain modified activated carbon; including: (5) Prepare AMT grafting solution and stir magnetically until completely dissolved; (6) Quickly transfer the activated carbon AC-· to the grafting solution, seal the container, and stir the reaction magnetically at room temperature.

5. The method according to any one of claims 1-4, characterized in that: It also includes post-processing and purification steps: washing and drying, preferably... (7) Separate the modified activated carbon by vacuum filtration, wash with anhydrous ethanol and deionized water, and filter until the filtrate is clear; (8) The washed activated carbon was vacuum dried to obtain AMT-modified activated carbon, denoted as AC-AMT.

6. The method according to any one of claims 1-5, characterized in that, The activated carbon raw material mentioned in step (1) is one or more of coal-based activated carbon, coconut shell activated carbon, and wood-based activated carbon. Preferably, the activated carbon is coal-based activated carbon. And / or, in step (1), after drying or air drying, the moisture content of the activated carbon is 3 to 10 wt%, preferably 3 to 6 wt%.

7. The method according to any one of claims 2-6, characterized in that, The acid solution mentioned in step (2) is one or a mixture of phosphoric acid, hydrochloric acid, nitric acid, and oxalic acid, preferably hydrochloric acid; and / or, the concentration of the acid solution is 0.05-0.2 mol / L, preferably 0.1-0.15 mol / L; and / or, the pickling time is 10-60 minutes, preferably 20-50 minutes; and / or, the solid-liquid mass ratio is 1:4-8, preferably 1:5-7; and / or, the water content of the dried activated carbon is 3-8 wt%, preferably 4-7 wt%.

8. The method according to any one of claims 3-7, characterized in that, The container vacuum pressure in step (3) is 5-30 Pa, and / or the inert gas is argon with a flow rate of 10-30 sccm.

9. The method according to any one of claims 3-8, characterized in that, The power of the radio frequency power supply mentioned in step (4) is 80-200W, preferably 100-150W; and / or the activation time mentioned in step (4) is 5-30 minutes, preferably 8-20 minutes.

10. The method according to any one of claims 4-9, characterized in that, The concentration of the AMT grafting solution mentioned in step (5) is 5 to 20 mg / mL, preferably 10 to 15 mg / mL.

11. The method according to any one of claims 4-10, characterized in that, The reaction time between the AMT graft solution and activated carbon in step (6) is 1 to 5 hours, preferably 2 to 4 hours.

12. The method according to any one of claims 5-11, characterized in that, The volume ratio of ethanol to deionized water in step (7) is 1:2 to 4, preferably 1:2.5 to 3.5; and / or the vacuum drying temperature in step (8) is 40 to 80°C, preferably 50 to 70°C; and / or the vacuum drying time is 4 to 10 hours, preferably 6 to 9 hours.

13. Use of the modified activated carbon obtained by any one of claims 1-12 as a decolorizing agent, particularly for the decolorization of m-phenylenediamine.

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