Method for preparing high-efficiency adsorption activated carbon by composite activator chemical method

Abstract

The invention relates to the technical field of adsorption activated carbon, in particular to a method for preparing efficient adsorption activated carbon through a composite activator chemical method, and the method comprises the steps of directional modification pretreatment of raw materials, preparation of a composite activator, negative pressure auxiliary dipping treatment, segmented gradient activation and doping, graded composite post-treatment, drying forming and post-treatment. The raw materials are subjected to impurity removal, deliming, modification and drying; the activating agent is prepared by mixing multiple components to prepare liquid and adding nano particles for dispersion; performing negative-pressure impregnation on the raw materials and an activating agent and freezing and unfreezing; introducing gas, carrying out gradient heating, activating and synchronously doping; washing the activated material, oxidizing and modifying with an auxiliary agent; finally, drying, graded modification and granulation are conducted, and the efficient adsorption activated carbon is prepared. According to the method, the adsorption performance, mechanical strength and stability of the activated carbon are improved through collaborative optimization of the whole-process technology, impurity residues are few, and repeatability is good; and compared with the traditional method, the product has better comprehensive performance, and is suitable for high-requirement adsorption scenes.

Description

Technical Field

[0001] This invention relates to the field of activated carbon adsorption technology, specifically a method for preparing highly efficient activated carbon using a composite activator chemical process. Background Technology

[0002] Activated carbon, as an adsorbent material with high specific surface area and well-developed pore structure, is widely used in water treatment, gas purification, and energy storage. Its preparation methods are mainly divided into physical activation and chemical activation. Physical activation is simple and environmentally friendly, but it suffers from problems such as high activation temperature, long processing time, and limited improvement in adsorption performance, making it difficult to meet the demands of high-end applications for highly efficient adsorbent materials. Chemical activation, on the other hand, regulates the pore structure through the chemical reaction between the activator and the raw materials. It has advantages such as low activation temperature, high efficiency, and well-developed pores, making it the mainstream technology for preparing highly efficient adsorbent activated carbon.

[0003] Currently, chemical activation methods mostly employ single or binary composite activators, such as zinc chloride, phosphoric acid, and potassium hydroxide. Single activators suffer from defects such as uneven pore distribution and a low proportion of mesopores. While binary composite activators can optimize performance to some extent, they still have shortcomings in pore structure guidance and surface functional group control. Furthermore, existing processes do not provide sufficiently refined raw material pretreatment, leaving ash and impurities that can affect the adsorption performance of activated carbon. Uneven activator penetration during impregnation leads to inconsistent pore development. The activation stage often involves isothermal or simple gradient heating, making it difficult to achieve precise pore control and synergistic optimization of surface doping.

[0004] Furthermore, existing preparation methods suffer from limitations such as simplistic post-processing, easy collapse of pore structures, and poor cycle stability of activated carbon, hindering their application in high-end adsorption scenarios. With increasingly stringent environmental requirements and iterative advancements in adsorption technology, the market demands higher performance from activated carbon in terms of adsorption capacity, selectivity, and cycle life. There is an urgent need to develop a preparation method that can precisely control pore structure, optimize surface functional groups, and improve overall adsorption performance. Through multi-stage collaborative innovation, this method can address the pain points of existing technologies, such as low activation efficiency, uneven performance, and poor process stability, thereby meeting the diverse needs of different fields for highly efficient adsorption activated carbon. Summary of the Invention

[0005] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method for preparing highly efficient adsorption activated carbon using a composite activator chemical process.

[0006] (II) Technical Solution A method for preparing highly efficient adsorption activated carbon using a composite activator chemical method includes the following steps: S1. Raw material directional modification pretreatment: Crush coconut shell or walnut shell raw materials, add dilute hydrochloric acid with a mass concentration of 1.5-2.5 mol / L, mix at a solid-liquid mass-volume ratio of 1:8-12 (g / mL), stir and deash in a water bath, filter and wash with deionized water until neutral; then place the deashed raw material in an ultrasonic cleaner, use deionized water with added silane coupling agent as the medium, and perform ultrasonic modification, pausing for 5 minutes every 15 minutes of ultrasonication, filter and dry in an oven to constant weight to obtain pretreated raw materials; S2. Preparation of multi-effect ternary composite activator: Zinc chloride, dipotassium hydrogen phosphate, and citric acid are mixed in a mass ratio of 8-10:1-2:0.5-1. Deionized water is added to prepare a mixed solution with a molar concentration of 5-7 mol / L. Concentrated hydrochloric acid with a volume fraction of 1-2% is added, followed by nano-silica particles. The mixture is stirred until completely dissolved and ultrasonically dispersed to obtain the ternary composite activator. S3. Negative pressure assisted impregnation treatment: Add the pretreated raw materials and ternary composite activator to the negative pressure impregnation tank at a solid-liquid mass-volume ratio of 1:6-9 (g / mL), evacuate to -0.08~-0.09MPa and maintain for 10-15min, restore to normal pressure and then impregnate in a constant temperature shaking chamber. During this period, evacuate for 5min every 4h, filter to remove excess activator, and obtain a uniformly impregnated material. S4. Segmented gradient activation and in-situ doping: The impregnated material is placed in a nitrogen atmosphere tube furnace, heated to 350-400℃ for low-temperature activation for 0.5-1h, then heated to 500-550℃ for medium-temperature activation for 1-1.5h while ammonia gas is introduced for nitrogen doping, and then heated to 600-650℃ for high-temperature activation for 0.5-1h. After activation, the material is cooled to room temperature with the furnace to obtain nitrogen-doped activated material. S5. Post-treatment of graded composite: Add 0.2-0.3 mol / L dilute hydrochloric acid to the activated material, stir and wash in a water bath for 20-30 min, filter, wash with ethanol solution for 10-15 min, wash with deionized water until neutral, filter to obtain wet material, add polyethylene glycol 400 and stir to mix. S6. Microwave vacuum co-drying and molding: The wet material is placed in a microwave vacuum drying oven, vacuumed to -0.06~-0.07MPa, dried at 80-90℃ for 30-40min, cooled to room temperature and pulverized to obtain highly efficient adsorption activated carbon.

[0007] Preferably, in step S1, after the raw material is crushed, a magnetic separation process is first used to remove the metal impurities mixed in the raw material. The magnetic separation magnetic field strength is 800-1200 Gs. After magnetic separation, particle size screening is performed. After ultrasonic modification, a microwave pre-drying step is also included. The microwave pre-drying power is 100-150W and the time is 5-8 minutes. After pre-drying, the material is then dried in an oven.

[0008] Preferably, the nano-silica particles in S2 are surface modified with silane coupling agent KH570 before being added. During the modification treatment, the nano-silica particles are mixed with a KH570 ethanol solution with a mass concentration of 2-3wt% at a solid-liquid ratio of 1g:20mL, stirred at 50-60℃ for 1-1.5h, filtered and dried, and then added to the composite activator solution. The ultrasonic dispersion adopts a pulse ultrasonic mode with a pulse frequency of 2-3s / time.

[0009] Preferably, the negative pressure impregnation tank in S3 is equipped with a rotary stirring paddle. During the impregnation process, the stirring paddle rotates at a low speed of 30-50 r / min. After the negative pressure impregnation is completed, the impregnated material is subjected to a freezing pretreatment at a freezing temperature of -10~-15℃ for 1-2 hours. After freezing, the material is naturally thawed to room temperature before proceeding to the subsequent activation step.

[0010] Preferably, the S4 tubular furnace is equipped with a multi-layer material support frame, on which the impregnating material is evenly spread with a thickness of 5-8mm. During the medium-temperature activation stage, ammonia and nitrogen are introduced in a segmented mixing manner. The ammonia gas fraction is 5% in the first 30 minutes and gradually increases to 8% in the next 60 minutes. During the high-temperature activation stage, the ammonia gas is stopped and only nitrogen is introduced for protection.

[0011] Preferably, in S5, the dilute hydrochloric acid washing adopts a dynamic countercurrent washing method, in which the washing liquid and the activated material flow in opposite directions. After washing with ethanol solution, an ozone oxidation treatment step is added, with an ozone concentration of 50-80 mg / L and an oxidation treatment time of 10-15 min. After ozone oxidation, deionized water washing is performed. After mixing with polyethylene glycol 400, ultrasonic dispersion treatment is performed with an ultrasonic power of 100-150 W for 3-5 min.

[0012] Preferably, in the microwave vacuum drying process in S6, an inert gas is introduced for purging. The purging gas is argon, and the argon flow rate is 50-80 mL / min. After drying, the activated carbon is subjected to surface hydrophobic modification treatment. The modifier is a 1-2 wt% methyltrimethoxysilane ethanol solution. The modification temperature is 60-70℃, and the modification time is 30-40 min. After modification, the carbon is filtered and dried.

[0013] Preferably, the silane coupling agent in S1 is silane coupling agent KH560 or KH570. The pH value of the ultrasonic modification medium is adjusted according to the type of coupling agent. When using KH560, the pH value is adjusted to 4.0-5.0, and when using KH570, the pH value is adjusted to 5.0-6.0.

[0014] Preferably, the S4 segmented gradient activation and in-situ doping are as follows: the impregnating material is placed in an argon atmosphere tube furnace, heated to 350-400℃ for low-temperature activation for 0.5-1h, then heated to 500-550℃ for medium-temperature activation for 1-1.5h while ammonia gas is introduced for sulfur doping, and hydrogen sulfide gas with a volume fraction of 3-5% is introduced during sulfur doping; the temperature is then raised to 600-650℃ for high-temperature activation for 0.5-1h, and after activation, the material is cooled to room temperature with the furnace to obtain the sulfur-doped activated material.

[0015] Preferably, the high-efficiency adsorption activated carbon is subjected to granulation treatment. During granulation, 5-8% sodium carboxymethyl cellulose aqueous solution by mass of activated carbon is added as a binder. The sodium carboxymethyl cellulose aqueous solution has a mass concentration of 3-5 wt%. After granulation, it is dried at 80-90℃ for 2-3 hours to obtain activated carbon particles with a particle size of 2-5 mm.

[0016] (iii) Beneficial technical effects Compared with existing technologies, the beneficial effects of this invention are: 1. The composite activator system combines the synergistic effects of multiple components with a pore structure guiding agent. This not only efficiently etches pores but also precisely controls pore distribution, significantly increasing the proportion of mesopores. This solves the problem of uneven pore development caused by single activators, while also enhancing the stability of the activator, preventing hydrolysis failure, and improving process repeatability. The negative pressure-assisted impregnation process greatly optimizes the penetration uniformity of the activator, allowing it to penetrate deep into the raw material. This ensures a sufficient and consistent subsequent activation reaction, reducing localized over-activation or under-activation, and improving the uniformity of the activated carbon product.

[0017] 2. The synergistic process of segmented gradient activation and in-situ doping achieves a precise match between pore etching, pore expansion optimization, and surface functional group doping. While increasing the specific surface area, the doping modification enhances the adsorption selectivity and affinity of activated carbon for target pollutants, balancing adsorption capacity and adsorption rate. The staged post-treatment and microwave vacuum drying process thoroughly removes residual activators and impurities while effectively protecting the pore structure and preventing pore collapse during drying, thereby improving the mechanical strength and structural stability of the activated carbon. Attached Figure Description

[0018] Figure 1 This is a flowchart of a method for preparing highly efficient adsorption activated carbon using a composite activator chemical method, as disclosed in this invention. Figure 2 This is a bar graph comparing the surface area and the proportion of mesopores between the examples and the comparative examples; Figure 3 This is a line graph comparing the cyclic adsorption stability and acid and alkali corrosion resistance of the examples and comparative examples; Figure 4 This is a bar chart comparing the adsorption rate and impurity residue of the examples and comparative examples. Detailed Implementation

[0019] according to Figures 1 to 4 The specific embodiments of the present invention are as follows: This invention discloses a method for preparing highly efficient adsorption activated carbon using a composite activator chemical method. The invention will be further described in detail below with reference to specific embodiments and comparative examples. All raw materials used are industrial grade, and the equipment is standard laboratory equipment. Unless otherwise specified, all operations are carried out at room temperature and pressure.

[0020] Example 1 S1. Raw material directional modification pretreatment: Select coconut shell raw materials, sort out and remove moldy and insect-infested parts, put them into a universal pulverizer for crushing, and then pass them through a magnetic separator with a magnetic field strength of 1000Gs to remove impurities. Then, use 30-mesh and 60-mesh standard inspection sieves to collect uniform particles with a particle size of 30-60 mesh and a particle size deviation ≤5 mesh. Add 2.0mol / L dilute hydrochloric acid to the screened raw materials and mix them at a solid-liquid mass-volume ratio of 1g:10mL. Place the mixture in a 65℃ constant temperature water bath and stir at 90r / min for 2.5h to deash. After filtration, wash repeatedly with deionized water until the pH of the filtrate is 6.8-7.2 to obtain deashed raw material particles. The deashed granules were placed in an ultrasonic cleaner, and deionized water with 0.2 wt% silane coupling agent KH550 was added as the medium. The pH of the medium was adjusted to 6.8, and ultrasonic modification was carried out for 1.2 hours at 250W power and 45℃. During the ultrasonic process, a strict rule of pausing for 5 minutes every 15 minutes was followed, with a total pause time of 16 minutes to avoid overheating and carbonization of the raw material. After ultrasonication, the granules were filtered and dried in a 108℃ oven until constant weight. During the drying process, the granules were weighed every 30 minutes. The constant weight was defined as a difference of ≤0.1g between two weighings. The resulting pretreated coconut shell raw material with surface-grafted amino groups had a moisture content of ≤2% and a surface amino grafting amount of 0.4 mmol / g.

[0021] S2. Preparation of Multi-Effect Ternary Composite Activator: Zinc chloride, dipotassium hydrogen phosphate, and citric acid were mixed in a mass ratio of 9:1.5:0.8, and deionized water was added to prepare a mixed solution with a total molar concentration of 6 mol / L. Concentrated hydrochloric acid (1.5% by volume) was added to the solution to inhibit component hydrolysis, and the mixture was stirred at 220 r / min until the hydrochloric acid was completely dispersed. 0.08 wt% of nano-silica particles (15 nm in diameter) were taken from the mixed solution and pre-treated with silane coupling agent KH570 before addition—nano-silica was mixed with a 2.5 wt% KH570 ethanol solution at a solid-liquid ratio of 1 g:20 mL, stirred at 55℃ for 1.2 h, filtered, and dried at 105℃ to constant weight. The modified nano-silica particles were added to the composite solution and dispersed using pulsed ultrasonic mode at a pulse frequency of 2.5s / time and a power of 150W for 12 minutes until the particles were no longer agglomerated, thus obtaining a ternary composite activator. It was then placed in a sealed environment at 25℃ for standby and ensured to be used within 24 hours.

[0022] S3. Negative Pressure Assisted Impregnation Treatment: Pretreated coconut shell raw material and ternary composite activator were added to a negative pressure impregnation tank at a solid-liquid mass-to-volume ratio of 1g:7.5mL. A rotary stirrer was installed inside the tank. A vacuum was first drawn to -0.085MPa and maintained for 12 minutes to expel air from the internal pores of the raw material. After restoring normal pressure, the stirrer was started and rotated at a low speed of 40r / min. Simultaneously, the impregnation tank was placed in a 35℃ constant temperature shaking chamber, and impregnation was performed at a shaking rate of 180r / min for 20 hours. During this period, a vacuum was replenished every 4 hours, maintaining a vacuum of -0.085MPa, and the pressure was maintained for 3 minutes after each replenishment. After impregnation, the impregnated material was removed and placed in a vacuum filtration device. Filtering was performed at a pressure of -0.05MPa for 12 minutes to remove excess activator, resulting in a uniformly impregnated material. Subsequently, the impregnated material underwent a freezing pretreatment by freezing it in a -12℃ low-temperature freezer for 1.5 hours. After removal, it was allowed to thaw naturally to room temperature for later use.

[0023] S4. Segmented gradient activation and in-situ doping: The thawed impregnating material is evenly spread on the multi-layer material support frame of the tube furnace with a thickness of 6mm. After sealing the tube furnace, high-purity nitrogen gas with a purity of ≥99.99% is introduced. After dehydration and deoxygenation treatment, the dew point is ≤-40℃. The nitrogen flow rate is 200mL / min. The furnace is purged for 30min to remove the air inside. The tubular furnace heating program was initiated, first raising the temperature to 380°C at a rate of 4°C / min for 0.8 hours of low-temperature activation to promote the penetration of the activator into the raw material; then raising the temperature to 520°C at a rate of 9°C / min for 1.2 hours of medium-temperature activation, while simultaneously introducing ammonia gas with a purity ≥99.9% for nitrogen doping. A segmented mixing method was used for gas supply—the ammonia gas fraction was 5% for the first 30 minutes, gradually increasing to 8% over the next 60 minutes, with the total flow rate of the ammonia and nitrogen mixture maintained at 200 mL / min; finally, the temperature was raised to 620°C at a rate of 2.5°C / min for 0.8 hours of high-temperature activation, during which ammonia gas supply was stopped, and only nitrogen gas was supplied for protection. The temperature uniformity deviation of the tubular furnace was controlled within ±2°C, and a slight positive pressure of 8 kPa was maintained inside the furnace. After activation, the heating device was turned off, and the nitrogen gas flow rate was kept constant, allowing the furnace to cool down to room temperature to obtain the nitrogen-doped activated material.

[0024] S5. Post-treatment after graded composite: Nitrogen-doped activator material was added to 0.25 mol / L dilute hydrochloric acid and washed using a dynamic countercurrent method, with the washing liquid flowing in the opposite direction to the activator material. The mixture was stirred and washed for 25 min at 130 rpm in a 75℃ water bath. After filtration, the ash content of the activator material was measured to be ≤1%. It was then sprayed with a 35% ethanol solution at a pressure of 0.15 MPa for 12 min to remove organic impurities. Subsequently, ozone (65 mg / L) was introduced for oxidation treatment for 12 min to optimize surface active sites. After oxidation, it was washed with deionized water (conductivity ≤10 μS / cm, pH 6.8-7.2) using a countercurrent wash for 3 stages until the filtrate was neutral. The wet material was obtained by filtration. 0.03 wt% of polyethylene glycol 400 was added to the wet material and stirred and mixed at 70 rpm for 6 min. Then, it was ultrasonically dispersed at 120 W for 4 min to ensure uniform adhesion of the polyethylene glycol, resulting in a modified wet material with a solid content of 45 wt%.

[0025] S6. Microwave Vacuum Co-drying Molding and Post-treatment: The modified wet material is placed in a microwave vacuum drying oven, evacuated to -0.065MPa, and purged with argon gas at a flow rate of 65mL / min. The drying program is started—microwave power 450W, temperature 85℃, heating rate 6℃ / min, drying for 35min, with a 1min pause every 2min of microwave operation, repeated 10 times. After drying, the material is removed, cooled to room temperature, and pulverized in a pulverizer. It is then graded using 80-mesh and 100-mesh airflow sieves, achieving a particle size qualification rate ≥98%, removing particles with a particle size deviation >3 mesh. Subsequently, surface hydrophobic modification was performed by placing the activated carbon in a 1.5 wt% methyltrimethoxysilane ethanol solution at 65°C for 35 min, filtering, and drying at 85°C for 1 h. Finally, a 6.5 wt% sodium carboxymethyl cellulose aqueous solution was added as a binder (sodium carboxymethyl cellulose aqueous solution concentration 4 wt%), and the mixture was granulated into 2-5 mm particles. After drying at 85°C for 2.5 h, a high-efficiency adsorption activated carbon product was obtained, with a particle compressive strength ≥100 N / particle.

[0026] Example 2 S1. Raw material targeted modification pretreatment: Select walnut shell raw materials, sort out and remove moldy and insect-infested parts, put them into a universal pulverizer for crushing, and then pass them through a magnetic separator with a magnetic field strength of 800Gs to remove impurities. Then, use 30-mesh and 60-mesh standard inspection sieves to collect uniform particles with a particle size of 30-60 mesh and a particle size deviation ≤5 mesh. Add 1.5mol / L dilute hydrochloric acid to the screened raw materials and mix them at a solid-liquid mass-volume ratio of 1g:8mL. Place the mixture in a 60℃ constant temperature water bath and stir at 80r / min for 3h to deash. After filtration, wash repeatedly with deionized water until the pH of the filtrate is 6.8-7.2 to obtain deashed raw material particles. The deashed granules were placed in an ultrasonic cleaner, and deionized water with 0.1 wt% silane coupling agent KH560 was added as the medium. The pH of the medium was adjusted to 4.5, and ultrasonic modification was carried out for 1 hour at 200W power and 40℃. During the ultrasonic process, a strict rule of pausing for 5 minutes every 15 minutes was followed, with a total pause time of 12 minutes to avoid overheating and carbonization of the raw material. After ultrasonication, the material was filtered, pre-dried by microwave at 100W for 8 minutes, and then placed in an oven at 105℃ to dry to constant weight. During this process, the material was weighed every 30 minutes, and the difference between two weighings was ≤0.1g to obtain the pretreated walnut shell raw material with surface-grafted functional groups and a moisture content ≤2%.

[0027] S2. Preparation of Multi-Effect Ternary Composite Activator: Zinc chloride, dipotassium hydrogen phosphate, and citric acid were mixed in a mass ratio of 8:1:0.5. Deionized water was added and stirred to prepare a mixed solution with a total molar concentration of 5 mol / L. 1% (v / v) concentrated hydrochloric acid was added to the solution to inhibit the hydrolysis of the components. The stirring speed was 200 r / min until the hydrochloric acid was completely dispersed. 0.05 wt% of nano-silica particles with a particle size of 10 nm were taken from the mixed solution. Before addition, the particles were surface-modified with silane coupling agent KH570—nano-silica was mixed with a 2 wt% (v / v) KH570 ethanol solution at a solid-liquid ratio of 1 g:20 mL, stirred at 50 °C for 1 h for modification, filtered, and dried at 105 °C to constant weight. The modified nano-silica particles were added to the composite solution and dispersed using pulsed ultrasonic mode with a pulse frequency of 2 seconds / time and a power of 150W for 10 minutes until the particles were no longer agglomerated, thus obtaining a ternary composite activator. It was then placed in a sealed environment at 25°C for standby and ensured to be used within 24 hours.

[0028] S3. Negative Pressure Assisted Impregnation Treatment: Pretreated walnut shell raw materials and ternary composite activator are added to a negative pressure impregnation tank at a solid-liquid mass-volume ratio of 1g:6mL. A rotary stirrer is installed inside the tank. First, a vacuum is drawn to -0.08MPa and maintained for 10 minutes to expel air from the internal pores of the raw materials. After restoring normal pressure, the stirrer is started and rotated at a low speed of 30r / min. Simultaneously, the impregnation tank is placed in a 30℃ constant temperature shaking chamber, and impregnation is performed at a shaking rate of 150r / min for 18 hours. During this period, a vacuum is replenished every 4 hours, maintaining a vacuum degree of -0.08MPa, and the pressure is maintained for 3 minutes after each replenishment. After impregnation, the impregnated material is removed and placed in a vacuum filtration device. Filtering is performed at a pressure of -0.05MPa for 10 minutes to remove excess activator, resulting in a uniformly impregnated material. Subsequently, the impregnated material undergoes a freezing pretreatment by freezing it in a -10℃ low-temperature freezer for 1 hour. After removal, it is allowed to thaw naturally to room temperature for later use.

[0029] S4. Segmented gradient activation and in-situ doping: The thawed impregnating material is evenly spread on the multi-layer material support frame of the tube furnace with a thickness of 5mm. After sealing the tube furnace, high-purity nitrogen gas with a purity of ≥99.99% is introduced. After dehydration and deoxygenation treatment, the dew point is ≤-40℃. The nitrogen flow rate is 150mL / min, and the furnace is purged for 25min to remove the air inside the furnace. The tubular furnace heating program was initiated, first raising the temperature to 350°C at a rate of 3°C / min for 1 hour of low-temperature activation to promote the penetration of the activator into the raw material; then raising the temperature to 500°C at a rate of 8°C / min for 1.5 hours of medium-temperature activation, while simultaneously introducing ammonia gas with a purity ≥99.9% for nitrogen doping. A staged mixing method was used for gas supply—the ammonia gas fraction was 5% for the first 30 minutes, gradually increasing to 8% over the next 60 minutes, with the total flow rate of ammonia and nitrogen maintained at 180 mL / min; finally, the temperature was raised to 600°C at a rate of 2°C / min for 1 hour of high-temperature activation, during which ammonia gas supply was stopped, and only nitrogen gas was supplied for protection. The temperature uniformity deviation of the tubular furnace was controlled within ±2°C, and a slight positive pressure of 5 kPa was maintained inside the furnace. After activation, the heating device was turned off, and the nitrogen gas flow rate was kept constant, allowing the furnace to cool down to room temperature to obtain the nitrogen-doped activated material.

[0030] S5. Post-treatment after graded composite: Nitrogen-doped activator material was added to 0.2 mol / L dilute hydrochloric acid and washed using a dynamic countercurrent method, with the washing liquid flowing in the opposite direction to the activator material. The mixture was stirred and washed for 30 min at 120 rpm in a 70℃ water bath. After filtration, the ash content of the activator material was measured to be ≤1%. It was then sprayed with a 30% (v / v) ethanol solution at a pressure of 0.1 MPa for 15 min to remove organic impurities. Subsequently, ozone (50 mg / L) was introduced for oxidation treatment for 15 min to optimize surface active sites. After oxidation, it was washed with deionized water (conductivity ≤10 μS / cm, pH 6.8-7.2) using a countercurrent wash for 3 stages until the filtrate was neutral. The wet material was then obtained by filtration. 0.02 wt% of polyethylene glycol 400 was added to the wet material and stirred and mixed at 80 rpm for 8 min. Then, it was ultrasonically dispersed at 100 W for 5 min to ensure uniform adhesion of the polyethylene glycol, resulting in a modified wet material with a solid content of 40 wt%.

[0031] S6. Microwave Vacuum Co-drying and Post-treatment: The modified wet material is placed in a microwave vacuum drying oven, evacuated to -0.06 MPa, and purged with argon gas at a flow rate of 50 mL / min. The drying program is started—microwave power 400 W, temperature 80℃, heating rate 5℃ / min, drying for 40 min, with a 1 min pause every 2 min of microwave operation, repeated 8 times. After drying, the material is removed, cooled to room temperature, and then pulverized in a pulverizer. It is then graded using 80-mesh and 100-mesh airflow sieves, achieving a particle size qualification rate ≥98%, removing particles with a particle size deviation >3 mesh. Subsequently, surface hydrophobic modification was performed by placing the activated carbon in a 1 wt% methyltrimethoxysilane ethanol solution at 60°C for 40 min, filtering, and drying at 80°C for 1.5 h. Finally, a 5 wt% sodium carboxymethyl cellulose aqueous solution was added as a binder (sodium carboxymethyl cellulose aqueous solution concentration 3 wt%), and the mixture was granulated into 2-5 mm particles. After drying at 80°C for 3 h, a high-efficiency adsorption activated carbon product was obtained, with a particle compressive strength ≥100 N / particle.

[0032] Example 3 S1. Raw material directional modification pretreatment: Select coconut shell raw materials, sort out and remove moldy and insect-infested parts, put them into a universal pulverizer for crushing, and then pass them through a magnetic separator with a magnetic field strength of 1200Gs to remove impurities. Then, use 30-mesh and 60-mesh standard inspection sieves to collect uniform particles with a particle size of 30-60 mesh and a particle size deviation ≤5 mesh. Add 2.5mol / L dilute hydrochloric acid to the screened raw materials and mix them at a solid-liquid mass-volume ratio of 1g:12mL. Place the mixture in a 70℃ constant temperature water bath and stir at 100r / min for 2 hours to remove ash. After filtration, wash repeatedly with deionized water until the pH of the filtrate is 6.8-7.2 to obtain deashed raw material particles. The deashed granules were placed in an ultrasonic cleaner, and deionized water with 0.3 wt% silane coupling agent KH570 was added as the medium. The pH of the medium was adjusted to 5.5, and ultrasonic modification was carried out for 1.5 hours at 300W power and 50℃. During the ultrasonic process, a strict rule of pausing for 5 minutes every 15 minutes was followed, with a total pause time of 20 minutes to avoid overheating and carbonization of the raw material. After ultrasonication, the granules were filtered, pre-dried by microwave at 150W for 5 minutes, and then placed in an oven at 110℃ to dry to constant weight. During this period, the granules were weighed every 30 minutes. The constant weight was defined as a difference of ≤0.1g between two weighings. The pretreated coconut shell raw material with surface-grafted amino groups was obtained, with a moisture content of ≤2% and a surface amino grafting amount of 0.5 mmol / g.

[0033] S2. Preparation of Multi-Effect Ternary Composite Activator: Zinc chloride, dipotassium hydrogen phosphate, and citric acid were mixed in a mass ratio of 10:2:1. Deionized water was added and stirred to prepare a mixed solution with a total molar concentration of 7 mol / L. 2% (v / v) concentrated hydrochloric acid was added to the solution to inhibit component hydrolysis, and the mixture was stirred at 250 r / min until the hydrochloric acid was completely dispersed. 0.1 wt% of nano-silica particles (20 nm in diameter) were taken from the mixed solution and pre-treated with silane coupling agent KH570 before addition. The nano-silica particles were mixed with a 3 wt% (v / v) KH570 ethanol solution at a solid-liquid ratio of 1 g:20 mL, stirred at 60℃ for 1.5 h, filtered, and dried at 105℃ to constant weight. The modified nano-silica particles were added to the composite solution and dispersed using pulsed ultrasonic mode at a pulse frequency of 3 seconds / time and a power of 150W for 15 minutes until the particles were no longer agglomerated, thus obtaining a ternary composite activator. It was then placed in a sealed environment at 25°C for standby and ensured to be used within 24 hours.

[0034] S3. Negative Pressure Assisted Impregnation Treatment: Pretreated coconut shell raw material and ternary composite activator were added to a negative pressure impregnation tank at a solid-liquid mass-to-volume ratio of 1g:9mL. A rotary stirrer was installed inside the tank. A vacuum was first drawn to -0.09MPa and maintained for 15 minutes to expel air from the internal pores of the raw material. After restoring normal pressure, the stirrer was started and rotated at a low speed of 50r / min. Simultaneously, the impregnation tank was placed in a 40℃ constant temperature shaking chamber, and impregnation was performed at a shaking rate of 200r / min for 22 hours. During this period, a vacuum was replenished every 4 hours, maintaining a vacuum of -0.09MPa, and the pressure was maintained for 3 minutes after each replenishment. After impregnation, the impregnated material was removed and placed in a vacuum filtration device. Filtering was performed at a pressure of -0.05MPa for 15 minutes to remove excess activator, resulting in a uniformly impregnated material. Subsequently, the impregnated material underwent a freezing pretreatment by freezing it in a -15℃ low-temperature freezer for 2 hours. After removal, it was allowed to thaw naturally to room temperature for later use.

[0035] S4. Segmented gradient activation and in-situ doping: The thawed impregnating material is evenly spread on the multi-layer material support frame of the tube furnace with a thickness of 8mm. After sealing the tube furnace, high-purity nitrogen gas with a purity of ≥99.99% is introduced. After dehydration and deoxygenation treatment, the dew point is ≤-40℃. The nitrogen flow rate is 250mL / min, and the air in the furnace is removed after purging for 35min. The tubular furnace heating program was initiated, first raising the temperature to 400℃ at a rate of 5℃ / min for 0.5 hours of low-temperature activation to promote the penetration of the activator into the raw material; then raising the temperature to 550℃ at a rate of 10℃ / min for 1 hour of medium-temperature activation, while simultaneously introducing ammonia gas with a purity ≥99.9% for nitrogen doping. A segmented mixing method was used for gas supply—the ammonia gas fraction was 5% for the first 30 minutes, gradually increasing to 8% for the next 30 minutes, with the total flow rate of ammonia and nitrogen maintained at 250 mL / min after mixing; finally, the temperature was raised to 650℃ at a rate of 3℃ / min for 0.5 hours of high-temperature activation, during which ammonia gas supply was stopped, and only nitrogen gas was supplied for protection. The temperature uniformity deviation of the tubular furnace was controlled within ±2℃, and a slight positive pressure of 10 kPa was maintained inside the furnace. After activation, the heating device was turned off, and the nitrogen gas flow rate was kept constant, allowing the furnace to cool down to room temperature to obtain the nitrogen-doped activated material.

[0036] S5. Post-treatment after graded composite: Nitrogen-doped activator material is added to 0.3 mol / L dilute hydrochloric acid and washed using a dynamic countercurrent method, with the washing solution flowing in the opposite direction to the activator material. The material is stirred and washed for 20 minutes at 150 rpm in an 80℃ water bath. After filtration, the ash content of the activator material is measured to be ≤1%. It is then sprayed with a 40% ethanol solution at a pressure of 0.2 MPa for 10 minutes to remove organic impurities. Subsequently, ozone (80 mg / L) is introduced for oxidation treatment for 10 minutes to optimize surface active sites. After oxidation, it is washed with deionized water (conductivity ≤10 μS / cm, pH 6.8-7.2) using a countercurrent wash for 3 stages until the filtrate is neutral. The wet material is then obtained by filtration. 0.05 wt% of polyethylene glycol 400 is added to the wet material and stirred at 60 rpm for 5 minutes. Then, it is ultrasonically dispersed at 150 W for 3 minutes to ensure uniform adhesion of the polyethylene glycol, resulting in a modified wet material with a solid content of 50 wt%.

[0037] S6. Microwave Vacuum Co-drying and Post-treatment: The modified wet material is placed in a microwave vacuum drying oven, evacuated to -0.07MPa, and purged with argon gas at a flow rate of 80mL / min. The drying program is started—microwave power 500W, temperature 90℃, heating rate 8℃ / min, drying for 30min, with a 1min pause every 2min of microwave operation, repeated 12 times. After drying, the material is removed, cooled to room temperature, and then pulverized using a pulverizer. The material is then graded using 80-mesh and 100-mesh airflow sieves, achieving a particle size qualification rate ≥98%, removing particles with a particle size deviation >3 mesh. Subsequently, surface hydrophobic modification was performed by placing the activated carbon in a 2wt% methyltrimethoxysilane ethanol solution at 70℃ for 30 min, filtering, and drying at 90℃ for 1 h. Finally, 8wt% sodium carboxymethyl cellulose aqueous solution (5wt% by weight of activated carbon) was added as a binder, and the mixture was granulated into 2-5 mm particles and dried at 90℃ for 2 h to obtain a high-efficiency adsorption activated carbon product with a particle compressive strength ≥100 N / particle.

[0038] Example 4 S1. Raw material targeted modification pretreatment: Select coconut shell raw materials, sort out and remove moldy and insect-infested parts, put them into a universal pulverizer for crushing, and then pass them through a magnetic separator with a magnetic field strength of 1100Gs to remove impurities. Then, use 30-mesh and 60-mesh standard inspection sieves to collect uniform particles with a particle size of 30-60 mesh and a particle size deviation ≤5 mesh. Add 2.2mol / L dilute hydrochloric acid to the screened raw materials and mix them at a solid-liquid mass-volume ratio of 1g:11mL. Place the mixture in a 68℃ constant temperature water bath and stir at 95r / min for 2.2h to deash. After filtration, wash repeatedly with deionized water until the pH of the filtrate is 6.8-7.2 to obtain deashed raw material particles. The deashed granules were placed in an ultrasonic cleaner, and deionized water with 0.25 wt% silane coupling agent KH570 was added as the medium. The pH of the medium was adjusted to 5.8, and ultrasonic modification was carried out for 1.3 hours at an ultrasonic power of 280W and a temperature of 48℃. During the ultrasonic process, a strict rule of pausing for 5 minutes every 15 minutes was followed, with a total pause time of 18 minutes to avoid overheating and carbonization of the raw material. After ultrasonication, the granules were filtered, pre-dried by microwave at 130W for 6 minutes, and then placed in an oven at 109℃ to dry to constant weight. During this period, the granules were weighed every 30 minutes, and the difference between two weighings was ≤0.1g to obtain the pretreated coconut shell raw material with surface-grafted amino groups, with a moisture content ≤2% and a surface amino grafting amount of 0.45 mmol / g.

[0039] S2. Preparation of Multi-Effect Ternary Composite Activator: Zinc chloride, dipotassium hydrogen phosphate, and citric acid were mixed in a mass ratio of 9.5:1.8:0.9. Deionized water was added and stirred to prepare a mixed solution with a total molar concentration of 6.5 mol / L. Concentrated hydrochloric acid (1.8% by volume) was added to the solution to inhibit component hydrolysis, and the mixture was stirred at 230 r / min until the hydrochloric acid was completely dispersed. 0.09 wt% of nano-silica particles (18 nm in diameter) from the mixed solution were taken and surface-modified with silane coupling agent KH570 before addition—nano-silica was mixed with a 2.8 wt% KH570 ethanol solution at a solid-liquid ratio of 1 g:20 mL, stirred at 58℃ for 1.3 h, filtered, and dried at 105℃ to constant weight. The modified nano-silica particles were added to the composite solution and dispersed using pulsed ultrasonic mode at a pulse frequency of 2.8s / time and a power of 150W for 13 minutes until the particles were no longer agglomerated, thus obtaining a ternary composite activator. It was then placed in a sealed environment at 25℃ for standby and ensured to be used within 24 hours.

[0040] S3. Negative Pressure Assisted Impregnation Treatment: Pretreated coconut shell raw material and ternary composite activator were added to a negative pressure impregnation tank at a solid-liquid mass-to-volume ratio of 1g:8mL. A rotary stirrer was installed inside the tank. A vacuum was first drawn to -0.088MPa and maintained for 13 minutes to allow air to escape from the pores inside the raw material. After restoring normal pressure, the stirrer was started and rotated at a low speed of 45r / min. Simultaneously, the impregnation tank was placed in a 38℃ constant temperature shaking chamber, and impregnation was performed at a shaking rate of 190r / min for 21 hours. During this period, a vacuum was replenished every 4 hours, maintaining a vacuum of -0.088MPa, and the pressure was maintained for 3 minutes after each replenishment. After impregnation, the impregnated material was removed and placed in a vacuum filtration device. Filtering was performed at a pressure of -0.05MPa for 13 minutes to remove excess activator, resulting in a uniformly impregnated material. Subsequently, the impregnated material underwent a freezing pretreatment by freezing it in a -13℃ low-temperature freezer for 1.8 hours. After removal, it was allowed to thaw naturally to room temperature for later use.

[0041] S4. Segmented gradient activation and in-situ sulfur doping: The thawed impregnating material is evenly spread on the multi-layer material support frame of the tube furnace with a thickness of 7mm. After sealing the tube furnace, high-purity argon gas with a purity of ≥99.99% is introduced. After dehydration and deoxygenation treatment, the dew point is ≤-40℃. The argon gas flow rate is 220mL / min. The furnace is purged for 32min to remove the air inside. The tubular furnace heating program was initiated, first raising the temperature to 390℃ at a rate of 4.5℃ / min for 0.7 hours of low-temperature activation to promote the penetration of the activator into the raw material; then raising the temperature to 530℃ at a rate of 9.5℃ / min for 1.1 hours of medium-temperature activation, while simultaneously introducing hydrogen sulfide gas with a purity ≥99.8% for sulfur doping (hydrogen sulfide volume fraction 4%), which was mixed with argon gas and maintained at a total flow rate of 220 mL / min, with the doping time consistent with the activation time; finally, raising the temperature to 640℃ at a rate of 2.8℃ / min for 0.7 hours of high-temperature activation, during which hydrogen sulfide gas was stopped, and only argon gas was supplied for protection. The temperature uniformity deviation of the tubular furnace was controlled within ±2℃, and a slight positive pressure of 9 kPa was maintained inside the furnace. After activation, the heating device was turned off, and the argon gas flow rate was kept constant, allowing the furnace to cool to room temperature to obtain the sulfur-doped activated material.

[0042] S5. Post-treatment after graded composite: The sulfur-doped activated material was added to 0.28 mol / L dilute hydrochloric acid and washed using a dynamic countercurrent method, with the washing liquid flowing in the opposite direction to the activated material. The material was stirred and washed for 22 min at 140 r / min in a 78℃ water bath. After filtration, the ash content of the activated material was found to be ≤1%. It was then sprayed with a 38% ethanol solution at a pressure of 0.18 MPa for 11 min to remove organic impurities. Subsequently, ozone (75 mg / L) was introduced for oxidation treatment for 11 min to optimize surface active sites. After oxidation, it was washed with deionized water (conductivity ≤10 μS / cm, pH 6.8-7.2) using a countercurrent washing method for 3 stages until the filtrate was neutral. The wet material was then obtained by filtration. Add 0.04wt% of polyethylene glycol 400 to the wet material, stir and mix at 75r / min for 7min, and then ultrasonically disperse at 140W for 3.5min to ensure uniform adhesion of polyethylene glycol, thus obtaining the modified wet material with a solid content of 48wt%.

[0043] S6. Microwave Vacuum Co-drying Molding and Post-treatment: The modified wet material is placed in a microwave vacuum drying oven, evacuated to -0.068MPa, and purged with argon gas at a flow rate of 70mL / min. The drying program is started—microwave power 480W, temperature 88℃, heating rate 7℃ / min, drying for 32min, with a 1min pause every 2min of microwave operation, repeated 11 times. After drying, the material is removed, cooled to room temperature, and pulverized in a pulverizer. It is then graded using 80-mesh and 100-mesh airflow sieves, achieving a particle size qualification rate ≥98%, removing particles with a particle size deviation >3 mesh. Subsequently, surface hydrophobic modification was performed by placing the activated carbon in a 1.8 wt% methyltrimethoxysilane ethanol solution at 68°C for 32 min, filtering, and drying at 88°C for 1 h. Finally, 7 wt% sodium carboxymethyl cellulose aqueous solution (4.5 wt% by weight of activated carbon) was added as a binder, and the mixture was granulated into 2-5 mm particles and dried at 88°C for 2.2 h to obtain a high-efficiency adsorption activated carbon product with a particle compressive strength ≥100 N / particle.

[0044] Comparative Example 1 (Traditional Chemical Activation Method) S1. Raw Material Pretreatment: Select coconut shell raw materials, sort out and remove moldy and insect-infested parts, put them into a universal pulverizer for crushing, and screen them with 30-mesh and 60-mesh standard inspection sieves to collect particles with a particle size of 30-60 mesh. Perform no magnetic separation for impurity removal, ultrasonic modification, or silane coupling agent grafting. Add 2.0 mol / L dilute hydrochloric acid to the screened raw materials, mix at a solid-liquid mass-volume ratio of 1g:10mL, place in a 65℃ constant temperature water bath, stir at 90 r / min for 2.5 h to remove ash, filter, wash repeatedly with deionized water until the filtrate is neutral, and directly place in a 108℃ oven to dry to constant weight to obtain pretreated coconut shell raw materials.

[0045] S2. Preparation of activator: Take only zinc chloride, add deionized water and stir to prepare a solution with a total molar concentration of 6 mol / L. There are no dipotassium hydrogen phosphate, citric acid and nano silica components. No concentrated hydrochloric acid is added to inhibit hydrolysis. After stirring evenly, it can be used directly. There is no time limit for sealed storage. It is a traditional single activator system.

[0046] S3. Impregnation treatment: Add the pretreated coconut shell raw material and zinc chloride solution to a regular container at a solid-liquid mass-volume ratio of 1g:7.5mL, place it in a 35℃ constant temperature shaking box, and impregnate for 20h at a shaking rate of 180r / min. There are no negative pressure assistance, stirring paddle rotation, vacuuming and freezing pretreatment steps. This is the traditional atmospheric pressure impregnation method. After impregnation, filter naturally to remove excess solution and use directly.

[0047] S4. Activation Treatment: The impregnating material is evenly spread on the support frame of the tubular furnace to a thickness of 6 mm. After sealing the tubular furnace, ordinary nitrogen gas with a purity ≥99% is introduced. No dehydration or deoxygenation treatment is performed. The nitrogen flow rate is 200 mL / min, and the furnace is purged for 30 minutes to remove air. The tubular furnace is started, and the temperature is directly increased to 620°C at a rate of 6°C / min. Activation is carried out at this temperature for 2.5 hours without gradient heating, segmented activation, or in-situ doping steps. Only nitrogen protection is maintained throughout the process, and the furnace is kept at atmospheric pressure. This is a traditional isothermal activation process. After activation, the heating device is turned off, and the furnace is cooled to room temperature to obtain the activated material.

[0048] S5. Post-treatment: Add the activated material to dilute hydrochloric acid with a mass concentration of 0.25 mol / L, and wash it in a 75℃ water bath at a speed of 130 r / min for 25 min. After filtration, wash it with deionized water until neutral. There are no dynamic countercurrent washing, ethanol spraying, ozone oxidation and polyethylene glycol modification steps. It is a traditional single water washing process, which directly obtains wet material.

[0049] S6. Drying and Shaping: The wet material is placed in a hot air drying oven and dried at 85°C for 4 hours, which is a traditional hot air drying method. After cooling to room temperature, it is placed in a pulverizer for crushing and graded using 80-mesh and 100-mesh sieves. There are no microwave vacuum drying, surface hydrophobic modification and granulation steps. The activated carbon product is obtained directly, which is a common activated carbon prepared by traditional process.

[0050] Comparative Example 2 S1. Raw material directional modification pretreatment: Select coconut shell raw materials, sort out and remove moldy and insect-infested parts, put them into a universal pulverizer for crushing, and then pass them through a magnetic separator with a magnetic field strength of 1000Gs to remove impurities. Then, use 30-mesh and 60-mesh standard inspection sieves to collect uniform particles with a particle size of 30-60 mesh and a particle size deviation ≤5 mesh. Add 2.0mol / L dilute hydrochloric acid to the screened raw materials and mix them at a solid-liquid mass-volume ratio of 1g:10mL. Place the mixture in a 65℃ constant temperature water bath and stir at 90r / min for 2.5h to deash. After filtration, wash repeatedly with deionized water until the pH of the filtrate is 6.8-7.2 to obtain deashed raw material particles. The deashed particles were placed in an ultrasonic cleaner, and deionized water with 0.2 wt% silane coupling agent KH550 was added as a medium. The pH of the medium was adjusted to 6.8, and ultrasonic modification was carried out at 250W and 45℃ for 1.2 hours. The process was paused for 5 minutes every 15 minutes, for a total of 16 minutes. After filtration, the particles were dried in an oven at 108℃ until constant weight, to obtain pretreated coconut shell raw material with surface-grafted amino groups.

[0051] S2. Preparation of Multi-Effect Ternary Composite Activator: Zinc chloride, dipotassium hydrogen phosphate, and citric acid were mixed in a mass ratio of 9:1.5:0.8. Deionized water was added and stirred to prepare a mixed solution with a total molar concentration of 6 mol / L. 1.5% (v / v) of concentrated hydrochloric acid was added to the solution to inhibit component hydrolysis, and the mixture was stirred at 220 r / min until the hydrochloric acid was completely dispersed. 0.08 wt% of nano-silica particles (15 nm in diameter) from the mixed solution were taken, modified with KH570, and then pulsed ultrasonically dispersed for 12 min to obtain the ternary composite activator. It was sealed at 25℃ for later use and should be used within 24 hours.

[0052] S3. Impregnation treatment: Add the pretreated coconut shell raw material and the ternary composite activator to a regular container at a solid-liquid mass-volume ratio of 1g:7.5mL, place it in a 35℃ constant temperature shaking box, and impregnate for 20h at a shaking rate of 180r / min. There are no negative pressure assistance, stirring paddle rotation, vacuuming and freezing pretreatment steps. After impregnation, vacuum filter to remove excess activator and use directly.

[0053] S4. Activation Treatment: The impregnating material is evenly spread on a multi-layer support frame of a tubular furnace to a thickness of 6 mm. After sealing the tubular furnace, high-purity nitrogen is introduced at a flow rate of 200 mL / min to purge the air inside the furnace for 30 minutes. The tubular furnace is then started, and the temperature is directly increased to 620°C at a rate of 5°C / min. Activation is carried out at this constant temperature for 2.5 hours, without gradient heating, segmented activation, or in-situ doping steps. Only nitrogen protection is maintained throughout the process, and a slight positive pressure of 8 kPa is maintained inside the furnace. After activation, the heating device is turned off, and the furnace is cooled to room temperature to obtain the activated material.

[0054] S5. Post-treatment after graded compounding: The activated material is added to 0.25 mol / L dilute hydrochloric acid and washed in a 75°C water bath at 130 r / min for 25 min with stirring. After filtration, it is washed with 35% ethanol solution for 12 min, and then washed with deionized water until neutral. The wet material is obtained by filtration. 0.03 wt% polyethylene glycol 400 is added to the wet material and stirred for 6 min. No dynamic countercurrent washing, ozone oxidation, or ultrasonic dispersion steps are performed to obtain the modified wet material.

[0055] S6. Microwave Vacuum Co-drying, Molding, and Post-treatment: The modified wet material was placed in a microwave vacuum drying oven, evacuated to -0.065 MPa, and purged with argon gas at a flow rate of 65 mL / min. The drying program was started with a microwave power of 450 W and a temperature of 85 °C, increasing at a rate of 6 °C / min for 35 min. The microwave was paused for 1 min every 2 min of operation, and this cycle was repeated 10 times. After drying, the material was pulverized and graded, and then subjected to surface hydrophobic modification and granulation, following the same steps as in Example 1, to obtain the finished activated carbon product.

[0056] The basic adsorption and structural properties of the examples and comparative examples are compared in the table below: Table 1 Performance indicators Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 <![CDATA[Specific surface area (m 2 / g)]]> 1850 1680 1920 1750 1120 1450 Percentage of holes (%) 42 38 45 40 22 31 Surface functional group loading (mmol / g) 1.85 1.52 1.98 1.67 0.72 1.21 Methylene blue adsorption capacity (mg / g) 310 275 325 290 185 230 Adsorption rate (min for reaching 80% saturation adsorption) 12 15 11 14 28 21 Particle uniformity (percentage of particles with a diameter deviation ≤ 3 mesh, %) 98.5 97.2 98.8 97.6 82.3 90.5 Mechanical strength (N / piece) 125 110 130 118 75 95 The stability and process adaptability of the examples and comparative examples are compared in the table below: Table 2 Performance indicators Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Cyclic adsorption stability (performance retention rate after 5 adsorption cycles, %) 92 88 94 90 65 78 Acid and alkali corrosion resistance (strength retention rate after immersion in pH 2-10, %) 95 91 96 93 72 83 Hydrophobic properties (water contact angle, °) 118 105 122 112 75 92 Impurity residue (ppm) 8.5 11.2 7.8 9.6 35.7 18.3 Process repeatability (performance deviation in 3 parallel experiments, %) 2.1 2.8 1.9 2.5 7.6 4.2 Industrialization adaptability (output per unit time, kg / h) 8.5 7.8 8.8 8.2 6.2 7.5 Environmental friendliness (waste liquid discharge per unit product, L / kg) 2.8 3.2 2.6 3.0 8.5 5.2 In summary, as shown in the two tables, the activated carbon prepared in Examples 1-4 of this invention significantly outperforms Comparative Examples 1 and 2 in all aspects of performance. Thanks to the optimized process of directional modification pretreatment, ternary composite activator, negative pressure impregnation, segmented gradient doping activation, and graded post-treatment, the specific surface area of ​​the examples is increased by 56.2%-71.4% compared to Comparative Example 1, the methylene blue adsorption capacity is increased by 56.8%-75.7%, and the adsorption performance retention rate after 5 cycles is 25%-29 percentage points higher. Furthermore, it exhibits excellent mechanical strength, corrosion resistance, hydrophobicity, and environmental friendliness. Example 3, with its more optimized process parameters, demonstrates the best overall performance, while the sulfur-doped system in Example 4 also exhibits good adsorption stability and structural characteristics.

[0057] Comparative Example 1 is limited by the traditional single process and its performance is lagging behind in all aspects; Comparative Example 2, due to the lack of key steps such as negative pressure impregnation and gradient activation, has performance between the examples and Comparative Example 1, which further confirms the importance of the synergistic effect of each process step in the present invention, and the activated carbon prepared is more suitable for industrial production and high-requirement adsorption scenarios.

[0058] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing highly efficient adsorption activated carbon using a composite activator chemical process, characterized in that, Includes the following steps: S1. Raw material directional modification pretreatment: Crush coconut shell or walnut shell raw materials, add dilute hydrochloric acid with a mass concentration of 1.5-2.5 mol / L, mix at a solid-liquid mass-volume ratio of 1:8-12 (g / mL), stir and deash in a water bath, filter and wash with deionized water until neutral; then place the deashed raw material in an ultrasonic cleaner, use deionized water with added silane coupling agent as the medium, and perform ultrasonic modification, pausing for 5 minutes every 15 minutes of ultrasonication, filter and dry in an oven to constant weight to obtain pretreated raw materials; S2. Preparation of multi-effect ternary composite activator: Zinc chloride, dipotassium hydrogen phosphate, and citric acid are mixed in a mass ratio of 8-10:1-2:0.5-1. Deionized water is added to prepare a mixed solution with a molar concentration of 5-7 mol / L. Concentrated hydrochloric acid with a volume fraction of 1-2% is added, followed by nano-silica particles. The mixture is stirred until completely dissolved and ultrasonically dispersed to obtain the ternary composite activator. S3. Negative pressure assisted impregnation treatment: Add the pretreated raw materials and ternary composite activator to the negative pressure impregnation tank at a solid-liquid mass-volume ratio of 1:6-9 (g / mL), evacuate to -0.08~-0.09MPa and maintain for 10-15min, restore to normal pressure and then impregnate in a constant temperature shaking chamber. During this period, evacuate for 5min every 4h, filter to remove excess activator, and obtain a uniformly impregnated material. S4. Segmented gradient activation and in-situ doping: The impregnated material is placed in a nitrogen atmosphere tube furnace, heated to 350-400℃ for low-temperature activation for 0.5-1h, then heated to 500-550℃ for medium-temperature activation for 1-1.5h while ammonia gas is introduced for nitrogen doping, and then heated to 600-650℃ for high-temperature activation for 0.5-1h. After activation, the material is cooled to room temperature with the furnace to obtain nitrogen-doped activated material. S5. Post-treatment of graded composite: Add 0.2-0.3 mol / L dilute hydrochloric acid to the activated material, stir and wash in a water bath for 20-30 min, filter, wash with ethanol solution for 10-15 min, wash with deionized water until neutral, filter to obtain wet material, add polyethylene glycol 400 and stir to mix. S6. Microwave vacuum co-drying and molding: The wet material is placed in a microwave vacuum drying oven, vacuumed to -0.06~-0.07MPa, dried at 80-90℃ for 30-40min, cooled to room temperature and pulverized to obtain highly efficient adsorption activated carbon.

2. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, After the raw materials in S1 are crushed, they are first subjected to magnetic separation to remove the metal impurities mixed in with the raw materials. The magnetic separation magnetic field strength is 800-1200Gs. After magnetic separation, particle size screening is carried out. After ultrasonic modification, a microwave pre-drying step is also included. The microwave pre-drying power is 100-150W and the time is 5-8min. After pre-drying, it is then put into an oven for drying.

3. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, Before adding the nano-silica particles in S2, the surface of the particles was modified with silane coupling agent KH570. During the modification process, the nano-silica particles were mixed with a KH570 ethanol solution with a mass concentration of 2-3wt% at a solid-liquid ratio of 1g:20mL. The mixture was stirred at 50-60℃ for 1-1.5h, filtered and dried, and then added to the composite activator solution. The ultrasonic dispersion was performed using a pulsed ultrasonic mode with a pulse frequency of 2-3s / time.

4. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, The negative pressure impregnation tank in S3 is equipped with a rotary agitator. During the impregnation process, the agitator rotates at a low speed of 30-50 r / min. After the negative pressure impregnation is completed, the impregnated material is subjected to a freezing pretreatment at a temperature of -10~-15℃ for 1-2 hours. After freezing, the material is naturally thawed to room temperature before proceeding to the subsequent activation step.

5. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, The S4 tubular furnace is equipped with multiple material support racks. The impregnating material is evenly spread on the support racks with a thickness of 5-8mm. During the medium-temperature activation stage, ammonia and nitrogen are introduced in a segmented mixing manner. The ammonia gas fraction is 5% in the first 30 minutes and gradually increases to 8% in the next 60 minutes. During the high-temperature activation stage, ammonia is stopped and only nitrogen is introduced for protection.

6. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, In S5, the dilute hydrochloric acid washing adopts a dynamic countercurrent washing method, with the washing liquid and the activated material flowing in opposite directions. After washing with ethanol solution, an ozone oxidation treatment step is added, with an ozone concentration of 50-80 mg / L and an oxidation treatment time of 10-15 min. After ozone oxidation, deionized water washing is performed. After mixing with polyethylene glycol 400, ultrasonic dispersion treatment is performed with an ultrasonic power of 100-150 W for 3-5 min.

7. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, In the microwave vacuum drying process of S6, an inert gas is introduced for purging. The purging gas is argon, and the argon flow rate is 50-80 mL / min. After drying, the activated carbon is subjected to surface hydrophobic modification treatment. The modifier is a 1-2 wt% methyltrimethoxysilane ethanol solution. The modification temperature is 60-70℃, and the modification time is 30-40 min. After modification, the carbon is filtered and dried.

8. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, The silane coupling agent in S1 is either silane coupling agent KH560 or KH570. The pH value of the ultrasonic modification medium is adjusted according to the type of coupling agent. When using KH560, the pH value is adjusted to 4.0-5.0, and when using KH570, the pH value is adjusted to 5.0-6.

0.

9. The method for preparing highly efficient adsorption activated carbon using a composite activator chemical method according to claim 1, characterized in that, The S4 segmented gradient activation and in-situ doping process is as follows: The impregnating material is placed in an argon atmosphere tube furnace, heated to 350-400℃ for low-temperature activation for 0.5-1h, then activated at 500-550℃ for 1-1.5h while ammonia gas is introduced for sulfur doping, and hydrogen sulfide gas with a volume fraction of 3-5% is introduced during sulfur doping; the temperature is then raised to 600-650℃ for high-temperature activation for 0.5-1h, and after activation, the furnace is cooled to room temperature to obtain the sulfur-doped activated material.

10. The method for preparing highly efficient adsorption activated carbon by chemical method using composite activators according to any one of claims 1-9, characterized in that, The high-efficiency adsorption activated carbon prepared was subjected to granulation. During granulation, 5-8% sodium carboxymethyl cellulose aqueous solution (3-5 wt%) of activated carbon was added as a binder. After granulation, the activated carbon particles were dried at 80-90℃ for 2-3 hours to obtain activated carbon particles with a particle size of 2-5 mm.

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