Preparation of bamboo-based activated carbon composite adsorption material and application thereof in wastewater treatment
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- JIANGXI SHINCO ENVIRONMENTAL PROTECTION CO LTD
- Filing Date
- 2026-05-21
- Publication Date
- 2026-06-30
Abstract
Description
Technical Field
[0001] This invention relates to the field of wastewater treatment technology, and in particular to the preparation of a bamboo-based activated carbon composite adsorption material and its application in wastewater treatment. Background Technology
[0002] Bamboo-based activated carbon is widely used in the field of industrial wastewater adsorption treatment due to its wide availability of raw materials and low preparation cost. However, its surface is naturally rich in negatively charged oxygen-containing functional groups such as hydroxyl and carboxyl groups, which have an electrostatic repulsion effect on anionic dye molecules. Especially in high-salt anionic dye wastewater containing high concentrations of sodium chloride and sodium sulfate, a large number of salt ions will compete with dye molecules for adsorption sites, resulting in a significant decrease in adsorption capacity and difficulty in regeneration, making it difficult to meet the actual engineering treatment needs.
[0003] To address this deficiency, existing technologies often employ acid-base oxidation and surfactant loading to modify bamboo-based activated carbon. However, acid-base oxidation can only introduce a small number of oxygen-containing functional groups, failing to form stable cation adsorption sites. Furthermore, strong oxidation conditions can easily damage the original pore structure of activated carbon, reducing its specific surface area. Additionally, the modification process can easily introduce secondary pollution. Surfactant loading, on the other hand, relies on physical adsorption, resulting in weak binding to activated carbon. Under high-salt conditions, cation sites are easily displaced and detached by salt ions, leading to poor adsorption stability. Moreover, the modification process is cumbersome.
[0004] Some studies have attempted to enhance positive charge by introducing imidazolium-based cationic monomers through free radical grafting. However, conventional grafting processes struggle to control monomer distribution within activated carbon pores: if monomers accumulate in large quantities on the outer surface, they can clog pores, affecting dye molecule mass transfer efficiency and resulting in short penetration volumes during dynamic column operation; insufficient grafting density within the pores fails to effectively suppress competitive adsorption of salt ions, leading to a significant decrease in adsorption capacity under high salt conditions. Furthermore, without targeted post-treatment, grafted materials are prone to swelling or loss of cationic sites under high salt conditions, resulting in high effluent color, low COD removal rate, and low grafting efficiency, making continuous and stable treatment difficult.
[0005] In addition, the existing drying processes for modified bamboo-based activated carbon do not take into account the thermal stability of the grafted layer. Excessive temperature can easily lead to the breakage of the grafted chains, further reducing the adsorption performance. Furthermore, the adaptability is poor, and it cannot meet the treatment needs of different high-salt anionic dye wastewater. Summary of the Invention
[0006] In view of this, the purpose of this invention is to propose a method for preparing bamboo-based activated carbon composite adsorbent materials and their application in wastewater treatment, so as to solve the problem that in the prior art, bamboo-based activated carbon has low adsorption capacity and poor dynamic mass transfer stability under salt competition when treating high-salt anionic dye wastewater due to the lack of effective cation site modification and structural regulation.
[0007] To achieve the above objectives, the present invention provides a method for preparing a bamboo-based activated carbon composite adsorbent material, comprising the following steps: (1) Bamboo-based activated carbon was treated with nitric acid and hydrogen peroxide to obtain oxidized bamboo-based activated carbon; (2) The oxidized bamboo-based activated carbon, ethanol, water and 1-vinyl-3-hexylimidazolium bromide were mixed and kept under reduced pressure, then nitrogen was introduced to restore normal pressure and allowed to stand to obtain the pre-set system; (3) Add an ethanol-water mixture to the pre-prepared system for elution and filtration to obtain a pre-prepared filter cake; (4) The pre-prepared filter cake is mixed with a grafting solution containing 1-vinyl-3-butylimidazolium bromide and ammonium persulfate, and the main grafting reaction is carried out under nitrogen protection and heating conditions; (5) Add a supplementary grafting solution containing 1-vinyl-3-hexylimidazolium bromide and ammonium persulfate to the system after the main grafting reaction, and continue the supplementary grafting reaction; (6) After the grafting reaction is completed, the bamboo-based activated carbon composite adsorbent is obtained by washing with a mixture of ethanol and water, treating with sodium chloride solution, washing with water and vacuum drying at 50-70℃.
[0008] Preferably, the bamboo-based activated carbon is pretreated before oxidation treatment. The pretreatment includes: washing the bamboo-based activated carbon with deionized water and anhydrous ethanol in sequence, stirring and filtering, repeating the washing with deionized water and anhydrous ethanol once each, and then drying, cooling, crushing and sieving to obtain 20-40 mesh bamboo-based activated carbon.
[0009] Preferably, the oxidation treatment includes: adding 220-260 parts by weight of deionized water based on 50 parts by weight of bamboo-based activated carbon, stirring under ice-water bath conditions; adding 50-70 parts by weight of 67% nitric acid dropwise, while controlling the system temperature to ≤30℃; subsequently adding 40-60 parts by weight of 30% hydrogen peroxide dropwise, while controlling the system temperature to ≤30℃; after the addition is completed, raising the system temperature to 55-65℃ and maintaining the temperature for 3-5 hours; after the reaction is completed, cooling, filtration, water washing, and vacuum drying to obtain oxidized bamboo-based activated carbon.
[0010] Preferably, the preparation of the pre-set system includes: adding 12-18 parts by weight of anhydrous ethanol, 12-18 parts by weight of deionized water and 0.45-0.75 parts by weight of 1-vinyl-3-hexylimidazolium bromide based on 30 parts by weight of oxidized bamboo-based activated carbon, sealing the system and reducing the pressure to 15-25 kPa absolute pressure and maintaining it for 15-25 min, then introducing nitrogen to restore normal pressure and letting it stand for 20-40 min.
[0011] Preferably, the grafting solution is prepared from 7-11 parts by weight of anhydrous ethanol, 7-11 parts by weight of deionized water, 1.5-2.1 parts by weight of 1-vinyl-3-butylimidazolium bromide and 0.09-0.15 parts by weight of ammonium persulfate; the main grafting reaction includes: mixing the pre-prepared filter cake with the grafting solution, purging with nitrogen for 10-20 min, then heating the system to 60-70°C and reacting under nitrogen protection for 40-70 min.
[0012] Preferably, the grafting solution is prepared from 2-4 parts by weight of anhydrous ethanol, 2-4 parts by weight of deionized water, 0.1-0.3 parts by weight of 1-vinyl-3-hexylimidazolium bromide and 0.02-0.04 parts by weight of ammonium persulfate; the grafting reaction includes: after the main grafting reaction for 40-70 min, maintaining 60-70°C and nitrogen protection, adding the grafting solution dropwise over 8-12 min, and continuing the reaction for 120-180 min.
[0013] Preferably, the sodium chloride solution treatment includes: adding the filter cake washed with the ethanol-water mixture into a sodium chloride solution, wherein the sodium chloride solution is prepared by 18-28 parts by weight of sodium chloride and 372-382 parts by weight of deionized water, stirring at 250-350 r / min for 25-35 min at 20-30°C, and then filtering.
[0014] Furthermore, the present invention also provides a bamboo-based activated carbon composite adsorbent material, which is prepared by a method for preparing bamboo-based activated carbon composite adsorbent materials.
[0015] Furthermore, the present invention also provides an application of bamboo-based activated carbon composite adsorbent material in the treatment of high-salt anionic dye wastewater.
[0016] Preferably, the high-salt anionic dye wastewater is anionic reactive dye wastewater containing sodium chloride and / or sodium sulfate. Beneficial effects
[0017] (1) This invention introduces a large number of oxygen-containing functional groups on the surface of bamboo-based activated carbon through nitric acid-hydrogen peroxide treatment, providing anchoring points for subsequent imidazolium monomer grafting. Combined with the vacuum-atmospheric pressure internal pore pre-setting process, hexylimidazolium monomer preferentially enters the mesopore. Then, through the time-sequential regulation of butylimidazolium main grafting and hexylimidazolium supplementary grafting, a synergistic structure of cation sites in the pore, hydrophobic spacer region, and outer stable layer is formed. This not only retains 57.8% of the mesopore volume ratio, but also endows the material with a positive Zeta potential of 21.86 mV. The high salt static adsorption capacity reaches 274.3 mg / g, and the salt background adsorption retention rate reaches 86.7%, effectively solving the problem of adsorption capacity reduction caused by salt competition.
[0018] (2) This invention stabilizes the cation sites by post-treatment with sodium chloride solution and retains the integrity of the grafted layer by low-temperature vacuum drying at 60°C, thereby increasing the dynamic penetration volume of the material to 178.4 BV, reducing the effluent color by 6 times, and achieving a COD removal rate of 85.6%. This solves the problems of easy deactivation of adsorption sites and unstable dynamic mass transfer in the prior art under high salt conditions. It can meet the continuous treatment requirements of anionic reactive dye wastewater containing sodium chloride / sodium sulfate, and the modification process leaves no strong acid or strong alkali residues, making it environmentally friendly. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.
[0020] The raw materials used are as follows: The bamboo-based activated carbon is water treatment grade bamboo granular activated carbon from Xianning Jiazhu New Material Technology Co., Ltd., with a specification of 4-8 mesh. It is crushed and sieved to 20-40 mesh before use; the Reactive Brilliant Blue KN-R used for performance testing is an industrial grade anionic reactive dye, which is not purified before use. Example
[0021] Step 1: Weigh 60g of bamboo-based activated carbon into a beaker, add 600g of deionized water, stir at 300r / min for 30min at 25℃, and then filter. Add 600g of anhydrous ethanol, stir at 300r / min for 30min at 25℃, and then filter. Repeat the above washing with deionized water and anhydrous ethanol once each. Place the filtered bamboo-based activated carbon in a 105℃ forced-air drying oven and dry for 12h. After cooling to 25℃, pulverize and sieve, collecting 20-40 mesh bamboo-based activated carbon for later use. Step 2: Weigh 50g of the bamboo-based activated carbon obtained in Step 1 and place it in a three-necked flask equipped with a condenser and thermometer. Add 240g of deionized water and stir at 300 rpm for 10 min under ice-water bath conditions. Add 60g of 67% nitric acid dropwise over 30 min, keeping the system temperature ≤30℃. Then add 50g of 30% hydrogen peroxide dropwise over 30 min, keeping the system temperature ≤30℃. After the addition is complete, remove the ice-water bath, raise the system temperature to 60℃ and keep it at that temperature for 4 h, stirring at 300 rpm. After the reaction is complete, cool to 25℃, filter, and wash the filter cake five times with 1000g of deionized water. Place the filter cake in an 80℃ vacuum drying oven and dry for 10 h to obtain oxidized bamboo-based activated carbon. Step 3: Weigh 30g of the oxidized bamboo-based activated carbon obtained in Step 2 and place it in a glass reaction flask with a nitrogen inlet. Add 15g of anhydrous ethanol, 15g of deionized water, and 600mg of 1-vinyl-3-hexylimidazolium bromide. After sealing, reduce the pressure inside the flask to 20kPa absolute pressure and maintain this pressure for 20min. Then, purge with nitrogen to restore the pressure to normal and let it stand for 30min. Subsequently, add 240g of anhydrous ethanol and 60g of deionized water. Stir at 120r / min for 90s at 25℃, then immediately filter under vacuum. Continue filtering under 20kPa absolute pressure until the total mass of the filter cake is 45g. Step 4: Transfer the 45g filter cake obtained in Step 3 into a three-necked flask equipped with a condenser, nitrogen inlet, and thermometer. Add a grafting solution prepared with 9g anhydrous ethanol, 9g deionized water, 1800mg 1-vinyl-3-butylimidazolium bromide, and 120mg ammonium persulfate. Purge with nitrogen for 15min at a flow rate of 100mL / min. Then, heat the system to 65℃ and react under nitrogen protection for 50min with a stirring speed of 120r / min. Step 5: After reacting for 50 minutes in Step 4, continue to maintain 65°C and nitrogen protection, and add a grafting solution prepared by 3g anhydrous ethanol, 3g deionized water, 200mg 1-vinyl-3-hexylimidazolium bromide and 30mg ammonium persulfate dropwise over 10 minutes. Continue to react for 150 minutes with a stirring speed of 120 r / min. After the reaction is completed, cool to 25°C. Step Six: Add 400g of an ethanol-water mixture prepared by 200g of anhydrous ethanol and 200g of deionized water to the reaction system obtained in Step Five. Stir at 300r / min for 20min at 25℃ and then filter. Repeat the washing with the ethanol-water mixture 3 times. Then add the filter cake to 400g of sodium chloride solution, which is prepared by 23g of sodium chloride and 377g of deionized water. Stir at 300r / min for 30min at 25℃ and then filter. Subsequently, wash the filter cake 5 times with 1000g of deionized water. Place the filter cake in a vacuum drying oven at 60℃ and dry for 12h to obtain bamboo-based activated carbon composite adsorbent material. Example
[0022] Step 1: Weigh 60g of bamboo-based activated carbon into a beaker, add 600g of deionized water, stir at 300r / min for 30min at 25℃, and then filter. Add 600g of anhydrous ethanol, stir at 300r / min for 30min at 25℃, and then filter. Repeat the above washing with deionized water and anhydrous ethanol once each. Place the filtered bamboo-based activated carbon in a 105℃ forced-air drying oven and dry for 12h. After cooling to 25℃, pulverize and sieve, collecting 20-40 mesh bamboo-based activated carbon for later use. Step 2: Weigh 50g of the bamboo-based activated carbon obtained in Step 1 and place it in a three-necked flask equipped with a condenser and thermometer. Add 220g of deionized water and stir at 300 rpm for 10 min under ice-water bath conditions. Add 50g of 67% nitric acid dropwise over 30 min, keeping the system temperature ≤30℃. Then add 40g of 30% hydrogen peroxide dropwise over 30 min, keeping the system temperature ≤30℃. After the addition is complete, remove the ice-water bath, raise the system temperature to 55℃ and keep it at that temperature for 5 h, stirring at 300 rpm. After the reaction is complete, cool to 25℃, filter, and wash the filter cake five times with 1000g of deionized water. Place the filter cake in an 80℃ vacuum drying oven and dry for 10 h to obtain oxidized bamboo-based activated carbon. Step 3: Weigh 30g of the oxidized bamboo-based activated carbon obtained in Step 2 and place it in a glass reaction flask with a nitrogen inlet. Add 12g of anhydrous ethanol, 12g of deionized water, and 450mg of 1-vinyl-3-hexylimidazolium bromide. After sealing, reduce the pressure inside the flask to 25kPa absolute pressure and maintain this pressure for 15min. Then, purge with nitrogen to restore atmospheric pressure and let it stand for 20min. Subsequently, add 220g of anhydrous ethanol and 50g of deionized water. Stir at 120r / min for 60s at 25℃, then immediately filter under vacuum. Continue filtering under 25kPa absolute pressure until the total mass of the filter cake is 42g. Step 4: Transfer the 42g filter cake obtained in Step 3 into a three-necked flask equipped with a condenser, nitrogen inlet, and thermometer. Add a grafting solution prepared with 7g anhydrous ethanol, 7g deionized water, 1500mg 1-vinyl-3-butylimidazolium bromide, and 90mg ammonium persulfate. Purge with nitrogen for 10 minutes at a flow rate of 80mL / min. Then, heat the system to 60℃ and react under nitrogen protection for 40 minutes with a stirring speed of 120r / min. Step 5: After reacting for 40 minutes in Step 4, continue to maintain 60°C and nitrogen protection, and add a grafting solution prepared by 2g anhydrous ethanol, 2g deionized water, 100mg 1-vinyl-3-hexylimidazolium bromide and 20mg ammonium persulfate dropwise over 8 minutes. Continue to react for 120 minutes with a stirring speed of 120 r / min. After the reaction is completed, cool to 25°C. Step Six: Add 350g of an ethanol-water mixture prepared by 175g of anhydrous ethanol and 175g of deionized water to the reaction system obtained in Step Five. Stir at 300r / min for 20min at 25℃ and then filter. Repeat the washing with the ethanol-water mixture 3 times. Then add the filter cake to 400g of sodium chloride solution, which is prepared by 18g of sodium chloride and 382g of deionized water. Stir at 300r / min for 30min at 25℃ and then filter. Subsequently, wash the filter cake 5 times with 1000g of deionized water. Place the filter cake in a vacuum drying oven at 50℃ and dry for 14h to obtain bamboo-based activated carbon composite adsorbent material. Example
[0023] Step 1: Weigh 60g of bamboo-based activated carbon into a beaker, add 600g of deionized water, stir at 300r / min for 30min at 25℃, and then filter. Add 600g of anhydrous ethanol, stir at 300r / min for 30min at 25℃, and then filter. Repeat the above washing with deionized water and anhydrous ethanol once each. Place the filtered bamboo-based activated carbon in a 105℃ forced-air drying oven and dry for 12h. After cooling to 25℃, pulverize and sieve, collecting 20-40 mesh bamboo-based activated carbon for later use. Step 2: Weigh 50g of the bamboo-based activated carbon obtained in Step 1 and place it in a three-necked flask equipped with a condenser and thermometer. Add 260g of deionized water and stir at 300 rpm for 10 min under ice-water bath conditions. Add 70g of 67% nitric acid dropwise over 30 min, keeping the system temperature ≤30℃. Then add 60g of 30% hydrogen peroxide dropwise over 30 min, keeping the system temperature ≤30℃. After the addition is complete, remove the ice-water bath, raise the system temperature to 65℃ and keep it at that temperature for 3 h, stirring at 300 rpm. After the reaction is complete, cool to 25℃, filter, and wash the filter cake five times with 1000g of deionized water. Place the filter cake in an 80℃ vacuum drying oven and dry for 10 h to obtain oxidized bamboo-based activated carbon. Step 3: Weigh 30g of the oxidized bamboo-based activated carbon obtained in Step 2 and place it in a glass reaction flask with a nitrogen inlet. Add 18g of anhydrous ethanol, 18g of deionized water, and 750mg of 1-vinyl-3-hexylimidazolium bromide. After sealing, reduce the pressure inside the flask to 15kPa absolute pressure and maintain this pressure for 25min. Then, purge with nitrogen to restore the pressure to normal and let it stand for 40min. Subsequently, add 260g of anhydrous ethanol and 70g of deionized water. Stir at 120r / min for 120s at 25℃, then immediately filter under vacuum. Continue filtering under 15kPa absolute pressure until the total mass of the filter cake is 48g. Step 4: Transfer the 48g filter cake obtained in Step 3 into a three-necked flask equipped with a condenser, nitrogen inlet, and thermometer. Add a grafting solution prepared with 11g anhydrous ethanol, 11g deionized water, 2100mg 1-vinyl-3-butylimidazolium bromide, and 150mg ammonium persulfate. Purge with nitrogen for 20 minutes at a flow rate of 120mL / min. Then, heat the system to 70℃ and react under nitrogen protection for 70 minutes with a stirring speed of 120r / min. Step 5: After reacting for 70 minutes in Step 4, continue to maintain 70°C and nitrogen protection, and add a grafting solution prepared by 4 g anhydrous ethanol, 4 g deionized water, 300 mg 1-vinyl-3-hexylimidazolium bromide and 40 mg ammonium persulfate dropwise over 12 minutes. Continue to react for 180 minutes with a stirring speed of 120 r / min. After the reaction is completed, cool to 25°C. Step Six: Add 450g of an ethanol-water mixture prepared by 225g of anhydrous ethanol and 225g of deionized water to the reaction system obtained in Step Five. Stir at 300r / min for 20min at 25℃ and then filter. Repeat the washing with the ethanol-water mixture 3 times. Then add the filter cake to 400g of sodium chloride solution, which is prepared by 28g of sodium chloride and 372g of deionized water. Stir at 300r / min for 30min at 25℃ and then filter. Subsequently, wash the filter cake 5 times with 1000g of deionized water. Place the filter cake in a vacuum drying oven at 70℃ and dry for 10h to obtain bamboo-based activated carbon composite adsorbent material. Example
[0024] Step 1: Weigh 60g of bamboo-based activated carbon into a beaker, add 600g of deionized water, stir at 300r / min for 30min at 25℃, and then filter. Add 600g of anhydrous ethanol, stir at 300r / min for 30min at 25℃, and then filter. Repeat the above washing with deionized water and anhydrous ethanol once each. Place the filtered bamboo-based activated carbon in a 105℃ forced-air drying oven and dry for 12h. After cooling to 25℃, pulverize and sieve, collecting 20-40 mesh bamboo-based activated carbon for later use. Step 2: Weigh 50g of the bamboo-based activated carbon obtained in Step 1 and place it in a three-necked flask equipped with a condenser and thermometer. Add 235g of deionized water and stir at 300 rpm for 10 min under ice-water bath conditions. Add 55g of 67% nitric acid dropwise over 30 min, keeping the system temperature ≤30℃. Then add 45g of 30% hydrogen peroxide dropwise over 30 min, keeping the system temperature ≤30℃. After the addition is complete, remove the ice-water bath, raise the system temperature to 60℃ and keep it at that temperature for 4.5 h, stirring at 300 rpm. After the reaction is complete, cool to 25℃, filter, and wash the filter cake five times with 1000g of deionized water. Place the filter cake in an 80℃ vacuum drying oven and dry for 10 h to obtain oxidized bamboo-based activated carbon. Step 3: Weigh 30g of the oxidized bamboo-based activated carbon obtained in Step 2 and place it in a glass reaction flask with a nitrogen inlet. Add 16g of anhydrous ethanol, 16g of deionized water, and 700mg of 1-vinyl-3-hexylimidazolium bromide. After sealing, reduce the pressure inside the flask to 20kPa absolute pressure and maintain this pressure for 22min. Then, purge with nitrogen to restore atmospheric pressure and let it stand for 35min. Subsequently, add 250g of anhydrous ethanol and 65g of deionized water. Stir at 120r / min for 100s at 25℃, then immediately filter under vacuum. Continue filtering under 20kPa absolute pressure until the total mass of the filter cake is 44g. Step 4: Transfer the 44g filter cake obtained in Step 3 into a three-necked flask equipped with a condenser, nitrogen inlet, and thermometer. Add a grafting solution prepared with 8g anhydrous ethanol, 8g deionized water, 1650mg 1-vinyl-3-butylimidazolium bromide, and 110mg ammonium persulfate. Purge with nitrogen for 15 minutes at a flow rate of 100mL / min. Then, heat the system to 65℃ and react under nitrogen protection for 60 minutes with a stirring speed of 120r / min. Step 5: After reacting for 60 minutes in Step 4, continue to maintain 65°C and nitrogen protection, and add a grafting solution prepared by 3g anhydrous ethanol, 3g deionized water, 150mg 1-vinyl-3-hexylimidazolium bromide and 25mg ammonium persulfate dropwise over 10 minutes. Continue to react for 135 minutes with a stirring speed of 120 r / min. After the reaction is completed, cool to 25°C. Step Six: Add 400g of an ethanol-water mixture prepared by 200g of anhydrous ethanol and 200g of deionized water to the reaction system obtained in Step Five. Stir at 300r / min for 20min at 25℃ and then filter. Repeat the washing with the ethanol-water mixture 3 times. Then add the filter cake to 400g of sodium chloride solution, which is prepared by 22g of sodium chloride and 378g of deionized water. Stir at 300r / min for 30min at 25℃ and then filter. Subsequently, wash the filter cake 5 times with 1000g of deionized water. Place the filter cake in a vacuum drying oven at 60℃ and dry for 12h to obtain bamboo-based activated carbon composite adsorbent material. Example
[0025] Step 1: Weigh 60g of bamboo-based activated carbon into a beaker, add 600g of deionized water, stir at 300r / min for 30min at 25℃, and then filter. Add 600g of anhydrous ethanol, stir at 300r / min for 30min at 25℃, and then filter. Repeat the above washing with deionized water and anhydrous ethanol once each. Place the filtered bamboo-based activated carbon in a 105℃ forced-air drying oven and dry for 12h. After cooling to 25℃, pulverize and sieve, collecting 20-40 mesh bamboo-based activated carbon for later use. Step 2: Weigh 50g of the bamboo-based activated carbon obtained in Step 1 and place it in a three-necked flask equipped with a condenser and thermometer. Add 250g of deionized water and stir at 300 rpm for 10 min under ice-water bath conditions. Add 65g of 67% nitric acid dropwise over 30 min, keeping the system temperature ≤30℃. Then add 55g of 30% hydrogen peroxide dropwise over 30 min, keeping the system temperature ≤30℃. After the addition is complete, remove the ice-water bath, raise the system temperature to 62℃ and keep it at that temperature for 3.5 h, stirring at 300 rpm. After the reaction is complete, cool to 25℃, filter, and wash the filter cake five times with 1000g of deionized water. Place the filter cake in an 80℃ vacuum drying oven and dry for 10 h to obtain oxidized bamboo-based activated carbon. Step 3: Weigh 30g of the oxidized bamboo-based activated carbon obtained in Step 2 and place it in a glass reaction flask with a nitrogen inlet. Add 14g of anhydrous ethanol, 14g of deionized water, and 500mg of 1-vinyl-3-hexylimidazolium bromide. After sealing, reduce the pressure inside the flask to 18kPa absolute pressure and maintain this pressure for 18min. Then, purge with nitrogen to restore atmospheric pressure and let it stand for 25min. Subsequently, add 235g of anhydrous ethanol and 55g of deionized water. Stir at 120r / min for 80s at 25℃, then immediately filter under vacuum. Continue filtering under 18kPa absolute pressure until the total mass of the filter cake is 46g. Step 4: Transfer the 46g filter cake obtained in Step 3 into a three-necked flask equipped with a condenser, nitrogen inlet, and thermometer. Add a grafting solution prepared with 10g anhydrous ethanol, 10g deionized water, 2000mg 1-vinyl-3-butylimidazolium bromide, and 140mg ammonium persulfate. Purge with nitrogen for 15min at a flow rate of 100mL / min. Then, heat the system to 66℃ and react under nitrogen protection for 45min with a stirring speed of 120r / min. Step 5: After reacting for 45 minutes in Step 4, continue to maintain 66°C and nitrogen protection, and add a grafting solution prepared by 3g anhydrous ethanol, 3g deionized water, 280mg 1-vinyl-3-hexylimidazolium bromide and 35mg ammonium persulfate dropwise over 10 minutes. Continue to react for 165 minutes with a stirring speed of 120 r / min. After the reaction is completed, cool to 25°C. Step Six: Add 420g of an ethanol-water mixture prepared by 210g of anhydrous ethanol and 210g of deionized water to the reaction system obtained in Step Five. Stir at 300r / min for 20min at 25℃ and then filter. Repeat the washing with the ethanol-water mixture 3 times. Then add the filter cake to 400g of sodium chloride solution, which is prepared by 25g of sodium chloride and 375g of deionized water. Stir at 300r / min for 30min at 25℃ and then filter. Subsequently, wash the filter cake 5 times with 1000g of deionized water. Place the filter cake in a vacuum drying oven at 65℃ and dry for 11h to obtain bamboo-based activated carbon composite adsorbent material.
[0026] Comparative Example 1: The difference from Example 1 is that: in step two, 67% nitric acid and 30% hydrogen peroxide are not added dropwise; in step two, only 50g of bamboo-based activated carbon obtained in step one is added to 350g of deionized water, stirred at 300r / min for 4h at 60℃, cooled to 25℃ and filtered, and the filter cake is washed 5 times with 1000g of deionized water. The filter cake is then placed in an 80℃ vacuum drying oven and dried for 10h; the remaining conditions are the same as in Example 1.
[0027] Comparative Example 2: The difference from Example 1 is that in step three, the pressure inside the bottle is not reduced to 20 kPa absolute pressure and maintained for 20 min. Instead, oxidized bamboo-based activated carbon, 15 g of anhydrous ethanol, 15 g of deionized water and 600 mg of 1-vinyl-3-hexylimidazolium bromide are mixed and allowed to stand for 50 min under normal pressure and nitrogen atmosphere; the other conditions are the same as in Example 1.
[0028] Comparative Example 3: The difference from Example 1 is that in step three, after nitrogen gas is introduced to restore normal pressure and the mixture is allowed to stand for 30 minutes, instead of adding 240g of anhydrous ethanol and 60g of deionized water for 90s of stirring and elution, the mixture is directly filtered under absolute pressure of 20kPa until the total mass of the filter cake is 45g; the other conditions are the same as in Example 1.
[0029] Comparative Example 4: The difference from Example 1 is that 600 mg of 1-vinyl-3-hexylimidazolium bromide is not added in step three, and the amount of 1-vinyl-3-hexylimidazolium bromide in step five is adjusted from 200 mg to 800 mg, so that the total amount of 1-vinyl-3-hexylimidazolium bromide remains unchanged; the other conditions are the same as in Example 1.
[0030] Comparative Example 5: The difference from Example 1 is that the amount of 1-vinyl-3-hexylimidazolium bromide in step three is adjusted from 600 mg to 800 mg, and 200 mg of 1-vinyl-3-hexylimidazolium bromide is not added in step five, so that the total amount of 1-vinyl-3-hexylimidazolium bromide remains unchanged; the other conditions are the same as in Example 1.
[0031] Comparative Example 6: The difference from Example 1 is that in step four, 1800 mg of 1-vinyl-3-butylimidazolium bromide is replaced with 2018 mg of 1-vinyl-3-hexylimidazolium bromide. After the replacement, the molar amount of imidazolium monomer in step four is the same as the molar amount of 1-vinyl-3-butylimidazolium bromide in step four of Example 1; the other conditions are the same as in Example 1.
[0032] Comparative Example 7: The difference from Example 1 is that in step six, the filter cake is not added to the 400g sodium chloride solution for treatment. Instead, after completing three washings with an ethanol-water mixture, the filter cake is directly washed five times with 1000g deionized water. The other conditions are the same as in Example 1.
[0033] Comparative Example 8: The difference from Example 1 is that the vacuum drying temperature of the filter cake in step six is adjusted from 60°C to 120°C, while the vacuum drying time remains 12 hours; the other conditions are the same as in Example 1.
[0034] Performance testing: All samples were dried in a vacuum drying oven at 60℃ for 6 hours before testing, cooled to 25℃, and then sealed for storage. Except for the samples used for Zeta potential testing, which required a small amount to be ground and sieved through a 200-mesh sieve, all other tests used samples with 20-40 mesh particles. Before dynamic column testing, 4.00 g of sample was weighed and added to 100 mL of deionized water for 12 hours. Then, it was wet-packed into a glass adsorption column with an inner diameter of 10 mm and a column length of 200 mm. 5 mm of quartz sand was placed on the top and bottom of the bed, and the height of the adsorbent bed was controlled to be 85 ± 5 mm. Deionized water was first circulated at 5.0 mL / min for 30 minutes to remove air bubbles from the bed, and then the flow was switched to simulate high-salt anionic dye wastewater. The simulated high-salt anionic dye wastewater was prepared using 300 mg / L Reactive Brilliant Blue KN-R, 5.0 g / L sodium chloride, and 30.0 g / L sodium sulfate, with deionized water used. The initial pH was adjusted to 7.0 ± 0.1, and the temperature was controlled at 25 ± 1℃.
[0035] Specific surface area, total pore volume, and mesopore volume ratio: Tested according to GB / T 7702.20-2025 "Test methods for coal-based granular activated carbon - Part 20: Determination of pore volume and specific surface area" and in conjunction with GB / T 19587-2017 "Determination of specific surface area of solid substances by gas adsorption BET method".
[0036] Zeta potential: Tested according to GB / T 32668-2016 "General Rules for Electrophoresis Method of Zeta Potential Analysis of Colloidal Particles".
[0037] High-salt static adsorption capacity and salt background adsorption retention rate: 0.050 g of each sample was weighed and added to a 250 mL stoppered conical flask, followed by 100 mL of simulated high-salt anionic dye wastewater. The mixture was shaken at 180 r / min for 240 min in a constant-temperature shaker at 25 ± 1 °C. After adsorption, the supernatant was collected, centrifuged at 6000 r / min for 5 min, and then filtered through a 0.45 μm aqueous filter membrane. The remaining concentration of Reactive Brilliant Blue KN-R was measured at 595 nm. A dye aqueous solution with the same dye concentration but without sodium chloride and sodium sulfate was used as a salt-free adsorption control. The adsorption was calculated using the formula q = (C0 - C...).t The adsorption capacity is calculated using V / m, where q is the adsorption capacity in mg / g; C0 is the initial dye concentration in mg / L; C t V represents the dye concentration after adsorption, in mg / L; V represents the solution volume, in L; and m represents the adsorbent mass, in g. The salt background adsorption retention rate is calculated by multiplying the ratio of the high-salt static adsorption amount to the salt-free static adsorption amount by 100%.
[0038] Dynamic breakthrough volume: The above-described wet-packed glass adsorption column was used for testing. High-salt anionic dye wastewater was simulated to pass through the adsorption column from top to bottom at a rate of 5.0 mL / min, with the column temperature maintained at 25±1℃. Effluent was collected every 20 bed volumes, and the absorbance at 595 nm was measured and converted to calculate the dye concentration in the effluent. The breakthrough point was defined as C / C0 = 0.05, where C is the dye concentration in the effluent and C0 is the dye concentration in the influent. The dynamic breakthrough volume was calculated by dividing the cumulative effluent volume at the breakthrough point by the bed volume, expressed in BV.
[0039] Effluent color and COD removal rate: The mixed effluent from the start of the simulated high-salt anionic dye wastewater introduction to the breakthrough point in the dynamic column test was taken as the effluent sample. The influent was the same batch of simulated high-salt anionic dye wastewater. The effluent color was determined according to HJ 1182-2021 "Determination of Color in Water - Dilution Factor Method", and the result is expressed as a dilution factor. COD was determined according to HJ828-2017 "Determination of Chemical Oxygen Demand in Water - Dichromate Method". Before the test, both the influent and effluent samples were diluted to 5 times their original volume to ensure that the chloride ion concentration after dilution was below 1000 mg / L, and mercuric sulfate solution was added to mask chloride ion interference according to the standard requirements. The COD removal rate was calculated by dividing the difference between the influent COD and the effluent COD by the influent COD and then multiplying by 100%.
[0040] Table 1 Performance Test Results sample <![CDATA[BET specific surface area / (m 2 / g)]]> <![CDATA[Total pore volume / (cm 3 / g)]]> Mesopore volume percentage / % Zeta potential (mV) Static adsorption capacity at high salt concentrations (mg / g) Salt background adsorption retention rate / % Dynamic penetration volume (BV) Water color (in times) COD removal rate / % Example 1 752.6 0.486 57.8 21.86 274.3 86.7 178.4 6 85.6 Example 2 821.4 0.527 53.4 16.94 221.6 78.5 136.7 14 77.8 Example 3 668.9 0.432 61.5 24.18 262.8 84.3 160.5 8 83.9 Example 4 781.7 0.503 56.1 19.72 248.4 82.1 151.2 10 81.4 Example 5 704.3 0.462 60.2 23.41 268.7 85.2 166.9 7 84.6 Comparative Example 1 946.8 0.612 44.3 6.28 98.7 55.4 52.6 42 58.9 Comparative Example 2 805.9 0.515 50.8 15.37 181.9 68.6 92.8 26 70.7 Comparative Example 3 624.7 0.397 48.1 25.06 239.5 73.4 83.5 31 68.5 Comparative Example 4 794.6 0.509 53.5 18.14 205.3 74.8 109.4 22 74.6 Comparative Example 5 736.2 0.471 57.4 17.63 214.7 76.9 121.8 19 76.5 Comparative Example 6 683.5 0.438 56.7 20.34 228.9 78.2 103.6 24 73.2 Comparative Example 7 766.8 0.492 55.6 23.02 235.8 63.5 96.7 28 69.9 Comparative Example 8 729.4 0.455 52.2 13.88 167.4 67.1 82.4 33 66.8 As shown in Table 1, Comparative Example 1, which was not treated with nitric acid and hydrogen peroxide, had a BET specific surface area and total pore volume of 946.8 m². 2 / g and 0.612cm 3 / g, but its Zeta potential is only 6.28mV. The static adsorption capacity, salt background adsorption retention rate and dynamic breakthrough volume are 98.7mg / g, 55.4% and 52.6BV, respectively. This indicates that unoxidized bamboo-based activated carbon is difficult to effectively fix subsequent imidazolium monomers. Relying solely on the original pore structure cannot meet the continuous treatment requirements of high-salt anionic dye wastewater.
[0041] In Comparative Example 2, after removing the vacuum-atmospheric pressure inner pore pre-setting, the dynamic penetration volume increased to 92.8 BV, but was still significantly lower than that of Example 1. This indicates that simply contacting the monomer with the oxidized bamboo-based activated carbon at atmospheric pressure is insufficient to fully form the cation adsorption sites distributed within the pores.
[0042] When the short-time ethanol-water elution step was omitted in Comparative Example 3, the Zeta potential rose to 25.06 mV, the static adsorption capacity of high salt reached 239.5 mg / g, but the dynamic breakthrough volume was only 83.5 BV, and the effluent color was 31 times higher. This indicates that although monomer enrichment at the outer surface or orifice can improve the apparent positive charge, it is not conducive to the diffusion and utilization of dye molecules under continuous flow conditions.
[0043] Comparative Examples 4 and 5 added 1-vinyl-3-hexylimidazolium bromide in the later or earlier stages, respectively, and their dynamic penetration volumes were only 109.4 BV and 121.8 BV, respectively, both lower than that of Example 1. This indicates that the pre-placement of the inner pores in the earlier stage and the grafting in the later stage need to be coordinated in time to maintain the stability of the adsorption sites in the pores and the outer structure at the same time.
[0044] In Comparative Example 6, after replacing all the main grafted monomers with hexylimidazolium monomers, the static adsorption capacity for high salt was 228.9 mg / g, but the dynamic breakthrough volume decreased to 103.6 BV. It is speculated that an excessively high proportion of longer alkyl chains will increase the hydrophobic occupancy of pores and the mass transfer resistance.
[0045] In Comparative Example 7, the Zeta potential remained at 23.02 mV after omitting sodium chloride posttreatment, but the salt background adsorption retention rate dropped to 63.5%, indicating that the cation sites without salt background stabilization treatment were not effectively retained in a high-salt environment.
[0046] The adsorption parameters of Comparative Example 8 decreased after vacuum drying at 120℃, indicating that excessively high drying temperatures may not be conducive to the effective preservation of the grafted layer.
[0047] Compared to the comparative examples above, the BET specific surface area of Example 1 remained at 752.6 m². 2 The biomass of the activated carbon (bamboo-based activated carbon) has a mesopore volume ratio of 57.8% and achieves a positive Zeta potential of 21.86 mV. Its high-salt static adsorption capacity, salt background adsorption retention rate, and dynamic breakthrough volume reach 274.3 mg / g, 86.7%, and 178.4 BV, respectively. The effluent color is reduced by 6 times, and the COD removal rate is 85.6%. This indicates that the present invention, through the synergistic arrangement of the pore structure of oxidized bamboo-based activated carbon, the butylimidazolium cation host site, and the hexylimidazolium hydrophobic spacer region, effectively balances anionic dye adsorption, salt competition inhibition, and dynamic mass transfer stability, thus demonstrating good continuous treatment performance for high-salt anionic dye wastewater.
[0048] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.
Claims
1. A method for preparing a bamboo-based activated carbon composite adsorbent material, characterized in that, Includes the following steps: (1) Bamboo-based activated carbon was treated with nitric acid and hydrogen peroxide to obtain oxidized bamboo-based activated carbon; (2) The oxidized bamboo-based activated carbon, ethanol, water and 1-vinyl-3-hexylimidazolium bromide were mixed and kept under reduced pressure, then nitrogen was introduced to restore normal pressure and allowed to stand to obtain the pre-set system; (3) Add an ethanol-water mixture to the pre-prepared system for elution and filtration to obtain a pre-prepared filter cake; (4) The pre-prepared filter cake is mixed with a grafting solution containing 1-vinyl-3-butylimidazolium bromide and ammonium persulfate, and the main grafting reaction is carried out under nitrogen protection and heating conditions; (5) Add a supplementary grafting solution containing 1-vinyl-3-hexylimidazolium bromide and ammonium persulfate to the system after the main grafting reaction, and continue the supplementary grafting reaction; (6) After the grafting reaction is completed, the bamboo-based activated carbon composite adsorbent is obtained by washing with a mixture of ethanol and water, treating with sodium chloride solution, washing with water and vacuum drying at 50-70℃.
2. The preparation method of the bamboo-based activated carbon composite adsorbent material according to claim 1, characterized in that, The bamboo-based activated carbon is pretreated before oxidation treatment. The pretreatment includes: washing the bamboo-based activated carbon with deionized water and anhydrous ethanol in sequence, stirring and filtering, repeating the washing with deionized water and anhydrous ethanol once each, and then drying, cooling, crushing and sieving to obtain 20-40 mesh bamboo-based activated carbon.
3. The preparation method of the bamboo-based activated carbon composite adsorbent material according to claim 1, characterized in that, The oxidation treatment includes: adding 220-260 parts by weight of deionized water based on 50 parts by weight of bamboo-based activated carbon, stirring under ice-water bath conditions; adding 50-70 parts by weight of 67% nitric acid dropwise, while controlling the system temperature to ≤30℃; then adding 40-60 parts by weight of 30% hydrogen peroxide dropwise, while controlling the system temperature to ≤30℃; after the addition is complete, raising the system temperature to 55-65℃ and maintaining the temperature for 3-5 hours; after the reaction is complete, cooling, filtration, water washing, and vacuum drying are performed to obtain oxidized bamboo-based activated carbon.
4. The preparation method of the bamboo-based activated carbon composite adsorbent material according to claim 1, characterized in that, The preparation of the pre-set system includes: adding 12-18 parts by weight of anhydrous ethanol, 12-18 parts by weight of deionized water and 0.45-0.75 parts by weight of 1-vinyl-3-hexylimidazolium bromide based on 30 parts by weight of oxidized bamboo-based activated carbon, sealing the system and reducing the pressure to 15-25 kPa absolute pressure and maintaining it for 15-25 min, then introducing nitrogen to restore normal pressure and letting it stand for 20-40 min.
5. The preparation method of the bamboo-based activated carbon composite adsorbent material according to claim 1, characterized in that, The grafting solution is prepared from 7-11 parts by weight of anhydrous ethanol, 7-11 parts by weight of deionized water, 1.5-2.1 parts by weight of 1-vinyl-3-butylimidazolium bromide and 0.09-0.15 parts by weight of ammonium persulfate; the main grafting reaction includes: mixing the pre-prepared filter cake with the grafting solution, purging with nitrogen for 10-20 min, then heating the system to 60-70°C and reacting under nitrogen protection for 40-70 min.
6. The preparation method of the bamboo-based activated carbon composite adsorbent material according to claim 1, characterized in that, The grafting solution is prepared from 2-4 parts by weight of anhydrous ethanol, 2-4 parts by weight of deionized water, 0.1-0.3 parts by weight of 1-vinyl-3-hexylimidazolium bromide and 0.02-0.04 parts by weight of ammonium persulfate; the grafting reaction includes: after the main grafting reaction for 40-70 min, maintaining 60-70℃ and nitrogen protection, adding the grafting solution dropwise over 8-12 min, and continuing the reaction for 120-180 min.
7. The preparation method of the bamboo-based activated carbon composite adsorbent material according to claim 1, characterized in that, The sodium chloride solution treatment includes: adding the filter cake washed with the ethanol-water mixture to the sodium chloride solution, which is prepared by 18-28 parts by weight of sodium chloride and 372-382 parts by weight of deionized water, stirring at 250-350 r / min for 25-35 min at 20-30℃, and then filtering.
8. A bamboo-based activated carbon composite adsorbent material, characterized in that, It is prepared by the preparation method according to any one of claims 1-7.
9. The application of the bamboo-based activated carbon composite adsorbent material according to claim 8 in the treatment of high-salt anionic dye wastewater.
10. The application according to claim 9, characterized in that, The high-salt anionic dye wastewater is anionic reactive dye wastewater containing sodium chloride and / or sodium sulfate.