A hydrophobic polyionic liquid-ACF composite adsorption material and its preparation

Abstract

The present invention discloses a polyionic liquid-ACF composite adsorption material and a preparation method thereof, wherein activated carbon fiber (ACF) is used as a substrate, and a polyionic liquid is loaded on the ACF. The preparation method comprises the following steps: adding the activated ACF to a mixed solution of an alkenyl silane coupling agent and methanol (volume ratio 1:20), filtering after a hydrothermal reaction at 50°C for 24 hours, and vacuum drying the filter residue at 50°C to obtain a silanized ACF; mixing the silanized ACF with an alkenyl-containing halogen anion ionic liquid monomer according to different mass percentages, and using ammonium persulfate as an initiator in a water system to initiate a polymerization reaction; after the polymerization reaction is completed, adding PF6ˉ to carry out anion exchange reaction, replacing the halogen anion with a hydrophobic PF6ˉ, and washing and freeze-drying to obtain a polyionic liquid-ACF composite adsorption material. The composite adsorption material enhances the hydrophobicity of ACF, has an unsaturated C=C double bond and an aromatic ring in the structure, and improves the adsorption effect of ACF on polycyclic aromatic hydrocarbons and aromatic heterocyclic compounds with larger molecular weight.

Description

Technical Field

[0001] The invention relates to the field of new materials, and in particular to a polyionic liquid-ACF composite adsorption material and a preparation method thereof. Background Art

[0002] Activated carbon fiber (ACF) is one of the third generation of carbon materials after the first generation of carbon materials (charcoal) and the second generation of carbon materials (graphite, carbon black). 2 / g, with a well-developed microporous structure, small pore size and narrow distribution, it is an adsorption material with large adsorption capacity, fast adsorption and desorption speed, and easy regeneration. It can also be processed into various forms such as cloth, felt, paper, and rope according to the needs of actual applications. At present, ACF has been widely used in the fields of air purification and wastewater treatment. ACF has good adsorption capacity for volatile organic compounds (VOCs) such as benzene, xylene, acetone, etc., as well as dye wastewater, and is easy to recycle and has a long cycle life. However, since the surface of ACF contains a large number of hydrophilic groups such as -OH, -COOH, etc., water molecules compete with the adsorbate during the adsorption process, and for some organic substances with larger molecular weights such as dyes, the adsorption rate and saturated adsorption capacity of ACF are limited.

[0003] Polyionic liquids (PILs) are a special type of polymer compound that possesses the excellent properties of both ionic liquids and polymers. The functional groups contained in the PILs structure interact with organic molecules in a variety of ways, including electrostatic forces, van der Waals forces, hydrogen bonding forces, hydrophobic interactions, and π-π forces. Therefore, PILs exhibit good adsorption effects on many organic substances, especially organic adsorbents with ionic groups or aromatic rings in their molecular structures, such as phenols and ionic dyes. Therefore, by compounding the functionalized PILs with ACF using a silane coupling agent, the hydrophobicity of ACF can be enhanced, and the adsorption performance of ACF can be improved. This new type of polyionic liquid-ACF adsorbent can not only be used for the adsorption treatment of azo dye wastewater, but can also be used in the adsorption of VOCs, CO2 capture, organic solvent recovery, and other fields. Summary of the invention

[0004] The purpose of the present invention is to provide a novel polyionic liquid-ACF composite adsorption material.

[0005] Another object of the present invention is to provide a method for preparing a novel polyionic liquid-ACF composite adsorption material.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The invention provides a novel polyionic liquid-ACF composite adsorption material, which uses a silane coupling agent as a cross-linking agent and loads the polyionic liquid on activated carbon fibers through an ionic liquid polymerization reaction in a water system.

[0008] The preparation method of a novel polyionic liquid-ACF composite adsorption material described in the present invention comprises the following steps:

[0009] (1) Wash the ACF with deionized water, anhydrous ethanol, and acetone several times in sequence, and vacuum dry it at 100°C for 24 h to obtain the activated ACF;

[0010] (2) adding a mixed solution of a silane coupling agent and methanol (volume ratio 1:(15-20)) to the activated ACF obtained in step (1), wherein the volume amount of the mixed liquid of the silane coupling agent and methanol is 8-15 mL / g (ACF), and performing a hydrothermal reaction at 40-60° C. for 24-48 h, and obtaining a silanized ACF after post-treatment;

[0011] (3) Add 5-25 wt% (ACF) of vinyl imidazole dicationic ionic liquid monomer to the silanized ACF obtained in step (2), 15-25 mL / g (ACF) of deionized water as solvent, and reflux reaction for 24 h with ammonium persulfate as initiator under nitrogen conditions at 80-90° C. to obtain a halogen anion polyionic liquid-ACF suspension;

[0012] (4) adding hexafluorophosphate (the molar ratio of hexafluorophosphate to ionic liquid monomer is 2.2:1) to the polyionic liquid-ACF suspension of halogen anions obtained in step (3), and reacting at 50-60° C. for 12-24 hours to obtain a polyionic liquid-ACF composite adsorption material;

[0013] (5) In step (3), ammonium persulfate is prepared into a 0.01 g / mL aqueous solution, and the amount used is 5% of the weight of the monomer. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 SEM showing the polyionic liquid-ACF composite adsorbent material.

[0015] Figure 2 It represents the DFT pore size distribution of polyionic liquid-ACF composite adsorbent material.

[0016] Figure 3 X-ray photoelectron spectrum showing polyionic liquid-ACF composite adsorbent

[0017] Figure 4 The adsorption performance of polyionic liquid-ACF adsorbent material on the original pH reactive brilliant red RR24 aqueous solution

[0018] Figure 5 Adsorption performance of polyionic liquid-ACF adsorption material for pH=2 reactive brilliant red RR24 aqueous solution DETAILED DESCRIPTION

[0019] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments. Without departing from the scope of the above-mentioned purpose, changes in implementation are all included in the technical scope of the present invention.

[0020] Embodiment 1:

[0021] ACF was washed with water and anhydrous ethanol several times, and then dried at 100℃ in vacuum for 24h. 1.0g ACF was added to 10mL of a mixed solution of vinyltrimethoxysilane and methanol (volume ratio 1:20), and hydrothermally reacted at 50℃ for 24h, then filtered, and the residue was washed with acetone, methanol and water in turn, and then dried in a 50℃ constant temperature drying oven for later use. In a three-necked flask, 1 g of silane-treated ACF and [VC4(Vim)2]Cl2 (mass ratio with ACF 5%:1) were added in sequence, and 15 mL of water was added as solvent. After 0.5 mL of 0.01 g / mL APS aqueous solution was added dropwise at 80°C, the mixture was refluxed at 80°C for 24 h, then the temperature was lowered to 50°C, 0.057 g of NH4PF6 was added, and the mixture was refluxed at 50°C for 12 h. The reaction liquid was filtered, and the residue was washed with water and ethanol several times in sequence, and then dried in a constant temperature drying oven at 100°C for 24 h to obtain a Poly-[VC4(Vim)2][PF6]2(5%)-ACF composite adsorption material.

[0022] The molecular structure of [VC4(Vim)2]Cl2 is as follows:

[0023]

[0024] Embodiment 2:

[0025] ACF was washed with water and anhydrous ethanol several times, and then dried at 100℃ in vacuum for 24h. 1.0g ACF was added to 10mL of a mixed solution of vinyltrimethoxysilane and methanol (volume ratio 1:20), and hydrothermally reacted at 50℃ for 24h, then filtered, and the residue was washed with acetone, methanol and water in turn, and then dried in a 50℃ constant temperature drying oven for later use. In a three-necked flask, 1 g of silane-treated ACF and [VC4(Vim)2]Cl2 (mass ratio with ACF 20%:1) were added in sequence, and 20 mL of water was added as solvent. After 2 mL of 0.01 g / mL APS aqueous solution was added dropwise at 80°C, the mixture was refluxed at 80°C for 24 h, then the temperature was lowered to 50°C, 0.228 g of NH4PF6 was added, and the mixture was refluxed at 50°C for 12 h. The reaction liquid was filtered, and the residue was washed with water and ethanol several times in sequence, and then dried in a constant temperature drying oven at 100°C for 24 h to obtain a Poly-[VC4(Vim)2][PF6]2(20%)-ACF composite adsorption material.

[0026] Embodiment 3:

[0027] ACF was washed with water and anhydrous ethanol several times, and then dried at 100℃ in vacuum for 24h. 1.0g ACF was added to 15mL of a mixed solution of vinyltrimethoxysilane and methanol (volume ratio 1:20), and hydrothermally reacted at 50℃ for 24h, then filtered, and the residue was washed with acetone, methanol and water in turn, and then dried in a 50℃ constant temperature drying oven for later use. In a three-necked flask, 1 g of silane-treated ACF and [C4(Vim)2]Br2 (mass ratio to ACF 20%:1) were added in sequence, and 20 mL of water was added as solvent. After 2 mL of 0.01 g / mL APS aqueous solution was added dropwise at 80°C, the mixture was refluxed at 85°C for 36 hours, then cooled to 50°C, 0.228 g of NH4PF6 was added, and the mixture was refluxed at 50°C for 12 hours. The reaction liquid was filtered, and the residue was washed with water and ethanol several times in sequence, and then dried in a constant temperature drying oven at 100°C for 24 hours to obtain a Poly-[C4(Vim)2][PF6]2(20%)-ACF composite adsorption material.

[0028] The structural diagram of [C4(Vim)2]Br2 is as follows:

[0029]

[0030] Embodiment 4:

[0031] 0.15 g of the polyionic liquid-ACF adsorbent material prepared in Example 3 was placed in 50 mL of 25 mg / L active brilliant red azo dye RR24, the initial pH was the original solution pH, the water bath constant temperature oscillator was set to an oscillation frequency of 150 r / min and a temperature of 30°C, and the absorbance change of the RR24 aqueous solution at 510 nm was tested by a UV-visible spectrophotometer, and the change of the residual concentration of RR24 in the RR24 aqueous solution within 0 to 40 min was calculated in combination with the standard working curve. The results are shown as follows: Figure 4 shown.

[0032] Embodiment 5:

[0033] 0.15 g of the polyionic liquid-ACF adsorbent material prepared in Example 2 was placed in 50 mL of 10 mg / L active brilliant red azo dye RR24, the initial pH was the original solution, the water bath constant temperature oscillator was set to an oscillation frequency of 150 r / min and a temperature of 30°C, and the absorbance change of the RR24 aqueous solution at 510 nm was tested by a UV-visible spectrophotometer, and the change of the residual concentration of RR24 in the RR24 aqueous solution within 0 to 50 min was calculated in combination with the standard working curve. The results are shown as follows: Figure 5 shown.

Claims

1. A hydrophobic polyionic liquid-ACF composite adsorption material, characterized in that: Activated carbon fiber (ACF) is used as a substrate, and a polyimidazolium dicationic ionic liquid is loaded on the substrate through an alkenyl silane coupling agent as a crosslinking agent. The main chain of the polyionic liquid has an imidazole dicationic repeating structural unit, and the main chain contains unsaturated alkenyl-C n H 2n-1 , anion is PF6 - The general structure formula of the vinyl imidazole dicationic ionic liquid monomer is as follows: Where X = Cl, Br, I.

2. The method for preparing a hydrophobic polyionic liquid-ACF composite adsorption material according to claim 1, characterized in that: The following steps are involved: Step 1: Wash the ACF with deionized water, anhydrous ethanol, and acetone for several times, and vacuum dry it at 100°C for 24 hours to obtain the activated ACF; Step 2: using an alkenyl silane coupling agent as a cross-linking agent and methanol as a solvent, the activated ACF is subjected to silanization treatment by a hydrothermal reaction method, specifically, a mixed solution of a silane coupling agent and methanol is added to the activated ACF obtained in step 1, and a hydrothermal reaction is performed; Step 3: adding vinyl imidazole dicationic ionic liquid monomer to the silanized ACF, using deionized water as solvent and ammonium persulfate as initiator to initiate polymerization under constant temperature reflux conditions; Step 4: After the polymerization reaction is completed, hexafluorophosphate is added to the polymerization system to carry out anion exchange reaction to obtain a hydrophobic polyionic liquid-ACF composite adsorption material.

3. The preparation method according to claim 2, characterized in that In step 2, the alkenyl silane coupling agent includes alkenyloxy silane or alkenyl chloride silane.

4. The preparation method according to claim 3, characterized in that: The alkenyloxy silanes include vinyltrimethoxysilane, triethoxyvinylsilane, diethoxymethylvinylsilane, allyltriethoxysilane, allyltrimethoxysilane, trimethoxy(7-octen-1-yl)silane, triisopropoxy(vinyl)silane, dimethylethoxyvinylsilane, dimethoxymethylvinylsilane or vinyltri(2-methoxyethoxy)silane; the alkenylchloro silanes include allyldimethylsilyl chloride, dimethylvinylchlorosilane or trichlorovinylsilane.

5. The preparation method according to claim 3, characterized in that: In step 2, the amount of the mixed solution of silane coupling agent and methanol is 8-15 mL / g ACF, the volume ratio of silane coupling agent to methanol is 1:(15-20), the hydrothermal reaction temperature is 40-60° C., the reaction time is 24 h, and after the reaction solution is filtered, the filter residue is washed with acetone, methanol and deionized water in turn, and then vacuum dried at 50° C. for 24 h to obtain silanized ACF.

6. The preparation method according to claim 3, characterized in that: In step 3, the mass ratio of the vinyl imidazole dicationic ionic liquid monomer to the silylated ACF is (5% to 25%): 1, the amount of deionized water solvent is 15 to 25 mL / g ACF, the amount of ammonium persulfate is 5wt% of the amount of the vinyl imidazole dicationic ionic liquid monomer, the polymerization temperature is 80 to 90° C., the reaction is carried out under the protection of an inert gas, the reaction mode is magnetic stirring condensation reflux, and the reaction time is 24 to 48 hours to obtain a halogen anion polyionic liquid-ACF suspension.

7. The preparation method according to claim 3, characterized in that: In step 4, the hexafluorophosphate includes ammonium hexafluorophosphate, potassium hexafluorophosphate or sodium hexafluorophosphate, the molar ratio of hexafluorophosphate to ionic liquid monomer is 2.2:1, the ion exchange reaction temperature is 50-60°C, the reaction time is 12-24h, and after the reaction solution is filtered, the filter residue is washed several times with deionized water and anhydrous ethanol in turn, and vacuum dried at 100°C for 24h to obtain a polyionic liquid-ACF composite adsorption material.

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