Hydrophobic carbon with hollow and hierarchical porous structures for efficient VOCs removal from complex exhaust gases: Experiments and DFT calculations
CHEMICAL ENGINEERING JOURNAL(2023)
Abstract
Water vapor and SO2 significantly diminish the adsorption performance of activated carbon (AC) for volatile organic compounds (VOCs) in exhaust gases. In this paper, a hydrophobic and hollow hierarchical porous activated carbon (HHRCs) was synthesized. The HHRC-8 possessed an ultra-high specific surface area (3373.5 m2/g), high mesopore proportion (47.33 %), and low O content (5.19 %). Under dry conditions, HHRC-8 exhibited excellent dynamic and static adsorption capacities both for weak-polar toluene and strong-polar 1,2dichloroethane, superior to many reported MOFs and carbon materials. Additionally, the static adsorption capacity of water vapor on HHRC-8 was 6.1 mmol/g at 70 RH%, presenting a higher hydrophobicity index. During the competitive adsorption between toluene and 1,2-dichloroethane, HHRC-8, with a substitution peak phenomenon of 1,2-dichloroethane, displayed a higher total adsorption capacity and a longer breakthrough time in complex waste gases. Single water vapor (70 RH%) or SO2 (200 mg/m3) had a negative impact on VOCs adsorption, among which, water vapor showed a greater influence on the adsorption capacity, while SO2 showed a greater effect on breakthrough time. When water vapor and SO2 coexisted, the negative impact superimposed, showing a greater effect on 1,2-dichloroethane. Density functional theory calculations revealed that surface functional groups could interact with water, SO2, 1,2-dichloroethane and toluene molecules. In addition, water vapor and SO2 could mutually promote adsorption through hydrogen bonds. HHRC-8, with hydrophobicity and hierarchical adsorption properties, exhibiting a superior competitive adsorption capacity and an excellent reusability, is a promising adsorbent for the multi-component VOCs removal in complex waste gas.
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Key words
VOCs,Water vapor,SO2,Competitive adsorption,Hierarchical porous carbon
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