A strategy for the enhancement of trapping efficiency of gaseous benzene on activated carbon (AC) through modification of their surface functionalities

Abstract Facile modification of activated carbon (AC) is a common, but effective, option to improve the uptake removal for target volatile organic compounds (VOCs; e.g., benzene) in gaseous streams. To help design the routes for such modification, this research built strategies to develop three types of modified ACs by incorporating amine/sulfur/amino-silane groups under solvothermal or microwave (MW) thermal conditions. The adsorption performance was tested using a total of six types of AC sorbents (three modified + three pristine forms) for the capture of 1 Pa benzene (1 atm and 298 K). The obtained results were evaluated in relation to their textural properties and surface functionalities. Accordingly, the enhancement of AC surface basicity (e.g., point of zero charge (PZC) =10.25), attained via the silylation process, led to the reduced adsorption of of benzene (a weak base). In contrast, ACs amended with amine/sulfur (electron-donating) groups using the MW technique acquired high surface acidity (PZC of 5.99 -6.05) to exhibit significantly improved benzene capturing capability (relative to all others) in terms of key performance metrics such as breakthrough volume (BTV10%: 163→443 L.g-1), adsorption capacity (Q10%: 4.82→13.6 mg.g-1), and partition coefficient (PC10%: 0.516→1.67 mol kg-1 Pa-1). Based on the kinetic analysis, the overall adsorption process was generally governed by pore diffusion as the main rate-determining step, along with surface interaction mechanisms. The results of this research clearly support the critical role of surface chemistry of AC adsorbents and their texture properties in upgrading air/gas purification systems.