Micro-mesoporous graphitized carbon fiber as hydrophobic adsorbent that removes volatile organic compounds from air

Activated carbon fibers (ACFs) are a popular class of adsorbents for volatile organic compounds (VOCs), however, their abundant hydrophilic functional groups greatly limit their selective adsorption capacity for organics under humid conditions. In this work, porous graphitized carbon fibers (PGCFs) with enhanced hydrophobicity were prepared by KOH-promoted catalytic graphitization of viscose-based ACF, and their adsorption capacity for representative VOCs was investigated. Characterizations showed that the PGCFs had reduced O/C ratios, high specific surface areas exceeding 2200 m2/g, and micro-mesoporous structure. Under dry conditions, the adsorption capacity of a typical PGCF for toluene, cyclohexane and ethanol reached 7.2, 4.6 and 2.0 mmol/g, respectively. At 80 % relative humidity, the adsorption capacity for toluene and cyclohexane retained 92 % and 85 %, respectively, while that for ethanol even increased by 54 %. The abundant π electrons and high polarizability of the PGCF strengthened the π-π interaction and dispersion force with non-polar organics, thereby enhancing their removal. The capillary condensed water in mesopores could act as absorbate for the uptake of polar ethanol under humid conditions. The toluene-adsorbed PGCF was effectively regenerated at a low temperature of 80 °C. Benefiting from their excellent adsorption capacity and moisture-resistance, PGCFs may be promising adsorbents to remove VOCs from air.