Adsorption of volatile organic compounds by mesoporous graphitized carbon: Enhanced organophilicity, humidity resistance, and mass transfer

Generally, air moisture strongly competes with airborne volatile organic compounds (VOCs) when activated carbons (ACs) are used as adsorbent, and the exclusively microporous texture of ACs hinders the mass transfer of the VOCs, lowering the sorbents' efficiency. Here, we introduced a porous graphitized carbon (PGC) with improved hydrophobicity and well-developed mesopores, thereby overcoming the drawbacks. Through Ni-catalyzed graphitization of AC and KOH activation, we fabricated the PGC, having a surface area >1200 m(2).g(-1). Characterization through X-ray photoelectron spectroscopy and Boehm titration confirmed that PGC exhibited significantly reduced surface oxygen-containing groups over the pristine AC. Thus, PGC features enhanced adsorptive affinity for VOCs, especially the nonpolar ones. In particular, PGC achieved the highest dynamic adsorption capacity (4.63 mmol.g(-1)) at 298 K toward toluene, attributed to the pi-pi interactions between the graphene sheet and the aromatic ring. Furthermore, PGC maintained over 70% of its adsorption capacity at a high relative humidity (RH) of 80%, even for a polar VOC (methyl ethyl ketone). Besides, PGC exhibited superior overall mass transfer coefficients and shortened mass transfer zone than AC. Through facile synthesis, the derived PGC could be a promising adsorbent for VOC removal, especially under humid conditions.