Preparation of hierarchically porous zeolite templated carbon from fly ash with investigation into the adsorption behavior towards volatile organic compound

Utilizing cost-effective solid waste, fly ash, the present study has successfully synthesized fly ash-based zeolite (FAZ) and systematically engineered fly ash-based zeolite template carbon (FA-ZTC) with regular pore structure. FA-ZTC exhibits an average pore diameter ranging from 4.95 nm to 6.74 nm, inheriting the hierarchical porosity characteristic of FAZ. This hierarchical porosity effectively alleviates the substantial diffusion limitations commonly encountered in volatile organic compounds adsorption processes associated with purely microporous substrates. FAZ and FA-ZTC achieved maximum o-xylene adsorption capacities of 94.1 mg/g and 338.6 mg/g, respectively. Significantly, the functional groups on the surface of the FA-ZTC within an air atmosphere facilitated its adsorption of o-xylene, while SO2 exhibited inhibitory effects. The Langmuir adsorption isotherm and Bangham kinetic models yielded excellent adsorption fitting results, revealing a primarily exothermic adsorption process driven by physical interactions, with pore diffusion as the key rate-determining factor. Adsorption heat (∆Hads=-13.78 kJ/mol) and Weber-Morris intraparticle diffusion model further confirmed the weaker adsorption affinity of FA-ZTC, highlighting the significant advantage of its hierarchical mesoporous structure in mass transport. Desorption and regeneration demonstrate that FA-ZTC exhibits low desorption temperatures and achieves effective thermal regeneration. These findings significantly underscore the potential commercial utility and cost-effectiveness of FA-ZTC as a promising adsorbent for gaseous o-xylene.