Adsorption of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans Vapors on Activated Carbon

Abstract

Activated carbon (AC) adsorption is an important method to control the emission of dioxins and dioxin-like congeners (polychlorinated dibenzo-p-dioxins and dibenzofurans [PCDD/Fs] and polychlorinated biphenyls [PCBs]), of other semi-volatiles (such as Polycyclic Aromatic Hydrocarbons) and heavy metals (mainly mercury) arising from municipal waste incineration and other effluents. Investigating the adsorption characteristics of AC for PCDD/Fs allows selection of the best AC types, to meet the new and more stringent PCDD/F emission standards. In this study, the adsorption of dioxins on three kinds of commercial AC was evaluated through three bench-scale experiments. A dioxin generator was applied to generate a PCDD/Fs containing gas stream with constant concentration. Physical properties of AC, including its density, Brunauer–Emmet–Teller–surface, pore volume, and pore size distribution, were considered. The results show that the removal efficiencies of PCDD/Fs correlate more strongly with pore volume (r2>0.93) than with the surface area (r2<0.48). Among the three types of AC tested, the coconut shell sample with wide pore size distribution reached the highest adsorption efficiency. Under the testing conditions used, the total removal efficiency reached over 96%, much more than the 81.7% efficiency achieved by lignite AC. In addition, the selectivity of lignite AC for 17 toxic PCDD/F congeners is distinct from the two other samples.