Vapor-phase sorption of hexachlorobenzene on typical municipal solid waste (MSW) incineration fly ashes, clay minerals and activated carbon

Column sorption experiments were conducted at 330 °C and 250 °C to study the vapor-phase sorption of hexachlorobenzene (HCB) on two kinds of municipal solid waste (MSW) incinerator fly ashes, kaolinite, montmorillonite and activated carbon (AC). Both Freundlich equation and linear equation well fitted the sorption isotherms of HCB vapor on fly ashes and clay minerals at 330 °C (r2 > 0.87), while the sorption isotherm of HCB vapor on AC at 330 °C was in the shape of Brunauer type-II adsorption. Catalytic dechlorination of HCB was found to occur on the surface of fly ashes, and pentachlorobenzene was the only dechlorination product detected in the effluent gas. Increasing temperature decreased the sorption of HCB vapor on fly ashes, and promoted the catalytic dechlorination of HCB. On the assumption that the organic carbon and clay minerals in fly ash were derived from AC, kaolinite and montmorillonite, the relative contributions of these components to the apparent sorption capacity of fly ashes at 330 °C were estimated. It was found that very small percentage of AC contributed the most to the apparent sorption of HCB vapor on fly ash. The sorption coefficient of HCB on montmorillonite at 250 °C was 37 times higher than that at 330 °C, suggesting montmorillonite could be a kind of low-cost sorbent to effectively reduce the emission of vapor-phase organochlorine compounds from MSW incinerators.