Promoted wet peroxide oxidation of chlorinated volatile organic compounds catalyzed by FeOCl supported on macro-microporous biomass-derived activated carbon.

Chlorinated volatile organic compounds (CVOCs) are a recalcitrant class of air pollutants, and the strongly oxidizing reactive oxygen species (ROS) generated in advanced oxidation processes (AOPs) are promising to degrade them. In this study, a FeOCl-loaded biomass-derived activated carbon (BAC) has been used as an adsorbent for accumulating CVOCs and catalyst for activating H2O2 to construct a wet scrubber for the removal of airborne CVOCs. In addition to well-developed micropores, the BAC has macropores mimicking those of biostructures, which allows CVOCs to diffuse easily to its adsorption sites and catalytic sites. Probe experiments have revealed HO• to be the dominant ROS in the FeOCl/BAC + H2O2 system. The wet scrubber performs well at pH 3 and H2O2 concentrations as low as a few mM. It is capable of removing over 90% of dichloroethane, trichloroethylene, dichloromethane and chlorobenzene from air. By applying pulsed dosing or continuous dosing to replenish H2O2 to maintain its appropriate concentration, the system achieves good long-term efficiency. A dichloroethane degradation pathway is proposed based on the analysis of intermediates. This work may provide inspiration for the design of catalyst exploiting the inherent structure of biomass for catalytic wet oxidation of CVOCs or other contaminants.

Adsorption-enforced Fenton-like process using activated carbon-supported iron oxychloride catalyst for wet scrubbing of airborne dichloroethane.

Wet scrubbing is a low-cost process for disposing of air pollutants. Nevertheless, this method is rarely used for the treatment of volatile organic compounds (VOCs) because of their poor water solubility. In this study, we used a unique wet scrubbing system containing H2O2 and activated carbon (AC)-supported iron oxychloride (FeOCl) nanoparticles to remove airborne dichloroethane (DCE). The operating conditions of the wet scrubber were optimized, and the mechanism was explored. The results showed that the adsorption of dissolved DCE onto AC promoted its transfer from air to water, while the accumulation of DCE on AC facilitated its oxidation by •OH generated on FeOCl catalyst. The wet scrubber performed well at pH 3 and low H2O2 concentrations. By pulsed or continuous dosing H2O2, the cooperative adsorption-catalytic oxidation allowed long-term DCE removal from air. Benefiting from satisfactory cost-effectiveness, avoidance of toxic byproduct formation, and less corrosion and catalyst poisoning, wet scrubbers coupled with cooperative adsorption and heterogeneous advanced oxidation processes could have broad application potentials in VOC control.