Treatment of PCDD/Fs and PCBs in fly ash extracts under mild conditions

A highly efficient catalytic hydrodehalogenation method for polyhalogenated organic compounds, including toxic dioxin-like pollutants, was applied to the treatment of hazardous solid wastes, such as municipal waste incineration fly ash. The catalyst of palladium/carbon (5%, w/w) showed higher activities for fly ash extracts during reaction at 40 degrees C under normal pressure in water-isopropanol solution, and some other interesting phenomena were found. Either ordinary or trace-quantity components, almost all of the polyhalogenated organic compounds, especially dioxin-like pollutants, in fly ash extracts were dehalogenated with more than 99% conversion within 6.5 h. The use of water was maintaining the higher catalytic activities of Pd/C catalyst for dehalogenation of aromatic halides and dioxin-like compounds, and was decreasing the costs of treatment. Isopropanol in the reaction system was increasing the solubilities of polyhalogenated organic compounds and accelerating the hydrodehalogenation rates by offering protons in the catalytic reaction. This hydrodehalogenation reaction was suitable for the treatment of dioxin-like pollutants in real environmental samples, and has significance in the practical application.