Effect of Adsorption Capacity of Dissolved Humic Matter on Leachability of Dioxins from Raw and Treated Fly Ashes of Municipal Solid Waste Incinerators

Abstract

The purposes of this study are to obtain information on the leachability of dioxins depending on the samples, to confirm the effect of dissolved humic matter (DHM) on the leachability of dioxins, and to evaluate the suitability of the detoxification treatments specified by the Japanese government for the reduction of leachability of dioxins. In this study, the leachability of dioxins from raw and treated fly ash was evaluated by a 24-hour batch leaching test and by an extraction test repeated three times with DHM solution, whose concentration was determined to be 700 mg-OC/L as an initial concentration based on organic carbon (OC) from adsorption tests of DHM to fly ash.

The leaching concentration from fly ash samples having high DHM adsorption capacity was low regardless of pH, and that from samples having relatively low adsorption capacity and high pH was largely increased. Therefore, it is expected that the leachability of dioxins from treated fly ashes would be reduced by avoiding high pH and enhancing the DHM adsorption capacity rather than by using the detoxification method specified. We also confirmed that increase of the leachability of HOPs due to DHM is not as large as known in condition that is composed of three phases of HOPs, DHM, and solid matrix.