Remediation of contaminated soil by fly ash containing dioxins from incineration by using flotation

Flotation was investigated to clean up the dioxin (Polychlorinated Dibenzo-p-Dioxins/Furans, PCDD/Fs and co-Planar Polychlorinated Biphenyls, co-PCBs)-contaminated soil, originated from fly ash contaminated by dioxins dispersed into soil. The primary purpose was to reduce the concentration of dioxins in soil by examining the conditions of flotation to remove selectively unburned carbons including a high dioxin concentration of fly ash generated from incineration processes. Three kind of materials were used, such as fly ash from an ESP (electrostatic precipitation) of an incinerator on vapor gas treatment (FA), artificial contaminated soil (mixture of soil and fly ash containing dioxins, ACS) and real dioxin-contaminated soil which excavated from a site of Japanese domestic incinerator area (CS). As a result, in the case of fly ash and artificial soil, fly ash containing dioxins would be enriched and then separated as float products by flotation under the conditions as follows, additional amount of kerosene and Dow 250, pulp density and pH were 40 kg/t, 7 kg/t, 5-30% and 2.8, respectively. In addition, it could be possible to recover approximately 80% of soil from dioxin-contaminated soil. The concentration of dioxins in the soil analyzed by Ah-Immunoassay after flotation was decreasing from 15 to 0.68 ng-DEQ/g and was satisfied with Japanese environmental regulation i.e. less than 10ng-DEQ/g (analyzed by Ah-Immunoassay) or 1 ng-TEQ/g (analyzed by GC-MS methods).