STABILIZATION AND HYDROMETALLURGICAL TREATMENT OF FLY-ASH FROM A MUNICIPAL INCINERATOR

Flyash from municipal solid waste (MSW) incinerators is frequently classified as a characteristic hazardous waste due to lead and cadmium content. Two alternate processing schemes for the treatment of flyash obtained from the MSW incinerator in Tuscaloosa, AL have been investigated; one involves stabilization of the flyash with portland cement, and the other involves the recovery and recycling of metal values by leaching and subsequent precipitation. Results indicate that flyash can be successfully stabilized in a 1:1 mixture of flyash and portland cement which meets environmental requirements. It has also been demonstrated that extraction of the metal content from flyash, specifically lead, cadmium and zinc, can be accomplished quickly and efficiently by leaching in hydrochloric acid solutions. Preliminary experiments on the subsequent recovery or precipitation of metallic lead and cadmium from these leaching solutions by cementation with zinc dust appear to be promising. Various means were used for characterization of the as-received material and several leaching residues including X-ray diffraction, particle size analysis, inductively coupled plasma spectroscopy, and atomic absorption spectroscopy. Results indicated that at least some of the lead in the flyash is present in the form of PbSO4 with smaller amounts of PbCl2.