BEHAVIOR OF MUNICIPAL SOLID-WASTE INCINERATOR FLY-ASH .1. GENERAL LEACHING STUDY

The understanding of the leaching behaviour of municipal solid waste (MSW) incinerator flyash is important from the environmental point of view, particularly for landfill disposal and also for hazardous metal detoxification or for metal recovery. In this paper, the leachability of metals from MSW flyash was compared for various solvents, including H2O, NaOH, HCl, H2SO4 HClO4, HNO3 and HAc. Hydrochloric acid was found to be a most effective solvent to remove heavy metals from flyash. The experiments with HCl concentrations from 0 to 6 M showed that HCl concentration does not affect the leachability of most elements above 0.5 M HCl. For lead and copper, leachability increases up to 1 M HCl, while for iron leachability increases with increasing HCl concentration through the whole concentration range tested, Silica gel was found to form quickly in concentrated HCl solutions, and caused poor solution filterability. The HCl-leached residue was shown to be non-hazardous.