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 v iew, particularly for landfill disposal and also for hazardous metal d etoxification or for metal recovery. In this paper, the leachability o f 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. Th e experiments with HCl concentrations from 0 to 6 M showed that HCl co ncentration does not affect the leachability of most elements above 0. 5 M HCl. For lead and copper, leachability increases up to 1 M HCl, wh ile 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 f ilterability. The HCl-leached residue was shown to be non-hazardous.