SYNTHESIS OF PROCESSES FOR RECOVERING MET ALS FROM INCINERATION FLY-ASH OF MUNICIPAL SOLID-WASTES

The purpose of this study is development of separation processes by wh ich metal elements worth using for raw materials of chemicals (for exa mples Cd, Cu, Mn, Ph, Zn and so on) are recovered from incineration fl y ash of municipal solid wastes. Candidate Process (D) evolved out of Candidate Process (C), which was synthesized with a computer-aided pro cedure. The process consists of addition of Na2S to nitric solution as leachate of the fly ash for forming precipitate of sulfides, and cons ecutive dissolution of sulfides with dil-H2SO4, conc-H2SO4 and HNO3 to separate Mn2+, Zn2+ and Cd2+ from each other and to leave CuS insolub le in the acids. For further purification of metals, Candidate Process (D) was modified into Candidate Process (E), in which solvent extract ion of Zn2+ from Mn2+ and Cd2+ fractions with bis (2-ethylhexyl) phosp horic acid (D 2 EHPA), and addition of NH(3)aq or (NH4) 2CO3 to form [ Cu(NH3)(4)](2+) and to leave PbS insoluble were adopted.