EXTRACTION BEHAVIORS OF LEAD AND ZINC FROM SECONDARY FLY ASH GENERATED IN MUNICIPAL INCINERATION PLANTS WITH SOME LIXIVIANTS

摘要

The dissolution behaviors of valuable metals, lead and zinc, from secondary fly ash generated in municipal incineration plants were investigated using some lixiviants: sulfuric and hydrochloric acids, acetic acid and some chelating reagents including L-asparaginic-N,N-diacetic acid (ASDA), a biodegradable, and therefore, environmentally benign novel chelating reagent. It was found that zinc exists mainly as ZnO, whereas Pb probably as PbOHCl and PbO, and the easily soluble components in SFA are KC1 and NaCl. Suitable amount of HC1 can dissolve all of lead and zinc from SFA. Sulfuric acid can selectively extract zinc leaving lead in the residue. Ethylenediaminetetraacetic acid (EDTA) is an effective chelating reagent to extract both zinc and lead. Although ASDA and diethylene-triaminepentaacetic acid (DTPA) can selectively extract more than half of lead from SFA, it would by no means be regarded as highly effective reagents for the extraction of these metal values.