Assessment of leaching characteristics of heavy metals from industrial leach waste

Leaching of valuable metals from residues generated by pyrometallurgical or hydrometallurgical process usually results in a large amount of wastes. In the present study, the leaching behavior of the zinc leach waste was investigated by utilizing a regression model with dummy variables. The results of different leaching methods indicate that addition of fly ash and blast furnace slag to the zinc leach waste reduces the heavy metal content in the effluent and that fly ash performs better than blast furnace slag. The results of thermal treatment showed that the zinc leach waste cannot be disposed of in the present form. The metal release from the zinc leach waste decreased in relation to increasing treatment temperature. Metal releases for residues treated at 1000-1200 °C decreased because of heat-induced formation of a glassy matrix. The levels of Zn, Pb and Mn released for 1200 °C treatment temperature were 1.05, 0.08, 0.07 mg/l, respectively. Therefore an immobilization treatment is necessary prior to disposal.