Remarks on the short-term chemical stability of primary lead smelting slag

Abstract

The short-term leaching behavior of a landfilled primary Pb smelter slag from the Santo Amaro (Brazil) smelter was investigated using about 1-day contact time with acid and alkaline solutions. Strong alteration of this slag was observed only below pH 3. In this extreme environment, in addition to the previously discussed behavior of Ca, Si, Fe, Pb and Zn, the As, Cd and Cu were solubilized; however, due to the small content of these elements in the slag, the solution has low content of them. The hierarchical cluster analysis of the results of several leaching tests shows that Pb, As and Cd are part of a group related to the metallic lead phase trapped in the matrix. There is a second group related to some components of the slag matrix (Zn, Ca and Fe) likely oxides; and Si alone is part of a third group related to the slag matrix. The sequential leaching experiments indicate that the main lead solubilization is related to the oxidant environment which confirms the predominance of lead as metallic particles inside the large particles of the slag matrix. These results indicate that, despite the fact that the landfilled slag removal is needful, it is a secondary task to reduce the contamination risk of the region of the former smelter.