Solid phase analyses of chemically and biologically leached smelter slag

摘要

Pyrometallurgical processes for sulfide concentrates produce slag waste streams that contain multiple metals as carry-over impurities. Varied quantities of the metal content can be solubilized from the slag through chemical acid leaching or bioleaching. In this study, copper smelter slags were leached with and without bacteria in acid, sulfate-rich solutions and the metals remaining in solid residues were determined by X-ray fluorescence. The samples (10% pulp density) were leached at 27 °C in stirred tanks at pH 2.5 and 3.0. The duration of the experiment was 37 d and the adjusted pH decreased to 2.3 in both sets of experiments. The primary metals of interest in the slag were Cu and Zn, with minor amounts of Ni and Co and As, Sb, and Pb at trace levels. The metals in the slag were distributed in fayalite, glassy silicates and magnetite phases as well as minor amounts in oxides, metallic Cu and sulfides. Fayalite was the most reactive mineral and Cu-sulfides were particularly refractory. The elemental composition of leached residues was compatible with solid phase changes and the distribution of metals in the mineral phases.