Selective recovery of valuable metals from partial silicated sphalerite at elevated temperature with sulfuric acid solution

The purpose of this work was to study the feasibility at laboratory-scale of a hydrometallurgical process for the selective recovery of valuable metals from partial silicated sphalerite in an oxygen pressure acid leaching system. The factors influencing dissolution efficiency of the ore were investigated and optimized. Under optimum conditions (i.e., temperature of 433 K, sulfuric acid concentration of 41.2 g/L, leaching time of 2.5 h, liquid/solid ratio of 6 mL/g, and pressure of 1.6 MPa) over 97% Zn was extracted into the leach liquor together with 0.3% SiO2 and 2.9% Pb. The leaching slurry had good solid–liquid separation characteristics, and the filtration rate could be as high as 716 L/m2 h. About 96% oxidation of sulfide sulfur to sulfate was achieved under these conditions. Analysis of the content of elemental sulfur in the leaching residues indicated that the fraction of sulfide sulfur determined as elemental sulfur was about 10% at 393 K, and that it decreased with temperature down to 0.5% at 453 K. Ultimate solid residues, which have been concentrated in silica and lead, can be oriented toward the lead smelter after alkali roasting-water washing pretreatment for metal recovery.