Fluidized roasting-stage leaching of a silver and gold bearing polymetallic sulfide concentrate

The process of fluidized roasting-stage leaching has been developed in this paper to extract silver and gold and their associated metals including copper, zinc and antimony from a complex polymetallic sulfide concentrate. Sintering of the concentrate with high Pb content might be avoided during fluidized bed roasting under appropriate operating parameters, and the SO2 concentration in flue gas was sufficiently high to produce sulfuric acid. After the roasting, Cu and Zn in the mixture of calcine and soot were effectively extracted by two-step countercurrent sulfuric acid leaching, while the dissolutions of Pb, Sb, Ag and Au were all negligible. Non-oxidative and oxidative chloride leaching was carried out successively after the sulfuric acid leaching. Ag and Sb in sulfuric acid leaching residue were well extracted by the non-oxidative leaching, and Au was effectively extracted by the oxidative leaching. Pb was still hardly dissolved by these two chloride leachings and concentrated in final residue.