Acid Bioleaching of Copper from Smelter Dust at Incremental Temperatures

Abstract

ABSTRACT Copper smelters produce solid waste streams that pose potential pollution problems because of the dust and metal content. Dust from flash and electric furnace smelters is normally recycled to the smelting process, but this decreases the capacity for concentrate feed, and increases impurities and carryovers in the dust with time. The purpose of this study was to test an acid bioleaching process for recovering copper from a sample of smelter dust. The dust sample contained delafossite, chalcocyanite, and chalcopyrite as the main Cu-minerals. Smelter dust (10% pulp) in acid leach solution was subjected to three microbial cultures in a sequence of 35°C, 50°C, and 70°C incremental temperatures for 2 days each. Up to 83% copper dissolution from the dust was achieved by the combined action of the three-phase bioleaching and chemical leaching over the contact time of 6 days. Chemical acid demand at 70°C solubilized 68% Cu from smelter dust within 2 h, attributed to chalcocyanite dissolution in the dust. The monovalent copper minerals chalcopyrite and delafossite were more recalcitrant than the sulfate phase chalcocyanite. A 16-day bioleaching experiment at 35°C and 50°C yielded copper recoveries, which were comparable to those obtained in the three-phase bioleaching. It was concluded that further increases in copper yields from smelter dust require extended contact time ideally at the extreme thermophilic temperature range and stirred bioreactor conditions to control key parameters.