Continuous Bioleaching of Copper from Copper Smelters Dust with a Mixed Culture of Mesophilic Bacteria

Abstract

Bioleaching of the copper flue dust of the smelting furnaces of Sarcheshmeh Copper Complex has been investigated. At present, the dust is recycled to the smelters, which reduces their efficiencies and increases the required energy for the smelting process. In this study, the bioleaching performance of two continuous systems consisting of a two-stage aerated stirred tank, and a series of two-stage airlift bioreactors were compared. Comparison has also been made with shake flask tests. The parameters which have been studied include oxidation-reduction potential (ORP), pH, copper and iron concentration, and the effect of pulp densities and time on the bioleaching of copper dust. With the pulp densities of 20 g/L and 40 g/L, both reactor systems have shown a stable redox potential. Copper recoveries for the pulp densities of 20, 40 and 70 g/L in the stirred tank series with retention times of 2.7, 4 and 6 days, were 91.8%, 90.3% and 87.6% respectively. Copper recoveries for the airlift series with the same pulp densities, and with retention times of 2.7, 4, and 5 days, were 90.1%, 89%, and 86.1%, at 32 °C, respectively. The shake flask recoveries for the same pulp densities after 23 days were 85.5%, 85.2% and 70.1%, respectively. The results show that the performance of the two bioreactor systems is nearly similar, and both series of bioreactors had better performance than shake flasks.