Microbial Leaching of Copper from Tailings of Low Grade Sulphide Ores in Zambia

Demand for copper is growing in the world,which makes it increasingly necessary to process low-grade ores and tailings that used to be considered as wastes. The development and application of bioleaching by acidophilic chemolithotrophic microorganisms, which obtain energy from the oxidation of sulfide minerals and use carbon dioxide for constructive metabolism, has been a major approach for processing the low-grade copper ores. In this study, mixed culture consisted of six iron and sulfur oxidizing microorganisms were used in leaching of flotation and acid-leaching tailings obtained from Zambia sulfide ores. The result showed that 62.7% and 61.7% copper were dissolved by bioleaching, while 53.8% and 57.4% by acid leaching in flotation and acid leaching tailings, respectively. In addition, mineralogical forms of copper were quite noteworthy since copper sulfide mineral extraction was significantly improved in bioleaching. XRD analysis showed wollastonite and diopside in acid tailing were undetectable after 23 days while others were difficult to be dissolved. No jarosite or sulphur was detected by XRD in residues.