Comparative economics of bacterial oxidation and roasting as a pre-treatment step for gold recovery from an auriferous pyrite concentrate

CIM Bulletin, Vol. 81, No. 910, 1988

S.R. GILBERT, C.O. BOUNDS and R.R. ICE, St. Joe Minerals Corporation, Monaca, Pennsylvania

Many ores are upgraded to produce auriferous sulphide concentrates (principally pyrite) which are not amenable to direct cyanidation. Often these refractory gold-bearing concentrates contain undesirable elements such as arsenic, antimony, etc., which present environmental and/or processing problems. The pretreatment techniques most often considered for processing these concentrates prior to cyanidation include roasting, pressure oxidation, chemical oxidation, pre-aeration, and recently, bacterial oxidation. In this paper, the technical performance and economics of bacterial pre-oxidation vs the classical roasting approach for treating a specific auriferous pyrite concentrate are compared. The results provide flow sheets, preliminary operating and capital cost estimates, and rates of return for the two processes and demonstrate the potential advantages of bacterial pre-oxidation.

Keywords: Bacterial oxidation, Economics, Gold, Pyrite, Refractory ore, Tailings, Biotechnology, Leaching, Roasting