Direct versus indirect bioleaching

New insights about the bacterial oxidation of arsenopyrite: A mineralogical scope

“…So, in the bio-oxidation processes, the main function of the microorganisms is the regeneration of Fe 3+ (Rodriguez et al, 2003), occurring as a major end product of the electron transport chain in A. ferrooxidans (Sand et al, 1999). In this work, there are two primary sources of iron, i.e.…”

O and S isotopic composition of dissolved and attached oxidation products of pyrite by Acidithiobacillus ferrooxidans: Comparison with abiotic oxidations

“…A parallel can be drawn with equilibrium isotopic fractionation between sulphides and dissolved H 2 S. Pyrite and molybdenite which are supposed to dissolve through a thiosulfate intermediate pathway (Hansford and Vargas, 1999;Sand et al, 1999) exhibit a positive D sulfides-H 2 S À (Ohmoto and Rye, 1979) while chalcopyrite and galena which are supposed to dissolve through a polysulfide intermediate pathway exhibit a negative D sulfides-H 2 S À. The fact that Raman spectra indicate the presence of different reactional intermediates, thiosulphates and polysulfides, during pyrite oxidation allows prediction of variations in D SO 4 -pyrite .…”

Coal Enrichment Methods by Using Microorganisms and Their Metabolites

“…Recently, this model has been revised and replaced by another one, which is not dependent on the differentiation between "direct" and "indirect" leaching mechanisms. The newly developed integral bioleaching model was described and discussed by many authors [Sand et al 1995, Sand et al 1999Sand et al 2001, Tributsch 2001. The model includes combined "direct" and "indirect" bioleaching and can be characterized in the following way: at first, physical contact of bacterial cells with surface of minerals are needed, then the cells produce and secrete exopolymers (extracellular polymeric substances EPS).…”