Factors affecting bio‐oxidation of sulfide minerals at high concentrations of solids: A review

Abstract

Bio-oxidation has proved to be a viable process for the oxidative pretreatment of refractory gold-bearing sulfides. Generally, the oxidation rate is maximal at 20% solids for high sulfide content materials [ca. 30% sulfur]. Low grade ores [1% sulfur] have been successfully oxidized at 55% solids, indicating a link between the sulfide grade of the material and the optimal solids concentration for operation. Concentrations of high solids have been reported to lower oxidation rates, increase lag times, and decrease the ultimate extent of oxidation. This review discusses the various factors that have been proposed as causes of these phenomena. The factors include oxygen and carbon dioxide availability, low bacteria-solids ratio; mechanical damage or inhibition of the bacteria, inhibition of bacterial attachment, and the buildup of toxic leach products or other detrimental substances such as some flotation reagents.

Inhibition of iron(II) oxidation by arsenic(III,V) in Thiobacillus ferrooxidans: Effects on arsenopyrite bioleaching

“…3A), which has been observed at high concentrations of solids (Bailey and Hansford, 1993). The same results were obtained with another bioleaching medium containing bacteria in an ironfree 9K medium, pH 1.5, the arsenic bioextraction yield was very low without bacteria (not shown).…”

Bioleaching of copper, nickel and cobalt from the low grade sulfidic tailing of Golgohar Iron Mine, Iran

“…5 and 8) induced at 5% pulp density, which was suitable for the leaching of cobalt and nickel sulfides and undesirable for the leaching of chalcopyrite. The low redox potential at the higher pulp density could be related to decreasing the mass transfer of oxygen or carbon dioxide to the microorganisms as previously mentioned by Bailey and Hansford (1993).…”

Optimization of pulp density and particle size in the biooxidation of a pyritic gold concentrate by Sulfolobus metallicus

“…It is recognized that increasing pulp densities and decreasing particle sizes have a positive effect in the volumetric rate of biooxidation, as both situations result in an increase in surface area. Nevertheless, it has also been noted that the interaction among these factors together with a variety of associated phenomena such as mechanical damage, metabolic stress and inhibitory concentrations of ferric ion, can limit this positive effect and even result in declining leaching rates (Bailey & Hansford 1993).…”