Silicate mineral dissolution during heap bioleaching

Abstract

Silicate minerals are present in association with metal sulfides in ores and their dissolution occurs when the sulfide minerals are bioleached in heaps for metal recovery. It has previously been suggested that silicate mineral dissolution can affect mineral bioleaching by acid consumption, release of trace elements, and increasing the viscosity of the leach solution. In this study, the effect of silicates present in three separate samples in conjunction with chalcopyrite and a complex multi-metal sulfide ore on heap bioleaching was evaluated in column bioreactors. Fe(2+) oxidation was inhibited in columns containing chalcopyrite samples A and C that leached 1.79 and 1.11 mM fluoride, respectively but not in sample B that contained 0.14 mM fluoride. Microbial Fe(2+) oxidation inhibition experiments containing elevated fluoride concentrations and measurements of fluoride release from the chalcopyrite ores supported that inhibition of Fe(2+) oxidation during column leaching of two of the chalcopyrite ores was due to fluoride toxicity. Column bioleaching of the complex sulfide ore was carried out at various temperatures (7-50 degrees C) and pH values (1.5-3.0). Column leaching at pH 1.5 and 2.0 resulted in increased acid consumption rates and silicate dissolution such that it became difficult to filter the leach solutions and for the leach liquor to percolate through the column. However, column temperature (at pH 2.5) only had a minor effect on the acid consumption and silicate dissolution rates. This study demonstrates the potential negative impact of silicate mineral dissolution on heap bioleaching by microbial inhibition and liquid flow.

Evaluation of Silicate Minerals for pH Control During Bioremediation: Application to Chlorinated Solvents

“…Possible feedbacks include the microbial enhancement of mineral weathering rates (Barker et al 1998;Ullman et al 1996;Vandevivere et al 1994) and the inhibition of bacteria by trace elements release during mineral dissolution (Dopson et al 2008 Fig. 1 Influence of pH on solubility of five silicate minerals (andradite, fayalite, forsterite, nepheline and wollastonite).…”

Low temperature removal of inorganic sulfur compounds from mining process waters

“…The inhibitory effect of fluoride is pH dependent (Sääf et al, 2009) but also depends on the general solution chemistry (Sundkvist et al, 2005;Suzuki et al, 1999). Fluoride (1.11 mM) completely inhibited metal release during column bioleaching with a mixed culture of acidophilic biomining microorganisms (Dopson et al, 2008a). Antimony resistance is ubiquitous in biomining microorganisms (reviewed in Dopson et al (2003)).…”

Probing the effect of aqueous impurities on the leaching of chalcopyrite under controlled conditions

“…carbonate minerals such as calcite and dolomite, and silicate minerals such as talc, chlorite and feldspar (Duan et al, 2003;Garlick, 1964;Mathur et al, 2000;Yoon, 1981), associated with chalcopyrite (and other copper) ores and may affect the leaching conditions and chalcopyrite leaching behaviour (Dopson et al, 2008(Dopson et al, , 2009). These species, besides affecting activities of, and complexing with, other aqueous ions, may also be involved in surface speciation possibly resulting in passivation via precipitation, or specific adsorption thus affecting the total reactive chalcopyrite surface area.…”