Biooxidation of Alaskan refractory gold ore concentrates (Draft version)

摘要

Alaskan refractory gold ore concentrates, containing 23.5 wt% arsenopyrite and 21.8wt% pyrite as major sulfide mineral components, were biooxidized using pure and defined mixed cultures of moderately thermophilic iron- and/or sulfur-oxidizing bacteria (Acidimicrobium ferrooxidans ICP, Sulfobacillus sibiricus NC, Acidithiobacillus caldus KU) in shake flask cultures at 45°C. Without initial addition of Fe(II), pure cultures of Am. ferrooxidans ICP and At. caldus KU were both as ineffective as sterile control cultures in mineral dissolution. Nonetheless, mixed culture of the two strains effectively accelerated the mineral oxidation, releasing 74% of soluble Fe. A pure culture of Sulfobacillus sibiricus NC dissolved 45% of Fe, which increased to 74% by mixing with At. caldus KU. The most effective mineral dissolution was observed in mixed culture of all three strains, releasing 80% of soluble Fe and 61% of soluble As. Although initial addition of 10 mM Fe(II) improved the mineral dissolution rates in Am. ferrooxidans ICP pure cultures and mixed culture of the two iron-oxidizers, the trend was reverse in case of other pure and mixed cultures. Applying the biooxidation pre-treatment using the mixed culture of all three moderate thermophiles significantly improved the recovery rates of gold and silver by cyanide leaching. Roles of individual microbe will be discussedin biooxidation cultures containing highly toxic As(III).