Аpproaches to improve the efficient bioleaching of arsenopyrite flotation concentrate

Bacterial leaching is known as a green technology for the recovery of valuable metals. However, it has some “bottle neck” problems too. Arsenopyrite, a gold-bearing ore, is a refractory mineral material which is hardly soluble and contains toxic arsenic compounds which worsen bioleaching results. The most common biotechnology used for this process includes the bacteria Acidithiobacillus ferrooxidans, which are autotrophic, acidophilic and resistant to inorganic arsenic compounds. Attempts to dissolve arsenopyrite with increasing volumes of sulfuric acid and supplements of iron, as an energy source for the leaching bacteria, provoke the following: an acidification of the environment and its pollution with excess of iron. We simplified this procedure by i) exchanging the sulfuric acid for HCl, ii) the use of a new active strain of A. ferrooxidans: AA-ZhNR. Bench scale experiments of the bioleaching of arsenopyrite flotation concentrate were produced to compare it with i) the common (classical) medium 9K based on sulfuric acid and iron and a known leaching strain, A. ferrooxidans TFbk, and ii) our HCl medium without iron supplements and with our strain. The degradation of the flotation concentrate was evaluated by the accumulation of dissolved sulfate. The experiments showed that the application of A. ferrooxidans AA-ZhNR, with the arsenopyrite flotation concentrate as a single source of energy, resulted in 4-fold higher production of dissolved sulfate. On the whole, the bioleching of arsenopyrite concentrates may be increased by the selection of new strains and their orientation towards the raw material as a single energy source.