The MICCUR project for improved copper recovery from chalcopyrite

Abstract

Bioleaching of copper minerals is usually performed in engineered heaps and this technology accounts for approximately 15-20% of the worldwide copper production. Presently there is an increase in the demand for metals while commercial biomining of chalcopyrite (the largest copper resource in the world) is not extensively employed due to slow metal release and limited copper recoveries. In this project, two laboratory-scale, proof-of-concept experiments to increase the efficiency of industrial bioleaching of chalcopyrite containing ores will be scaled up to ultimately reach demonstration in pilot bioheaps. Both strategies are aimed at excluding Leptospirillum ferriphilum that as a ‘strong’ iron oxidizer, raises the redox potential above the desired range for efficient chalcopyrite dissolution at moderately thermophilic temperatures. The first strategy is to maintain the redox potential of a chalcopyrite bioleaching system in the favorable range by using ‘weak’ iron oxidizing microbes such as Sulfobacillus thermosulfidooxidans and the second strategy exploits the lower tolerance of L. ferriphilum to chloride ions (i.e. salt tolerance) as compared to S. thermosulfidooxidans. In addition, it has been demonstrated that signal molecules control biofilm formation on pyrite and it will be tested if they suppress the growth of L. ferriphilum when grown on chalcopyrite. Although proof-of-concept strategies to suppress L. ferriphilum have been described, the project aims to elucidate how the desired microbial consortium can be maintained in the large-scale bioheaps employed by industry.