Bioleaching Operations of The Low-Grade Chalcopyrite Ore in the Chloride Conditions Using Adapted Indigenous Microorganisms

Dissolution of chalcopyrite is one of the most important challenges of hydrometallurgy because it is difficult to leach due to its inactivation by passive precipitates like jarosites. The combination of the benefits of microbial leaching (three strains of native mesophiles, moderate thermophiles, and extreme thermophiles), and chloride leaching was the main purpose to enhance the copper recovery, especially from the low-grade chalcopyrite sources.

The native microorganisms were isolated from Sarcheshmeh mine, and adapted (4 months with chloride media). Then, the bioleaching operation was systematically performed using the columns containing low chalcopyrite ore (less than 0.3% Cu) to investigate the effect of the chlorine on the bioleaching process. Different analyzes of the leaching and feed residues were used to closely examine the process and mechanisms involved (A 23% increase in recovery (81% with chlorine and 58% with no chlorine)).

Based on the analyses of the bio-leaching residues, overcoming the problems caused by the unwanted precipitates like jarosite during chlorinated bioprocess (2 g / l chloride) was one of the main reasons for these results which were identified using SEM, EDS analysis. And, the elemental mapping of the solid residues from microbial leaching operations proved this possible reason.

Controlling the undesirable precipitates in the process was the most important lever to improve copper recovery (more than 81% of copper over 120 days). This was achieved by regulating the growth process and activity of microorganisms from mesophiles to extreme thermophiles with sodium chloride salt additive.