Bioleaching of Low-Grade Ni-Sulfide Samples with a Mesophilic Consortium of Iron- and Sulfur-Oxidizing Acidophiles

Abstract

The bioleaching of nickel-containing sulfide minerals from five ophiolitic ore samples was investigated in this study, using a mesophilic, acidophilic consortium that included Acidithiobacillus thiooxidans, Acidithiobacillus ferrooxidans, and Leptospirillum ferrooxidans. The experiments were carried out in the presence and absence of ferrous iron and elemental sulfur as additional energy sources for the bacteria. After 30 days of contact at 5% pulp density, nickel dissolution was in the range of 15–29% in the chemical leaching and 58–83% in the bioleaching. Accessory forsterite (Mg₂SiO₄) in the ophiolitic ore samples increased the acid consumption, attributed to the protonation of Mg-silicate surfaces. The ore samples with low Cr₂O₃/MgO ratios had high acid consumption. Post-leaching examination of solid residues showed the presence of a jarosite and sulfur layers, indicating mineral surface passivation and diffusion limitation.

Research highlights

• The chemical and bioleaching of five Ni-sulfide samples was investigated

• Ni bioleaching from some samples responded to Fe and sulfur addition

• Leaching of samples with pentlandite yielded the highest Ni recoveries

• Sulfur and a jarosite-type precipitate were formed as secondary phases

• Lizardite was formed as a serpentinization alteration product of Mg-silicates

Keywords:

• Bioleaching
• mesophilic bacteria
• Mg-silicates
• nickel leaching
• pentlandite leaching

Acknowledgments

The authors gratefully acknowledge the X-ray Laboratory of the School of Mining, College of Engineering, University of Tehran for analytical services. Technical support by the staff in the Mineral Processing and Geochemistry Laboratories is also gratefully acknowledged. We thank the three anonymous reviewers for their helpful comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.