Bacterial leaching of complex sulfide ore samples in bench-scale column reactors

• Published in: Hydrometallurgy Vol. 37; no. 1; pp. 1 - 21
• Main Authors: Ahonen, Lasse, Tuovinen, Olli H.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.01.1995; Elsevier
• Subjects: Applied sciences; Exact sciences and technology; Hydrometallurgy; Metals. Metallurgy; Production of metals; Production of non ferrous metals. Process materials; Quartzites; Mineralogy; Bacterial leaching; Experimental study; Cobalt; Zinc; Sulfide ore; Chalcopyrite; Pyrite; Pyrrhotite; Ore treatment; pH; Bacteria; Lixiviation; Redox potential; Copper; Hydrometallurgy
• ISSN: 0304-386X; 1879-1158
• DOI: 10.1016/0304-386X(94)00011-Q

Several variables were examined in column bioleaching of a complex sulfide ore material which contained chalcopyrite, pentlandite, pyrite, pyrrhotite and sphalerite as the main sulfide minerals. Samples were used with varying proportions of pyrrhotite, pyrite, quartzite (low acid consumption) and skarn (high acid consumption). The experiments were carried out using bench-scale column leaching reactors which were inoculated with acidophilic, Fe- and S-oxidizing bacteria, initially derived from the source mine water. Leaching rates in sterile controls were negligible. In inoculated columns new solid phases (covellite, jarosite, Fe (III) oxide and elemental sulfur) were formed. Acid consumption was highest under low pH and low redox potential conditions. The solubility of ferric iron was controlled by jarosite and an Fe (III) hydroxide (initially amorphous). The leaching rates of Co (from pyrite and pentlandite), Cu (chalcopyrite), and Zn (sphalerite) showed a tendency to increase with dissolved ferric iron concentration. The leaching of Ni (from pyrrhotite and pentlandite) did not correlate with the concentration of ferric iron in solution. Microscopic counts of bacteria in solution, deemed insufficient to represent total bacterial counts, showed a tendency to be higher at the lower pH and intermediate redox potential ranges. Trickle-leaching conditions yielded higher acid production and redox-potential values compared with flood leaching. The leaching rates of Co, Cu, Ni and Zn each responded differently to redox potential and pH regimes. The accelerating effect of a decreasing particle size on the metal leaching rates was amplified by low pH values.