Microbiological leaching of sulfide minerals with different percolation regimes

Summary The microbiological leaching of Fe, Al, Zn, Cu, Ni and Co from sulfide ore material was evaluated with four percolation regimes involving trickle and flood leaching. Continuous circulation of the leach solution associated with flood leaching resulted in the highest rates of leaching of Ni (44% recovery), Zn (25%), Co (18%), and Cu (8%) over a period of about half a year. Iron and aluminum recoveries remained low because of their precipitation. Bacterial counts increased from 3.2×10⁶ to 4.8×10⁷ iron-oxidizers and from 6.6×10⁶ to 1.8×10⁷ glucose-oxidizers per ml leach solution. Microscopic counts reached a maximum of 4.9×10⁸ cells per ml. Neither microscopic nor viable counts reflected the time course and the progress of the leaching. However, both the microscopic and viable counts were highest with the continuous flooding technique which also yielded the fastest rates of metal solubilization.