Abstract
This study tackles the pressing demand for sustainable and cost-effective technologies to recover critical metals needed in battery electric vehicles, specifically nickel (Ni) and cobalt (Co). Pyrrhotite tailings in the Sudbury region contain significant quantities of Ni and Co, and bioleaching could be a sustainable way to reprocess the mine waste material. The development of an effective bioleaching process suitable for an industrial-scale application includes optimization and piloting. Data will be presented from the initial phase of developing a continuous pilot bioleaching system for tailings reprocessing, including the results of metal solubilization rates, reagent consumption, pulp density, and residence time. In addition, prokaryotic diversity was investigated via modern genomic tools, with a focus on sulphide oxidizing prokaryotes. We will illustrate how the application of an interdisciplinary approach can improve the monitoring and control of the bioleaching process, reduce a lag phases, and improve metal recovery rates. Two campaigns of continuous bioleaching of pyrrhotite tailings (10% (m/V)) were performed at pH 2.0 and 3.0, with mean retention times of 11.9 L day-1 and 14.8 L day-1, resulting in over 93% Ni and 95% Co solubilization. The processes were catalyzed by Sulfobacillus spp. and Acidithiobacillus caldus, with minor abundance of Acidibacillus ferrooxidans. Additionally, the acid/base accounting indicated that acid adjustment was required only during the initial batch phases, followed by alkali additions during the subsequent continuous phases, with the base consumption ranging from 0.04 to 0.11 kg soda ash/kg dry pyrrhotite feed. Large-scale bioleaching would provide an environmentally friendly solution for the production of critical minerals from tailings or other secondary waste materials.