Catalytic Effect of Mechanically Activated Pyrite on the Bioleaching of Chalcopyrite Concentrates

Bioleaching is the process of extracting copper from chalcopyrite concentrates (CuFeS2) which provides approximately 70 percent of the world’s known copper reserves. Using pyrite in this process increases the dissolution rate of Cu. In this paper, we study the effect of mechanically activated pyrite on bioleaching in detail. First, we synthesize the pyrite nanoparticles using high-energy mechanical ball milling to expand the surface area of pyrite particles. Next, we characterize unmilled and milled pyrite samples using different methods, namely scanning electron microscopy, X-ray diffraction, and Fourier transforms infrared spectroscopy. Furthermore, we use a mixed culture of mesophilic and moderately thermophilic microorganisms at an initial pH of 1.5 with the extra addition of 0.02% (w/w) yeast extract in our bioleaching tests. The finding of this paper indicates that the addition of mechanically activated pyrite to the system considerably improves copper extraction in terms of the catalytic activity of pyrite particles, particularly in the presence of moderately thermophilic microorganisms such as sulfur-oxidizing microorganisms. Moreover, our results show that the mass ratio of pyrite-to-chalcopyrite has an important role on Cu recovery in the bioleaching process. As part of future work, we will consider the generation of toxic reactive oxygen species (ROS) from mechanically activated nanopyrite and its effect on bioleaching. We will also investigate the catalytic effect of nanopyrite on the leaching of chalcopyrite concentrates in electrobiochemical systems.