Characterization of passivation layers in bioleaching of sulfides

During the process for the bioleaching of sulfides, the surface of the target mineral is sometimes covered with intermediates, and the final products that interfere with the extraction of the target metal. Understanding the characterization and formation order of the secondary minerals responsible for passivation is a key to resolving the passivation mechanism. The present article reviews identification of secondary minerals and intermediates in a process of bioleaching of several sulfides by X-ray photoelectron spectroscopy, Raman spectroscopy, identification of the jarosite group minerals using Raman spectroscopy, and expectation of the formation order of the secondary minerals by SEM-EDX and TEM. The TEM observation in a nano-domain provides useful information about amorphous the secondary minerals. A passivation model was proposed to keep maximizing Cu recovery and minimizing As solubilization for the bioleaching of arsenic-bearing copper sulfides using super-thermophilic archaea, which are expected to be new target minerals in the near future.