Experimental Geochemical Studies on Oxidation of Pyrite at Ambient Temperatures.

Pyrite dissolution at ambient temperatures is one of the important reactions in biogeochemical processes. It is related to the formation of acid mine drainage, where iron- and sulfur- oxidizing bacteria often grow actively and play an important role in pyrite weathering. In this article experimental studies on the oxidation of pyrite are reviewed, including pretreatment method to obtain the well-defined surface of pyrite particles, the mechanisms of pyrite oxidation by both bacteria and oxidizing agents (Fe(III) ions and oxygen), and suppressing factors of the reactions. Microbially mediated dissolution of pyrite in acidic environments proceeds mainly by the indirect contact mechanism of the iron-oxidizing bacteria, Thiobacillus ferrooxidans, that is, the bacteria mainly take part in the oxidation of Fe(II) ions to Fe(III) ions. Therefore, to suppress the weathering the reaction of pyrite with Fe(III) ions must be inhibited. In addition to the reduction and complexation of Fe(III) ions, masking of active sites on the pyrite surface by the preferential adsorption of other species is the most important factor. Based on the experimental studies, utilization of natural organic acids involved in botanical wastes is proposed for remediation and prevention of damage caused by acid mine drainage due to pyrite weathering.