Oxidation of isochemical FeS_2 (marcasite-pyrite) by Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans

摘要

A research-grade mineral sample that contained marcasite and pyrite (FeS_2) was subjected to the oxidation by Acidithiobacillus fer-rooxidans and Acidithiobacillus thiooxidans. Oxidation of FeS_2 by A. ferrooxidans produced acid, and the redox potential increased with sulfide dissolution and the oxidation of Fe~(2+). Jarosite was detected in solids from spent cultures. Preferential oxidation of either mineral was not consistently observed across all treatments. Neither iron sulfide was oxidized by A. thiooxidans. The bacterial oxidation of Fe-sulfides plays a central role in the formation of acid mine drainage and in bioleaching processes. Their oxidation by Acidithiobacillus ferrooxidans results in the formation of sulfuric acid and Fe~(3+), the primary chemical components of acid mine drainage. In the bioleaching of sulfide ores, these oxidation products satisfy acid and oxidant demand, Marcasite and pyrite, both isochemical forms of FeSi, have different min-eralogical properties, chemical reactivity, and oxidation kinetics. Marcasite has an orthorhombic lattice and is considered less stable than cubic pyrite when oxidation rates are normalized to surface area (Wiersma and Rimstidt, 1984). The oxidation of marcasite by iron-oxidizing acidi-thiobacilli has received relatively little attention. Among