Overview: Pyrite oxidation in mine tailings and waste rock piles leads to acid drainage posing serious environmental risk. The results of this study will lead to more accurate reaction models and improved ecological risk analysis of mining and proposed mining sites. Understanding pyrite oxidation is critical for the mineral processing industry particularly in the use of flotation methods for ore enrichment. Additionally, materials scientists interested in pyrite for photovoltaic and liquid junction solar applications, and electrochemical storage devices will benefit from this knowledge. This study will continue to foster collaboration between the departments of Earth and Environmental Sciences, Civil and Environmental Engineering, Physics, and Chemistry at Vanderbilt University.
Figure 1. Mine tailings containing pyrite and producing
acidic drainage (Western US)
Results: In an ongoing electrochemical study using synthetically grown single pyrite crystals doped with As, Co, and Ni, we have shown that bulk electronic structure, as influenced by these electroactive impurities, influences the rate of oxidation (Lehner, 2004; Lehner et al., 2006). The highest observed rates are from pyrite with As impurity followed by that with Co and then Ni impurity. Lowest rates are from pyrite with negligible impurities. This suggests that electroactive impurities fundamentally affect the rate of pyrite oxidation.
Literature Cited:
- Lehner, S. W., 2004, The effect of impurities on the electronic properties of pyrite crystals: Studies of synthetic pyrite (FeS2) doped with As, Co, and Ni [Masters thesis]: Vanderbilt University, 84 p.
- Lehner, S. W., Savage, K. S., and Ayers, J. C., 2006, Vapor growth and characterization of pyrite (FeS2) doped with Co, Ni, and As: Variations in semiconducting properties: Journal of Crystal Growth, v. 286, no. 2, p. 306-317.