A Reactor to Measure Pyrite Oxidation in Air

Acid mine drainage is a major environmental problem worldwide. A key to remediating this problem is understanding the rate and mechanisms of the complex, multistep pyrite oxidation reaction under geologically relevant conditions. Because many waste piles are not submerged, a large amount of pyrite oxidation actually occurs in air. We have designed a Barcroft-manometer reactor to measure the rate of pyrite oxidation in air as a function of relative humidity and oxygen partial pressure. The reactor consists of two chambers joined by a manometer. Each experiment occurs at constant temperature, initial oxygen partial pressure, and relative humidity, although these variable can be changed between runs. Oxygen consumption was measured and pyrite oxidation rates were calculated from those data. Initial data indicate that rate of pyrite oxidation by oxygen in humid air is much faster than the rate of oxidation by oxygen in solution. The rates determined by this study can be used to develop better remediation techniques for acidic mine waters.