Ferrous iron oxidation by Thiobacillus ferrooxidans: inhibition with benzoic acid, sorbic acid, and sodium lauryl sulfate.
Acid mine drainage is formed by the weathering or oxidation of pyritic material exposed during the mining of coal deposits and is a major water pollution problem in the Appalachian region of the United States. The rate of pyritic material oxidation can be greatly accelerated by certain acidophilic bacteria such as thiobacillus ferrooxidans. These bacteria promote indirect oxidation of pyrite through the catalysis of the oxidation of ferrous iron to ferric iron. These bacteria also may catalyze direct oxidation of pyrite to oxygen. A number of organic compounds, under laboratory conditions, can apparently inhibit both the oxidation of ferrous iron to ferric iron by t. Ferrooxidans, and the weathering of pyritic material by mixed cultures of acid mine drainage microorganisms. Sodium lauryl sulfate (sls), an anionic surfactant, has proved effective in this regard. Benzoic acid, sorbic acid, and sls at low concentrations, each effectively inhibited bacterial oxidation of ferrous iron in batch cultures of t. Ferrooxidans. The rate of chemical oxidation of ferrous iron in low-ph, sterile batch reactors was not substantially affected at the tested concentrations of any of the compounds.