Reactive oxygen species formation driven by acidophiles mediated pyrite oxidation and its potential role on 2,4-dichlorophenol transformation

Abstract Researches of reactive oxygen species (ROS) generation from pyrite oxidation and its impact on contaminants transformation has been constrained to abiotic conditions. However, pyrite oxidation by acidophiles is widespread in acidic environments. The potential role of these microorganisms on pyrite-induced ROS formation and pollutants processing is not understood well. Here, ROS production and 2,4-DCP transformation during pyrite oxidation under oxic and anoxic atmospheres by Acidithiobacillus ferrooxidans (A. ferrooxidans) were explored. 2,4-DCP removal was enhanced in biosystem. Under oxic and anoxic conditions, microbially mediated pyrite oxidation resulted in removing 93.66% and 43.77% 2,4-DCP, which were 1.14- and 1.51-fold greater than that without cells. Based on intermediates identified by LC-MS, the transformation pathway of 2,4-DCP was proposed. The trapping experiments demonstrated ROS contributed during 2,4-DCP transformation. The improving effect of A. ferrooxidans on 2,4-DCP degradation was mainly due to ROS increase. A. ferrooxidans was to promote pyrite surface renew, exposing more Fe(II) and Fe(III) sites that facilitated O2 reduction and H2O dissociation for ROS generation. Biogenic ROS and sulfite bio-oxidation with the free radical mechanism provided other ROS sources. ESR revealed A. ferrooxidans-pyrite interaction led to sustainable ROS production, indicating it could be a significant pathway in driving geochemical cycles of elements.