title: Quantifying Fenton reaction pathways driven by self-generated H2O2on pyrite surfaces.
abstract: Oxidation of pyrite (FeS2) plays a significant role in the redox cycling of iron and sulfur on Earth and is the primary cause of acid mine drainage (AMD). It has been established that this process involves multi-step electron-transfer reactions between surface defects and adsorbed O2and H2O, releasing sulfoxy species (e.g., S2O32-, SO42-) and ferrous iron (Fe2+) to the solution and also producing intermediate by-products, such as hydrogen peroxide (H2O2) and other reactive oxygen species (ROS), however, our understanding of the kinetics of these transient species is still limited. We investigated the kinetics of H2O2formation in aqueous suspensions of FeS2microparticles by monitoring, in real time, the H2O2and dissolved O2concentration under oxic and anoxic conditions using amperometric microsensors. Additional spectroscopic and structural analyses were done to track the dependencies between the process of FeS2dissolution and the degradation of H2O2through the Fenton reaction. Based on our experimental results, we built a kinetic model which explains the observed trend of H2O2, showing that FeS2dissolution can act as a natural Fenton reagent, influencing the oxidation of third-party species during the long term evolution of geochemical systems, even in oxygen-limited environments.
authors.affiliation: Centro de Astrobiología (CSIC-INTA), 28850 Torrejón de Ardoz, Madrid, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Gil-Lozano
authors.affiliation: Carl Sagan Center at the SETI Institute, 189 Bernardo Avenue, Suite 100, Mountain View, CA 94043, USA.
authors.forename: A F
authors.initials: AF
authors.lastname: Davila
authors.affiliation: Centro de Astrobiología (CSIC-INTA), 28850 Torrejón de Ardoz, Madrid, Spain.|Departamento de Geociencias Marinas, Universidad de Vigo, Lagoas Marcosende, 36310-Vigo, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Losa-Adams
authors.affiliation: Centro de Astrobiología (CSIC-INTA), 28850 Torrejón de Ardoz, Madrid, Spain.|Department of Astronomy, Cornell University, Ithaca, 14853 NY, USA.
authors.forename: A G
authors.initials: AG
authors.lastname: Fairén
authors.affiliation: Departamento de Geociencias Marinas, Universidad de Vigo, Lagoas Marcosende, 36310-Vigo, Spain.
authors.forename: L
authors.initials: L
authors.lastname: Gago-Duport