Pyrite Oxidation Mechanism by Oxygen in Aqueous Medium

The mechanism of the initial steps of pyrite (100) surface oxidation was investigated in detail by means of density functional theory/plane-wave calculations. Pyrite oxidation is related to many environmental and technological issues, and its mechanism has not been completely understood. A chemical picture of the pyrite oxidation process in the presence of oxygen and water was proposed in the present investigation. The reaction steps of the oxidation mechanism can be separated into two types. Type I reactions present lower activation energies and are redox processes that involve oxidation of two Fe(II) sites on the surface to form predominantly the Fe(III)–OH–. This species is formed from hydrogen transfer between the adsorbed water to the adsorbed oxygen molecule on the Fe(II) sites. Type II reactions present higher activation energies and lead to the formation of a S═O bond through the hydrogen atom transference from a water molecule to the Fe(III)–OH– species, forming Fe(II)–OH2. These reactions presen...