Influence of atmospheric surface oxidation on the formation of H2O2 and ∙OH at pyrite-water interface: Mechanism and kinetic model

Abstract

Numerous studies have reported that the atmospheric surface oxidation of pyrite profoundly affects its surface characterization and species. However, controversy remains regarding the influence of atmospheric surface oxidation on the reaction activity of pyrite. Kinetic experiments, the Monte Carlo (MC) simulation, and a kinetic model were used to comprehensively investigate the effect of atmospheric surface oxidation on the production of hydroxyl radicals (·OH) and hydrogen peroxide (H2O2) by pyrite and its reaction activity. The production of ·OH and H2O2 by dissolved Fe(II) (Fe(II)aq) in the suspensions of surface-oxidized pyrite (SOP) was impeded. The primary reason is that Fe (hydr)oxide on the SOP surface can decompose H2O2 to H2O, and the production of ·OH via the Fenton reaction was inhibited subsequently. However, the production of ·OH and H2O2 by Fe(II) sites on the SOP surface (Fe(II)pyrite) was promoted because Fe(III) sites in Fe (hydr)oxide (Fe(III)oxide) enhanced the electron transfer from Fe(II)pyrite to O2. The proportion of Fe(III) sites determined the degree of influence on the production of ·OH and H2O2 by Fe(II)aq and Fe(II)pyrite. The Sb(III) oxidation reaction also indicated that atmospheric surface oxidation altered the oxidation activity of pyrite. In conclusion, atmospheric surface oxidation has a significant effect on the environmental behavior of pyrite and the fate of redox-active substances.