title: Pyrite oxidation in the presence of hematite and alumina: I. Batch leaching experiments and kinetic modeling calculations.
abstract: Pyrite is one of the most common and geochemically important sulfide minerals in nature because of its role in the redox recycling of iron (Fe). It is also the primary cause of acid mine drainage (AMD) that is considered as a serious and widespread problem facing the mining and mineral processing industries. In the environment, pyrite oxidation occurs in the presence of ubiquitous metal oxides, but the roles that they play in this process remain largely unknown. This study evaluates the effects of hematite (α-Fe2O3) and alumina (α-Al2O3) on pyrite oxidation by batch-reactor type experiments, surface-sensitive characterization of the oxidation layer and thermodynamic/kinetic modeling calculations. In the presence of hematite, dissolved sulfur (S) concentration dramatically decreased independent of the pH, and the formation of intermediate sulfoxy anionic species on the surface of pyrite was retarded. These results indicate that hematite minimized the overall extent of pyrite oxidation, but the kinetic model could not explain how this suppression occurred. In contrast, pyrite oxidation was enhanced in the alumina suspension as suggested by the higher dissolved S concentration and stronger infrared (IR) absorption bands of surface-bound oxidation products. Based on the kinetic model, alumina enhanced the oxidative dissolution of pyrite because of its strong acid buffering capacity, which increased the suspension pH. The higher pH values increased the oxidation of Fe2+to Fe3+by dissolved O2(DO) that enhanced the overall oxidative dissolution kinetics of pyrite.
authors.affiliation: Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan. Electronic address: carlito.tabelin@gmail.com.
authors.forename: Carlito Baltazar
authors.initials: CB
authors.lastname: Tabelin
authors.affiliation: Department of Mining and Petroleum Engineering, Faculty of Engineering, Chulalongkorn University, Bangkok 10330, Thailand.
authors.forename: Suchol
authors.initials: S
authors.lastname: Veerawattananun
authors.affiliation: Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Ito
authors.affiliation: Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
authors.forename: Naoki
authors.initials: N
authors.lastname: Hiroyoshi
authors.affiliation: Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan.
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Igarashi
keywords: Acid mine drainage; Alumina; Hematite; Kinetic modeling; Oxidation; Pyrite