Structural contributions of different manganese oxide minerals on the redox transformations and proliferation of iodine

The redox capabilities of birnessite minerals are contingent upon the physical characteristics of the solid, indicating that different allotropes have various reactivities. Here, the role of these structural differences on the oxidation of iodine, a risk driving environmental contaminant in several federal complexes, was investigated. The mechanism of which can be seen here, with one of the minerals of study, acid birnessite. The pH range chosen for this study was pH 5–6. Throughout the experiments it was seen that the average oxidation state (AOS) had the greatest contribution to the differences in redox capabilities of the various birnessite minerals. Several trends were observed throughout this study: as AOS decreased, oxidation of iodide (I−) increased; as specific surface area (SSA) increased, the sorption of iodate (IO3−) increased. Additional experiments were conducted at trace levels of iodine, to better model environmental conditions. In that case, a one-step conversion of I− to IO3− occurred, to a greater extent than under artificially elevated concentrations.