Behaviour of impurity elements during the weathering of ilmenite

2019-09-06 13:42:35

absorption edge Fe3 ray ilmenite

责任者: Grey, Ian;MacRae, C.;Silvester, E.;Susini, J. 单位: CSIRO Minerals, Clayton, Vic. 3168, Australia 来源出处: Mineralogical Magazine,2005,69(4):437-446 摘要: X-ray spectromicroscopy has been applied to the characterization of weathered ilmenite sand samples from Australian localities. X-ray absorption near edge spectroscopy (XANES) studies were performed at the K-edges of the major elements Fe and Ti and minor impurity elements Mn and Cr. An extended suite of reference samples with crystallite sizes ranging from 1 mn to μm size were measured to establish if the absorption edge characteristics were influenced by crystal size effects. No changes were detected for oxides of Cr3+, Fe3+ or Ti4+, but the mixed Fe2+/ Fe3+ oxide, Fe3O4, showed an edge shift to higher energies (by 1.5 eV) in a nanocrystalline sample. The XANES study of a composite ilmenite grain with an unweathered primary ilmenite core and a highly weathered rim showed that Fe was present as Fe2+ in the core and Fe3+ in the rim whereas Mn was present as Mn2+ in both core and rim. Chromium, which is incorporated into the grains during weathering, is present predominantly as Cr3+ although minor ( [similar to] 15%) Cr6+ also occurs in highly weathered grains. The absorption K-edges of Fe3+ and Mn2+ are shifted markedly (by 2-3 eV) to higher energies in titanate phases relative to the binary oxides Fe2O3 and MnO. © 2005 The Mineralogical Society. 关键词: Ilmenite;Sand;Weathering;Impurities;Crystal structure;Grain size and shape;Nanostructured materials;Absorption;Titanate minerals;X ray spectroscopy;X ray microscopes;Ilmenite weathering;X-ray absorption near edge spectroscopy (XANES);Ilmenite sand;Electron microprobe (EMP)