Refinement of the isomorphic substitutions in goethite and hematite by the Rietveld method, and relevance to bauxite characterisation and processing

摘要: Abstract Although bauxites usually have a quite simple mineralogy – gibbsite (+boehmite), quartz, kaolinite, hematite, goethite, anatase (+rutile) and minor or less common phases, fine particle size, low crystallinity variable compositions of the iron minerals might render phase quantification difficult, as well impairing bauxite processing. A reliable complete characterisation is therefore necessary in order to predict processing performance ensure compliance plant specifications. X-ray diffraction most important single tool for characterisation, constrained refinement Al-for-Fe substitution goethite during one-step by fundamental parameters Rietveld method has been successfully used. The same was developed analyse coupled OH−-for-O2− substitutions hematite. tested against Mossbauer spectroscopy distribution on samples with large compositional range, Certified Reference Materials from main Brazilian mines, improved results widened range conclusions that can be drawn related