Evaluation of the iron in kaolin from different Brazilian regions

Full text: Over the past decades, kaolin has been intensively used in the paper industry as coating and filling. For this type of application, kaolin must have a high level of brightness/whiteness, which strongly depends on its content of impurities (mainly iron oxides and hydroxides), and it can be improved by benefit processes involving particle size classification, magnetic separation and chemical treatment [1,2]. The study was conducted with eight Brazilian kaolin samples from different geographical and geological origins (São Paulo, Pará, Amapá, Rio Grande do Norte, Bahia and Minas Gerais). For all samples, the amount and nature of iron impurities were determined by X-ray fluorescence (XRF), electron paramagnetic resonance (EPR) and Mössbauer spectroscopy ⁵⁷Fe. The iron ion (Fe³⁺ and Fe²⁺) is present in the samples studied, in different amounts, in the kaolinite structure and also in iron minerals (magnetite, hematite and goethite). The beneficiation promoted an increase of the index of whiteness, but of the iron remains in the kaolinite structure. (author)