Correlations between geological track and bentonite quality in the mercosur trade block.

• Ano de defesa: 2018
• Autor(a) principal: Machado, Gabriel Gonzalo
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Bentonita (Aplicações industriais); Bentonites (Industrial applications) Diagenesis; Caracterização tecnológica de minérios; Diagênese; Difração por raio X; Mercosul; Mercosur; Mineral characterization; X-ray difraction
• Link de acesso: http://www.teses.usp.br/teses/disponiveis/3/3134/tde-01032019-090527/

It is undoubtable that the geological path followed by a bentonite natural occurrence, will set a birthmark in terms of grade and quality, the former being expressed in terms of mineralogical composition, smectite content and other aspects derived from the bulk sample characterization, and the latter being expressed in terms of the crystal chemistry of smectite species present and derived from the clay size fraction observations. The influence of parent rock composition, genesis mode, burial history and preservation conditions after alteration, would set the fingerprint on bentonite and inherent structural features in smectites species, which determines potential industrial and scientific uses. The following thesis aims to evaluate physicochemical properties of 12 bentonite samples, coming from the six most relevant bentonite bearing geological areas located in the Mercosur economic block (Argentina, Brazil and Uruguay)1; in order to stablish possible correlations between distinctive geological contexts, and observed characteristics from whole rock providing information regarding grade and the clay size fraction will provide information regarding quality. Mineralogical composition corroborated the tendency to be influenced by the geochemical signature of parent rock firstly, and secondly genesis mode (probably due to lack of information in this aspect). Age, on the other hand, could on the contrary, be a misleading parameter; in the sense that preservation is not necessarily time dependent. Poor grade and the presence of mixed layers and accessory clay mineral phases (mostly kaolinite but also I/S, illite and pyrophyllite) appear to be associated with hydrothermal to sedimentary alteration modes, higher grade bentonites with tendency to yield extreme relative values of physical properties, measured in layer charge, swelling and organic sorption, were found in association to diagenetic bentonites. In terms of smectite species, all members found belong to the montmorillonite-beidellite series, and rhyolitic to dacitic volcanic source, tends to alter into the montmorillonite end member of the series; and accordingly, basic precursors (basalt) to intermediary (andesite), show a tendency to alter into transitional up to beidellite Fe-rich end members of the series respectively. To evaluate implications on possible applications, crystal chemistry was evaluated over the <1 µm size fractions by XRD and XRF along with other accessory techniques (FTIR, SEM-EDS and size distribution analysis), finding a clear trend, between layer charge relative magnitude, as a function organo-sorption behavior; by simply evaluating the d-001 XRD reflections on oriented slides after first K-saturation and sequential ethylene glycol solvation, against (CTAC)-montmorillonite d001 basal reflection , being inversely proportional and resulting in a broad variety Organophilic XRD patterns, showing distinctive expandability behavior ranging from 15,2 Å To 21,68 Å. As a function of alkyl chain size and the known sorption isotherm, basically all patterns of organo-compound sorption where observed, going from lateral monolayer to paraffin type sorption behavior.