Two bentonite clays with different mineralogical compositions from Mendoza, Argentine, were activated with H2SO4 solutions of 4 and 8 N at 90ºC for 3.5 hours. This treatment affected clay structural properties, as was shown by thermogravimetry, infrared spectrometry and chemical analysis. Bleaching efficiency for sunflower oil was strongly dependent on the acid concentration used for clay activation. The samples have bleaching capacity comparable to that observed with a commercial adsorbent standard. The mineralogical composition of natural clays influenced the properties of the activated clays.

Natural occurring bentonites may show very little activity for bleaching oils and fats. For that reason, acid-activation of bentonites with inorganic acids is usually carried out to promote earths' adsorptive capacity during clarification of vegetable and animal oils and fats, as well as mineral oils. In this work we used two acid-activated natural bentonites from Mendoza, Argentina, with different mineral compositions and submitted them to acid treatment with hydrochloric acid to further clarify cottonseed oil. Both clays were treated with HCl at 4 and 8N for two hours in order to evaluate important structural properties modifications that may affect oil bleaching. X-ray diffraction, thermal and chemical composition analyses were performed. Cottonseed oil clarification experiments were run in previously established appropriated laboratory conditions. It was shown that clarification efficiency is strongly dependent on the acid concentration and natural clay mineral compositions used to activate the bentonites for the clarification process.

A ativação ácida de uma argila tem por finalidade aumentar as suas propriedades adsortivas e catalíticas. Nesse estudo, uma amostra de argila bentonítica, proveniente da Província de Mendoza (Argentina), foi ativada com diferentes concentrações (4 e 8 N) por ácido sulfúrico e clorídrico. Para verificar a influência das concentrações e do tipo de ácido usado na ativação da argila, utilizou-se técnicas de difração de raios X, análise térmica diferencial e termogravimétrica e análise química. Os resultados mostraram que houve modificação na estrutura do material argiloso após o ataque ácido. O tratamento com ácido sulfúrico e clorídrico sobre uma mesma bentonita originou produtos com diferentes características estruturais.

The clay acid activation has the purpose of increasing its adsorbent and catalytic properties. In this study, a bentonite clay sample from Mendoza (Argentine) was activated in different concentrations (4 N and 8 N) through the use of sulphuric and hydrochloric acid. To verify the influence of concentrations and the kind of acid utilized in the clay activation, it was utilized techniques of X-ray diffraction, thermogravimetric and differential thermal analysis and chemical analysis. The results have shown that the clay structure was modified after acid attack. Sulphuric and hydrochloric acid treatment in the same bentonite originated products with different structural characteristics.