Instituto de Química
URI Permanente desta comunidadehttps://repositorio.ufrn.br/handle/123456789/31488
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Navegando Instituto de Química por Assunto "Acid treatment"
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Artigo Acid treatments of montmorillonite-rich clay for Fe removal using a factorial design method(ABM, ABC, ABPol, 2013) Bieseki, Lindiane; Bertell, Francine; Treichel, Helen; Penha, Fabio G.; Pergher, Sibele Berenice CastellãMontmorillonite clays are of great interest for industrial processes such as catalysis and adsorption. The textural properties of clays can be modified in an attempt to increase their uses. This paper describes the acid treatment of natural montmorillonite clay. The materials were characterized using X-ray diffraction (XRD), atomic absorption spectroscopy (AA) and BET surface area measurements. Three different acids (HCl, HNO3 and H2SO4) were tested, and HCl and H2SO4 were more efficient for removing Fe from the clay. The results indicate that HCl better preserves the material structure because less Al is removed. A central composite design (CCD) 22 was applied to evaluate the treatment using HCl. The temperature and concentration presented positive effects on the removal of Fe, Al and Mg. Combinations of the HCl acid solution concentration and temperature, such as 4 mol.L-1/50 °C and 1 mol.L-1/75 °C, assured that Fe was removed with less damage to the structure.Artigo Porous materials obtained by acid treatment processing followed by pillaring of montmorillonite clays(Elsevier, 2013-11) Bieseki, Lindiane; Treichel, Helen; Araujo, Antonio S.; Pergher, Sibele Berenice CastellãMontmorillonite clay was treated with hydrochloric acid and subsequently pillared with aluminum polyoxocations. The acid-treated samples were evaluated for the removal of structural elements (Al, Fe and Mg) and for conservation of the lamellar organization. The more severe the treatment, the greater the specific area obtained. Despite the loss of structural organization, all samples were pillared, with a displacement of peak (001) to 2θ lower angles. The pillaring of all acid-treated samples promoted an increase in the specific area of these materials. Pillared samples previously treated at 50 °C with HCl concentrations of 2 and 4 mol L− 1 underwent an increase in their specific areas of approximately 45%. Pillared samples treated with 4 mol L− 1 of HCl at 80 °C underwent the lowest percent increase in surface area, approximately 10%, compared to the untreated samples. All samples possessed greater uniformity in pore size. Acid treatment prior to pillaring promoted an increase in the number of acid sites of moderate strength compared to pillared natural clay.