Mineralogical characterization of natural clays from Brazilian Southeast region for industrial applications

Abstract Characterization studies of clays are often performed to identify possible markets for these materials. Bearing this in mind, two samples of natural clays from the Southeast region of Brazil were studied. Conventional techniques of characterization were used. Granulometric analysis and determination of cationic exchange capacity of these clays were also performed. Nitrogen adsorption-desorption measurements were used to determine the Brunauer-Emmett-Teller specific surface area, and Barrett-Joyner-Halenda and t-plot pore size analysis were carried out. The results obtained were similar for the two clays. Both present high clay fraction (above 80 wt%) composed of illite, kaolinite and quartz minerals. Stratified illite-smectite structures were also observed. Traces of calcite were detected in one of the clay samples, while traces of montmorillonite were observed in the other sample. These results were corroborated by the low cationic exchange capacity values obtained for both clays. These clays showed good adsorptive properties, evidenced by their specific surface areas, with predominantly mesoporous structures and slit-like pores. According to their features, these clays have potential use as adsorbents to replace more expensive materials due to their easy availability and low cost. Resumo Estudos de caracterização de argilas são comumente realizadas para identificar possíveis mercados para esses materiais. Com esse objetivo duas amostras de argilas naturais provenientes do Sudeste brasileiro foram estudadas. Técnicas de caracterização convencionais foram utilizadas. Análise granulométrica e determinação da capacidade de troca catiônica foram também efetuadas. Medições de adsorção/dessorção de nitrogênio foram utilizadas, tanto para obter os valores de área superficial específica das amostras, de acordo com o método de Brunauer, Emmet e Teller, tanto como para a análise do tamanho de poros, usando os métodos de Barret-Joyner-Halenda e t-plot. Os resultados obtidos indicaram que as argilas apresentaram propriedades similares. As duas amostras apresentaram alto conteúdo de fração argila (acima de 80% em massa) composta basicamente dos minerais ilita, caulinita e quartzo. Estruturas estratificadas ilita-esmectita também foram observadas. Uma das amostras apresentou traços de calcita, enquanto a outra apresentou traços de montmorilonita. Os valores baixos de capacidade de troca catiônica obtidos corroboraram estes resultados. As argilas apresentaram b