Influence of alkaline activation over swelling and cation exchange capacity on bentonite

The performance of the alkaline processes on the properties of cation exchange capacity (CEC) and swelling was studied in three different types of bentonite from Brazil, Argentina and Mozambique. Alkaline activations were performed by means of mechanochemical reactions with solutions of NaOH and Na₂CO₃, to increase the sodium content of bentonite clays and, thus, improve the properties above. Clay samples were characterized by X-ray diffraction, to obtain the constituent phases. Activated samples were evaluated according to their cation exchange capacity - determined by the methylene blue test, and swelling index - measured by the Foster's method. Results showed that the activation improved the properties of all bentonite types, especially the Brazilian clay, which achieved the most significant raises. There was also an indication that the type of clay affect the processing. (author)