Abstract
Bentonite is a type of clay composed mainly of montmorillonite, shows excellent properties of adsorption and, as main features, high cation exchange capacity, swelling capacity, large surface area and low hydraulic conductivity. Bentonite is used as a raw material in over 40 industrial applications. The lyophilization process is a drying process of a product through a sublimation step for removing water using low pressure. This process prevents any biological activity and chemical reactions. The lyophilization process is effective in product shrinkage, loss of volatiles, thermal decomposition, enzymatic activities and protein denaturation as compared to other drying means, as it maintains the integrity of the product. This study evaluated the behavior and characterized the more and less active sodium bentonites, before and after the lyophilization process. It was considered as more active the bentonite that presented more cation exchange capacity related to sodium ions (Na+). Chemical and mineralogical analyzes, cation exchange capacity, microbiological analysis, FTIR and swelling capacity were evaluated. An increment on swelling capacity of the more active freeze-dried bentonite of approximately 32% in comparison to the standard was observed.
Keywords:
bentonite; lyophilization; characterization; cation exchange; swelling
