Influence of calcium in moisture retention clay

ABSTRACT Bentonite as a raw material is an economical alternative to produce desiccants. The literature indicates that it is a good water adsorbent in relation to the desiccants commonly used in industry (silica gel, molecular sieve). In this sense, it is a valid alternative and an economic option since the clay is a natural compound, which makes it environmentally friendly. In this way, it is possible to protect products from moisture with the addi-tional advantage that its desiccant capacity remains practically constant after successive cycles of adsorption - regeneration, using low temperatures (100°C) for the latter process. Considering the interest of increasing the exploitation of bentonite in Argentina, previous studies evaluated its retention capacity, using, among others, a Patagonian bentonite. The adsorption of water vapor is affected by the concentration of the smectite clay mineral, the relative humidity, the drying of the samples, and the type of interlaminar cation of the smectite. In the present work it is determined that there is an increase of adsorption in relation to the starting material after the addition of increasing concentrations of Ca by ion exchange. In these samples the adsorption is carried out mainly by the hydrated ion present in the interlaminar space. Also, the desiccant materials benton-ite-Ca showed structural and textural differences in relation to natural bentonite.