Comparative study of the cooling rates of bentonite, sepiolite and common clays for their use in pelotherapy

The thermal behaviour of muds and clays for pelotherapic purposes is a very important parameter because its directly relation with the therapeutic action of peloids. Usually common clays are used for maduration in pelotherapy but rarely are used pure clays as bentonites or sepiolite. Under study in this work are the thermal properties of almost pure samples of Al-bentonite (montmorillonite), Mg-bentonite (saponite) and sepiolite, and their comparison with three common clays composed of mixtures of kaolinite, illite and smectite with other silicates and carbonates. The samples have been characterized by means of mineralogical techniques (XRD) but also by chemical analysis (XRF, AA), microfabric studies (SEM) and physical and physico-chemical determinations (granulometry, BET surface area, plasticity index, water absorption and CEC). Results indicate noteworthy differences between common clays and pure clays, especially with Mg-bentonite. Besides water absorption capacity other physical and physico-chemical properties seem to play an important role in the cooling kinetic and therefore in the selection of candidate clays for pelotherapy.