Study of traditional Tunisian medina clays used in therapeutic and cosmetic mud-packs

摘要

The present study was carried out to access the suitability of eleven clay samples (green and brown) from five Tunisian medina markets, traditionally used in home-made mud-packs. The mineralogical composition was determined from X-ray powder diffraction and X-ray fluorescence data. Scanning electron microscopy coupled with energy-dispersive X-ray microanalysis was also carried out, as well as thermogravimetric analysis of raw clay samples. To determine the performance of the samples in mud-pack thermotherapy, cooling kinetics of clay pastes were fitted to obtain the corresponding specific heats. According to their mineralogical composition, the studied medina clay samples were mainly composed by illite and kaolinite, with exception of two Mg smectite-rich samples and other two calcite-rich samples. The presence of relatively high amounts of crystalline silica (quartz) in some of the samples advises against their not controlled manipulation, even if there are no quantitative limits (widely approved) of crystalline silica content above which the usage of commercial clays can be prohibited. The cooling rates and specific heats of the studied pastes were adequate to their use in the preparation of hot mud-packs, able to transfer heat to the skin during a period of at least 15 min after application.