Characterization of Tunisian clay suitable for pharmaceutical and cosmetic applications

Abstract The aim of this study is to assess the suitability of purified Tunisian clay for its possible pharmaceutical and cosmetic uses. Mineralogical, chemical and physicochemical characterization was performed with the aid of tools like X-ray diffraction (XRD), Chemical composition, DTA/TGA analysis, Cation exchange capacity (CEC), particle size distribution by laser dispersion (PSD), surface area (BET method), Point of zero charge (PZC) and surface charge density σ H . Pharmacopoeia tests were also carried: Swelling capacity, sedimentation volume and pH measurement. For microbiological tests, the absence of Salmonella species, Escherichia coli , Staphylococcus aureus and Pseudomonas aeruginosa was tested. The X-ray diffraction data revealed that the Tunisian sample is an interstratified illite-smectite. The percentage of smectitic fraction is estimated to be 78%. The chemical, textural and porosimetric results show important values suggesting that this mineral clay can function in creams, powders and emulsions. In view of the fundamentals of major pharmacopoeias for use of bentonite in pharmacy and considering the swelling capacity and sedimentation volume values, and microbiological results we could designate a pharmaceutical acceptable denomination for Tunisian purified clay.