Pharmaceutical studies on Egyptian kaolins for healthcare uses

Resumen

The present study aims to evaluate, by the first time, the potentiality of the Egyptian Abu Zenima kaolin deposits of the estimated reserve 120 million tons, for healthcare uses. The studied kaolin district covers about 333 Km2 of cultivated and accessible land that lies at west central Sinai Peninsula, between longitude 33˚ 14΄ 00˝ and 33˚ 24΄ 00˝ E and latitude 28˚ 52΄ 00˝ and 29˚ 10΄ 00˝ N. The objectives of the study are also to conclude the pharmaceutical quality characteristics that considered as mineralogical and technological parameters used for controlling the kaolins purity upgrading with limiting the applicability of exploiting their low grade zones, and criteria of developments for functionality in pharmaceutical and biomedical applications. Sixty-five representative samples were collected carefully to avoid any contaminations and properly as proportional with both of layers thicknesses and their lateral extents within the outcropped sections of the studied kaolin deposits. Three composite sections exposed at Wadi Khaboba (12 samples, coded by K; total thickness 20 m; at 29˚ 05΄ 01˝ N and 33˚ 14΄ 46˝ E), Gabal Hazbar (5 samples; coded by H;12 m; at 29˚ 04΄ 45˝ N and 33˚ 22΄ 05˝ E) and Wadi Abu Natash (12samples; coded by N;19 m;28˚ 56΄ 45˝ N and 33˚ 19΄ 24˝ E) sites which belong to the Carboniferous sediments; besides other three sections related to the Cretaceous sediments that outcropped at Gabal El Dehessa(10 samples, coded by D, 14 m, at 28˚ 55΄ 55˝ N and 33˚ 17΄ 59˝ E), Gabal Farsh El Ghozlan (13 samples, coded by F;21 m; at 28˚ 55΄ 40˝ N and 33˚ 18΄ 10˝ E) and Wadi Budra (13 samples, coded by B; 20 m; at 28˚ 55΄ 06˝ N and 33˚ 19΄ 16˝ E) localities. Firstly, all the pharmaceutical and therapeutical uses of kaolinite, that have been studied so far and reported through this recent decade, were critically reviewed and analyzed in order to understand their roles, specifications, limits, criteria, activities and controlling parameters required for these applications. The results and conclusions of these previous studies are considered as important information and guidance for the possibilities of exploitations as well as revealing new hypotheses and trends for functionalities of the variant kaolin grades. For kaolin pre-formulation assessment, the studied samples were prepared and characterized generally by means of mineralogical(XRD) and chemical (XRF) analyses for determining the bulk major oxides, trace elements and for calculating the kaolin mineral and associated impurities contents, besides the kaolinite structural order-disorder degrees and crystallite size. In additions, the performed pharmaceutical technological characterizations and pharmacopoeial specifications include: the colorimetry by spectrophotometer for measuring the CIE-lab chromatic and whiteness parameters, rheological properties and thixotropy, particle geometry and size distribution and grading parameters by laser granulometry and particle micromorphology by scanning electron microscopy (SEM); other specific studies were performed to the highest grade samples include: complementary chemical analysis by the TEM for determining kaolinite micrompositions and by the ICP for assaying the toxic heavy metals, as well as pharmacopoeial tests. On the other hand, thermal properties of 50% kaolin aqueous suspensions were characterized by means of cooling kinetics using differential scanning calorimetry (DSC). The results proved that 50% of the total raw samples of the economic Egyptian Abu Zenima kaolin deposits contain > 75%, and 20% of the samples showed > 90% of kaolinite. The high grade samples are suitable for pharmaceutical industries. The lower grades have specific functionalities and they also can be easily upgraded and improved to reach the pharmaceutical grade. The present study summarized all the possible uses and recent applications of kaolins that have been known so far, and hence this is considered as important orientation regarded to an added economic value for exploitation and marketing of the Egyptian kaolin resources as well as an academic vale for the future developmental researches on kaolinite for healthcare applications. Moreover, the present study also confirmed the suitability of the Egyptian kaolins in pelotherapy and tested new technological parameters for developing this application from pharmaceutical point of view, as one of the major medicinal branches of applied clays in the physical therapy.