Physicochemical and mineralogical composition studies of clays from Share and Tshonga areas, Northern Bida Basin, Nigeria: Implications for Geophagia

Abstract

This study is focused on the evaluation of the geophagic characteristics of the sedimentary clay deposits at Share and Tshonga areas, northern Bida Basin, Nigeria. The methods used include particle size distribution, cation exchange capacity (CEC), acidity and alkalinity (pH), X-ray diffractometry, and bulk inorganic geochemical analysis (X-ray fluorescence and inductively coupled plasma mass spectrophotometer). The investigated clays are classified as dominantly clayey–silt with minor clayey–sand type, which conforms with the textural standard of geophagic clays obtained from different parts of the world. The whitish coloration of the clays with an occasional red stain also compares well with geophagic clays from Kenya and parts of South Africa and is therefore considered suitable for consumption. The observed low CEC (1.71–5.06 cmol(+)/kg) and acidic pH (4.54–6.87) values of the clay samples would make them effective against nausea and excessive salivation during pregnancy. The mineralogical compositions of these clay samples show the dominance of kaolinite with minor non-clay minerals, which makes it suitable not only for food detoxification but also as an alleviation of gastrointestinal disorders such as diarrhea. Chemical analysis shows a low percentage per weight of certain elements that are of nutritional value, though not in the present state but better as excipients in the pharmaceutical industry. It was observed, however, that consumption of more of the studied clay may lead to adverse health due to the presence of some heavy metals (Co, Cu, Ni, Cd, Ag, and Pb) with concentrations in excess of the permissible limit.