Physico-Chemical and Mineralogical Analysis of Geophagic Clays in Lubumbashi and Assessment of the Risks Associated with Geophagy

In view of the increasing local exploitation of clays used in geophagy in Lubumbashi, and with the aim of adding value to it, this work has identified and characterized three of them. Organoleptic tests showed that these clays vary in colour from brownish yellow to yellow-brown, "stick" to the tongue and are crunchy when chewed. X-ray fluorescence spectrometry (XRF) highlighted major oxides: SiO2 (54.8-64.7%), Al2O3 (20.0-24.0%), Fe2O3 (1.8-5.0%), TiO2 (1.4-2.8%) and K2O (0.9-2.4%). Cation exchange capacity (CEC) varied from 21.4 to 26.0 meq/100 g, loss on ignition varied from 5.1% to 13.2%, moisture content range from 2.40% to 2.96% with a swelling index from 53.57% to 55.27%, density and organic matter were too low. The pH water and pH KCl were between 4.04 and 5.96 and between 3.72 and 5.49 respectively. High levels of certain metallic elements such as As, Cd, Pb and Ni, and the presence of uraniumbearing substances, were also revealed by inductively coupled plasma-atomic emission spectrometry (ICP-AES).This study revealed that geophagic clays were plastic based on their oxides, illites and/or chlorites, also depending on their CEC, acidic considering their pH and that they were contaminated by compounds that could be harmful to the health of geophagists.