ETUDE COMPARATIVE DE LA CARACTERISATION PHYSICO-CHIMIQUE DES ARGILES (LATERITE ET ZANGA) DE LA CITE DE LUKALA/KONGO CENTRAL/REPUBLIQUE DEMOCRATIQUE DU CONGO

Abstract

This study aims to comparatively characterize two natural clayey matrices from Lukala, located in the Kongo Central province of the Democratic Republic of the Congo. Analyses of physicochemical parameters (pH and loss on ignition), X-ray fluorescence (XRF), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR) spectroscopy made it possible to distinguish between two aluminosilicate matrices based on their distinct accessory mineral assemblages, despite a shared kaolinitic background.

The "Zanga" clay has a near-neutral pH (7.14) and a loss on ignition (LOI) of 8.21%, whereas the laterite exhibits an alkaline pH (8.16) and an LOI of 6.08%. X-ray fluorescence reveals that the Zanga clay is highly siliceous (SiO₂ = 73.62%; SiO₂/Al₂O₃ ratio = 5.27), whereas the laterite displays a sesquioxidic profile rich in iron (Fe₂O₃ = 27.52%; SiO₂/Al₂O₃ ratio = 1.83). These characteristics are confirmed by XRD and FTIR analyses, which show that the Zanga clay consists of a mixture of kaolinite (20%), tectosilicates (albite 20%, quartz 8%), illite-muscovite (13%), and carbonates (14% calcite-dolomite). In contrast, the laterite is characterized by a kaolinitic framework (16%) mixed with chamosite-ferrocarpholite (26%), as well as a massive accumulation of iron and aluminum oxy-hydroxides (37% hematite, goethite, and gibbsite). These results provide important data regarding the potential for utilizing these two local resources from Kongo Central.