Mineralogy and physico-chemical properties of alluvial clays from far-north region of Cameroon: A tool for an environmental problem

Abstract

In a view to evaluate their potential use as adsorbent for wastewater treatment, the mineralogical and physico-chemical properties of alluvial clays from far north region of Cameroon has been determined. Chemical, X- ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and transmission electron microscopy (TEM) analysis of the alluvial clays reveal that the main mineral present is smectite, kaolinite and quartz. Particle size distribution of the clay is centered around particles of 2, 5 and 30 µm dimension. Cation exchange capacity (CEC) and specific surface area of the raw clay fraction are 62 meq/100 g and 104 m2/g respectively. Those results lie within the values usually found for smectites. Mild acid attack (use of 0.5 M HCl solution) did not induce any noticeable change of clay structure and texture, but the exchangeable cation (Ca2+, Na+, Mg2+) are removed. It is also observed that Fe2+ and K+ atoms are part of clay lattice. The overall formula of the clay mineral which was established are: smectite, [Si3.42Al0.58]tetra[Al0.87Fe0.96 Mg0.17 ]octa O10(OH)2 (C+)0.75; and kaolinite, Si2Al1.95Fe0.05O5(OH)4. Acid activation was attributed to the protonation of negative charge of smectite at low pH and by replacement of H+ ion by Na+ ion at high pH.   Key words: Alluvial clays, Cameroon, mineralogy, crystal-chemistry, smectites, textural properties.