Preparation and Characterization of Clay Soils for Applications in Cyanide Removal from Mining Wastewater

In Burkina Faso, water resources in mining areas are polluted by cyanide, which is released into the environment through mining activities. To mitigate this pollution, two clays named Koro and Kaya were collected in Burkina Faso and characterized using analytical technics. This work aimed to find out a cheap technology based on local soils for water treatment. The objective of the work was to prepare and characterize two local clays for application in mining effluent treatment. Specific surface area and pore dimensions were analyzed using Brunauer, Emmett and Teller method. In addition, anion exchange capacities, chemical composition through X-ray fluorescence and chemical functions by Fourier-transformed Infrared spectroscopy were determined. Mineralogical composition, thermal behavior, microstructure, and surface elemental composition of clays were examined using techniques of X-ray diffraction and scanning electron microscopy coupled with energy dispersive spectroscopy. Results showed that the surface areas of two anionic clays were 64 m2/g and 50 m2/g for Koro and Kaya, respectively. An anion exchange capacity of 126.68 cmol/kg for Koro and 125.13 cmol/kg at pH 11 was found. Chemical and mineralogical analysis showed that the clays were rich in minerals, mainly of illite (24 - 27)%, montmorillonite (23 - 24)% and kaolinite (17 - 26)%, orthosis (9 - 13)%, quartz (5 - 12)%, goethite (3 - 6)% and anorthite (2 - 6)%. Application of clays for the treatment of cyanide solution led to a decrease in intensities of chemical functions and a modification of the surface morphology. Consequently, those clay soils can be used as adsorbents in cyanide removal through column and batch experiments.