Batch experiments on the removal of U(VI) ions in aqueous solutions by adsorption onto a natural clay surface

Abstract

The efficiency of the clay from Bikougou deposit (Gabon) as adsorbent for removing U(VI) ions dissolved artificially in aqueous solutions has been studied. Batch experiments have been performed for that by varying pH, U(VI) ions solution concentration, ionic solution strength, clay dosage, interaction duration and temperature. The U(VI) ions uptake per unit mass of clay, increases with the increase in pH (2-7), U(VI) ions solution concentrations and temperature. It decreases with the increase in ionic solution strength and clay dosage. The adsorption isotherm is best described by Dubinin-Kaganer-Radushkevich isotherm model. The kinetics of the adsorption of U(VI) ions on clay surface follows the pseudo-second-order kinetic model and the interaction realized spontaneously is exothermic. The mean values of thermodynamic constants ?H°, ?S° and ?G° obtained at 308k are respectively-62.54kJ/mol, -0.18kJ/K.mol and -8.68 kJ/mol.

Keywords: Adsorption capacity, adsorbent, U(VI) ions solution, isotherm model, distribution constant