Adsorption of caesium from aqueous solution on binary mixture of iron pillared layered montmorillonite and goethite

Caesium adsorption was carried out on two materials namely iron pillared layered montmorillonite (Fe-PILM) and goethite (alpha-FeOOH), and their mixture (Fe-PILM: alpha-FeOOH). The characteristics of these two adsorbents were determined by using X-ray diffraction, Fourier transform infrared spectrum. A set of experiments was done to estimate cation exchange capacities and zero point of charge pH,pc of used materials. Adsorption of Cs as a function of pH, mass fraction of goethite in the mixture, initial concentration and ionic strength was investigated. The kinetic study showed that sorption followed pseudo-first-order kinetics with a good correlation coefficient (R-2=0.997). Optimal Cs ions elimination was favoured at the pH range 5-9. The obtained results revealed that the maximum adsorption of 93%, took place at 20% composition of goethite in the mixture. The Cs sorption data onto optimal mixture were described using Freundlich. Langmuir and Dubinin-Radushkevich (D-R) models. The thermodynamic parameters Delta H degrees, Delta S degrees and Delta G degrees for the Cs adsorption were determined by using four temperatures (288, 308, 338 and 360 K). Results show that the adsorption process was exothermic and favoured at low temperature. (C) 2011 Elsevier B.V. All rights reserved.