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 (α-FeOOH), and their mixture (Fe-PILM; α-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 pHzpc 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 (R2 = 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 ΔH°, ΔS° and ΔG° 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.

► Mixture of iron pillared clays and goethite as adsorbents of Cs. ► Effect of operating parameters and thermodynamic study were investigated. ► Sorption process was spontaneous and favoured at low temperature. ► Optimal composition of mixture gives a maximum uptake of 93% at best conditions.