Cesium and barium removal from aqueous solutions in the presence of humic acid and competing cations by a Greek bentonite from Kimolos Island

Abstract The Cs- and Ba-sorption, onto bentonite from Kimolos island (Cyclades, Greece) was investigated in aqueous solutions in the presence of Na+, Ca2+ and humic acid. Batch experiments were performed using as tracers 137Cs and 133Ba and γ-ray spectroscopy. The sorption significantly depended on initial concentration, ionic strength and temperature of the solutions. The sorption isotherms were satisfactorily reproduced by the Langmuir and Freundlich equations. The kinetic experiments at 293, 308 and 323 K and the calculation of the thermodynamic parameters (ΔH, ΔS° and ΔG°) indicated that Cs- and Ba-sorption was spontaneous and endothermic process. The sorbent was characterized before and after the sorption experiments using Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM-EDS). It was demonstrated that the Kimolos bentonite is a good sorbent for cesium and barium from highly contaminated solutions and its sorption capacity reduced in presence of humic acid and competing cations.