Tb/Eu-AV-9: A lanthanide silicate for the sensing and removal of cesium ions from aqueous solutions

Abstract

The ion exchange of Cs+ from aqueous solutions was studied using a novel microporous lanthanide silicate with photoluminescence properties, Tb/Eu-AV-9. This mixed lanthanide silicate was prepared by hydrothermal synthesis, characterized by scanning electron microscopy, powder X-ray diffraction, and photoluminescence spectroscopy. Batch ion exchange experiments were performed at room temperature (295 K) to measure isotherm and kinetics (removal curves). The Langmuir-Freundlich equation provided a good fit to the equilibrium data. A kinetic model based on the Maxwell-Stefan equations was implemented and adjusted to the cesium removal curves, and achieved average deviation of 8.37%. The model parameters were the diffusion coefficients, while the convective mass transfer coefficient was purely estimated. The Maxwell-Stefan diffusivities for the interaction of the counter ions Cs+ and K+ with the solid exchanger were D-AS = 8.373 x 10(-15) m(2) s(-1) and D-BS = 2.795 x 10(-14) m(2) s(-1), respectively, being consistent with other values in the literature. With respect to photoluminescence studies, the differences found between the emission spectra of native and CS+-exchanged Tb/Eu-AV-9 disclosed the potential of this sorbent for qualitative/quantitative CS+ sensing purposes. (C) 2015 Elsevier B.V. All rights reserved.