Ion exchange properties of cesium ion sieve based on zirconium molybdopyrophosphate

Cesium ion sieve (Cs-IS) based on a novel ion exchanger, zirconium molybdopyrophosphate, was prepared via an impregnation–recrystallisation–leaching procedure. The physicochemical properties were determined using X-ray photoelectron spectra (XPS), simultaneous thermal analysis (DSC-TGA), nitrogen adsorption–desorption and scanning electron microscopy (SEM). The synthesized material was found to have a cesium exchange capacity (CEC) up to 1.38 mmol/g, a good thermal stability up to 1000 °C and an average mesopore size of 13.54 nm. The surface characterizations revealed that cesium was distributed over the rough surface of the irregular particles. The removal of cesium from acidic media in batch conditions was evaluated focusing on kinetic, isotherm and selectivity. Ion exchange equilibrium was attained within 15 h and best fitted into pseudo-second-order model. The calculated empirical thermodynamic functions hinted the ion exchange of cesium onto Cs-IS could be simplified to an enthalpy-driven, physical adsorption process. The effects of initial pH and ionic strength were explored. The selectivity of Cs-IS for cesium ion was found to be fairly desirable considering the solution acidity and the presence of a substantial amount of sodium ions.