Iron based nanoparticles-zeolite composites for the removal of cesium from aqueous solutions

Removal of cesium from waters is an emerging issue after the accident at Fukushima Daiichi Nuclear Power Plant. In this work, new nanoscale zero valent iron-zeolite (nZVI-Z) and nano-Fe/Cu-zeolite (nFe/Cu-Z) composites for cesium removal were fabricated through ion exchange process followed by liquid-phase reduction. The characterization by XRD and SEM-EDS demonstrated that nZVI and nano-Fe/Cu particles were successfully loaded onto zeolite. The performance of the composites for the removal of cesium from aqueous solutions with the ability to separate the adsorbent magnetically was investigated. Batch sorption experiments were systematically carried out to assess the effect of different parameters such as pH, initial concentration, contact time, adsorbent dosage and temperature. The removal kinetics of cesium was adequately described by the pseudo-second order kinetic model, which indicates that the uptake mechanism was chemisorption. The rate constant values for adsorption by nFe/Cu-Z were greater than the values obtained for nZVI-Z, meaning that nFe/Cu-Z had faster adsorption kinetics towards cesium solutions. The equilibrium adsorption data gave better mathematical fitting towards Langmuir and Freundlich isotherm models, where the maximum adsorption capacity of nFe/Cu-Z (77.51 mg/g) was found to be higher than that for nZVI-Z (71.12 mg/g). The observed thermodynamic parameters showed that the adsorption of cesium was endothermic process and spontaneous in nature. The composites were efficiently recovered from solution after the adsorption experiments by an easy, simple and rapid magnetic separation. The obtained results suggested that both composites could be used as a promising technique for the treatment of waters containing cesium. (C) 2018 Elsevier B.V. All rights reserved.