Factorial design analysis for optimizing the removal of cesium and strontium ions on synthetic nano-sized zeolite

Cesium and strontium ions removal from aqueous solution onto nano-sized zeolite was investigated using uni-variant and multi-variant procedures. Nano-zeolite Y was prepared using hydrothermal method and characterized by X-ray diffraction, X-ray fluorescence, transmission electron microscopy, and Fourier transformed infrared spectroscopy. Direct space approach was adopted to simulate the crystallographic structure and calculate the chemical formula. Removal kinetics and equilibrium isotherms were studied and the reaction nature, parameters, and most suitable models to predict sorption capacity were identified using linear and non-linear regression techniques. Multi-variant procedure was used to optimize the removal process and deduce equation to predict the removal efficiency. The results indicated that the prepared material belongs to nano-dehydrated zeolite Y family and referred to the possibility of metal ion entrapping within zeolite framework. Cs+ ions have higher removal than Sr2+, and the removal is controlled by external mass transfer through the boundary within the first 40 min then controlled by intra-particle diffusion. Temperature and pH are the most influential variables, whereas initial metal concentration and time affect the process to lesser extent. Cs+ removal was found more reliable under different operating conditions than Sr2+. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.