Evaluation of Sr and Cs ions adsorption capacities with zeolitic materials synthesized from various mass ratios of NaOH to coal fly ash

Abstract

The adsorptive aqueous removal of Sr2+ and Cs+ was performed using zeolitic materials prepared with fused coal fly ash (CFA) using a hydrothermal method. The influence of the mass ratio of NaOH to CFA of 0.3-1.2 in the synthesis of zeolitic material was evaluated its crystallization properties by X-ray diffraction (XRD) analysis. The zeolitic materials synthesized at the mass ratio of NaOH to CFA of 0.6-1.2 could be identified to have the same location as the XRD peaks of Na-A zeolite at 2θ = 7.18 - 34.18. They appeared to be zeolitic materials which were crystalline particles with a cubic structure by scanning electron microscopy (SEM). The experimental adsorption data for Sr2+ and Cs+ using the zeolitic materials were estimated satisfactory using pseudo-2nd-order kinetics and Langmuir isotherm models. The highest maximum adsorption capacities (qm) of 147.6 mg/g for Sr2+ and 160.2 mg/g for Cs+ were estimated by using the zeolitic material. This material demostrated superior crystallinity and was synthesized at a mass ratio of NaOH to CFA of 0.6. Consequently, the zeolitic material prepared from the fused CFA through the hydrothermal method could be used effectively for the adsorption of Sr2+ and Cs+ in aqueous solutions.