Hydrothermal synthesis and sorption performance to Cs(I) and Sr(II) of zirconia-analcime composites derived from coal fly ash cenospheres

Abstract

The paper is concerned with (i) the hydrothermal synthesis of hydrous zirconium dioxide (HZD) bearing analcime (HZD–ANA, zirconia-analcime) and (ii) its sorption properties with respect to Cs+ and Sr2+. The HZD–ANA particles were synthesized from coal fly ash cenospheres composed of aluminosilicate glass with (SiO2/Al2O3)wt.=3.1 and characterized by PXRD, SEM-EDS, STA, and low-temperature N2 adsorption. The non-radioactive simulant solutions of different acidity (pH = 2–10) and Cs+/Sr2+ content (0.5–50.0 mg/L) were used in the work. The effect of synthesis conditions on the HZD–ANA particle size, zirconia content and localization as well as the sorption behavior with respect to Cs+ and Sr2+ (capacity, KD) were clarified. It was found that the small-sized HZD–ANA composites surpasses the Zr-free analcime and large-sized HZD–ANA material in the Cs+ and Sr2+ sorption parameters (KD ~ 104–106 mL/g). The conditions to synthesize the zirconiaanalcime composite of the highly enhanced sorption ability with respect to Sr2+ (KD ~ 106 mL/g) were determined. The high-temperature solid-phase re-crystallization of Cs+/Sr2+-exchanged HZD–ANA composites was shown to occur at 1000 °C, resulting in a polyphase system based on nepheline, tetragonal ZrO2, and glass phase.