Adsorption characteristics of Cs+ onto artificial zeolites synthesized from coal fly ash and diatomite

Abstract

The radioactive decontamination of water, soil and other materials requires cheap and effective adsorbents. Artificial zeolites synthesized from an industrial waste (coal fly ash: Na-P1 type zeolite) and a natural material (diatomite: mordenite type zeolite) have a high Cs+ adsorptivity in the adsorption experiments using 0.1 g of the zeolite and 50mL of up to 7.5mM CsCl. The coexisting cation suppressed the Cs+ adsorption onto the zeolites, and the effect of the suppression was in the order, K+ > Na+ > Ca2+ > Mg2+. A thermodynamic analysis proved that the Cs+ adsorption onto the two zeolites was exothermic favoring a lower temperature. The artificial mordenite showed a greater Cs+ adsorption strength, higher distribution coefficient and lower "G°, especially at low Cs+ concentrations. Adsorption isotherm analysis by the Langmuir, Freundlich, Temkin and Dubinin- Radushkevich models showed a greater Cs+ adsorption selectivity for the artificial mordenite even at a low pH.