Cesium Removal from Nonexpandable Illite Clay by Chloride Salt Treatment

Abstract

Extracting cesium (Cs) from nonexpandable illite clay is important in the remediation of radioactive Cs-contaminated soil. In this study, we investigated a chloride salt treatment technique for the removal of Cs from illite. Cs-loaded illite samples with initial Cs concentrations of 2430 and 690 ppm were treated using a NaCl-MgCl2-CaCl2 ternary salt system at 400-850 °C under ambient pressure to suppress Cs loss by vaporization. As a result of the treatment at 850 °C, wherein the salt was in a molten state, the Cs concentration was reduced by 99.5% (to 11.6 ppm) in the first sample and by 99.4% (to 3.86 ppm) in the second sample. Cs removal was achieved for these two samples even in a solid-state reaction at 400 °C, with reductions of 83.3% (407 ppm) and 73.3% (184 ppm), respectively. CsCl was formed by the reaction and remained stable in the salt. The incorporation of cations from the salt (mainly Mg2+) to illite induced structural evolution forming an indialite phase to expel Cs from the clay samples.