Cesium removal from contaminated montmorillonite using ethylene glycol monoethyl ether and Freezing-Thawing process

The unexpected nuclear accidents and uncontrolled leakages of radioactive cesium (¹³⁷Cs) can contaminate the soils nearby nuclear power plants (NPPs). Radioactive ¹³⁷Cs ions (Cs⁺) tend to strongly sorb on 2:1 phyllosilicate clay minerals, especially expandable clay minerals such as montmorillonite (MMT) and vermiculite. However, removal of ¹³⁷Cs from the contaminated soils has been relatively inefficient due to the strong and irreversible interaction of Cs with the frayed edge sites in clays. This study employs the intercalation of ethylene glycol monoethyl ether (EGME) and the Freezing-Thawing (FT) approach to enhance the removal rate of cesium (Cs⁺) from Cs-contaminated montmorillonite (CsMMT) by the enhanced K⁺ ion exchange process. The EGME intercalated into the interlayer of the CsMMT and induced the interlayer expansion. The interlayer spacing of the CsMMT was expanded from 19.09 Å to 22.01 Å when 3.8 mmol EGME/g MMT was treated. For ion exchange with 4 mmol/g CsMMT of K⁺ without EGME intercalation, the Cs removal rate was observed to only 34.71 %, which was enhanced to 59.34 % after 3.8 mmol EGME/g CsMMT of treatment. In addition, the FT process further increased Cs removal up to 82.31 % by inducing the expansion of the interlayer and exfoliating the MMT. We believe that CsMMT can be efficiently decontaminated by applying both the intercalation of EGME and FT approach together.