Comparative study of the cesium adsorption behavior of montmorillonite and illite based on their mineralogical properties and interlayer cations

Abstract

Among clay minerals, montmorillonite (MMT) and illite are generally used to remove radioactive cesium (137Cs) from radioactive wastewater. The objectives of this study were to investigate the mineralogical properties of MMT and illite with their Cs adsorption behavior and then demonstrate the type of clay mineral that should be used for removing high- and low-concentrations of Cs. The Ca-type MMT used in this study was exchanged with sodium (Na), magnesium (Mg), and potassium (K) to compare the Cs adsorption behavior based on the interlayer cation type, including that of illite. The basal d-spacing (d001) of MMTs (swelling) ranged from 1.011 to 1.396 according to the interlayer cation type. Illite (non-swelling) had d001 of about 1.0 nm. Among the types, Na-MMT had the highest Cs adsorption capacity (204.67 mg/g), while illite exhibited the highest Cs distribution coefficient (Kd) (161.1 mL/g). The results indicated that the relative charge density of cations and interlayer properties, such as swelling and non-swelling, of clay minerals significantly affect Cs adsorption capacity and selectivity. Therefore, the selection of clay minerals should vary according to the type of high- and low-concentrated Cs wastewater. MMT and illite are advantageous for removing Cs from high- and low-concentration radioactive wastewater, respectively.