Adsorption properties of europium on bentonites

The adsorption properties of europium on bentonites have been studied by batch methods. Europium ion was preferentially adsorbed on bentonites, yielding a high distribution coefficient (KEu>103cm3/g) in the acidic region of pH 1-4. The bentonites calcined up to 500degC gave high KEu values, while at higher temperatures the KEu value markedly decreased, owing to the dehydration of structural water and thermal decomposition of bentonites. The KEu value tended to increase with equilibrium pH; a linear relationship between log KEu and pH suggested the ion exchange of Eu3+ in layer structure. The KEu value and the saturation capacity were independent of conditioning form of bentonites. The adsorption of Eu on bentonites followed a Langmuir type isotherm, and the saturation capacity (Qmax) and the Langmuir constant (K) were 0.24mmol/g and 3.8x104cm3/mmol, respectively. The concentration dependence of KEu can be estimated from these values. (author)