Ion exchange of radionuclides on natural and modified mica minerals

Uptake of Cs-134, Sr-85 and Co-60 on three mica minerals, muscovite, biotit e, and phlogopite, was investigated. Two forms of mica minerals were studie d: the natural, with potassium as exchangeable cation, and the sodium conve rted forms. Biotite and phlogopite in the sodium form were found to be very selective to cobalt with the distribution coefficients K-d over 10(5) ml/g , and the potassium form of muscovite exhibits almost similar selectivity t o cesium. None of the mica minerals were selective to strontium. The distri bution coefficients were strongly pH-dependent. For the sodium form of phlo gopite the distribution coefficient increased over a pH range of 3.5 and 7 insignificantly, but from pH 7 to pH 8 it increased by more than three orde rs of magnitude. Phlogopite and biotite can be converted to the sodium form quantitively, and muscovite, to 5%.