SYNTHESIS AND ION-EXCHANGE PROPERTIES OF VARIOUS FORMS OF MANGANESE-DIOXIDE FOR CATIONS OF THE I-GROUP AND II-GROUP

Various crystalline forms of manganese oxides were synthesized by redo x reaction between alkali metal permanganates and manganese sulphate. The structure of samples precipitated from KMnO4, RbMnO4 and NH4MnO4 w ere similar to those reported for alpha-crystalline form of MnO2 and e xhibited a high selectivity for the cations whose ionic radii are incl uded in the range 135-155 pm i.e. K+, NH4+, Rb+, Ba2+ and Ra2+. The sa mples precipitated from NaMnO4 were more similar to the gamma-form of MnO2 and exhibit much lower affinity for the Ra2+ cations. High select ive alpha-type MnKO2 samples can also be obtained in strong acidic sol utions. The obtained alpha-MnO2 samples can be used for the determinat ion of Ra-226,Ra-228 in natural water at a very low level of radioacti vity.