Abstract: | The structure of aqua complexes of alkali metal ions Me+(H2O)
n
, n = 1−6, where Me is Li, Na, K, Rb, and Cs, and complexes of 2,6-dimethylphenolate anion (CH3)2PhO− selected as a model of the elementary unit of phenol-formaldehyde ion exchanger with hydrated alkali metal cations Me+(H2O)
n
, n = 0−5, was studied by the density functional method. The energies of successive hydration of the cations and the energies
of binding of alkali metal hydrated cations with (CH3)2PhO− depending on the number of water molecules n were calculated. It was shown that the dimethylphenolate ion did not have specific selectivity with respect to cesium and
rubidium ions. The energies of hydration and the energies of binding of alkali metal cations with (CH3)2PhO− decreased in the series Li+ > Na+ > K+ > Rb+ > Cs+ as n increased. The conclusion was drawn that the reason for selectivity of phenol-formaldehyde and other phenol compounds with
respect to cesium and rubidium ions was the predomination of the ion dehydration stage in the transfer from an aqueous solution
to the phenol phase compared with the stage of binding with ion exchange groups. |