SPECIFIC AND NONSPECIFIC INTERACTIONS OF AMMINE COMPLEXES OF SILVER, ZINC, AND CADMIUM WITH ION-EXCHANGERS

Distribution of Ag+, Zn2+ Cd2+ at trace level between various ion exch angers and alkaline aqueous ammonia solutions was studied. To describe adsorption of the metal-ammonia solvates on complexing ion exchangers (hydrous titanium oxide, carboxylic and iminodiacetic resins), a mode l has been presented, which assumes that formation of coordinate bonds between the metal ion and functional groups of the exchanger is accom panied by the release of one or more solvating ammonia molecules from the first coordination sphere. The number of the released ligand molec ules was evaluated from the relationships between the distribution coe fficients and ammonia activity in solution; the composition of metal c omplexes adsorbed by the ion exchangers was thus determined. Distribut ion of metal ions between complexing ion exchangers and aqueous ammoni a solution depends on the stability of the highest ammine complex(es) and coordination number of the ion.