ION-EXCHANGE OF CESIUM ON POTASSIUM NICKEL HEXACYANOFERRATE(II)S

The ion exchange of Cs+ on a nonstoichiometric compound K0.87Ni0.57[Ni Fe(CN)(6)]. nH(2)O (KNiFC) was examined by batch methods. The distribu tion coefficient of Cs+, K-d,K-Cs, was independent of Na+ concentratio n up to 5 M (=mol/dm(3)), while it decreased with increasing concentra tions of both K+ and NH4+. The separation factor for Cs/Rb, alpha(Cs/R b), was 4.7 X 10(2) in the presence of 5 M Na+ The decreasing order of K-d,K-Cs in the coexisting cations was found to be NH4+>K+, H+>Na+, C a2+. The uptake of Cs+ on KNiFC followed a Langmuir-type isotherm and the maximum amount of Cs+ taken up was estimated to be 2.57+/-0.074 mm ol/g. The free energy of K(+)reversible arrow Cs+ ion exchange was cal culated to be -15.4+/-1.3 kJ/mol by Kielland plot.