Ion Exchange of Cesium on Potassium Nickel Hexacyanoferrate (II)s

Abstract

The ion exchange of Cs+ on a nonstoichiometric compound K0.87Ni0.57[NiFe(CN)6]·nH2O (KNiFC) was examined by batch methods. The distribution coefficient of Cs+, Kd,Cs, was independent of Na+ concentration up to 5M (=mol/dm3), while it decreased with increasing concentrations of both K+ and NH4 +. The separation factor for Cs/Rb, αcs/Rb, was 4.7×102 in the presence of 5M Na+. The decreasing order of Kd,Cs in the coexisting cations was found to be NH4 +K+, H+Na+, Ca2+. 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±0.074mmol/g. The free energy of K+←Cs+ ion exchange was calculated to be −15.4±1.4kJ/mol by Kielland plot.