Abstract
The salts of FeIII, CoII, and NiIII form precipitates with Na4- or K4 [FeII(CN)6], the so-called mixed hexacyanoferrates (II) (HCF). Experiments with radioactive tracers (24Na, 42K, 59FeIII, 60CoII, 59FeII(CN),4⊖, and 204TlI) have shown that the composition of HCF depends on the nature as well as on the initial concentration of the metal ions involved and can be described by the general formula ExMzR·n E Y. Ε stands for univalent cations (e.g. H, Na, K, Tl, and others more), M for a heavy metal ion, R for Fe(CN)6 4⊖, and Y for anions (e. g. Cl, SO4 2⊖, OH®). The mixed HCF are cation- and anion-exchangers, the equilibrium between solid and liquid phase depending on the nature and concentration of cations and anions in both phases. The binding stability of cations increases proportionally to the effective ionic radius: H⊕⊕⊕. Because of its favourable ionic radius, Tl exhibits a high affinity towards the mixed HCF and can be separated from solution with a high efficiency.

This publication has 0 references indexed in Scilit: