A description is given of the preparation and properties of potassium hexacyanocobalt (II) ferrate (II) (KCFC) and the composite, potassium hexacyanocobalt (II) ferrate (II)-polyacrylonitrile (KCFC-PAN). The materials were dried at high temperatures and characterized by chemical analysis, scanning electron microscope, X-ray diffraction, inductively coupled plasma and infrared. The ion exchange of alkaline earth metals and molybdenum on a nonstoichiometric compound K-2[CoFe(CN)(6)] and its PAN based absorber was examined by batch methods. The adsorption of molybdenum from aqueous solutions on KCFC-PAN was investigated and optimized as a function of equilibration time and pH. The materials which were dried at optimum high temperature of 110 degrees C were found to be stable in water, dilute acids, alkaline solutions and relatively high temperature. The distribution coefficient values K-d for alkaline earth metals, followed the same trend of increase for both sets of absorbers studied, i.e. Ba2+ > Sr2+ > Ca2+ > Mg2+, which closely resembles to the order of the size of the hydrated cations. However, the K-d values show a significant increase for PAN based absorbers in comparison to KCFC absorbers. (c) 2006 Elsevier B.V. All rights reserved.