The catalytic oxidation of cyanide ions was carried out in an aqueous aerated suspension containing modified with iron Co-oxide system. The dependence of both cyanide oxidation rate and selectivity of the process on the initial pH and the catalyst amount was investigated. The results obtained show that the cyanide degradation proceeds most effectively and with high selectivity to the environmentally harmless carbon dioxide at pH < 9.5. The increase of the alkalinity (with other constant parameters) causes both a decrease in the cyanide conversion degree and lowering the selectivity in respect to complete oxidation products. The activity of Co-Fe-oxide system was compared to that of an individual Co-oxide. The observed high activity of the doped sample is explained by the influence of Fe as a modifying additive, which leads to the appearance of new active sites in the fresh samples-Fe(III)-ions in octahedral coordination and to increasing the mobility of the reactive oxygen. (C) 2004 Elsevier B.V. All rights reserved.