Catalytic activity of mixed Ni−Fe oxide systems with respect to air oxidation of aqueous cyanide solution at 308 K was investigated. The catalysts employed were prepared by an oxidation-precipitation method at room temperature and were characterized by powder X-ray diffraction (XRD), Mössbauer spectroscopy, and chemical analysis. The cyanide oxidation rate was found to be dependent on the catalyst's calcination temperature, pH of the medium, and catalyst loading. Results revealed that the catalyst calcined at 120°C is the most active where up to 90% of free cyanide (4 mM) was removed after oxidation for 30 minutes in the presence of 2.5 g/L catalyst at pH 9.5. The cyanide conversion becomes less favorable as the pH of the solution increases (with other constant parameters). The selectivity data showed that carbon dioxide is the main oxidation product, regardless of pH of the solution.
 D.W. Grosse: “Treatment technologies for hazardous wastes. 4. A review of alternative treatment processes for metal bearing hazardous-waste streams”, J. Air Pollut. Control Asoc., Vol. 36, (1986), pp. 603–614.
 S.Q. Hassan, M.P. Vitello, M.J. Kupferle and D.W. Grosse: “Treatment technology evaluation for aqueous metal and cyanide bearing hazardous wastes (F007),” J. Air Waste Manage. Assoc., Vol. 41, (1991), pp. 710–715.
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