Ferrate(VI) oxidation of aqueous cyanide

The rates of oxidation of cyanide with Fe(VI) were measured as a function of pH (8.0-12) and temperature (15-30 degrees C). The reaction was found to be first order for each reactant. The rates decrease with increasing pH. The energy of activation was found to be 38.9 +/- 1.0 kJ mol(-1) at pH 9.0. The removal of cyanide by oxidation with Fe(VI) was studied at pH 7.5, 9.0, and 12.0. Fe(VI) removal efficiency was greater at pH 9.0 than at pH 7.5 and 12.0. At pH 9.0, Fe(VI) molar consumption was nearly equal to that of oxidized cyanide. Cyanate and nitrite ions were identified as the products of the reaction at pH 7.5. The experiments indicated 1:1 stoichiometric conversion of cyanide to nitrite ion at pH 9.0 and 12.0. Experiments were conducted to test the Fe(VI) removal efficiency of cyanide in electroplating rinsewater. The results indicate that Fe(VI) has the potential to serve as a reliable and safe oxidative treatment for removing cyanide in wastewater effluent.