In recent years, cyanide contamination problem is becoming more and more serious. Cyanides widely occur in the wastewater from metallurgical industry and electroplating industry. The efficiency for cyanides removal of conventional physical and chemical methods is not very satisfactory. Therefore, it is urgent to develop highly efficient and environmental friendly methods for the removal of cyanides. As an environmental-friendly oxidant, potassium persulfate is widely used in the treatment of organic pollutants. The destruction of Cu(CN)32- was investigated by homogeneous K2S2O8 under alkaline conditions, and the reaction mechanism was analyzed. The effects of the amount of K2S2O8 and the ratio of Cu+/CN- on the degradation of CN- were studied. With the increase of K2S2O8 dose, the rate of CN-oxidation was accelerated. The removal efficiency of CN- reached 89.6% after 60 min of reaction in the presence of 2 mmol·L-1 K2S2O8. Oxidation of CN- was accelerated with Cu+/CN- increasing from 2.0 to 5.0. Cu+ was oxidized to Cu2+ and copper oxide was formed during the reaction. The reactive radicals were analyzed using electron spin resonance and radical quenching experiments, and the results indicated that both radicals oxidation pathway and non-radical oxidation pathway were responsible for the removal of Cu(CN)32- by K2S2O8.
Keywords: cyanide; cyanide and copper complex; non-radical oxidation; potassium persulfate; sulfate radical oxidation.