Electrochemical treatment of diluted cyanide aqueous wastes

The electrochemical oxidation of diluted cyanide aqueous wastes has been studied in a single compartment electrochemical flow cell. It has been determined that the anode material influences greatly the process's performance. Boron doped diamond and PbO2 anodes can oxidize these wastes in the presence of both sulfate or chloride anions. On the contrary, dimensional stable anodes cannot oxidize cyanide in sulfate-containing wastewaters, and require the presence of chloride ions. The oxidation of cyanides leads to the formation of cyanate in a first step, and later to the formation of carbon dioxide and nitrogen. There is a net consumption of hydroxyl ions during the process. Energy consumptions in the range 20-70 kWh m(-3) are required to decrease the initial pollutant load by 70-80%. Global current efficiencies in the range 3-8% are obtained. These low current efficiencies are justified by the low cyanide concentrations that the wastes used in this work contain. (c) 2005 Society of Chemical Industry