Electrochemical reduction of cyanides at metallic cathodes - A comparison with biological HCN reduction

The electrochemical reduction of cyanides has been studied at a number of c athodes both in near-neutral and in alkaline solutions. Nickel appears as t he most effective cathode material, promoting cyanide reduction with curren t efficiencies close to 70%, even in moderately alkaline solutions. In all cases, the eletroreduction of cyanides leads to a mixture of 4e(-) (methyla mine) and 6e(-)products (methane and ammonia). The use of Nafion films load ed with Ni microparticles enabled us to markedly increase the effective cur rent densities for cyanide reduction. The electrochemical reduction of HCN/ CN- is shown to present interesting similarities and differences with the b iological cyanide reduction process. (C) 2001 The Electrochemical Society.