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 cathodes both in near-neutral and in alkaline solutions. Nickel appears as the most effective cathode material, promoting cyanide reduction with current efficiencies close to 70%, even in moderately alkaline solutions. In all cases, the eletroreduction of cyanides leads to a mixture of 4e(-) (methylamine) and 6e(-)products (methane and ammonia). The use of Nafion films loaded with Ni microparticles enabled us to markedly increase the effective current densities for cyanide reduction. The electrochemical reduction of HCN/CN- is shown to present interesting similarities and differences with the biological cyanide reduction process. (C) 2001 The Electrochemical Society.