Ammonia oxidation to nitrogen mediated by electrogenerated active chlorine on Ti/PtOx-IrO2

The electrochemical oxidation of ammonia (NH3 and/or NH4+) in the presence of chloride was investigated on a Ti/PtOx-IrO2 electrode. It was shown that ammonia is effectively removed from solution via electrogenerated active chlorine. Based on mass balances, nitrogen is postulated to be the main product of ammonia electrolysis. In the bulk, the concentration of chloramines was low. This could be explained by the fact that the oxidation of ammonia takes place close to the electrode surface where an excess of chlorine relative to ammonia is ensured during the process. This results in the oxidation of ammonia to N-2 and in a local pH decrease. As a result, chloramines were decomposed in the proximity of the electrode prior to diffusing into the bulk. (C) 2010 Elsevier B.V. All rights reserved.