Electrochemical removal of nitrite using an activated copper rotating cylinder electrode

Abstract

An undivided electrochemical reactor with a rotating cylinder electrode was examined for the removal of nitrite from a synthetic effluent, 30 mmol dm−3 NaNO2 in 0.1 mol dm−3 Na2SO4 as supporting electrolyte. Nitrite was reduced to ammonia at a copper cathode activated by a film of copper oxides, which was anodically produced at a potential of 18 mV against saturated calomel electrode, SCE, in the supporting electrolyte. The deactivation of the cathode was avoided by application of a periodic potential reversal, PPR, technique making the rotating electrode work 5 min as a cathode and 5 min in reactivation. The reactor performance was improved applying both strategies, cathode activation and use of a PPR procedure. The best results were obtained at a cathodic potential of −1.3 V vs. SCE, ammonia being the main product of the reduction of nitrite, obtaining a molar yield of 94% and a current efficiency of 59% with a nitrite conversion of 92% in an experiment of 1 h.