A dual-cathode electro-Fenton oxidation coupled with anodic oxidation system used for 4-nitrophenol degradation

The degradation of 4-nitrophenol was investigated using a novel electrochemical oxidation system, in which the anodic oxidation at Ti/SnO2-Sb2O5-IrO2 electrode and the electro-Fenton oxidation with two cathodes were involved. In this system, gas diffusion electrode (GDE) was used to generate H2O2 by O-2 reduction and graphite electrode was employed for the reduction of Fe3+ regenerating Fe2+. When the potential values of GDE and graphite cathode were controlled at -0.80 and -0.10 V/SCE respectively, the optimum Fe2+ concentration for 4-nitrophenol degradation was about 0.10 mM, much lower than the concentration of 0.25 mM obtained in the single-cathode system. Due to the combination of electro-Fenton oxidation and anodic oxidation, an effective degradation and a high mineralization current efficiency (MCE) were achieved. After 600 min treatment, 74.5% of the original TOC was removed by the dual-cathode oxidation system. Moreover, it was confirmed that 57.0% of the original nitrogen could be removed in gaseous form from the simulated wastewater. These results indicate that this electrochemical oxidation process might provide an alternative for the degradation of organic pollutants. (C) 2011 Elsevier B.V. All rights reserved.