Dimethyl phthalate degradation at novel and efficient electro-Fenton cathode

A novel three-dimensional porous carbon nanotube sponge (CNTS) with high electrical conductivity was prepared, characterized and investigated as the catalytic cathode for oxygen reduction and employed for an electro-Fenton process to degrade dimethyl phthalate (DMP) in aqueous solution. For comparison, the conventional electro-Fenton cathode, graphite gas diffusion electrode (GDE) and graphite electrode, was also tested. Experiments showed that the side reaction of H-2 evolution was avoided and the H2O2 accumulation concentration arrived at the maximal value at CNTS cathode as the cathode potential was set at -0.5 V (vs. SCE). The apparent rate constant for DMP degradation was 0.057 min(-1) at CNTS cathode, much higher than 0.005 min(-1) at graphite cathode and 0.011min(-1) at graphite GDE. Meanwhile, CNTS possessed desirable stability without performance decay after 20 times reaction. It was also found that more negative cathode potential than -0.5 V could cause the side reaction of H2 evolution and thus leading to a deteriorated DMP degradation. Moreover, the initial DMP concentration affected the apparent rate constant of DMP degradation. Compared to the case of higher initial DMP concentration, DMP degraded faster in the case of lower initial DMP concentration. The pH value and initial Fe2+ concentration for DMP degradation at CNTS cathode were optimized to be 3.0 and 0.5 mmol L-1, respectively. The CNTS is promising to be potentially used as the cathode for electro-Fenton system to remove organic pollutants in wastewater. (C) 2014 Elsevier B.V. All rights reserved.