Cu, Ni and multi-walled carbon-nanotube-modified graphite felt electrode for nitrate electroreduction in water

Abstract

A three-dimensional bimetal carbon-based electrode, CuNi/multi-walled carbon nanotube/graphite felt (CuNi/M/GF), was designed for the electrochemical reduction of nitrate. Multi-walled carbon nanotubes (MWCNTs) served as the interlayer and skeleton, which increased the electrochemical reduction activity of GF to nitrate. CuNi/M/GF with different atomic ratios of copper and nickel was prepared by adjusting the electrodeposition potential. The performance of the CuNi/M/GF, Cu foam, Ni foam, M/GF and GF in a dual-chamber cell and single-chamber cell was evaluated for different concentrations of chlorine, current density, energy consumption and degradation. In a solution of 100 mg/L NO3−-N, the removal of NO3−-N and total nitrogen (TN) by the optimal electrode in a single-chamber cell (SCC) can reach 99%. Aeration in the dual-chamber cell cathode can blow out more than 99% of the ammonia nitrogen that is converted from NO3−-N. More than 95% of the TN in a 100 ml, 700 mg/L NO3−-N solution was removed within 6 h. CuNi/M/GF showed excellent corrosion resistance and stability in the cyclic tests. CuNi–1.3/M/GF is more resistant to corrosion in the DCC than in the SCC which may be attributed to contact of the cathode with the oxidizing substance in the SCC. The application of CuNi/M/GF in practical wastewater that contained a high concentration of NaCl and nitrate-N shows that the electrode has considerable application prospects in TN removal.