Optimization of the cathode material for nitrate removal by a paired electrolysis process

Ni, Cu, Cu90Ni10 and Cu70Ni30 were evaluated as cathode materials for the conversion of nitrate to nitrogen by a paired electrolysis process using an undivided flow-through electrolyzer. Firstly, corrosion measurements revealed that Ni and Cu70Ni30 electrodes have a much better corrosion resistance than Cu and Cu90Ni10 in the presence of chloride, nitrate and ammonia. Secondly, nitrate electroreduction experiments showed that the cupro-nickel electrodes are the most efficient for reducing nitrate to ammonia with a selectivity of 100%. Finally, paired electrolysis experiments confirmed the efficiency of Cu70Ni30 and Cu90Ni10 cathodes for the conversion of nitrate to nitrogen. During a typical electrolysis, the concentration of nitrate varied from 620 ppm to less than 50 ppm NO3- with an N-2 selectivity of 100% and a mean energy consumption of 20 kWh/kg NO3- (compared to similar to 35 and similar to 220 kWh/kg NO3- with Cu and Ni cathodes. respectively). (C) 2011 Elsevier B.V. All rights reserved.