The electrochemical mineralization of oxalic and oxamic acids using modified electrodes based on carbon nanotubes

Abstract

Constant current and constant potential electrolyses of oxalic and oxamic acids were carried out on multiwalled carbon nanotubes (CNT) and on monometallic (Pd and Pt) and bimetallic (Ru–Cu) catalysts supported on multiwalled carbon nanotubes. Both carboxylic acids were mineralized with high conversions via hypochlorite ion produced in situ, in 0.10M NaCl medium. Highest current efficiency, corresponding to 97%, and highest reaction rate constant for oxalic acid mineralization were obtained for the Ru–Cu/CNT modified electrode, in 0.10M NaCl medium. The mineralization of oxamic acid was achieved with a faradic yield of 96% and an energy consumption of 14.6kWh (kg of pollutant)−1in the same medium. The conversion values obtained for the oxidation of oxalic acid in 0.50M NaOH medium, on Pt/CNT, Pd/CNT and Ru–Cu/CNT modified electrodes, were respectively 42%, 60% and 85%. In this last medium, 88% of the initial oxamic acid (15.8mM) was transformed to carbonate ion and nitrogen at Pt/CNT modified anode.