Comparing the effects of Cu-Ti/RuO2-IrO2 electrode configuration on the electro-reduction of nitrate

Abstract

Nitrate pollution is a global problem as it affects both the environment and human health. The objective of this research was to study the effect of electrode configuration on the electro-reduction of nitrate. Coaxial cylindrical (inner rod and outer tube copper cathodes) and vertical plate parallel copper cathodes paired with Ti/RuO2-IrO2 (rod, tube, and plate) configurations were studied under various current densities and initial nitrate concentrations. The efficiency of each configuration was determined based on the removal efficiency of nitrate, specific energy consumption, mass transfer coefficients, and first order rate constants. Additionally, the overall systems’ resistance and geometric factors are discussed. It was found that the performances of the inner rod and outer tube copper cathodes were similar. The vertical plate parallel configuration was superior to the coaxial cylindrical electrode setup, as evident from a higher maximum nitrate removal of 74 and 56% at a current density of 7 mA/cm2 and lower energy consumption of 46.7 × 10−3 and 54.3 × 10−3 kWh/mmol NO3− at 36.4 mA/cm2, respectively. In addition, the mass transfer coefficients and first order rate constants were higher in all conditions tested for the vertical plate parallel configuration. HIGHLIGHTS Copper cathode was paired with Ti/RuO2-IrO2 anode for nitrate electro-reduction.; Performance of coaxial cylindrical and vertical plate configurations were compared.; The resistance, geometric factor and mass transfer coefficients were determined.; The effects of current density and initial nitrate concentrations were studied.; The coaxial cylindrical electrode setup was outperformed by the vertical plate parallel configuration.;

Keywords

• copper cathode
• current density
• energy consumption
• geometric factor
• mono-polar