Development and optimization of Ti/Cu cathode and Ti/IrO₂ anode for electrochemical denitrification

Abstract

Nitrate is a known culprit behind methemoglobinemia. Long-term consumption of drinking water rich in nitrate can be carcinogenic. Electrochemical denitrification is one of the attractive technologies which can be used in denitrification. Although electrochemical nitrate removal is reported in the literature, little attention is paid towards the development of novel electrode materials considering the factors pertaining to efficient nitrate removal. In this research, attention was paid on developing novel electrode materials (i.e. anode and cathode). A novel cathode was prepared and optimized by coating Cu on Ti substrate. Applied current, plating duration, and Cu²⁺ concentration are the three parameters which were used to optimize the cathode material. Anode was developed and optimized by applying IrO₂ on Ti substrate. Calcination time and calcination temperature were varied in order to obtain optimum conditions to develop the anode material. Both electrodes showed promising results even in chloride-free synthetic electrolytes. Nitrate removal efficiency of the developed technology was 99% for actual groundwater. The current density was as small as 20 mA cm⁻². For groundwater samples, it was able to remove nitrate concentration from 176.7 to 1.34 mg L⁻¹ within 2 h of reaction achieving the World Health Organization (WHO) guidelines for drinking water. Safety studies for nitrite and ammonia showed concentrations well below the WHO guidelines for drinking water. Neutron activation analysis showed no Ir was present in the treated water. Developed electrodes were successful in treating nitrate-rich water and provided potable water.

Keywords:

• Anode
• Cathode
• Electrochemical nitrate reduction
• Electrode material optimization
• Groundwater

Acknowledgments

The authors thank the National Science Foundation—Sri Lanka (Grant: RG/2011/BS/01) for funding this research.