Fabrication and Characterization of a Cu-Zn-TiO2 Nanotube Array Polymetallic Nanoelectrode for Electrochemically Removing Nitrate from Groundwater

Abstract

A novel Cu-Zn-TiO2 nanotube array (TNTA) polymetallic nanoelectrode, intended to improve the electrochemical nitrate removal efficiency, was fabricated. The nanoelectrode was fabricated by plating Cu onto a Ti nanoelectrode and then plating Zn onto the Cu/Ti bilayer electrode produced. The Ti nanostructures on the Cu-Zn-TNTA nanoelectrode surface gave the nanoelectrode a large specific surface area, and the Zn and Cu gave the nanoelectrode a high electrocatalytic activity for reducing nitrate. Scanning electron microscopy images showed that the Cu-Zn-TNTA polymetallic nanoelectrode had a honeycomb structure with spongy deposits. X-ray diffractometry results showed that the Cu-Zn-TNTA nanoelectrode predominantly contained Cu, O, Ti, and Zn. The nitrate removal efficiency of the Cu-Zn-TNTA nanoelectrode was 345.7% of the removal efficiency for a Ti nanoelectrode. The presence of NaCl allowed both the cathodic reduction of nitrate and the anodic oxidation of the ammonia and nitrite byproducts to be achieved with high removal efficiencies, especially using an IrO2 anode. In the present of NaCl, nitrate removal rate was 93.4% in current density of 30 mA/cm2 after 90 min. Nitrate was completely removed using the IrO2 anode, and little ammonia was detected in the treated solution. The reduction efficiency increased slightly as the initial nitrate concentration increased through the range 20–100 mg/L, and the pH had little effect on the nitrate reduction efficiency.