Developing the sensing features of copper electrodes as an environmental friendly detection tool for chemical oxygen demand

Abstract

The chemical oxygen demand (COD) of water bodies is an essential indicator of organic contaminants. The majority of current testing methods have the drawbacks of requiring multiple processes, being time-consuming, and requiring the use of harmful and hazardous reagents. In this work, a low-cost copper wire (Cu-wire) electrode was designed and fabricated to be used as a sensing electrode for the detection of chemical oxygen demand in water. The sensing features were developed by electrodeposition of copper nanoparticles (nano-Cu) that were prepared by fast-scan cyclic voltammetry (FSCV) deposition at the optimum preparation conditions. For improving the adherence and stability of the deposited nano-Cu thin layer, the Cu-wire electrode was scratched to increase the surface roughness. The surface morphology of the prepared nano-Cu/Cu-wire electrode was investigated by scanning electron microscope (SEM). Energy-dispersive X-ray spectrometer (EDX) was used for elemental analysis characterization. The non-modified and the nano-copper modified electrode were utilized and optimized for electrochemical assay of COD using glycine as a standard in 0.075 M NaOH as an electrolyte solution. The calibration curves (COD, mg L⁻¹ vs. I, mA) were plotted from linear sweep voltammetry (LSV) and chronoamperometry (I–t) curves for a wide range of COD under the optimized conditions. It shows that the electroanalytical features of the proposed nano-Cu-based COD sensor exhibit a linear range from 2 to 595 mg L⁻¹ and a lower limit of detection (LOD) of 2.6 mg L⁻¹ (S/N = 3). The established electrochemical method demonstrated a high tolerance level to Cl⁻ ions where 1.0 M Cl⁻ exhibited a negligible influence. The sensor was employed for detecting the COD in diverse real water samples and the attained results were validated using the standard dichromate method. The obtained results could open the window toward using simple and cost effective tools in order to monitor the water quality.