Development of 3D network of Zn-oxide nanorods assisted with PbO2/Pb electrode for electrochemical oxidation of methylene blue in aqueous phase

Abstract

Background: A three-dimensional (3D)-network of zinc oxide (ZnO) nanorods is deposited on lead-oxide/lead (PbO2/Pb), to improve anodic oxidation activity via in-situ generation of hydroxyl radical (•OH) used for Methylene blue (MB) removal in a batch process. The performance of modified electrode (ZnO-PbO2/Pb) as anode for decolorization of MB in the aqueous phase is compared with commercially available PbO2/Pb electrode. Methods: Hydrothermal synthesis method is used to develop nano/micro 3D network of (metal-oxides of ZnO and PbO2, respectively), examined through scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDX) and X-Ray Diffraction (XRD) analysis were performed for compositional analysis. Synthesis conditions were optimized based on MB removal via electro-chemical oxidation (ECO) process. ZnO-PbO2/Pb electrode exhibited improved oxygen evolution potential (1.37 V) owing to 3D network of metal-oxide with enhanced electrochemical activity. Findings: Under optimum conditions (100 mg/L, 60 mA/cm2, 0.1 M Na2SO4 and pH 4), a high MB removal efficiency 96.26% and 76% COD removal was achieved. Removal results indicates that 22.60% higher COD removal was achieved for ZnO-PbO2/Pb electrode than PbO2/Pb electrode. Trapping experiment confirmed •OH radical is possibly responsible for decolorization of MB. Service life time of modified electrode is stable up to 24 h, which is two folds higher than pristine PbO2/Pb electrodes (12 h). Based on results, surface modification of PbO2/Pb electrode followed pseudo-first-order rate kinetics is obtained for modified anode material. © 2023 Taiwan Institute of Chemical Engineers