Removal of OMPs from WWTP Effluent: Fabrication and Application of Solar-driven Zinc Oxide/Bismuth Vanadate Photoanode

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The presence of organic micro-pollutants (OMPs) in water bodies has become a major hindrance to protecting water quality in recent years. One of the main sources of OMPs is wastewater treatment plant (WWTP) effluents. One of the most recent Advanced Oxidation Processes (AOPs) technology is photo-electrocatalysis (PEC), which can produce radicals to oxide OMPs in an aqueous medium driven by solar energy and an external bias potential. In this study, ultrasonic spray pyrolysis was determined as a proper method to fabricate the ZnO/BiVO4 heterojunction. Then, the prepared photoanodes were characterised by X-ray Photoelectron spectroscopy (XPS), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), UV-vis and Incident Photo-to-electron Conversion Efficiency (IPCE). The results demonstrated the ZnO/BiVO4 heterojunction was successfully fabricated on the Fluorine-Tin-Oxide (FTO) glass. Moreover, the LSV and EIS analysis were carried out in this study to analyse its photo-electrochemical properties. The PEC degradation experiments were carried out in 10 μg/L of 11 OMPs spiked in MiliQ and in real WWTP effluent under simulated solar illumination at 1 V potential bias for three hours. Nine and four of 11 OMPs had achieved more than 70 % degradation efficiency when ZnO/BiVO4 photoanode was conducted to degrade spiked MiliQ and spiked real WWTP effluent. Except for diclofenac and sotalol, the real effluent showed inhibition to the degradation efficiencies and kinetic coefficient of the other nine OMPs. The concentrations of TOC, COD and NO3-N increased after the PEC process. The increase was found to be related to the disintegration of the carbon stick cathode. To further enhance the PEC process, the ZnO@GD/BiVO4 photoanode and adding persulfate were conducted the PEC degradation experiments separately in spiked real WWTPs effluent. Both two approaches showed an enhancement of the PEC process and improved degradation efficiencies. The results obtained in the present work reveal that the PEC process has excellent potential for the removal of OMPs from WWTPs effluent.