Simultaneous removal of multiple organic micropollutants via UV-visible light driven BiVO4/TiO2-GO photoanode: Experimental and CFD study

Abstract

In this study, we investigated the use of BiVO₄/TiO₂-GO heterojunction photoanode in a PEC based AOP to simultaneously remove four organic micropollutants (OMPs): benzotriazole (BTA), carbamazepine (CBZ), caffeine (CAF) and diclofenac (DIC) from demineralized water. Each OMP had an initial concentration of 40 µg L⁻¹. Ultrasonic spray pyrolysis (USP) was used to deposit BiVO₄ and TiO₂-GO layers on fluorine doped tin oxide (FTO) electrodes. The heterojunction photoanode at an applied voltage of 1 V (vs Ag/AgCl) achieved simultaneous removal efficiencies of 100 % for DIC, 54 % for CBZ, 36 % for BTA and 33 % for BTA under simulated solar light. Compared to the pristine BiVO₄ photoanode, the heterojunction photoanode showed 50 % higher removal efficiency for BTA, CBZ and CAF. The reaction kinetics revealed that the first order rate coefficient for DIC removal was about nine times higher than that of CBZ and fifteen times higher than those of BTA and CAF. To assess scalability, a computational fluid dynamics (CFD) model incorporating the experimentally determined reaction kinetics was developed for a conceptually designed up-scaled PEC reactor. The model analyzed the effect of reactor design and fluid flow conditions on the removal of OMPs. Under turbulent flow conditions, enhanced removal efficiency was observed for all four OMPs, which was attributed to the effects of eddy diffusion and convective mixing. The optimized reactor design under turbulent flow condition achieved an 80 % removal efficiency for all four OMPs within 25 min under a light intensity of 400 W m⁻². The findings highlight the potential of BiVO₄/TiO₂-GO heterojunction photoanodes for efficient and scalable PEC water treatment, showing a promising approach for the elimination of OMPs from wastewater.