Enhanced photodegradation of antibiotics using a novel BiVO4/P-doped TiO2 heterostructure: performance evaluation, property and kinetic modelling

Abstract

This study presents the performance evaluation of a novel P-doped TiO₂–BiVO₄ heterostructured photocatalyst against two model antibiotics, metronidazole (MNZ) and ciprofloxacin (CIP), in both single and binary solution system. The morphological analysis confirms the successful incorporation of anatase P-TiO₂ into monoclinic BiVO₄ and the reduction in BiVO₄ particle size with increasing surface roughness. Two multivariable linear regression models were developed to predict the crystallite sizes and bandgap of the photocatalyst. Among the seven photocatalysts, the composite with 80 wt% P-TiO₂ in BiVO₄ exhibited the highest degradation for CIP and MNZ (94.48% and 96.07%, respectively), with a crystallite size of 14 nm and an optimized bandgap of 2.59 eV. Kinetic studies revealed that the degradation followed a first-order model, with P-TiO₂/BiVO₄-80 exhibiting rate constants 4.92 and 9.50 times those of pristine TiO₂ and BiVO₄, respectively. Additionally, the estimated catalytic potential and the synergy index showed the effectiveness of coupling P-TiO₂ with BiVO₄ for potential use in AOPs. The effects of operational parameters were evaluated to identify the optimized conditions (10 ppm antibiotics, 1.2 g L⁻¹ catalyst loading, natural pH, and 20 mM H₂O₂), under which nearly complete degradation of both MNZ and CIP was achieved. Similar degradation efficiency in the binary antibiotic mixture, and while retaining 78% efficiency after five cycles, demonstrated the robustness, recyclability, and stability of the photocatalytic activity of the synthesized photocatalyst. Hence, we believe that the demonstrated insights of the proposed highly efficient novel P-TiO₂/BiVO₄ can further facilitate the transition towards sustainable wastewater treatment, providing clean and safer water for everyone.