Fabrication of TiO2/InVO4 as an effective photocatalyst under visible light for degradation of rifampicin

Abstract

TiO₂ nanoparticles were modified with InVO₄ via the green synthesis method using mango (Mangifera indica L.) leaf extract. The water fraction of mango leaf extract consisted of secondary metabolites, which act as sources of weak bases and capping agents. TiO₂ nanoparticles and TiO₂/InVO₄ nanocomposites were characterized using FTIR, UV–Vis DRS, XRD, FESEM, EDX, PSA and HRTEM. The nanocomposite exhibited a reduced band gap of 2.70 eV, enabling visible light absorption. HRTEM, which revealed a primary particle size ranging from 55 to 80 nm and confirmed the crystalline nature of the material, showing distinct lattice fringes corresponding to the (101) plane of anatase TiO₂ and the (122) plane of the TiO₂/InVO₄ composite, providing direct evidence for the formation of a crystalline heterojunction. The photocatalytic activity of TiO₂/InVO₄ nanocomposites against rifampicin under visible light irradiation was probed by a UV–Vis spectrophotometer. The TiO₂/InVO₄ nanocomposite exhibited superior photocatalytic performance compared to individual TiO₂ and InVO₄ nanoparticles, achieving a degradation efficiency of 97.18 % within 120 min. Kinetic studies revealed that the photocatalytic degradation of rifampicin by TiO₂/InVO₄ followed a pseudo-first-order reaction, as indicated by a high R² value and a reaction rate constant (k) of 9.34 × 10⁻³. A radical scavenger test identified the primary reactive species involved in the degradation process, showing that holes (h⁺) were the most crucial, followed by hydroxyl (•OH) and superoxide (•O₂⁻) radicals. The material also demonstrated stability and reusability, maintaining 84.65 % of its initial activity after fifth successive cycles. The escalation of photocatalytic activity could be attributable to a reduced band gap compared to pure TiO₂, enabling visible light absorption. This study addresses the pressing issue of pharmaceutical pollution by developing a highly efficient photocatalyst for the degradation of rifampicin, a persistent organic pollutant that poses severe threats to aquatic ecosystems and human health.