The mechanism and reaction kinetics of visible light active bismuth oxide deposited on titanium vanadium oxide for aqueous diclofenac photocatalysis

Non-uniform, non-spherical bismuth oxide deposited on titanium vanadium oxide (3%-BVT₁) was successfully synthesized via co-precipitation method and assessed for visible light degradation of aqueous diclofenac. The synthesized photocatalysts were characterized using X-ray diffraction, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. Up to 80.7% diclofenac degradation was observed with a significant increment in reaction rate compared to commercially available Degussa P25 (k_app = 0.0013 → 0.0083 min⁻¹) achieved within 3 h treatment time under optimized parameters of diclofenac concentration (10 mg L⁻¹), catalyst loading (0.1 g L⁻¹), and pH (5). The enhanced photocatalysis could be due to electron–hole separation and contribution of powerful oxidative species ^•OH > O₂^•− > h⁺ > > e⁻. The recyclability experiments indicate that 3%-BVT₁ retained its efficiency up to 74.1% over five reaction cycles. Gas chromatography–mass spectrometry analysis indicated the formation of several transformation products during the degradation pathway. The studies of interfering ions depicted mild interference by sulfates, while interference by phosphates and nitrates was negligible during photocatalytic process, i.e., 70, 78.01, and 78.43% for the selected concentrations of 50, 25, and 40 mg L⁻¹ as per their maximum concentrations detected in the natural wastewaters. Thus, 3%-BVT₁ is a potential versatile candidate to treat various organic pollutants including pharmaceuticals.