Visible-light photocatalytic degradation of metronidazole using an S-scheme amino acid glycine–modified TiO2/Fe3O4 heterojunction immobilized on chitosan–Polyacrylonitrile in a batch photoreactor

Abstract

The persistent presence of Metronidazole (MTZ), a commonly used antibiotic, in water bodies is a serious environmental and health concern because of its genotoxic and carcinogenic potential. Here, we report an effective visible-light photocatalyst system comprising an S-scheme glycine–modified TiO2/Fe3O4 heterojunction immobilized on chitosan–polyacrylonitrile nanofibers. The photocatalyst nanocomposite was synthesized through a sol–gel and ultrasonication process coupled with electrospinning-assisted immobilization. Structural, morphological, and optical studies corroborated the successful formation of the heterojunction, enhanced light absorption, reduced electron–hole recombination, and elevated charge separation. Photocatalytic activity was evaluated in a visible light batch slurry photoreactor with as high as 95.7 % MTZ removal under optimal conditions (initial concentration: 40 mg/L, pH 4.5, catalyst dosage: 0.50 g/L, irradiation time: 120 min), with only around 3 % deviation from the design of experiments (DOE) model's predicted value (∼ 98.9 %). The composite exhibited high reusability with over 85 % retention of its photocatalytic activity over five cycles. © 2025 Elsevier B.V.