Highly efficient KBN@TiO2@rGO composite for photodegradation of antibiotics under visible light irradiation

Abstract

Antibiotic pollution in surface and groundwater systems raises significant concerns on both ecological and human health, necessitating the development of efficient remediation strategies. To address this challenge, a novel composite material, KBN@TiO2@rGO, was synthesised through a two-step procedure: i) the sol–gel method was employed to prepare KBN-doped TiO2 nanoparticles, and ii) these particles were subsequently dispersed onto reduced graphene oxide (rGO) via hydrothermal treatment for ciprofloxacin (CIP) photooxidation applications. The synthesised nanomaterials and photocatalytic composites were characterised using diverse analytical techniques, including X-ray photoelectron spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, optical spectroscopy, and photoluminescence. The KBN@TiO2@rGO composite exhibited outstanding photocatalytic activity, achieving 99.21 % degradation of CIP and a 75.09 % reduction in total organic carbon during illumination (950 W m−2). Notably, this corresponds to a 3.3-fold increase in the CIP removal efficiency compared to simple TiO2, highlighting the synergistic effect of ternary atom (B, N, and K) doping and rGO integration. Divalent cations, including Mg2+ and Ca2+, slightly inhibited the CIP removal. In contrast, anions such as Cl−, NO3−, and HCO3− enhanced CIP degradation, while SO42−, PO43−, and humic acid exerted inhibitory effects. Furthermore, the degradation performance of the prepared photocatalyst was investigated across different water matrices, showing slightly lower efficiency due to the presence of natural radical quenchers and organic materials. The formation of reactive oxygen species, including •OH, O2•−, and 1O2, was verified through electron spin resonance spectroscopy and chemical scavenger experiments. Finally, possible CIP degradation pathways were elucidated using UPLC-MS/MS analysis. These findings highlight the promising potential of the KBN@TiO2@rGO photocatalytic system for CIP degradation in various water matrices.