Magnetically recoverable N-doped graphene/ZnFe-LDO composite for synergistic adsorption-photocatalytic removal of tetracycline in water

The persistent presence of tetracycline (TC) in aquatic ecosystems poses significant environmental and public health risks. Conventional adsorption-photocatalysis systems often suffer from limited visible-light utilization, sluggish degradation kinetics, and inadequate recyclability. In this study, a magnetically recoverable N-doped graphene/ZnFe-layered double oxide (N/G ZnFe-LDO) composite was developed for combined adsorption-photocatalytic elimination of TC. This N/G ZnFe-LDO achieved high TC adsorption (169.22 mg/g) through synergistic electrostatic interactions and surface complexation. Upon visible-light irradiation, the adsorbed TC underwent efficient photocatalytic degradation, achieving 64.33% removal within 180 min (k_obs = 0.012 min⁻¹), primarily driven by •OH radicals. The integrated approach led to an overall TC removal efficiency of 85.24%. High-performance liquid chromatography-mass spectrometry analysis revealed degradation pathways involving N -demethylation and hydroxylation, followed by ring-opening reactions, ultimately mineralizing TC into CO₂ and H₂O. The catalyst demonstrated robust performance across a wide pH range (5–11) and in the presence of competing anions, while maintaining 93.25% activity retention after six reuse cycles. Tests in real water matrices demonstrated its practical applicability. This work provides a promising strategy for the design of dual-functional materials for the efficient treatment of antibiotic-contaminated water. © 2026 Elsevier B.V.