A novel oxygen-based manganese oxides modified membrane reactor for TC oxidative degradation

Tetracycline (TC), one of the most widely used antibiotics, is frequently detected in wastewater, imposing high risks to human health. In this study, a novel O2-based membrane MnOx film reactor (O2-MMnfR) for TC oxidative degradation was established, with O2 directly delivered to the in-situ-coated MnOx nanoparticles (NPs) on the surface of hollow-fiber gas-transfer membranes. The O2 within the MnOx NPs effectively facilitated the oxidation degradation of TC, with a first-order kinetic constant of 0.1535 h−1. Ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) analysis elucidated three primary transformation products (TPs) from TC degradation. Additionally, Fourier-Transform Infrared Spectroscopy (FTIR) analysis of MnOxNPs revealed the formation of primary and secondary amines, while X-ray Photoelectron Spectroscopy (XPS) indicated an increase in functional groups, including C-O-(H, C), CO, and C-(O, N). These findings collectively suggest that TC undergoes hydroxylation and demethylation during degradation. Furthermore, E. coli toxicity assays demonstrated that these TPs exhibit substantially lower toxicity compared to TC. The quantification of Mn(II) via Inductively Coupled Plasma Mass Spectrometry (ICP-MS), coupled with XPS analysis of MnO composition in MnOxNPs, revealed that the loss of Mn(II) in O2-MMnfR is considerably lower than in anoxic conditions. X-ray diffraction (XRD) analysis displayed a pronounced sharpening of the peak at 2θ = 31.028°, corroborating the regeneration of Mn(II) during TC degradation. Conclusively, this investigation provides insightful perspectives on the catalytic degradation of TC and propounds viable strategies for the effective elimination of antibiotics from wastewater.