Insight into catalytic activation of bisulfite for lomefloxacin degradation by simple composite of calcinated red mud

Antibiotic was detected in many environments, and it had posed a serious threat to human health. The advanced oxidation process has been considered an effective way to treat antibiotics. In this work, using industrial waste red mud (RM) as raw material, a series of modified RM (MRM-T; T donates the calcination temperature) was obtained via a facile calcination method and applied to activate sodium bisulfite (NaHSO₃) for the lomefloxacin (LOM) degradation. Among all MRM-T, MRM-700 exhibited superior catalytic activity, and approximately 89% of LOM (10 mg/L) was degraded at 30 min through the activation of NaHSO₃ ([NaHSO₃] = 0.5 g/L) by MRM-700 ([MRM-700] = 0.9 g/L). Moreover, the kinetic constant of LOM removal in the MRM-700/NaHSO₃ system (0.082 min^-1) was 16.4 times higher than that of the RM-raw/NaHSO₃ system (0.005 min^-1). The as-synthesized product of MRM-700 was characterized by N₂ adsorption-desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectra. The result indicated that the catalyst possessed excellent pore structure, high specific area, and abundant Fe³⁺ sites, and the lattice of Fe₂O₃ was doped after calcination, both of which were favorable for the activation of NaHSO₃. The quenching experiment proved that •SO₄^- and •OH^- active species were produced in MRM-700/NaHSO₃ system, and •SO₄^- played a dominant role in LOM removal. In addition, the potential LOM degradation pathway was analyzed via UPLC-MS technology and density functional theory (DFT) calculation, and the toxicity of the treated LOM solution was tested by the culture of mung bean sprouts. This study not only provided a feasible strategy for the valuable use of RM to activate NaHSO₃ but also offered a cost-effective catalyst for the efficient removal of pollutants in wastewater.