A CeFe₂O₄-CeO₂ composite for the electrochemical detection and advanced oxidation of the antibiotic Sparfloxacin

Antibiotics, such as fluoroquinolones, are frequently found in aquatic environments, making their detection and removal crucial from both an environmental and health perspective. In this study, a CeFe₂O₄ spinel was combined with CeO₂ to give a new composite material (CFO), which was then supported by carbon nanofibers (CNFs). This CFO-CNFs composite facilitated the selective and sensitive electrochemical detection of sparfloxacin, a third-generation fluoroquinolone. A linear concentration range extending from 0.06 to 240 μM with a limit of detection of 49.0 nM and a sensitivity of 0.524 μA μM^-1 cm^-2 were observed. Excellent selectivity in the presence of various inorganic ions, commonly found in aquatic systems, was achieved, while good recovery (90.4-96.2 %) from real water samples was also evident. The CFO with additional CeO₂ was immobilised onto carbon cloth, a sustainable and environmentally acceptable substrate, and successfully used in the activation of peroxymonosulfate (PMS) to generate radical species that degraded the sparfloxacin. The optimal removal was seen at a pH of 7.0, with a first-order rate constant of 0.075 min^-1 in 0.1 mM PMS and 50 μM sparfloxacin. The immobilised catalyst was easily regenerated using a dilute solution of NaBH₄ (0.5 mM). Interestingly, this immobilised catalyst at carbon cloth also facilitated the electrochemical detection of sparfloxacin, with an impressive LOD of 14.0 nM.