Electrocatalytic oxidation of ranitidine using a fluorinated blue titanium dioxide nanotube array electrode

Herein, a novel fluorinated blue titanium dioxide nanotube array (F-BTNA) electrode is fabricated via a simple one-step solution immersion method for the efficient electrochemical degradation of ranitidine (RAN), a typical pharmaceutical contaminant in aquatic environment. Characterization reveals that fluorine is successfully incorporated into the TiO 2 lattice, forming stable Ti–F bonds and increasing the contents of surface Ti³ ⁺ (from 53.4 % to 57.8 %) and oxygen vacancies (from 31.04 % to 39.39 %). These modifications enhance the electroactive surface area (from 0.643 to 0.707 m² g −1 ), oxygen evolution potential (from 2.53 to 2.79 V vs. SCE), hydroxyl radical (•OH) yield (from 0.254 to 1.261 mmol min −1 cm −2 ), and interfacial charge-transfer efficiency (from 0.025 to 0.106) compared to pristine TiO 2 (TNA) and blue TiO 2 nanotube arrays (BTNA). The F-BTNA electrode achieves 96.2 % degradation of RAN within 30 min, primarily through •OH-mediated indirect oxidation and direct electron transfer. RAN removal is favored by the presence of Cl – , lower pH and RAN concentration, whereas NO 3 – shows inhibitory effects. Eight degradation intermediates are identified by UPLC-MS/MS, with possible pathways involving C–N/C–S bond cleavage, hydroxylation, and ring-opening reactions. The system achieves 38.3 % TOC removal within 120 min, and toxicity evaluation confirmed that harmful intermediates are further transformed into less toxic products. The F-BTNA electrode exhibits high stability over five consecutive cycles (>86.5 % removal efficiency) and broad-spectrum applicability for degrading various PPCPs. These results demonstrate the F-BTNA electrode's great potential as a practical and robust material for the electrochemical treatment of pharmaceutical-contaminated wastewater.