Effective degradation of aqueous carbamazepine on a novel blue-colored TiO2 nanotube arrays membrane filter anode

Highlights: • Novel BC-TiO₂NTA membrane filter electrode is developed. • Electrochemical oxidation of carbamazepine in aqueous solution is investigated. • Electrochemical degradation of carbamazepine follows pseudo-first-order reaction kinetics. • Possible electrochemical degradation mechanisms of carbamazepine are proposed. The effective electrochemical oxidation of aqueous carbamazepine (CBZ) using a novel blue-colored TiO₂ nanotube arrays (BC-TiO₂NTA) membrane filter anode was studied. The BC-TiO₂NTA was characterized using SEM, TEM, BET, mercury intrusion porosimetry, XPS, XRD, CV, and LSV. The BC-TiO₂NTA had reserved pore structure, formed mesopores, specific and electroactive surface areas of 2.01 m² g⁻¹ and 9.32 cm² cm⁻², respectively. The oxygen evolution potential was 2.61 V vs. SCE. CBZ could be degraded by OH, SO₄⁻ and O₂⁻ on BC-TiO₂NTA in accordance to pseudo-first-order kinetic, which was greatly enhanced in flow-through mode. The optimal kinetic rate constant of CBZ degradation of 0.403 min⁻¹ was achieved at 3 mA cm⁻², while energy consumption per order was 0.086 kW h m⁻³. The mineralization efficiency and mineralization current efficiency were 50.8 % and 9.5 % at 180 min, respectively. The presence of Cl⁻ (0.3−3 mM) accelerated electrochemical degradation of CBZ, while NO₃⁻ (0.1−2 mM) inhibited the reaction. Based on density functional theory calculation and UPLC-Orbitrap-MS/MS measurement, we found that electrochemical degradation of CBZ was initialized by cleavage of −CONH₂ group and attack of OH on the olefinic double bond of the central heterocyclic ring.