Electrochemical degradation of doxycycline hydrochloride on Bi/Ce co-doped Ti/PbO2 anodes: Efficiency and mechanism

Abstract

Doxycycline hydrochloride (DOX), a widely used broad-spectrum antibiotic, was used in large quantities and its residues in the environment caused a series of environmental problems. In this study, small amounts of bismuth (Bi) and cerium (Ce) were co-doped in the titanium matrix lead dioxide anode (Ti/PbO2) using the electro-deposition method. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used for the characterization of the electrodes. And the prepared PbO2 anode was found to be mainly composed of β-PbO2, and Ti/PbO2/Bi-Ce 03 (co-doped with 0.5 mmol·L−1Bi and 0.5 mmol·L−1 Ce in PbO2 anodes) had the best catalytic effect and surface structure. Compared with Ti/PbO2, doping improved its corrosion potential (21.82%), accelerated lifetime (108.33%), and degradation efficiency (43.62%) while reducing the electrochemical impedance (17.91%). It was proved by a single-factor experiment that the degradation rate of DOX was 100% at 10 min with a current density of 10 mA·cm−2, electrolyte concentration [Na2SO4]= 0.1 mol·L−1, and pH= 4, which was the best degradation condition for DOX. In addition, the degradation of DOX fitted the first-order kinetic equation. The DOX degradation on Ti/PbO2/Bi-Ce 03 electrode was mainly attributed to direct oxidation and SO4•-. Four possible degradation pathways were postulated using the results of high-performance liquid chromatography-mass spectrometry (HPLC-MS). The paper provided a new way for preparing Ti/PbO2 electrodes with high catalytic activity and longer lifetime, and also an efficient way for degradation of antibiotic DOX.