BiFeO3/graphitic-carbon/PVDF composite with an electrical percolation network to enhance ciprofloxacin removal by photoelectrocatalytic ozonation

Abstract

Ternary BiFeO₃ (BFO)/Graphitic-Carbon/polyvinylidene fluoride (PVDF) composite photoanodes are fabricated at different compositions: 76:12:12, 80:10:10, and 90:5:5 wt% to account their influence during the degradation of 20 mg L⁻¹ ciprofloxacin (CIP, C₁₇H₁₈N₃FO₃) in synthetic water, using photoelectrocatalytic ozonation (PECO). BFO acts as active phase, Graphitic-Carbon as electronic conductor, and PVDF as binder. The crystalline structure of BFO synthesized by a high–energy ball milling method is confirmed by X-ray diffraction (XRD), Rietveld Refinement and Raman analysis; while Scanning Electronic Microscopy (SEM) images reveal an adequate dispersion on the substrate of all components for the 80:10:10 wt % composition, which differ in other composite ratios. Cross-sectional SEM imaging are also collected for the composites. XPS analysis confirms the presence of Bi³⁺ and Fe³⁺ species associated with the BFO phase. Optoelectronic and electrochemical characterizations conducted for all composites reveal that the 80:10:10 wt % composite generates a remarkable enhancement of 90 % CIP degradation after 60 min (Total Organic Carbon removal = 74.83 %) of treatment, according to high-performance liquid chromatography (HPLC) measurements. This was achieved due to the effective charge carriers separation (e⁻ and h⁺) in the BFO photoanode which is an n-type semiconductor, whence it requires the establishment of an interconnected network with a good electronic conductor like graphite expediting the charge transport to the cathode, and a binder to provide mechanical integrity to the entire composite. This is explained in terms of a photoelectrocatalytic mechanism rationalizing the electrical percolation network in the composites. The reaction mechanism of the CIP abatement is discussed along with the oxidants responsible for its elimination, detected by trapping tests with different scavengers. Toxicity bioassays conducted with Daphnia magna confirm that the water treated with the synergic PECO method is not toxic. Additionally, no physical, cardiac effects or alterations are observed in the swimming behavior of these organisms.