Degradation of levofloxacin in wastewater by photoelectric and ultrasonic synergy with TiO2/g-C3N4@AC combined electrode

Abstract

A novel particle combined electrode named TiO2/g-C3N4@AC (TGCN-AC) was prepared by loading TiO2 and g-C3N4 on activated carbon through gel method, which was used to degrade levofloxacin (LEF) in pharmaceutical wastewater by photoelectric process. The remarkable physicochemical features of particle electrodes were verified by using diverse characterization techniques including SEM-EDS, XRD, FT-IR, BET and pHZPC. EIS-CV and photocurrent showed excellent electrocatalysis and photoelectrocatalysis performance of particle electrodes. The photocatalytic characteristics and fluorescence properties of the particle electrode were proved by UV–vis DRS and PL spectra measurements. Combined with Tauc's plot and Mott-Schottky plots curves, the ECB and EVB of particle electrodes were determined. The experiments on different influence factors such as pH, ultrasonic, aeration, current density and the concentration of LEF were carried out in the photoelectric reactor. Under the conditions of pH values 3.0, 200 W ultrasonic, 8 L/min aeration, the mass ratio of g-C3N4 and TiO2 is 8%, after 4.0 h of photoelectric process, about 94.76% of LEF (20 mg/L) in water was degraded. TGCN-AC also has excellent reusability. The degradation rate of LEF can still reach 71.17% after repeated use for 6 times. Scavenger studies showed that h+ and O2− were the main active species. By observing the colony size of E. coli, it was proved that the LEF in the effluent had no antibacterial activity. The degradation pathways of LEF was analyzed and drawn by HPLC-MS spectra.