Photoelectric activation of persulfate with a new type of red mud-based CuFe2O4 particle electrode for the efficient degradation of ciprofloxacin: Preparation, influencing factors and mechanism

In our study, a new type composite of red mud-based CuFe2O4 particle electrode (CuFe2O4/RM) was prepared by a solid-phase method, and was applied in the photoelectric activation of PS for the ciprofloxacin (CIP) degradation. The optimal preparation conditions of CuFe2O4/RM were as follows: mass ratios of Cu(NO3)2·3H2O to RM 0.5 g/1 g, calcination temperature 800 °C and calcination time 2 h. The prepared CuFe2O4/RM were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectrometer (XPS). The maximum removal ratio (71.39 %) of CIP was achieved after 60 min treatment under the optimal operating conditions of CuFe2O4/RM dosage 1.0 g/L, PS concentration 9 mmol/L, initial pH 7 and applied current 640 mA. The maximum removal ratios of chemical oxygen demand (CODCr) and total organic carbon (TOC) of the CIP solution were about 49.21 % and 35.7 % after 60 min treatment, respectively. It was found that there was a synergistic effect of visible light, electric field, PS and CuFe2O4/RM in the photoelectric-activated PS system. Combined with the results of XPS, quenching experiment and Electron spin resonance (ESR), the possible catalytic mechanisms of photoelectric-activated PS system were proposed. Besides, the CuFe2O4/RM remained its excellent stability after four cycles. In conclusion, the photoelectric-activated PS system catalyzed by CuFe2O4/RM particle electrodes was proved to be a promising technology for the degradation of CIP in water.