Optimization of Visible-Light-Driven Ciprofloxacin Degradation Using a Z-Scheme Semiconductor MgFe<sub>2</sub>O<sub>4</sub>/UiO-67
Zoha Nasari, Masoumeh Taherimehr
Abstract
A heterogeneous photocatalyst, MgFe 2 O 4 /UiO-67 (MU- x ), was successfully synthesized by doping magnetic magnesium ferrite nanoparticles (MgFe 2 O 4 ) with the UiO-67 metal–organic framework at various weight ratios (MgFe 2 O 4: UiO-67 at 30, 50, 70, and 90 wt %). Various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), photoluminescence (PL), vibrating sample magnetometry (VSM), electrochemical impedance spectroscopy (EIS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), were used to characterize the prepared photocatalysts. The photocatalytic performance of MU- x in the degradation of ciprofloxacin (CIP) under visible light was assessed. The CIP degradation efficiency was found to increase as the amount of MgFe 2 O 4 in the composite was increased up to 70 wt %. Experimental conditions were optimized using response surface methodology (RSM) based on central composite design (CCD) with three factors: initial pH, catalyst loading, and CIP concentration. Using the obtained model, the optimal conditions were determined as follows: initial pH of 8.025, catalyst loading of 33.8 wt %, and CIP concentration of 10.8 mg/L. Under these optimal conditions, a notable improvement was achieved, with 99.62% of CIP removal achieved within 90 min, surpassing the performance of previously reported photocatalysts. Total organic carbon (TOC) analysis revealed a high degree of mineralization, at 81.25%. The degradation pathway of CIP was investigated based on liquid chromatography–mass spectrometry (LC-MS) analysis. Finally, the values of E CB and E VB of the photocatalyst were determined and the possible degradation mechanism of CIP was investigated based on Mott–Schottky and the applied scavengers. The hydroxyl radical ( • OH) was identified as the dominant species in the removal of CIP through a trapping experiment. The photocatalyst with 70 wt % of MgFe 2 O 4 (MU-70) exhibited excellent stability and recoverability with an external magnet, demonstrating 86.33% CIP removal after four cycles. According to the obtained results, MU-70 is a promising visible-light-active photocatalyst with great potential for water treatment applications and convenient recovery.