Photocatalytic degradation of cefixime using visible light-driven Z-scheme ZnO nanorod/Zn₂TiO₄/GO heterostructure

ZnO nanorod along with a Zn₂TiO₄/GO heterostructure with enhanced charge transfer capability was synthesized by a facile sol-gel method. FT-IR, XRD, XPS, TEM, SEM, EDX, UV-Vis DRS, photocurrent response and PL analyses were applied to characterize the as-prepared photocatalysts. To investigate the photocatalytic activity of the composite, Cefixime (CEF) removal under visible light was evaluated. The ZnO nanorod/Zn₂TiO₄/GO, including 65 wt% ZnO and 3 wt% graphene oxide, showed the highest CEF degradation and was selected as the optimal ternary composite. Reduction of electron-hole pair recombination rate, successful interfacial charge transfers, and more visible light reception in the Z-scheme system were the important reasons for improving the photocatalytic properties of ZnO nanorod/Zn₂TiO₄/GO. Effective operating parameters in the CEF photocatalytic removal process were optimized employing the response surface method and were as follows: photocatalyst dosage = 0.88 g/L, pH = 5, radiation time = 115 min, and CEF concentration = 10 ppm. The photocatalytic degradation% of CEF and total organic carbon (TOC) removal% under the optimal conditions were 71.4 and 57.5%, respectively, for the three-component composite indicating the production of intermediate species during the process. This photocatalytic reaction confirmed the first-order kinetic and using the ZnO nanorod/Zn₂TiO₄/GO composite was able to improve the reaction rate by about 2.7 and 6.2 times more than ZnO nanorod/Zn₂TiO₄ and ZnO, respectively. The effects of radiation intensity and temperature were investigated and 175 W/m² and 35 °C were obtained as optimum values. Eventually, according to the trapping test, h⁺, superoxide radical, and hydroxyl radical are the most effective active species in this photocatalytic reaction, respectively.