3RD INTERNATIONAL CONGRESS ON TECHNOLOGY - ENGINEERING & SCIENCE - Kuala Lumpur - Malaysia (2017-02-09)

Degradation Of Organic Pollutants By Zno Decorated Fe3o4/rgo Ternary Nanocomposite

Herein, we report a magnetically-separable tertiary composite, zinc oxide-decorated Fe3O4/rGO, as a heterogeneous catalyst for photo-Fenton degradation of organic pollutants in aqueous media under ambient conditions. In this study, zinc oxide nanoparticles were hydrothermally deposited on the surface of Fe3O4/GO composite that was synthesized by a solvothermal process. The physicochemical properties of the as–synthesized composite were explored using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and photoluminescence (PL) studies. The as-prepared catalyst showed superior stability and, due to the presence of the magnetic Fe3O4 nanospheres, could be conveniently separated from the reaction system with an external magnet for reuse. The photo-Fenton activity of the as-prepared catalysts was evaluated by analyzing the photodegradation of MB in an aqueous solution under visible irradiation. For the degradation of MB, 20 mg of the as-prepared catalyst was used into a 100 mL reactor containing 50 mL of an aqueous solution of 10 mg/L MB and 30 µM H2O2. The pH of the reaction mixture was maintained at 7. The photocatalytic activities of the as-prepared composites were evaluated by monitoring the discoloration of methylene blue (MB) under visible-light irradiation (λ ≥ 420 nm). The concentration of the MB solution was analyzed by measuring the absorbance peak at characteristic 664nm wavelength using a UV–vis spectrophotometer. The as-synthesized, ZnO-decorated Fe3O4/rGO composite exhibited superior catalytic activity for the degradation of azo-dye compared to pristine ZnO, ZnO/Fe3O4, Fe3O4, and Fe3O4/GO. These results revealed the synergistic effects between the different components of the catalyst and confirmed the rapid redox reaction between Fe2+ and Fe3+. Overall, with visible irradiation, the electron transfer between the ferric ions and the ferrous ions is accelerated by rGO and ZnO, thereby promoting the continuous generation of •OH radicals. These resulting •OH radicals are responsible for the degradation of MB. It was also observed that the catalytic reduction efficiency of the as-synthesized composite was almost the same after four successive reactions without a considerable decrease in efficiency. All of these merits indicate that the composite catalyst is a promising candidate for the degradation of organic compounds under visible light in environmental remediation applications.
Devi Prashad Ojha, Han Joo Kim