Photocatalytic Degradation of Methylene Blue using Green Synthesized Fe3O4/rGO/ZnO Magnetic Nanocomposite Utilizing Moringa Oleifera and Amaranthus Viridis Leaf Extract Nugraheni Puspita Rini (a), Larrisa Jestha Mahardhika (a), Hafil Perdana Kusumah (a), Zurnansyah (a), Putri Dwi Jayanti (a), Rivaldo Marsel Tumbelaka (a), Nurul Imani Istiqomah (a), Nining Sumawati Asri (b), Hasniah Aliah (c), and Edi Suharyadi (a*)
(a) Department of Physics, Universitas Gadjah Mada, Yogyakarta, Indonesia
(b) Research Center for Advanced Materials, National Research and Innovation Agency (BRIN), Tangerang Selatan, Indonesia
(c) Department of Physics, UIN Sunan Gunung Djati, Bandung, Indonesia
*Corresponding author: esuharyadi[at]ugm.ac.id
Abstract
Fe3O4 nanoparticles easily agglomerate into larger particles, reducing specific surface area and dispersibility and limiting catalytic activity. ZnO is attached on rGO surface, wrapped Fe3O4 magnetic nanoparticles, whereas rGO acts as efficient interlayer to optimize synergistic impact of ZnO and Fe3O4 and enhance photocatalytic activity. Herein, we report magnetically separable, green synthesized Fe3O4/rGO/ZnO, as heterogeneous catalyst for photo Fenton degradation of organic pollutants in aqueous solution under certain treatments. Fe3O4 nanoparticles was green synthesized under coprecipitation method using Moringa oleifera leaf extract, while rGO was fabricated by sonicating GO which has been added with hydrazine. Fe3O4/rGO was composited under sonication treatment. Afterwards, Fe3O4/rGO/ZnO was green synthesized using precipitation method with Amaranthus viridis leaf extract addition. X ray diffraction and selected area electron diffraction showed that Fe3O4 and ZnO had spinel cubic and hexagonal structure, respectively- another phase appeared as Fe2O3 spinel cubic structure. Crystallite size was increased as the ZnO concentration increased. Morphology image showed almost spherical, non uniform, and slightly dispersed particle under agglomerated condition, attaching to rGO sheets. Green synthesized Fe3O4, Fe3O4/rGO, and green synthesized Fe3O4/rGO/ZnO with molar ratio of 1:1 had average particle size of 14.3- 14.2- and 10.4 nm, respectively. Besides, the corresponding chemical elements were confirmed by energy dispersive X ray spectroscopy. Fourier transform infrared spectra showed metallic functional groups, such as Fe O and Zn O at 562 until 589 and 462 until 478 cm (minus one) also suggests nanoparticles formation. However, blue shift absorption and band gap widening were observed with ZnO addition. Vibrating sample magnetometer showed that green-synthesized Fe3O4/rGO/ZnO exhibited superparamagnetic properties. Removal efficiency of photodegradation methylene blue was optimal for green synthesized Fe3O4/rGO/ZnO under sonication treatment, reached 100% degradation within 3 h for uptake every 30 min. Photodegradation was also analyzed using Langmuir Hinshelwood kinetic model, resulting rate constant of 34.4 (times ten to the power of minus three) (minus one) and half life time of 20.1 min at optimum treatment. Reusability of photocatalytic activity after 3 cycles showed only a tiny drop in catalytic efficiency. Meanwhile, it possesses high stability in catalytic activity and structure.
