Photocatalytic degradation of ternary dye mixture using RGO, γ-Fe2O3 and ZnO based binary and ternary nanocomposites

Abstract

In this work, we report on the improved photocatalytic degradation of a ternary dye mixture of Malachite green (MG), Methyl orange (MO), and Rhodamine B (RhB), by RGO-based binary (RGO/γ-Fe2O3) and ternary (RGO/γ-Fe2O3/ZnO) nanocomposites (NCs). These NCs are synthesized with a green, facile, and rapid microwave irradiation route using Mangifera Indica leaf extract as a reducing agent. X-ray diffraction (XRD) and scanning electron microscopy (SEM) give clear insight into the phase purity and uniform growth of γ-Fe2O3 and γ-Fe2O3-ZnO nanoparticles over the RGO sheets which confirms the reduction of iron and zinc precursors, and graphene oxide via Mangifera to form NCs. The binary and ternary NCs show 100 % degradation of ternary dye mixture in 40 min and 21 min, respectively, under UV irradiation. UV–Visible spectra confirm a reduced energy band gap, 1.96 eV for ternary NCs, and 2 eV for binary NCs as compared to 2.3 eV for γ-Fe2O3. The reduction in band gap and synergism amid RGO and nanoparticles of γ-Fe2O3 and ZnO presents that suppressed charge carrier recombination, enhanced charge carrier lifetime, improved interfacial charge transfer and availability of more active sites in RGO/γ-Fe2O3/ZnO ternary NCs are responsible for highly efficient photocatalytic activities. Reaction kinetics analysis reveals the suitability of the pseudo first-order kinetics and Freundlich model for dye degradation.