Nanoflowers and nanorods of ZnO were synthesized via hydrothermal route. These morphologies of zinc oxide (ZnO) were then decorated over graphene oxide (GO) to yield hybrid nanocomposites, namely, GO-ZnOnR and GO-ZnOnF. The decoration of ZnO nanorods and nanoflowers on GO layers was confirmed through FESEM images. The synthesized nanocomposites were subjected to degrade the Orange G under identical conditions. The band gap energies determined using diffused reflectance spectra were 2.87, 2.89 eV for GO-ZnOnR, and GO-ZnOnF, whereas, for both ZnOnR and ZnOnF, it was 3.14 eV. For 50 min of UV irradiations (at 6 pH), 100% degradation was achieved corresponding to GO-ZnOnR (44.1 m2 g-1) followed by 90.1%, 70.2%, and 68.3% with GO-ZnOnF (35.9 m2 g-1), ZnOnR (20 m2 g-1), and ZnOnF (15.1 m2 g-1), respectively. Significant boost in the degradation of Orange G, with GO-ZnOnR, was attributed to its reduced band gap, higher surface area, and enhanced charge separation. Kinetic study confirms the pseudo-first-order reaction rate. Mineralization efficiency of 91% in 120 min indicated the efficient reduction of Orange G and its intermediates. Further, reactive species trapping experiments revealed that photo-induced •OH are dominant radicals for the degradation followed by •O2- and h+. Liquid chromatography mass spectra data has been used to predict the plausible reaction pathways. Reusability studies indicated that GO-ZnOnR can be used for four successive degradation cycles, without any significant activity loss.
Keywords: Degradation pathways; Graphene oxide; Mineralization; Orange G; Trapping experiment; ZnO.
© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.