Photocatalytic activity of graphene oxide/zinc oxide nanocomposite derived from rice husk for the degradation of phenanthrene under ultraviolet-visible light

Abstract

Environmental concerns have arisen due to the persistent nature and carcinogenicity of polycyclic aromatic hydrocarbons (PAHs). This study used the doping approach to successfully develop a nanocomposite photocatalyst based on graphene oxide (GO) and zinc oxide (ZnO). The nanocomposites were investigated by Fourier transform infrared (FTIR) spectroscopy, UV–Visible diffuse reflectance spectroscopy (UV–Vis DRS), x-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive x-ray (EDX), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET), and Raman spectroscopy. GO/ZnO nanocomposite showed excellent ability to degrade 25 ppm of phenanthrene (86.06%) in 120 min under UV–Visible light exposure followed by photolysis (no photocatalyst) (15.56%), GO/ZnO without stirring (40.28%), GO/ZnO in the dark with stirring (47.40%), and commercial ZnO (62.84%). This is due to the largest surface area, which was enhanced by the doping of GO in commercial ZnO. Phenanthrene photodegradation by GO/ZnO nanocomposite followed first-order kinetics with a rate constant of 0.0375 min−1. The smaller byproducts like (Z)-3-hydroxy acrylic acid (1b; m/z = 88) and (Z)-4-oxobut-2-enoic acid (1c; m/z = 100) identified in GC–MS, clearly demonstrated e− excitement from encapsulated nanocatalyst followed by [rad]OH (active species) based oxidation of phenanthrene. Consequently, the GO/ZnO nanocomposite could be a versatile photocatalyst for the photodegradation of phenanthrene in wastewater treatment.