Effect of Dissolved Oxygen Content on Photocatalytic Performance of Graphene Oxide

Author(s): M Bakhtiar Azim, Md Intaqer Arafat, Farzana Nargis, Sajib Aninda Dhar, Md. Rakibul Qadir, Md. Abdul Gafur, Fahmida Gulshan

Graphene is a two-dimensional carbon-based photocatalyst that shows great promise. This study compared the photocatalytic degradation of a new organic dye, Methylene Blue (MB), using graphene oxide (GO) to traditional water treatment procedures such as ion exchange and adsorption. In this study, the photocatalytic activity of GO and hydrogen peroxide (H2O2) was assessed by photodegrading Methylene Blue (MB) in an aqueous solution. The resultant GO nanoparticles were examined using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDX), and Fourier Transform Infrared Ray Spectroscopy (FTIR). The XRD data verifies the strong peak centered at 2θ≈10.44°, corresponding to the (002) reflection of GO. Our study found that GO nanoparticles and H2O2 achieved ~92% photo decolorization of MB, compared to ~63% for H2O2 under natural sunshine irradiation at pH~7 in 60 minutes. Furthermore, the influence of dissolved oxygen (DOC) and H2O2 on MB degradation was studied. The experimental results showed that oxygen was a decisive factor in enhancing photocatalytic degradation. Direct photocatalysis (MB/GO) and H2O2-assisted photocatalysis (MB/H2O2/GO) resulted in an increase in the degradation rate constant (k1) from 0.019 to 0.042 min−1 for DOC 3.5 mgL−1. In this case, H2O2 worked as an electron and hydroxyl radical (•OH) scavenger; however, the addition of H2O2 should be at the right dose to increase MB breakdown. Increasing the initial DOC content from 2.8 to 3.9 mgL−1 resulted in an increase in the degradation rate constant (k1) from 0.035 to 0.062 min−1. The photodegradation mechanism and kinetics were investigated for both direct and H2O2-assisted photocatalysis.