Green and eco-friendly synthesis of Nickel oxide nanoparticles and its photocatalytic activity for methyl orange degradation

In this study the catalytic ability of green synthesized nickel oxide nanoparticles (NiO NPs) is investigated for degradation of methyl orange as a hazardous environmentally contamination in water. The NiO NPs was prepared at ambient conditions using the antioxidant content of Punica granatum L. (pomegranate) juice extract and their bio-reducing ability were studied in details. This process is entirely green process, free from toxic and hazardous solvent. The biosynthesized NiO NPs were in nano scale and their morphology, sizes, surface area and optical properties were characterized using field emission scanning electron microscope (FE-SEM), BET surface area analysis, thermogravimetric analysis, energy dispersive x-ray spectroscopy (EDX), X-ray diffraction (XRD) and ultraviolet–visible spectroscopy (UV–Vis). The biosynthesized NiO NPs were found to be active catalysts, particularly with the reducing agents for instance sodium borohydride, for the degradation of the toxic organic dyes such as methyl orange (MO) in contaminated water. The NiO NPs are stable and reusable for reducing MO to its leuco-form, in a short time, in an aqueous medium in the absence of reducing agents. This method is much cheaper than the other methods. The catalytic activity of NiO NPs can be explained by its small size, compared with the bulk materials, which produce numerous active sites due to its big surface area per unit volume.