Green synthesis of ZnO-NPs from prickly pear peels extract and their methylene blue degradation activities

Bionanotechnology is a promising field for the preparation of nano-sized substances in an environmentally safe manner. This study presents the facile preparation of zinc oxide nanoparticles (ZnO-NPs) from prickly pear peels extract by a green chemistry method. Rietveld structural refinement of the X-ray diffraction (XRD) pattern approved the creation of the hexagonal wurtzite structure of ZnO-NPs. The prepared nanoparticles were also identified by X-ray photoelectron spectroscopy (XPS) analysis to check up the chemical states and purity. The peak of optical absorption of the nanoparticle has been observed at 370 nm. The band gap energy of ZnO-NPs is 3.2 eV. The morphology of the nanoparticles is spherical with a particle size of around 10–30 nm and the interplanar lattice spacing is 0.29 nm. ZnO-NPs were found to be a potential candidate for the photodegradation of Methylene Blue (MB, one of the organic dyes) leading to 85% efficiency as for its oxidative degradation when using hydrogen peroxide in aqueous medium (88% efficiency). Similarly, it shows significant photocatalytic activity with solar energy in less than 20 min compared to MB elimination when H 2 O 2 is used. The nanoparticles have shown a considerable catalytic performance and present the advantage of being easily separated from the treatment medium, since they remain stable after the catalytic process.