Photocatalytic activities of Mg doped NiO NPs for degradation of Methylene blue dye for harmful contaminants: A kinetics, mechanism and recyclability

The pure Nickel oxide (NiO) nanoparticles (NPs) and Mg doped NiO (Mg:NiO) were prepared by one pot-auto combustion process in the presence of citric acid. Phase identification of Mg: NiO NPs was carried out by X-ray diffraction (XRD) and FT-Raman spectroscopy. The values of crystallite sizes 20.5, 20.1 19.8, 20.0, and 19.2 nm and lattice strains 1.225 x10-4, 1.473x 10-4, 0.977x 10-4, 1.597x 10-4,and 0.742x10-4 have been evaluated using Williamson-Hall plots analysis of the prepared NPs. Spherical shape morphology of Mg:NiO NPs was observed by FESEM images. The average particle size distributions were evaluated as 48.4, 60.8, 28.0, 33.4, and 35.3 nm for 0.0, 1.0, 2.0, 3.0 and 5.0 wt% Mg: NiO NPs, respectively. The presence of chemical elements, and their stoichiometric amount in prepared Mg:NiO NPs were determined by EDAX. The oxidation states Ni (2P3/2), Ni (2P1/2), O (1s), and Mg (2s) were recorded by X-ray photoelectron spectroscopy (XPS). Kubelka-Munk (K-M) function was employed to determine the optical band gaps of the prepared NPs by recording diffuse reflectance spectroscopy (DRS). The energy gaps of 3.538, 3.535, 3.487, 3.532, and 3.490 eV were estimated for 0.0, 1.0, 2.0, 3.0, and 5.0 wt% Mg: NiO, respectively. Methylene blue (MB) dye solution was employed to investigate the photocatalytic activity of as-prepared NPs in the presence of UV light. The degradation of MB was examined using visible photo application of pure NiO and Mg: NiO NPs. The 3 wt% Mg:NiO photocatalyst degrades the MB dye up to 98% after 75 min under UV light irradiation. Photocatalytic degradation of 3 wt% Mg:NiO NPs results showed that the NiO NPs are potential photocatalysts in the degradation of MB dye and can be utilized in wastewater treatment.