Abstract
Nickel oxide (NiO) nanoparticles (NPs) were synthesized using chemical and biological methods to evaluate their photocatalytic efficiency in degrading organic pollutants. The NiO-NPs were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, Fourier-transform infrared spectroscopy, and zeta potential analysis. Their photocatalytic activity was tested using methylene blue (MB) and 4-nitrophenol (4-NP) as model pollutants under visible light irradiation. Biosynthesized NiO-NPs exhibited higher photocatalytic activity and faster degradation rates. The biosynthesized NiO-NPs decolorized MB dye by 90% in 1 min, while chemically synthesized NPs required 5 min. Additionally, biosynthesized NiO-NPs degraded 4-NP more efficiently, achieving 65% decolorization in 25 min. The photocatalytic potential of the NiO-NPs was further demonstrated by the degradation of azo dyes, including reactive red-120, reactive black-5, brilliant yellow, and brilliant blue-R. In dye-loaded textile wastewater, NiO-NPs-B and NiO-NPs-C decolorized 84.8 ± 4.7% and 67.2 ± 3.4% of added RB5, and 70.3 ± 5.0% and 56.5 ± 2.3% of added RR120, respectively. Additionally, NiO-NPs-B removed 62.4 ± 3.7% of COD from wastewater spiked with RB5, while NiO-NPs-C removed 57.1 ± 3.3%. These findings suggest that biogenic NiO-NPs are highly efficient photocatalysts for organic pollutant degradation, offering a promising alternative to conventional chemical methods.