Comparative efficacy of biologically and chemically synthesized nickel oxide nanoparticles for catalytic degradation of dyes and wastewater treatment

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.