Enhanced UV-light photocatalytic degradation of methylene blue by microwave-synthesized NiO nanocrystalline samples

Abstract This study explores the photocatalytic (PC) degradation of Methylene Blue (MB) using nickel oxide (NiO) nanocrystalline powders synthesized via a microwave-assisted method. The synthesized NiO samples were characterized by optical and structural analyses using UV–Vis spectroscopy and XRD. An optical band gap of 4.0 eV was obtained by UV-Vis spectroscopy, which is due to the size effects in nanocrystalline NiO. The XRD results showed that the NiO product was a single-phase product, and the average crystallite size (calculated by the Scherrer equation) of NiO was 25.6 nm with a high degree of crystallinity. The PC system reached its highest performance during UV light exposure because it achieved an 85% MB degradation after 90 min but visible light exposure only produced less than 10% degradation It is point out that the results indicate that the activity of PC is dependent on the optical band gap and UV absorption of NiO and it is also suggest that the NiO synthesized using microwave technology can be used as a potential photocatalyst for treatment of wastewater under UV irradiation. This study is intended as a proof-of-concept investigation focusing on the intrinsic UV-driven photocatalytic behavior of phase-dominant NiO synthesized via a rapid microwave-assisted route, rather than performance optimization against benchmark photocatalysts. Photocatalytic degradation kinetics were evaluated using a pseudo-first-order model based on UV–Vis absorption data.