High-performance photocatalytic degradation of methylene blue from industrial wastewater using bio-inspired ZnO nanoparticles under visible light
Eslam A. Mohamed, Amal A. Altalhi, Hend M. Ahmed, Nabel A. Negm
Abstract
Water pollution caused by organic pollutants and dyes, such as methylene blue (MB), is a significant environmental concern. Traditional wastewater treatment methods often have limitations in effectively removing these pollutants. Photocatalysis, a green and sustainable technology, has developed as a favourable approach to this issue. The main objectives of this study were the biosynthesis of ZnO nanoparticles (NPs) using citrus peel extract, which acts as a biological capping and reducing agent; this approach was employed to produce economic, pure, and more stable ZnO NPs. The second aim was to use the bio-synthesized ZnO NPs in the photocatalytic degradation of MB dyes under visible light irradiation. The structures of bio-synthesized ZnO NPs were deeply described by TGA, XRD, BET, SEM, PL, UV-Vis spectroscopy and TEM measurements. The UV–visible absorption analysis of ZnO NPs showed a characteristic absorption band at 355 nm, and a calculated energy band gap was 3.1 eV. Under optimized conditions (1.0 g/L catalyst, 50 mg/L MB, pH 8, visible light with λ ≥ 420 nm), the ZnO NPs achieved a remarkable degradation efficiency of 94.5 %. This research seeks to develop an efficient and eco-friendly method for eliminating organic pollutants from wastewater using ZnO NPs under visible light, with successful seven cycles. • Facile, one-step green synthesis of ZnO NPs using citrus peel, eliminating hazardous chemicals and high energy inputs. • Effectively valorizes agricultural waste into a high-performance functional nanomaterial, supporting the circular economy. • The synthesized ZnO NPs showed highly visible-light photocatalytic wastewater treatment efficiency using solar energy. • ZnO NPs band gap was 3.16 eV, and low electron-hole recombination rate for degradation of Methylene blue dye pollutants. • The maximum ZnO NPs-photocatalytic degradation of MB was 94 % after 90 min.