Sustainable photocatalytic degradation of methylene blue dye induced through biogenic synthesis of metal oxide nanoparticles mediated orange peel extract

Abstract

Synthetic azo dyes, widely used in various industries, pose serious environmental and health risks due to their toxic, non-biodegradable, and carcinogenic nature when released into aquatic ecosystems. This research focuses on synthesizing and evaluating orange peel-green synthesized zinc oxide nanoparticles (OZONp) as an efficient photocatalytic nanomaterial for the degradation of methylene blue (MB) dye. OZONp were prepared at different concentrations (0.01-0.1 M) of zinc acetate dihydrate and characterised through UV-VIS spectrophotometer, Fourier Transform Infrared (FT-IR) and Scanning Electron Microscope (SEM). The molecular insight into the geometry of phytochemicals of orange peel extract in the activity of OZONp was studied using density functional theory computations. The morphology variations driven by the precursor concentration using SEM analysis were not regular as it changed to irregular spheres and nanoflowers. UV-Vis spectra proved the formation of OZONp with an absorption band within 250-320 nm. FTIR spectra signals the presence of phytochemicals that mediate reduction and stabilization. Photocatalytic degradation experiments of various MB concentrations (5-50 mg/L), revealed that the higher the Zinc salt concentration, the higher the MB degraded, especially under 0.1 M and 5 mgL^-1 of the dye MB. Pseudo- first-order reaction behavior was followed by kinetic modelling with R² values greater than or equal to 0.99. Computational studies revealed that orange peel extract has ferulic acid, hesperidin and narirutin which have desirable electronic properties, which makes them good candidates in the formation of OZONp. The properties are probably beneficial to the process of photocatalytic degradation of methylene blue dye, especially when light is present