Sustainable Valorization of Banana Peel Waste into a Biochar-Integrated BiOBr/rGO Ternary Nanocomposite for Photocatalytic Decomposition of Prednisolone

Abstract

The persistent occurrence of steroidal pharmaceuticals such as prednisolone (PS) in aquatic systems poses significant ecological threats due to their endocrine-disrupting potential and resistance to conventional treatment technologies. In this study, banana peel waste was valorized into biochar and integrated with BiOBr and rGO to synthesize a ternary BiOBr/rGO/biochar (BiGB5) nanocomposite via a facile coprecipitation route. X-ray diffraction revealed distinct reflections corresponding to individual phases, confirming the coexistence of separate crystalline structures. FTIR spectra exhibited strong absorption around 600 cm–1, attributed to Bi–O vibrations, while FESEM and HRTEM analyses demonstrated well-defined morphologies. XPS confirmed the presence of Bi3+, Br–, C, and O species. The composite exhibited a specific surface area of 8.9 m2 g–1. PL studies indicated suppressed electron–hole recombination, and UV–vis diffuse reflectance spectroscopy determined an optical band gap of 2.79 eV. Under sunlight irradiation, BiGB5 achieved ∼91% degradation of PS within 180 min, surpassing pristine BiOBr and binary counterparts. The superior photocatalytic efficiency was attributed to synergistic charge transfer via rGO and abundant active sites on biochar, facilitating hydroxyl radical (•OH) generation. LC-MS analysis enabled a proposed degradation pathway, establishing BiGB5 as a sustainable photocatalyst for efficient removal of recalcitrant pharmaceutical contaminants.