Citrus aurantiifolia Peel-Facilitated Synthesis of Zinc Oxide, Interfaced with Biomass-Assisted Graphene Oxide for Enhanced Photocatalytic Degradation of Dye

This study synthesizes zinc oxide (ZnO) and graphene oxide (GO) nanomaterials using a green and sustainable method. ZnO nanoparticles were synthesized from lime peel extract, while GO was obtained utilizing oil palm empty fruit bunch (OPEFB) fibre. The resulting ZnO/GO nanocomposites were characterized using Fourier transform infrared (FTIR), photoluminescence (PL), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflectance spectroscopy (UVDRS), and Raman spectroscopy (RS), confirming their successful synthesis, reduced particle size, altered band gap, and enhanced charge separation properties. The photocatalytic activities of the ZnO/GO nanocomposites were evaluated for MB degradation under visible light. Notably, the ZnO/GO (7%) composite exhibited better degradation efficiency (87% in 90 min) compared to commercial and synthesized ZnO. The study also optimized key parameters including catalyst loading (1 g L⁻¹), initial dye concentration (0.03 mM), and pH (pH 12 showed highest efficiency). The kinetic studies confirmed a pseudo-first-order reaction, with ZnO/GO (7%) showing the highest rate constant (0.0208 min⁻¹). The scavenger tests identified hydroxyl radicals (^•OH) as the dominant reactive species. This research presents a sustainable and efficient approach for wastewater treatment, utilizing waste materials to produce high-performance photocatalysts for environmental remediation.