Green synthesis of reduced graphene oxide-zinc oxide (rGO-ZnO) nanocomposite using neem (Azadirachta indica) leaf extract for efficient removal of organic dyes from wastewater

This research used a green synthesis method to create Reduced Graphene Oxide-Zinc Oxide (rGO-ZnO) nanocomposites using Azadirachta indica (Neem) leaf extract, which show high efficiency in removing organic pollutants ( Maxilon Pink Dye) from wastewater. The environmentally friendly synthesis route eliminates hazardous chemicals while making the material synthesis process more sustainable. The composite was thoroughly characterized using XRD, FTIR, SEM, EDX, and DLS analytical techniques to assess its crystalline nature, functionalities, surface morphology, elemental composition, and size. The XRD pattern of the nanocomposite showed the presence of a hexagonal wurtzite phase of ZnO in the nanocomposite. SEM analysis demonstrated a rough, porous morphology with uniform dispersion of ZnO nanoparticles (NPs) on rGO sheets, and EDX confirmed the elemental composition. Optical studies showed a significant band gap reduction from 3.08 eV (ZnO) to 2.72 eV and 2.52 eV for 5% and 10% rGO–ZnO, respectively, indicating enhanced visible-light absorption. The composite was then employed to remove commercial textile MP dye from aqueous medium. The % dye removal efficiency increased with increasing pH and time, while the optimization of catalyst dosage, reaction time, and initial dye concentrations was also studied. The kinetic study suggested that the photocatalytic degradation followed the pseudo-second-order kinetic model. After five cycles of use, the nanocomposites demonstrated a ∼52% degradation percentage. The residual toxicity analysis also showed excellent cell viability of the model organism after treatment. Under optimized conditions (20 mg in 20 mL dye solution, with an initial concentration of 20 ppm and pH 8), the rGO-ZnO composite demonstrated a remarkable 92.229% removal efficiency of MP dye from aqueous solutions, with a removal capacity of 18.4458 mg/g.