Green synthesis of ZnO nanoparticles and its application for methyl green dye adsorption

This research presents a facile and inexpensive method for synthesizing ZnO nanoparticles using Nauclea latifolia fruit extract as a bioreductant and stabilizer. The prepared particles were characterized using some analytical techniques, including X-ray diffraction (XRD) for crystallinity and phase identification, scanning electron microscopy (SEM) to study surface morphology, Fourier transform infrared (FTIR) spectroscopy for functional groups analysis, transmission electron microscopy (TEM) for grain size analysis, UV–Vis spectroscopy for optical properties, and Brunauer-Emmett-Teller (BET) for surface area analysis. XRD analysis revealed a hexagonal wurtzite structure with an average crystallite size of 14.40 nm. FTIR showed absorption peaks at 3659, 1341, and 460 cm⁻¹, corresponding to hydroxyl, carboxylic, and Zn–O, respectively. SEM image showed an agglomerated surface morphology with a flower-like shape. TEM estimated the particle size range to be 12.54–17.35 nm. UV–Vis scanning showed a broad peak at 373 nm. BET revealed 277.420 m²/g as the specific surface area. A batch adsorption experiment conducted on the performance of the nanoparticles for methyl green (MG) removal from aqueous solution showed highest efficiency of 99.96% at 60 min agitation time and pH of 7, with 0.05 g of the ZnO NPs, confirming the efficiency of the particles. The results of adsorption modelling revealed that the adsorption data were best fit to Freundlich isotherm and general-order kinetic models. Thermodynamic investigation confirmed the adsorption process as spontaneous, feasible, endothermic, and physical. Finally, the simplicity of the synthesis method and the performance evaluation of the ZnO nanoparticles indicate that an efficient and cost-effective adsorbent for MG recovery from aqueous solution has been successfully prepared.