Green synthesis of zinc oxide nanoparticles for the removal of phenol from textile wastewater

Abstract

This study investigated the use of zinc oxide nanoparticles (ZnO NPs) as an adsorbent for removing total phenols from textile wastewater. The ZnO NPs were synthesized by reducing Zn(NO3)2⋅6H2O using an extract from Neem leaves (Azadirachta indica). Characterization of the adsorbent was performed using Fourier Transform Infrared (FTIR) spectroscopy to identify functional group modifications, high-resolution scanning electron microscopy (HRSEM) for structural orientation, energy dispersive spectroscopy (EDS) for elemental analysis, and X-Ray diffraction analysis (XRD) for crystallinity, revealing particle crystallinity around 200 nm. Adsorption experiments were conducted over contact times of 20–60 min, with adsorbent loadings between 0.2 and 1 g/100 mL, and temperatures ranging from 30 to 50 °C. Optimal phenol removal, achieving 55.93% (0.67 mg/L), occurred at 43.40 min, 33.70 °C, and an adsorbent dosage of 0.69 g/L of textile wastewater. The phenol adsorption process using ZnO NPs was exothermic, spontaneous, and required low energy, fitting well with the Langmuir isotherm and following a pseudo-second-order kinetic model.