Green synthesis of ZnO nanoparticle using Trema orientalis (L) leaf: an efficient photocatalyst for degradation of zoxamide fungicide in aqueous organic media under UV light irradiation

Abstract

ABSTRACT This article reports the green synthesis of zinc oxide nanoparticles (ZnO NPs) by using the aqueous leaf extract of Trema orientalis (L). The ZnO NPs were synthesised by using zinc nitrate hexahydrate acts as the precursor and leaf extract acts as the reducing and capping agent. The synthesis of ZnO NPs was confirmed by the powder X-ray diffraction (XRD) analysis and the average crystalline size was calculated by Scherrer’s formula (24 nm) and as well as Williamson-Hall (W-H) equation (26 nm). The Dynamic Light Scattering (DLS) analysis showed the stability and particle size of approximately 65–67 nm of the synthesised ZnO NPs. The Fourier Transform Infrared Spectroscopy (FTIR) analysis confirmed the presence of various functional groups in the synthesised NPs. The UV absorption wavelength is observed at 370 nm, and the calculated direct band gap was found to be 3.13 eV. The surface morphology, the crystalline shape of the synthesised ZnO NPs was determined by using Scanning Electron Microscopy (SEM). The effectiveness of the ZnO NPs on photocatalytic degradation of zoxamide, a benzamide class of fungicide was tested under UV irradiation (λ max ≥ 250 nm). The calculated half-lives of photodegradation of zoxamide in acetonitrile/water solvent system were found to be in the range of 4.09 − 10.46 h. Moreover, the effect of pH, the initial concentration of zoxamide and photocatalyst ZnO NPs dosage were investigated. The experimental kinetic data followed the pseudo-first-order model. The reaction rate constant (kobs) was decreased from 0.1695 to 0.1511 h−1 with increasing initial zoxamide concentration from 120 to 260 mg/L, respectively. Langmuir–Hinshelwood (L–H) kinetic model was proposed for the rate equation of the zoxamide degradation in presence of ZnO NPs under UV irradiation.