Hazard free green synthesis of ZnO nano-photo-catalyst using Artocarpus Heterophyllus leaf extract for the degradation of Congo red dye in water treatment applications

Abstract

The present study describes the use Artocarpus Heterophyllus leaves extract for the synthesis of Zinc oxide nanoparticles (ZnO NPs). The particles were calcined at 400, 600 and 800°C for 1h. Powder X-Ray Diffraction (PXRD) results showed the ZnO NPs calcined at different temperature to be crystalline with hexagonal wurtzite phase. The morphology was studied using scanning electron microscopy (SEM) and elemental composition investigated using energy dispersive spectroscopy (EDS) showed peaks for Zn and O only. The exact size of ZnO particles and its crystalline nature were investigated from transmission electron microscopy (TEM),High resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The TEM showed the size range of the ZnO NPs to be ∼ 10–15nm at 400°C, ∼ 15–25nm at 600°C and ∼ 25–30 at 800°C which are in good agreement with the SEM observation. The band gap energy was calculated from UV diffuse reflectance spectra and found to be 3.42, 3.38 and 3.35eV for 400, 600 and 800°C respectively. The fourier transform infra-red spectroscopy (FTIR) spectra of leaf extract confirmed the presence of phyto constituents such as amines, amides, quinines and ketones in the leaf extract. The ZnO NPs calcined at 400°C having higher band gap energy and smaller size was used for photocatalytic degradation. The studies showed the efficiency greater than 90% towards degradation of 20ppm Congo red dye solution at 0.24g/L ZnO NPs in 1h at pH 9.