Kinetic and isothermal study of effect of transition metal doping on adsorptive property of zinc oxide nanoparticles synthesized via green route using Moringa oleifera leaf extract

Abstract

In this study, a green route has been adopted to successfully synthesize pure zinc oxide nanoparticles (ZnONPs) as well as Cu doped zinc oxide nanoparticles (Cu-ZnONPs) which is quite a novel work. The synthesized nanoparticles (NPs) were used as adsorbent for removal of Congo red (CR) dye from aqueous solution and efficiency of both doped and undoped ZnONPs was investigated and evaluated. The synthesized products were further characterized and confirmed by UV–visible (UV–vis), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), Thermo gravimetric Analysis (TGA), Transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Cu-ZnONPs were found to be more efficient adsorbent as compared to undoped ZnONPs. The adsorption process of CR on both the synthesized NPs were scrutinized using kinetics and isothermal parameter respectively, which depicted that the adsorption process in case of doped ZnONPs was faster (adsorption reached equilibrium in 120 min) as compared to undoped ZnONPs (which took 180 min) and followed a pseudo-second-order kinetics in both the cases. When pure ZnONPs was used as adsorbent, it correlated more with the Freundlich isotherm and Temkin isotherm as compared to Langmuir isotherm, however, when Cu-ZnONPs was used as adsorbent, the data fitted well to Langmuir and Freundlich models.