Green synthesis of zinc nanoparticles using <i>Ipomoea asarifolia</i> leaves extract and its adsorption properties for the removal of dyes

Abstract

In this paper, a green method is reported for the synthesis and characterization of zinc nanoparticles using Ipomoea asarifolia leaf extract as reducing and capping agent together with polyethylene glycol (PEG-10000) as stabilizing agent. The biosynthesized zinc nanoparticles were characterized by UV-Vis absorption spectroscopy, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM); and were used as adsorbent for the removal of Bromophenol blue (BPB), and Eriochrome black T (EBT) dyes. Isotherms, kinetics and thermodynamics of the adsorption process were studied with the view to understand the adsorption mechanism. The adsorption isotherms were closely described by Freundlich isotherm model with correlation coefficient (R²) of 0.99. The adsorption kinetics data were well fitted by the pseudo-second-order rate model with high regression coefficient (0.998). The intra particle diffusion of BPB anId EBT on ZnNPs represents the rate-limiting step. The adsorption capacity increases with the increase in temperature (from 298 to 318K) and thermodynamic calculations suggested that the adsorption of the dyes onto ZnNPs is an endothermic process with ΔH values of 10.78kJ/mol for BPB and 14.14 kJ/mol for EBT respectively.

Keywords: Adsorption, Bromophenol blue, Eriochrome black T, Ipomoea asarifolia, Zinc nanoparticles