Adsorptive performances and characterisations of biologically synthesised zinc oxide based nanosorbent (ZOBN)

Abstract

In the present study, we have synthesised zinc oxide based nanosorbent (ZOBN) by using the leaves extract of Shorea robusta (Sal) and removed Pb2+ and Cd2+ ions from waste water. Biologically synthesised ZOBN has been characterised by using different analytical methods such as UV–Visible spectroscopy, FTIR, powder XRD, FESEM and EDX. Adsorption study of Pb2+ and Cd2+ ions onto ZOBN from waste water was performed under the batch adsorption experiments and maximum adsorption of Pb2+ and Cd2+ ions found at optimized conditions such as higher contact time, higher acidic pH and moderate temperature. The adsorption efficiencies of Pb2+ and Cd2+ ions have been recorded as 52.5% and 35.5% at contact time 60 min, 92.9% and 89.9% at pH 6 and 45.1% and 39.9% at temperature 60OC, respectively. Regression values indicated that the Pseudo first order kinetic model was best fitted to the adsorption of Pb2+ and intra particle diffusion model for Cd2+ ions onto ZOBN. The diffusion constant (kd) for Pb2+ and Cd2+ ions have been evaluated as 0.41 and 0.28 mg/g min1/2. Langmuir isotherm model was found highly suitable for the equilibrium data of adsorption as compared to Freundlich, Temkin and Dubbin-Radushkevich isotherm models. The values of Langmuir equilibrium constant (L/g) and theoretical monolayer saturation capacity have been evaluated for Pb2+ ions as 7.19 L/g and 0.092 and for Cd2+ ions as 12.01 L/g and 0.03, respectively.