LAUSR

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.