Pb(II) removal from aqueous solution by Myriophyllum spicatum and its compost: equilibrium, kinetic and thermodynamic study

Abstract

BACKGROUND Lead is one of the frequent contaminants of industrial wastewater. Since it has been shown that aquatic plants can be used for the removal of heavy metals, herein Pb(II) biosorption by Myriophyllum spicatum and its compost were investigated. Effects of pH, ionic strength and contact time were analyzed using a batch experiment. Biomasses were characterized chemically and by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction techniques. RESULTS The adsorption process of both biosorbents followed a pseudo-second-order kinetic model. Compost exhibits better Pb(II) removal from solution (71%) compared with the plant (61%). Lead binding capacities for M. spicatum and its compost were 0.234 mmol g(-1) and 0.287 mmol g(-1) at pH 5.0, respectively. Lead binding takes place mainly through an ion exchange mechanism, but chemisorption via identified functional groups cannot be neglected. The Langmuir, Freundlich and Sips adsorption models for compost were applied. The Sips isotherm model gave the best fit with the equilibrium experimental data. The sorption process by compost was endothermic and spontaneous. CONCLUSION Aquatic weed compost as a low cost biosorbent with high biosorption capacity can potentially be used for the removal of lead from wastewaters.