Positron annihilation study on polyaniline nanocomposite used for Pb(II) ion removal

Abstract

Nanocomposites of polyaniline (PANI) with three different concentrations of micrometre-sized sawdust are prepared in aqueous media via chemical casting method at room temperature. Thereafter, the removal efficiency of the obtained composites for lead (Pb) ion from aqueous solutions is studied. The influence of sawdust concentrations on chemical structure and morphology of the composites is investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. In order to investigate the removal efficiency of nanocomposites, a number of studies are performed, such as influence of pH, contact time, metal loading and nanocomposite concentrations. Our investigation suggests that the optimum conditions to obtain the highest efficiency are 5% of sawdust in nanocomposite, pH 5 and 3 min equilibrium time. A novel method of positron annihilation measurement is performed in order to study the mechanism behind adsorption of PANI and composites. Results obtained from positron annihilation are also consistent with that of adsorption experiments. Furthermore, the adsorption kinetic has been studied using the Langmuir adsorption isotherm and the Freundlich adsorption isotherm models; among the two models, Freundlich adsorption isotherm model is found to be better with respect to equilibrium aspect.