Adsorptive removal of Pb(II) ions from polluted water by newly synthesized chitosan–polyacrylonitrile blend: Equilibrium, kinetic, mechanism and thermodynamic approach

Abstract

The adsorption of Pb(II) ions onto a biopolymer based composite, chitosan blended polyacrylonitrile (chitosan/PAN), has been studied in a batch mode operation. The operating parameters such as solution pH, adsorbent dose, initial Pb(II) ions concentration, contact time and temperature were experimentally optimized for the maximum removal of Pb(II) ions. The optimum conditions for the 99.82% removal of Pb(II) ions for an initial Pb(II) ions concentration of 10mg/L was found to be: chitosan/PAN blend dose of 2g/L, pH of 5.0, equilibrium time of 30min and temperature of 30̊C. The adsorption isotherm data were fitted with the different adsorption isotherm models such as Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models to know the types of adsorption process. The results of the adsorption isotherm studies were applicable to confirm that the present adsorption system was favourable and the process was physisorption. The maximum monolayer adsorption capacity of chitosan/PAN for Pb(II) ions adsorption was found to be of 20.08mg/g. The adsorption kinetics and mechanism were analyzed by pseudo-first order, pseudo-second order, intraparticle diffusion and Boyd kinetic models. The pseudo-second order kinetic model provide the best fit for Pb(II) ions-chitosan/PAN adsorption system which indicates that the adsorption process was controlled by chemisorption. The kinetic results further indicated that the adsorption process controlled was by either film or particle diffusion or both. The adsorption process was found to be of spontaneous and exothermic in nature. The overall results indicated that the prepared adsorbent may be an alternative to the already existing adsorbents.