Adsorption of Pb(II) and Ni(II) from aqueous solution by nanosized graphite carbon-impregnated calcium alginate bead

A composite adsorbent was prepared by immobilizing nanosized graphite carbon, obtained from an electrochemical process, in calcium alginate beads to remove Pb(II) and Ni(II) from aqueous solution. Potential of the adsorbent was evaluated by comparing adsorption kinetics and capacity of the nanosized graphite carbon-impregnated calcium alginate beads (NGCAB) with those of the pure calcium alginate beads (AB) in batch experimental reactors. Kinetic studies indicated that both ions onto AB and NGCAB reached adsorption equilibria at 16 and 12 h, respectively, and the experimental kinetic data were well described by a pseudo-second-order regression model. Relatively rapid uptake of both ions occurred within the first 2 h, followed by slower sorption process which was well explained by the intraparticle diffusion model of Weber and Morris. The maximum equilibrium uptake of Pb(II) and Ni(II) by NGCAB with the initial concentration range of 903 and 1023 mg/L were approximately 460.9 and 93.3 mg/g, respectively. Adsorption isotherm of Pb(II) onto AB was well fitted by Langmuir isotherm model, while that of NGCAB showed a good prediction using the Freundlich isotherm model. The Freundlich isotherm model was more suitable to describe Ni(II) adsorption by both adsorbents. The overall results demonstrated a potential applicability of NGCAB for Pb(II) and Ni(II) removal from aqueous solutions.