Metal ions binding onto lignocellulosic biosorbent.

This paper describes the use of a lignocellulosic biosorbent for the adsorption and ion exchange of nine different heavy metals ions. Batch isothermal equilibrium and continuous column adsorption experiments were carried out in an effort to evaluate the maximum adsorption capacity, pH dependence and to study the mechanism of removal of metal ions onto the biosorbent. Bio-sorption data were interpreted using Langmuir isotherm which reflect the influence of metal concentration on the uptake of the metal ion. Potentiometric titrations were used to determine the contents of total functional groups. The biosorbent showed the strongest affinity for Pb2+, Hg2+ and Cu2+. The metal ions such as Cd2+, Cu2+, Ni2+, Co2+, and Mn2+ seemed to be exclusively involved in ion-exchange mechanism with Ca2+ ions. The column adsorption experiment of multiple metals revealed the role of another cation in effective removal of Pb2+, Hg2+ and Zn2+. The biosorbent has been found to be a good electron donor for the reduction of Cr(VI) in an acidic medium.