Forward (M2+-H+) and reverse (H+-M2+) ion exchange kinetics of the heavy metals on polyaniline Ce(IV) molybdate: A simple practical approach for the determination of regeneration and separation capability of ion exchanger

The Nernst-Plank equation is applied to study the forward (M2+-H+) and reverse (H+-M2+) ion exchange kinetics of the heavy metal ions like Cd2+, Cu2+, Pb2+ and Zn2+ on the surface of composite cation exchanger polyaniline Ce(IV) molybdate. Both the exchanges are favored under particle diffusion control phenomenon. It was observed that the reverse ion exchange rate is some how slower than the forward ion exchange process, however, achieved successfully. To understand the mechanism of exchange various physical parameters like fractional attainment of equilibrium U(tau), self-diffusion coefficient (D-0), energy of activation (E-d) and entropy of activation (Delta S*) are evaluated. The regeneration and separation capability of this cation exchanger is well established as the differences in activation energy and enthalpy of activation for forward and reverse ion exchange processes are considerable. (C) 2011 Elsevier B.V. All rights reserved.