Ion-exchange kinetic studies for Cd(II), Co(II), Cu(II), and Pb(II) metal ions over a composite cation exchanger

Explicit Nernst-Planck approximation is used to study the kinetics of H(I)-metal ion-exchange processes for ions having different effective diffusion coefficients, that is, for non-isotopic exchange process. Kinetic studies of four heavy metal ions (Cd2+, Co2+, Cu2+, and Pb2+) of environmental importance on the surface of acetonitrile stannic(IV) selenite composite cation exchanger were carried out successfully. On the basis of kinetic studies, various physical parameters, that is, fractional attainment of equilibrium U(tau), self-diffusion coefficients (D-o), energy of activation (E-a), and entropy of activation (Delta S*) are estimated to evaluate the mechanism of ion exchange on the surface of composite ion-exchange material. The activation entropy and energy revealed that the greater degree and minimum energy was achieved during forward ion-exchange process. The results revealed that the kinetic studies are very important for the economic and industrial applications of ion-exchange materials.