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 (Cd 2+ , Co 2+ , Cu 2+ , and Pb 2+ ) 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(τ), self-diffusion coefficients (D o ), energy of activation (E a ), and entropy of activation (ΔS*) 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.

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In this study, sulfonated polyvinyl alcohol/phosphomolybdic acid composite cation exchange membrane was prepared by solution casting method. Some of the ionb exchange peroperties such as ion exchange capacity for alkali and alkali metal ions, effect of temperature on ion exchange capacity, elution behavior, effect of eluent concentration, distribution coefficient were studied. On the basis of selectivity coefficient values some important binary separation of heavy metal ion pairs such as Hg (II)-Zn (II), Hg (II)-Cd (II), Hg (II)-Ni (II) and Hg (II)-Cu (II) were carried out. It was observed that elution of heavy metal ions depends upon the metal-eluting ligand stability. Mercury remained in column for a longer time than that of other heavy metal ions. The separations are fairly sharp and recovery of Hg (II) ions is quantitative and reproducible.