The kinetics and mechanism for the ion-exchange processes like Mg2+-H+, Sr2+-H+, Ba2+-H+, Ni2+-H+, Cu2+-H+, Mn2+-H+ and Zn2+-H+ at different temperatures using approximated Nernst-Plank equation under the particle diffusion controlled phenomenon were studied for the poly-o-methoxyaniline Zr(IV) molybdate composite cation-exchanger. Some physical parameters, i.e. fractional attainment of equilibrium U(tau), self-diffusion coefficients (D-0), energy of activation (E-a) and entropy of activation (Delta S*) have been estimated. These investigations revealed that the equilibrium is attained faster at higher temperature probably due to availability of thermally enlarged matrix of poly-o-methoxyaniline Zr(IV) molybdate composite cation exchange material. These results are useful for predicting the ion-exchange process occurring on the surface of this cation-exchanger. (C) 2010 Elsevier B.V. All rights reserved.