Аннотация:The possibility of identification of the kinetic mechanism is discussed for ion exchange systems in which counterions can exist in the resin phase in two states (free and bound). Selectivity within the resin bead is described by the relation between the free ions in the pore liquid and the bound ions fixed on the matrix. The dependences of the exchange rate in the bead on solution concentration and exchange isotherm shape (selectivity) are obtained for systems including complex forming, weakly dissociating and structurally inhomogeneous ion exchangers. This dependence is formally analogous to that for film-diffusion exchange kinetics. The relation between the mass transfer rate in the ion exchanger phase and in the solution film is analysed by use of experimental results on Cl- / Ag(S2O3)23- and Cl- / CNS- exchanges at various solution concentrations and with three types of resins of different porous structure (gel or macroporous).