Selectivity of polyampholyte ANKB-35 for Ni, Cu, Zn and Cd ions was studied. The exchange capacity of the resin did not depend on concentration of counterions in dilute solutions. Parameters of ion adsorption from highly concentrated solutions such as pH, concentration and flow rates of solutions were established in order to determine regeneration conditions of the resin. The influence of the size of polyampholyte granules on adsorption efficiency was studied. After calculation of ion diffusion coefficients in resin samples with different granule radii it became apparent that the rate of ion exchange in the resin was limited by diffusion in gel phase. Change in solution pH and deformation of polymer chains of the resin during cation adsorption led to variation in moisture content and change in the water state in it. These parameters were quantified based on endotherms of ice melting in the resin.