This paper reports the results obtained by experimental and theoretical study of the dynamics of ion exchange accompanied by the ion-exchange isothermal supersaturation (IXISS) effect. This effect is observed for a number of ion-exchange systems where the frontal or the reverse frontal separation is accompanied by the formation of extremely stable supersaturated solutions of low solubility substances in the interstitial space of ion-exchange columns. After leaving the column, a supersaturated solution crystallizes spontaneously, which allows for designing a practically ideal ion-exchange process where a crystalline product is obtained directly after the ion-exchange treatment cycle. The paper comprises results on the experimental investigation of IXISS of magnesium carbonate on carboxylic resins, which is observed in desorption of Mg2+ from the resin in the Mg form with Na2CO3 solutions or with solutions of Na2CO3- NaHCO3 mixtures. The physical and mathematical models of the kinetics and the dynamics of the ion-exchange processes proceeding in a colloid system comprising a supersaturated solution and an ion exchanger, which surface is partially blocked by adsorbed precrystalline aggregated (micelles), are proposed, and their validity is experimentally confirmed.