This paper reviews the development of reagent-free (and therefore ecologically clean) ion-exchange separation techniques. These methods are based on the shift of the ion exchanger selectivity induced by the modulation of some physico-chemical parameters of the system such as temperature, solution concentration, pH, etc. This approach avoids the use of auxiliary reagents and additional operations such as the regeneration of ion-exchange resin and auxiliary chemicals for their reuse. It also minimizes the amount of toxic wastes produced.