Abstract: An improved, closed-cycle process for regeneration of weakly acidic spent cation resins and for the recovery and recycle of the regenerants is disclosed. The improvement resides in the use of hydroxy or alkoxy substituted carboxylic acids as the cation resin regenerant. These acids and their metal salts are soluble and are high boiling and do not form azeotropes. When the spent cation regenerant is combined with the spent anion regenerant such as an amine salt, a weak, dissociable complex of the regenerants is formed and the metal salt is reconstituted. The complex is dissociated, preferably by distillation, into the separate regenerants which are recycled and the salt is recovered.