Abstract: A process for the enrichment and separation of oxides of heavy hydrogen isotopes from acid, aqueous solutions or other aqueous streams employs macrocyclic aminopolyether (APE) and organic cation exchange agents. The aqueous solution or the aqueous stream is mixed with at least one organic solvent which is miscible with water to form a liquid mixture. An organic acid cation exchange agent in the H-form is charged with a protonized APE to form a solid phase. The liquid mixture is brought into contact with the solid phase to bring about the enrichment of the heavy hydrogen isotope on the solid phase at a low temperature. The heavy hydrogen isotope from the solid phase is then released at a temperature that is higher by between 30.degree. K. and 150.degree. K. than the temperature at which the enrichment occurred.