Deuterium oxide (D2O) is a special variety of water that serves as a crucial resource in a range of applications, but it is a costly and unusual resource. We therefore developed a new D2O concentration system that combines a polymer electrolyte water electrolyzer and a catalytic combustor for recycling used D2O. In this study, 1.6 L of used D2O, with a concentration of 93.1%, was electrolyzed for 13.6 h to obtain 0.62 L of D2O, with a concentration of 99.3%. In addition, the recombined water obtained by burning electrolytic gas using the catalytic combustor was also electrolyzed for 8.8 h to obtain 0.22 L of D2O, with a concentration of 99.0%. The estimated separation factor of this electrolyzer at 25 °C was 3.6, which is very close to the equilibrium constant of the water/hydrogen isotope exchange reaction. Recycled D2O was used as a deuterium source for the deuteration reaction of sodium octanoate, and 93.6% deuterated sodium octanoate was obtained. It is concluded that there were no impurities in the recycled D2O that interfered with the deuteration reaction. These results can lead to the development of a cost-effective deuteration method for these materials.
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