硫酸銅結晶水の吸蔵・脱離における同位体効果

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Recovery and storage of tritiated water is one of the most important problems for experiments using tritium. As a first step to apply the hydration phenomenon of inorganic compounds for this purpose, we investigated the hydration and dehydration process of CuSO4 with H2O, D2O and HTO (93μCi/cc) by using thermal desorption spectroscopy. Three desorption peaks appeared in the desorption spectra for CuSO45H2O and CuSO45D2O at 60, 80 and 180℃. It indicates that there are three distinct bound states of absorbed water molecules (denoted as Ⅰ, Ⅱ and Ⅲ). The ratio among the amounts of absorption in each of the states were 2:2:1. With respect to CuSO45HTO, the first and second peaks appeared at the same temperature as those for H2O, whereas the third peak was observed at 183℃, being 3℃ higher than that of H2O. Tritiated water was homogeneously distributed among the three states at first and redistributed during storage at room temperature in a closed container for several days. The concentration of the tritiated water in state Ⅰ decreased and that in state Ⅲ increased. The analysis of desorption spectra made it clear that the rate determining step for the dehydration was a random nucleation processes for each of the absorbed states. The actovation energies were 20, 23 and 35 kcal/mol for state Ⅰ, Ⅱ and Ⅲ, respectively. No isotope effect was observed in this term. The kinetic isotope effect only appeared in the frequency factor for the desorption of water in state Ⅲ: that is, the frequency factor for state Ⅰ and Ⅱ were 1.1x1010 and 1.1 x1011 sec-1, respectively: they were valid for the three kinds of water molecules. On the other hand, those for H2O and D2O in state Ⅲ were 8.3x1013 sec-1 and that for HTO was 5.3x1013 sec-1. During storage of the sample in a closed container, HTO removed from state Ⅰ to state Ⅲ via the gas phase, being concentrated in state Ⅲ.
富山大学の論文

硫酸銅結晶水の吸蔵・脱離における同位体効果

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