Specific equilibrium behavior of hydrogen isotopes adsorbed onto synthetic zeolite A-type governed by lithium cations

Abstract

Since synthetic zeolites (SZs) are powerfully adsorptive for hydrogen isotopes at cryogenic temperatures such as liquefied nitrogen, adsorption processes using these have been considered applicable to such as recovery of tritium from the lithium blanket of DT fusion reactor system. Onto these zeolites the adsorptions isotherms for hydrogen isotopes onto SZ-NaA, SZ-CaA and SZ-NaX at 77.4K were already clarified experimentally and analytically. These isotherms exhibit similar profiles of Langmuir type. In this work, adsorption isotherms were examined for H2 and D2 on SZ-LiA at 77.4K. SZ-LiA was made from SZ-NaA by exchanging its sodium ions for lithium ones, provided by TOSOH Corp. The experimental results demonstrate the specific equilibrium behavior of hydrogen isotopes adsorbed on SZ-LiA, deviating from isothermal profiles on SZ-CaA and SZ-NaX. SZ-LiA show the isothermal profiles of adsorption for H2 and D2 similar to on the conventional zeolites in the range from around 1kPa to the atmospheric pressure, but exhibit a plateau around 1mol/kg between 0.1Pa and 100Pa, while other zeolites show linearly profiling isotherms. This deviation indicates the adsorptive power of SZ-LiA remarkably greater than that of the others.