Application of Alkali Metal-Graphite Intercalation Compounds to Hydrogen Isotope Separation

Abstract

Absorption behavior of hydrogen isotopes on alkali metal-graphite intercalation compounds (GICs) is reviewed from the viewpoint of its application to hydrogen isotope separation. From the isotope effect and the change of equilibrium pressure with the amount of uptake, potassium-graphite intercalation compound (K-GIC) is considered to be the most promising compound of all alkali metal-GICs. Sorption behavior of hydrogen isotopes in K-GIC depends on the kinf of the starting carbon materials for GIC such as carbon fiber, HOPG and petroleum coke with different heat treatment temperature (HTT). Judging from the HTT dependences of the shape of the isocherm, the sorption amount and the isotopic partition coefficient, it has been concluded that KC12 from the petroleum coke heat-treated at 1500°C (HTT-1500) is the best of all the compounds investigated.Tritium enrichment was demonstrated by a multi-cascade operation to confirm the usefulness of the system using K-GIC for HT enrichment from H2 gas of the order of one liter in volume. The chemical reactivity of K-GIC was estimated from the literature values, and it was concluded that the instability of this compound at room temperature in air might not become a critical disadvantage.