ADSORPTION EQUILIBRIA OF HYDROGEN, DEUTERIUM, AND THEIR MIXTURES. PART II

Abstract

An investigation has been made of the fundamental factors which determine isotope separation factors on adsorbents, based on hydrogen and deuterium isotherms reported in Part I. Through the use of a semiempirical thermodynamic approach, the binary separation factors α have been related to the single component isotherms (p = f(v)), and these in turn broken down into a number of terms involving the isosteric heat of adsorption q, temperature T, and surface coverage. If the less important contributions are neglected, the treatment leads to the following sequence of approximate relations:[Formula: see text]where ε0 = total vibrational zero-point energy of adsorbed molecules.The rigorous form of equation [I] agrees well with the experimental results, and semi-quantitative agreement with the data is shown by equation [II]. A qualitative discussion of [III] is given. It is suggested that the horizontal zero-point vibrations of the adsorbed species in some cases constitute an important contributing factor in addition to the vertical vibrations previously thought to be solely responsible for differences in isotope behavior.