Absorption isotherms for H2(D2)-Pd0.8Ag0.2 (198-323 K)

Isotherms for H-2/D-2-Pd0.8Ag0.2 systems have been measured over a low temperature range, 198-323 K. Such low temperature data for this system have not been obtained previously. The absorption kinetics was found to be fast. The isotherms at low temperatures are compared with literature values at or above 313 K, as well as those for H-2(D-2)-Pd systems. The H/D isotope effect and the separation factors in the plateau range over Pd0.8Ag0.2 are calculated at various temperatures and discussed, based on the isotherms. Enthalpies are extracted from van't Hoff plots and compared with calorimetric values and the results from the literature for both absorption and desorption processes. A method is given for using isotherm information from single isotope systems to estimate the separation factor for the mixed isotope systems and this is a helpful tool. The challenge of measuring absorption isotherms at low temperatures and low pressures is discussed. Sample pre-treatment, non-soluble impurity accumulation in an absorption process and thermal transpiration effects are examined. (C) 2009 Elsevier B.V. All rights reserved.