Abstract
Na-A type zeolite has been synthesized from the waste solution with the red mud exhausted from the Bayer process. The heats of water-vapor absorption of the Na–A and cation exchanged zeolites were measured by means of an adiabatic water-vapor absorption calorimeter which had been devised for investigating heat pump effect of zeolites. The integrated hydration enthalpy of A-zeolite is in the same order as those of mordenite and clinoptilolite. However, A-zeolite shows twice the total heat amount obtainable from unit weight samples of a natural zeolite, because natural zeolites contain impurity phases, and their dehydration amount around 100°C is much smaller. Mg-exchanged A-zeolite dehydrated at 100°C showed the largest amount of hydration enthalpy of 65.1kJ/mol, and a weight loss on dehydration of 14.7%. The Mg-A-zeolite will be the most efficient heat pump media of all zeolites dehydrated at 100°C in the present work.
