Abstract
Mg2++-exchange characters have been investigated on the effects of the concentration of exchange solution, temperature, treating duration and number of exchange times. Higher exchange of Mg2++ was achieved for the A-zeolite treated with the solution of lower concentration, 0.1 mol / dm3(pH = 5.5) of Mg2++ rather than the concentrated solution of 2.0 mol / dm3(pH = 4.4). The maximum exchange, 89 %, by Mg2++ (Mg89-A) was obtained after repeating the exchange by three times with 0.1 mol / dm3 MgCl2-solution at 353 K for 5h. TG-measurements were effective to characterize hydration states of the products. Mg89-A showed the maximum dehydration, 30.1 %, at 1,073 K and has the largest dehydration ratio above 473 K, but the ratio is the largest for Mg44-A at the temperature around 363 ∼ 423 K. DTG-curves show distinctive nature in peak distributions: one peak at 413 K for Na-A, double peaks at around 360 ∼ 373 K and at around 421 ∼ 428 K for increasing Mg-content, and the one peak at 424 K for Mg89-A. Energetic states of water molecules in Mg2++-exchanged A-zeolites are therefore not always simple with increasing amounts of Mg2++. The appropriate Mg2++-exchange ratio should be adaptable for the dehydration temperature used for a heat pump system.
