SELECTIVE WATER SORBENTS FOR MULTIPLE APPLICATIONS .1. CACL2 CONFINEDIN MESOPORES OF SILICA-GEL - SORPTION PROPERTIES

This paper presents sorption properties of a selective water sorbent b ased on mesoporous KSKG silica gel as a host matrix and calcium chlori de as a hygroscopic salt. Sorption isobars, isochores and isotherms at T = 20 - 150 degrees C and vapor partial pressures of 8 - 133 mbar cl early showed two types of water sorption: 1) the formation of solid cr ystal hydrates at low amounts N of sorbed water, and 2) vapor absorpti on mainly by the salt solution at higher N. Sorption properties of CaC l2 crystal hydrates were found to change strongly due to their impregn ation into mesoporous silica gel, whereas the solution confinement to the mesopores did not change its water sorption properties with respec t to the bulk solution Isosteric sorption heat was measured to depend on water sorption and to change from 62.5 kJ/mol for solid hydrates to 42.2 - 45.6 kJ/mol for solution.