On the ESR Line Widths of Hydrated Cu-2+ in Zeolites

Abstract

In this study, the electron spin resonance (e.s.r.) of Cu(H2O)62+ ions were used to investigate the mobility and the freezing properties of water adsorbed on the synthetic zeolites of types 3A, 4A, 5A, and 13X with pore diameters of 3, 4, 5, and 10 angstrom, respectively, and the natural zeolites, heulandite and clinoptilolite. The temperature dependencies of the e.s.r. line widths of the zeolites with pore diameters of 3, 4, and 5 angstrom indicated that the first layers of water molecules from the surfaces are restricted in motion even at room temperature, and beyond these, the water molecules are mobile. The water molecules in the 13X zeolite, heulandite, and clinoptilolite behave like liquid water.