AN EPR STUDY ON VO2+ AND MN2+ IONS IN SOME ZEOLITES

The electron paramagnetic resonance (EPR) of hydrated VOSO4 . 3H(2)O a nd MnCl2 . 2H(2)O, adsorbed on the synthetic zeolites 3A, 4A, 5A and 1 3X of pore diameters 0.3, 0.4, 0.5, and 1.0 nm, respectively, and the natural zeolites heulandite and clinoptilolite was investigated. The s pectra indicated that the coordination structures are VO(H2O)5(2+) and Mn(H2O)(6)(2+) and that their EPR line widths vary with the pore diam eters and the surface areas of the zeolites. The spectra of VO(H2O)(5) (2+) in natural zeolites at room temperature display an isotropic beha vior and therefore indicate that the water ligands are mobile. The EPR spin Hamiltonian parameters, the molecule orbital constant beta(2)(2 ), and the Fermi contact term K-eff were determined and are discussed. The spectra of Mn(H2O)(6)(2+) for narrow-pore zeolites indicate the e xistence of mobile and immobile water, whereas for wide-pore and natur al zeolites they indicated the existence of only mobile water. The obt ained Mn(H2O)(6)(2+) spectra are discussed.