RAMAN-SPECTROSCOPY OF WATER TRACER DIFFUSION IN ZEOLITE SINGLE-CRYSTALS

The water tracer diffusion in single crystals of natrolite, scolecite, mesolite, heulandite, and chabazite has been studied by Raman micro-s pectroscopy, A model of water tracer diffusion is proposed. The H2O, H DO, and D2O molecule concentrations are calculated for a crystal of or thorhombic symmetry on deuteration of the initial H2O-sample. A way is shown to find the diffusion coefficients, the constant of equilibrium , and the deuteron-proton exchange rate from experimental data. The wa ter diffusion coefficients for natrolite placed in liquid D2O appeared to be 1.5-2 times higher than those for a sample in vaporous D2O. For natrolite at room temperature, 1.5-1.6 times higher water diffusion o ccurs along [001] than along [110].