Diffusion Characteristics of Hydrogen-Isotopic Water Molecules in Zeolite Crystals

2007 ◽  
Vol 52 (4) ◽  
pp. 995-1001 ◽  
Author(s):  
Kenji Kotoh ◽  
Kazuhiko Kudo
Keyword(s):  
Water Molecules ◽  
Diffusion Characteristics ◽  
Isotopic Water ◽  
Zeolite Crystals

scholarly journals Water Infiltration in ZSM-5 Zeolites: Effect of Pore Volume and Water Structure

2012 ◽  
Author(s):  
Shalabh C. Maroo ◽  
Tom Humplik ◽  
Tahar Laoui ◽  
Evelyn N. Wang
Keyword(s):  
Water Structure ◽  
Water Desalination ◽  
Water Infiltration ◽  
Water Molecules ◽  
Geometric Approximation ◽  
Dynamics Simulations ◽  
Experimental Findings ◽  
Nano Crystal ◽  
Infiltration Behavior ◽  
Zeolite Crystals

This study investigates the infiltration of water in ZSM-5 zeolite crystals via molecular dynamics simulations and experiments. A zeolite nano-crystal is constructed in the simulations and is surrounded by water molecules which enter and saturate the pores. The average number of water molecules per unit cell of the zeolite is determined along with the radial distribution function of water inside the zeolites. A geometric approximation of the zeolite pores and intersections is proposed and verified. Partial charge on the zeolite atoms is found to be a crucial parameter which governs the water infiltration behavior. ZSM-5 zeolite crystals were also synthesized and water infiltration experiments were conducted using an Instron. The simulation and experimental findings are compared and discussed. The understanding gained from these studies will be important for the development of zeolite based reverse osmosis membranes for water desalination.

scholarly journals Theory of isotope fractionation on facetted ice crystals

2011 ◽  
Vol 11 (6) ◽  
pp. 17423-17445
Author(s):  
J. Nelson
Keyword(s):  
Isotope Fractionation ◽  
Surface Processes ◽  
Water Isotopes ◽  
Water Molecules ◽  
Temperature Changes ◽  
Temperature Reconstructions ◽  
Fractionation Model ◽  
Kinetic Fractionation ◽  
Isotopic Water ◽  
Fractionation Coefficient

Abstract. Present models of the differential incorporation of isotopic water molecules into vapor-grown ice omit surface processes that may be important in temperature reconstructions. This article introduces a model that includes such surface processes and shows that differences in deposition coefficients for water isotopes can produce isotope fractionation coefficients that significantly differ from those of existing theory. For example, if the deposition coefficient of H218O differs by just 5 % from that of ordinary water (H216O), the resulting fractionation coefficient at 20 % supersaturation may deviate from the kinetic fractionation (KF) prediction by up to about ±17 ‰. Like the KF model, this "surface-kinetic" fractionation model generally predicts greater deviation from the equilibrium prediction at higher supersaturations; indeed, the sensitivity to supersaturation far exceeds that to temperature. Moreover, the model introduces possible new temperature dependencies from the deposition coefficients. These parameters need to be constrained by new laboratory measurements; nevertheless, the theory suggests that observed δ18O changes in ice samples are unlikely to be due solely to temperature changes.

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