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Ultrafiltration by a compacted clay membrane. I - Oxygen and hydrogen isotopic fractionation. II - Sodium ion exclusion at various ionic strengths.Laboratory experiments were carried out to determine the magnitude of the isotopic fractionation of distilled water and of 0.01N NaCl forced to flow at ambient temperature under a hydraulic pressure drop of 100 bars across a montmorillonite disk compacted to a porosity of 35% by a pressure of 330 bars. The ultrafiltrates in both experiments were depleted in D by 2.5% and in O-18 by 0.8% relative to the residual solution. No additional isotopic fractionation due to a salt-filtering mechanism was observed at NaCl concentrations up to 0.01N. Adsorption is most likely the principal mechanism which produces isotopic fractionation, but molecular diffusion may play a minor role. The results suggest that oxygen and hydrogen isotopic fractionation of ground water during passage through compacted clayey sediments should be a common occurrence, in accord with published interpretations of isotopic data from the Illinois and Alberta basins. It is shown how it is possible to proceed from the ion exchange capacity of clay minerals and, by means of the Donnan membrane equilibrium concept and the Teorell-Meyer-Siever theory, develop a theory to explain why and to what extent ultrafiltration occurs when solutions of known concentration are forced to flow through a clay membrane.
Document ID
19730059043
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Coplen, T. B.
(Chicago, University Chicago, Ill., United States)
Hanshaw, B. B.
(U.S. Geological Survey Denver, Colo., United States)
Date Acquired
August 7, 2013
Publication Date
October 1, 1973
Publication Information
Publication: Geochimica et Cosmochimica Acta
Volume: 37
Subject Category
Geophysics
Report/Patent Number
AD-778719
AROD-5830-7-EN
Accession Number
73A43845
Funding Number(s)
CONTRACT_GRANT: NSF GA-1390
CONTRACT_GRANT: NAS9-7888
CONTRACT_GRANT: DA-ARO(D)-5830-EN
Distribution Limits
Public
Copyright
Other

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