Ultrafiltration by a compacted clay membrane-I. Oxygen and hydrogen isotopic fractionation

T.B. Coplen; B.B. Hanshaw

doi:10.1016/0016-7037(73)90105-1

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Ultrafiltration by a compacted clay membrane-I. Oxygen and hydrogen isotopic fractionation

T.B. Coplen·B.B. Hanshaw

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Abstract

Laboratory experiments were carried out to determine the magnitude of the isotopic fractionation of distilled water and of 0.01 N NaCl forced to flow at ambient temperature under a hydraulic pressure drop of 100 bars across a montmorillonite disc compacted to a porosity of 35 per cent 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 0.01 N. 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.

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T.B. Coplen, B.B. Hanshaw. 1973. Ultrafiltration by a compacted clay membrane-I. Oxygen and hydrogen isotopic fractionation. https://doi.org/10.1016/0016-7037(73)90105-1

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