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Extension of the EQ3/6 Computer Codes to Geochemical Modeling of Brines

Published online by Cambridge University Press:  26 February 2011

Kenneth J. Jackson  and
Thomas J. Wolery
Kenneth J. Jackson
Affiliation:
Lawrence Livermore National Laboratory Livermore, CA 94550 USA
Thomas J. Wolery
Affiliation:
Lawrence Livermore National Laboratory Livermore, CA 94550 USA
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Abstract

Recent modifications to the EQ3/6 geochemical modeling software package [1–3] provide for the use of Pitzer's [4] equations to calculate the activity coefficients of aqueous species and the activity of water. These changes extend the range of solute concentrations over which the codes can be used to dependably calculate equilibria in geochemical systems, and permit the inclusion of ion pairs, complexes, and undissociated acids and bases as explicit component species in the Pitzer model. Comparisons of calculations made by the EQ3NR and EQ6 computer codes with experimental data confirm that the modifications not only allow the codes to accurately evaluate activity coefficients in concentrated solutions, but also permit prediction of solubility limits of evaporite minerals in brines at 25°C and elevated temperatures. Calculations for a few salts can be made at temperatures up to ∼300°C, but the temperature range for most electrolytes is constrained by the availability of requisite data to values ≤100°C. The implementation of Pitzer's equations in EQ3/6 allows application of these codes to problems involving calculation of geochemical equilibria in brines; such as evaluation of the chemical environment which might be anticipated for nuclear waste canisters located in a salt repository.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 44: Symposium N – Scientific Basis for Nuclear Waste Management VIII , 1984 , 507
Copyright
Copyright © Materials Research Society 1985

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