Reactive transport modeling of plug-flow reactor experiments: quartz and tuff dissolution at 240°C

Extension of reactive transport modeling to predict the coupled thermal, hydrological, and chemical evolution of complex geological systems is predicated on successful application of the approach to simulate well-constrained physical experiments. In this study, steady-state effluent concentrations a...

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Bibliographic Details
Published in:Journal of hydrology (Amsterdam) 1998-08, Vol.209 (1), p.81-111
Main Authors: Johnson, James W, Knauss, Kevin G, Glassley, William E, DeLoach, Laura D, Tompson, Andrew F.B
Format: Article
Language:English
Subjects:
Kinetic data
Kinetic rate law
Modeling
Plug-flow reactor
Reactive transport
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Summary:Extension of reactive transport modeling to predict the coupled thermal, hydrological, and chemical evolution of complex geological systems is predicated on successful application of the approach to simulate well-constrained physical experiments. In this study, steady-state effluent concentrations and dissolution/precipitation features associated with crushed quartz and tuff dissolution at 240°C have been determined experimentally using a plug-flow reactor (PFR) and scanning electron microscopy (SEM) techniques, then modeled with the reactive transport simulator GIMRT ( Steefel and Yabusaki, 1996) using a linear rate law from transition state theory (TST) . For quartz dissolution, interdependence of the specific surface area ( A m ) and reaction rate constant ( k m ) predicted from the modeling agrees closely with that obtained from an analytical solution to the reaction–transport equation without diffusion/dispersion, verifying the advection-dominant nature of the PFR experiments. Independently-determined A qtz and k qtz from the literature are shown to be internally consistent with respect to the model and analytical interdependence, implying appropriateness of the linear TST rate law and adequacy of BET-determined A m for use in modeling PFR experiments. Applications of this integrated approach for monomineralic dissolution include assessment of internal consistency among independent A m and k m data, estimation of k m from BET-determined A m , and rapid evaluation of alternative rate laws. For tuff dissolution, accurate simulation of the experimental steady-state effluent concentrations (to within 3% for Na, Al and K; to within 15% for Si and Ca) and dearth of alteration phases (
ISSN:0022-1694
1879-2707
DOI:10.1016/S0022-1694(98)00159-0