Quantitative description of multi-component reactive transport in porous media: An empirical approach

Borkovec, Michal; Bürgisser, Christa S.; Černík, Miroslav; Glättli, Urs; Sticher, H.

doi:10.1007/bf00135855

Cited by 9 publications

(3 citation statements)

References 17 publications

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“…resembles scaled Freundlich coefficients or K d values with respect to pH, organic carbon, and clay content (Boekhold & van der Zee, 1992; Lee et al ., 1996; Elzinga et al ., 1999). If n M = – n Ca, M for a specific soil at constant pH, then represents a reformulation of the binary Rothmund–Kornfeld exchange coefficient (Rothmund & Kornfeld, 1918; Langmuir, 1981; Bond, 1995; Voegelin et al ., 2000) and yields an adsorption isotherm that meets the criteria for thermodynamic consistency (Borkovec et al ., 1996). By fitting experimental data in Ca background electrolyte, however, we usually find exponents n M and n Ca, M of opposite sign but with different absolute value.…”

Section: Formulation Of the Modelmentioning

confidence: 99%

Modelling sorption and mobility of cadmium and zinc in soils with scaled exchange coefficients

Voegelin

Kretzschmar

2003

European J Soil Science

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Summary Adsorption isotherms of Cd or Zn in soils of varying composition are often described using generalized Freundlich equations with scaled model parameters. However, this approach fails to describe the competition of several different metal cations for adsorption sites. To overcome this problem, we developed an empirical model based on cation exchange equations with scaled selectivity coefficients for Cd–Ca and Zn–Ca exchange. A large set of experimental data on the sorption of Cd and Zn to soils suspended in Ca(NO3)2, CaCl2, or Ca(ClO4)2 electrolyte solutions was compiled from the literature. The data covered wide ranges in solution concentrations (Zn: 10−8 to 10−2 m; Cd: 10−9 to 10−3 m), pH (3.9–7.7), and soil composition (organic carbon: 2 to 170 g kg−1; clay: 9 to 732 g kg−1). Selectivity coefficients for Cd–Ca and Zn–Ca exchange were scaled by expressing them as functions of organic carbon content, clay content, and solution activities of H+, Ca2+, and Zn2+ or Cd2+. The exchange selectivity coefficients and corresponding scaling factors were determined by fitting to experimental data. The model describes adsorbed amounts of Cd and Zn within a 95% confidence interval of approximately ± 0.5 logarithms (in mol kg−1). The model adequately reproduced adsorption isotherms of Cd and Zn and also the coupled transport of Cd and Ca through a loamy soil. To test the predictive capabilities of the model, we conducted leaching experiments in columns packed with four contaminated soils, which were not part of the calibration data set. Using the generalized model parameters obtained from fitting the literature data, we calculated the concentrations of Zn, Cd, Mg, K, and Ca in the effluent and compared them with experimental results. The observed concentrations of Cd and Zn in the effluent were predicted rather well; that is, predictions were generally within the expected 95% confidence interval obtained for the model. In the most acidic soil an excellent prediction of the elution patterns of Zn, Cd, Mg, and Ca was obtained. The parameters of the generalized model can easily be fine‐tuned to obtain an accurate description of the sorption and transport of Cd and Zn in a particular soil. However, in many practical situations detailed experimental data are lacking. In such cases, the parameters of the model can be used to predict pore water concentrations and leaching of Cd and Zn in contaminated soils.

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Section: Formulation Of the Modelmentioning

confidence: 99%

Modelling sorption and mobility of cadmium and zinc in soils with scaled exchange coefficients

Voegelin

Kretzschmar

2003

European J Soil Science

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“…Partitioning of chemicals between the solid and liquid phase determines the fate of reactive chemicals in subsurface environments ( − ). Accurate predictions of the transport behavior of sorbing chemicals can be often achieved based on the knowledge of the sorption equilibria of the chemicals in question.…”

Section: Introductionmentioning

confidence: 99%

Cation Competition in a Natural Subsurface Material: Modeling of Sorption Equilibria

Vulava

Kretzschmar

Rusch

et al. 2000

Environ. Sci. Technol.

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Accurate models of cation exchange are a prerequisite for predicting the transport of cations in soils and groundwater aquifers. In this paper, we investigate the competitive sorption of two major cations, Ca2+ and Na+, to a natural loamy soil material. The experimental data set is unique since competitive sorption isotherms of Ca2+ and Na+ were measured for both cations and over a wide range of conditions by two different techniques (i.e., classical batch and flow-through reactor). A few classical one-site cation-exchange equations did describe the data set poorly, while the Gaines−Thomas and the Vanselow models are able to model the data semiquantitatively despite the heterogeneity of the sorbent. A quantitative description of the data was possible with a distribution of cation-exchange selectivities. Multisite cation-exchange models allowing for noninteger exchange ratios between Na+ and Ca2+ provided an accurate description of the experimental data. Such multisite models are thermodynamically consistent and reflect the chemical heterogeneity of the natural soil material.

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“…These approaches, in turn, call for model development of the pertinent physical, chemical, and biological processes. Enormous progress could be recently witnessed in the quantitative understanding of water flow and the various transport pathways of dissolved chemicals ( − ). However, as soon as mobilization and translocation of colloidal particles is involved in the transport pathway, our predictive capabili ties are more limited ().…”

Section: Introductionmentioning

confidence: 99%

Long-Term Release Kinetics of Colloidal Particles from Natural Porous Media

Grolimund

Borkovec

1999

Environ. Sci. Technol.

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Release of colloidal particles from natural porous media saturated with monovalent cations is studied with saturated laboratory column experiments packed with a noncalcareous soil material. The column outflow was monitored over 1000 pore volumes. The composition of released particles remains constant over the course of the experiment. The major finding of the present study is that the release process cannot be modeled with simple first-order kinetics, but the effluent concentration decays in a nonexponential fashion. The experimentally observed effluent concentration decays as t -(1+α) where the exponent α typically has values between of 0.01 and 0.3. Such a power-law decay can be rationalized in terms of an exponential distribution of the activation energies of release rate coefficients, and the exponent α turns out to be inversely proportional to the average activation energy. We observe a strong dependence of the release on the ionic strength, which can be interpreted as a systematic increase of the average activation energy for particle release with increasing ionic strength. In the present system pH was accurately controlled, and the release pattern was surprisingly insensitive to pH variations.

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Quantitative description of multi-component reactive transport in porous media: An empirical approach

Cited by 9 publications

References 17 publications

Modelling sorption and mobility of cadmium and zinc in soils with scaled exchange coefficients

Modelling sorption and mobility of cadmium and zinc in soils with scaled exchange coefficients

Cation Competition in a Natural Subsurface Material: Modeling of Sorption Equilibria

Long-Term Release Kinetics of Colloidal Particles from Natural Porous Media

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