EQ6, a computer program for reaction path modeling of aqueous geochemical systems: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 4

Wolery, Thomas J.; Daveler, S.A.

doi:10.2172/138820

Cited by 226 publications

(184 citation statements)

References 67 publications

Supporting

Mentioning

181

Contrasting

Unclassified

Order By: Relevance

“…Consequently, it appears that a fairly large glass composition region will likely meet the required performance objectives for the ILAW disposal system. 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 , an additional set of secondary phases was identified by modeling the dissolution of LAWABP1 glass in deionized water with the EQ3/6 code package [42] and the data0.com.R8 database [43]. We eliminated a large number of the phases listed in the EQ3/6 database from consideration by: 1) recognizing that formation of the phase is kinetically prohibited at the disposal system temperature of 15°C, 2) noting that selection of the phase would violate the Gibbs phase rule, 3) comparing simulations with experiments and eliminating phases that generated solution compositions that were inconsistent with the experiments, or 4) considering phase stability over the range of chemical environments expected for the ILAW disposal system.…”

Section: Resultsmentioning

confidence: 99%

Waste Form Release Data Package for the 2001 Immobilized Low-Activity Waste Performance Assessment

McGrail¹,

Icenhower²,

Martin³

et al. 2001

View full text Add to dashboard Cite

SUMMARYThis data package documents the experimentally derived input data on the representative waste glasses LAWABP1 and HLP-31 that will be used for simulations of the immobilized lowactivity waste disposal system with the Subsurface Transport Over R eactive Multiphases (STORM) code. The STORM code will be used to provide the near-field radionuclide release source term for a performance assessment to be issued in March of 2001. Documented in this data package are data related to 1) kinetic rate law parameters for glass dissolution, 2) alkali-H ion exchange rate, 3) chemical reaction network of secondary phases that form in accelerated weathering tests, and 4) thermodynamic equilibrium constants assigned to these secondary phases. The kinetic rate law and Na + -H + ion exchange rate were determined from single-pass flow-through experiments. Pressurized unsaturated flow and vapor hydration experiments were used for accelerated weathering or aging of the glasses. The majority of the thermodynamic data were extracted from the thermodynamic database package shipped with the geochemical code EQ3/6. However, several secondary reaction products identified from laboratory tests with prototypical LAW glasses were not included in this database, nor are the thermo dynamic data available in the open literature. One of these phases, herschelite, was determined to have a potentially significant impact on the release calculations and so a solubility product was estimated using a polymer structure model developed for zeolites.Although this data package is relatively complete, final selection of ILAW glass compositions has not been done by the waste treatment plant contractor. Consequently, revisions to this data package to address new ILAW glass formulations are to be regularly expected.v CONTENTS

show abstract

Section: Resultsmentioning

confidence: 99%

Waste Form Release Data Package for the 2001 Immobilized Low-Activity Waste Performance Assessment

McGrail¹,

Icenhower²,

Martin³

et al. 2001

View full text Add to dashboard Cite

show abstract

“…We used the database Llnl.dat, which is derived from the EQ3/6 database (Wolery, 1992;Wolery and Daveler, 1992). This thermodynamic database does not contain iron-rich smectite, but it does include a few smectites end members.…”

Section: Methodsmentioning

confidence: 99%

Conditions and mechanism for the formation of iron-rich Montmorillonite in deep sea sediments (Costa Rica margin): Coupling high resolution mineralogical characterization and geochemical modeling

Charpentier

Buatier

Jacquot³

et al. 2011

Geochimica et Cosmochimica Acta

View full text Add to dashboard Cite

Wheat. Conditions and mechanism for the formation of iron-rich Montmorillonite in deep sea sediments (Costa Rica margin): Coupling high resolution mineralogical characterization and geochemical modeling. Geochimica et Cosmochimica Acta, Elsevier, 2011Elsevier, , 75 (6), pp.1397Elsevier, -1410Elsevier, . 10.1016Elsevier, /j.gca.2010 Conditions and mechanism for the formation of iron- AbstractIron-rich smectite is commonly described in the diagenetic fraction of deep-sea sediment, as millimeter to centimeter aggregates dispersed in the sediment, or as a coating on sedimentary particles or nodules. This study examines several factors to elucidate formation mechanisms of a particular iron-rich smectite and its potential transformation to glauconite. The study combines a detailed mineralogical investigation on natural samples and a chemical modeling approach to assess mineralogical reactions and pathways.Transmission electron microscopy (TEM) observations and analytical electron microscopy (TEM-AEM) analyses were conducted on microtomed samples of millimeter-to centimeter-long green grains. These grains are widespread in pelagic calcareous sediment from the Costa Rica margin. They are composed of pyrites that are partially dissolved and are surrounded by amorphous or very poorly crystallized iron-rich particles. Iron-rich montmorillonite grows from an amorphous precursor and its formation requires the input of Si, O, Mg, K, Na and Ca; our results suggest that these inputs are supported by the dissolution of sedimentary phases such as volcanic glasses, siliceous fossils and silicates.Thermodynamic modeling of fluid-sediment interactions was conducted with the geochemical computer code PhreeqC, using mineralogical and pore fluid compositions from sediment samples and calculated estimates for thermodynamic constants of smectites that are not maintained by the computer code. Simulations confirm the possibility that the green grains are the product of pyrite alteration by seawater under oxidizing conditions. The extent of smectite production is controlled by the kinetics of pyrite dissolution and fluid migration. The absence of aluminum in the Costa Rica margin system explains the formation of an iron-rich montmorillonite instead of glauconite, whereas the presence of calcite that buffers the system explains the formation of an iron-rich montmorillonite instead of iron oxides.

show abstract

“…Thermodynamic data for Al-bearing aqueous species, however, were from , while experimental data from Ho et al (2001), , and Ho et al (1994) were used for HCl (aq)°, KCl (aq)°, and NaCl (aq)°, respectively. In practice, calculations needed to assess mineral saturation states, pH (in situ) (see below), and derive ion-activity diagrams were performed using the EQ3/6 computer code (Wolery and Daveler, 1992). Standard state thermodynamic properties for all Al-bearing minerals were from .…”

Section: Methodsmentioning

confidence: 99%

A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

Chen¹

2008

View full text Add to dashboard Cite

Currently, DOE is conducting pilot CO 2 injection tests to evaluate the concept of geological sequestration. The injected CO 2 is expected to react with the host rocks and these reactions can potentially alter the porosity, permeability, and mechanical properties of the host or cap rocks. Reactions can also result in precipitation of carbonate-containing minerals that favorably and permanently trap CO 2 underground. Many numerical models have been used to predict these reactions for the carbon sequestration program. However, a firm experimental basis for predicting silicate reaction kinetics in CO 2 injected geological formations is urgently needed to assure the reliability of the geochemical models used for the assessments of carbon sequestration strategies. The funded experimental and theoretical study attempts to resolve this outstanding scientific issue by novel experimental design and theoretical interpretation of silicate dissolution rates at conditions pertinent to geological carbon sequestration.In this four year research grant (three years plus a one year no cost extension), seven (7) laboratory experiments of CO 2 -rock-water interactions were carried out. An experimental design allowed the collection of water samples during experiments in situ and thus prevented back reactions. Analysis of the in situ samples delineated the temporal evolution of aqueous chemistry because of CO 2 -rock-water interactions. The solid products of the experiments were retrieved at the end of the experimental run, and analyzed with a suite of advanced analytical and electron microscopic techniques (i.e., atomic resolution transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron microprobe, X-ray diffraction, X-ray photoelectron spectroscopy (XPS)). As a result, the research project probably has produced one of the best data sets for CO 2 -rock-water interactions in terms of both aqueous solution chemistry and solid characterization. Three experiments were performed using the Navajo sandstone. Navajo sandstone is geologically equivalent to the Nugget sandstone, which is a target formation for a regional partnership injection project. Our experiments provided the experimental data on the potential CO 2 -rock-water interactions that are likely to occur in the aquifer. Geochemical modeling was performed to interpret the experimental results.Our single mineral (feldspar) experiments addressed a basic research need. i.e., the coupled nature of dissolution and precipitation reactions, which has universal implication to the reaction kinetics as it applied to CO 2 sequestration. Our whole rock experiments (Navajo sandstone) addressed the applied research component, e.g., reacting Navajo sandstone with brine and CO 2 has direct relevance on the activities of a number of regional partnerships.The following are the major findings from this project:1. The project generated a large amount of experimental data that is central to evaluating CO 2 -water-rcok interactions and providing ground truth to pred...

show abstract

EQ6, a computer program for reaction path modeling of aqueous geochemical systems: Theoretical manual, user`s guide, and related documentation (Version 7.0); Part 4

Cited by 226 publications

References 67 publications

Waste Form Release Data Package for the 2001 Immobilized Low-Activity Waste Performance Assessment

Waste Form Release Data Package for the 2001 Immobilized Low-Activity Waste Performance Assessment

Conditions and mechanism for the formation of iron-rich Montmorillonite in deep sea sediments (Costa Rica margin): Coupling high resolution mineralogical characterization and geochemical modeling

A Novel Approach to Experimental Studies of Mineral Dissolution Kinetics

Contact Info

Product

Resources

About