Document Detail


In situ XRD Study of Na+ Saturated Montmorillonite Exposed to Variably Wet Super Critical CO2.
MedLine Citation:
PMID:  22404533     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Reactions involving variably hydrated super critical CO2 (scCO2) and a Na saturated dioctahedral smectite (Na-STX-1) were examined by in situ high-pressure x-ray diffraction at 50°C and 90 bars; conditions that are relevant to long term geologic storage of CO2. Both hydration and dehydration reactions were rapid with appreciable reaction occurring in minutes and near steady state within an hour. Hydration occurred stepwise as a function of increasing H2O in the system; 1W, 2W-3W, and >3W clay hydration states were stable from ~ 2-30%, ~31-55<64%, and ≥ ~71% H2O saturation in scCO2, respectively. Exposure of sub 1W clay to anhydrous scCO2 caused interlayer expansion, not contraction as expected for dehydration; suggesting that CO2 intercalated the interlayer region of the sub 1W clay, which might provide a secondary trapping mechanism for CO2. In contrast, control experiments using pressurized N2 and similar initial conditions as in the scCO2 study, showed little to no change in the d001 spacing, or hydration states, of the clay. A salient implication for cap rock integrity is that clays can dehydrate when exposed to wet scCO2. For example, a clay in the ~3W hydration state appears could collapse by ~3 Å in the c* direction, or ~15%, if exposed to scCO2 at less than or equal to about 64% H2O saturation.
Authors:
Eugene S Ilton; Herbert Todd Schaef; Odeta Qafoku; Kevin Michael Rosso; Andrew R Felmy
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-3-11
Journal Detail:
Title:  Environmental science & technology     Volume:  -     ISSN:  1520-5851     ISO Abbreviation:  -     Publication Date:  2012 Mar 
Date Detail:
Created Date:  2012-3-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0213155     Medline TA:  Environ Sci Technol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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