CO₂ Sorption to Subsingle Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction Measurements

Journal Article · Wed Jan 02 00:00:00 EST 2013 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es301382y· OSTI ID:1060646

Rother, Gernot; Ilton, Eugene S.; Wallacher, Dirk; Hauβ, Thomas; Schaef, Herbert T.; Qafoku, Odeta; Rosso, Kevin M.; Felmy, Andrew R.; Krukowski, Elizabeth G.; Stack, Andrew G.; Grimm, Nico; Bodnar, Robert J.

Geologic storage of CO₂ requires that the caprock sealing the storage rock is highly impermeable to CO₂. Swelling clays, which are important components of caprocks, may interact with CO₂ leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO₂ with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of ≈0.15 g/cm³, followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO₂ bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO₂ are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO₂ in the clay pores is relatively stable over a wide range of CO₂ pressures at a given temperature, indicating the formation of a clay-CO₂ phase. Finally, at the excess sorption maximum, increasing CO₂ sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1060646
• Report Number(s): PNNL-SA-90289; KC0302060
• Journal Information: Environmental Science and Technology, Vol. 47, Issue 1; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English