CO2 sorption to subsingle hydration layer montmorillonite clay studied by excess sorption and neutron diffraction measurements.
Geologic storage of CO(2) requires that the caprock sealing the storage rock is highly impermeable to CO(2). Swelling clays, which are important components of caprocks, may interact with CO(2) leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO(2) 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 CO(2) densities of ≈ 0.15 g/cm(3), followed by an approximately linear decrease of excess sorption to zero and negative values with increasing CO(2) bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO(2) 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 CO(2) in the clay pores is relatively stable over a wide range of CO(2) pressures at a given temperature, indicating the formation of a clay-CO(2) phase. At the excess sorption maximum, increasing CO(2) sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.
Geochemistry and Interfacial Science Group, Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6110, United States. rotherg@ornl.gov
Gernot
G
Rother
Eugene S
ES
Ilton
Dirk
D
Wallacher
Thomas
T
Hauβ
Herbert T
HT
Schaef
Odeta
O
Qafoku
Kevin M
KM
Rosso
Andrew R
AR
Felmy
Elizabeth G
EG
Krukowski
Andrew G
AG
Stack
Nico
N
Grimm
Robert J
RJ
Bodnar
D000327:Adsorption; D001546:Bentonite / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry*; D057965:Carbon Sequestration; D033363:Neutron Diffraction
D001546:Bentonite; D002245:Carbon Dioxide