Abstract
The fundamental adsorption of CO 2 onto poorly crystalline kaolinite (KGa-2) under conditions relevant to geologic sequestration has been investigated using a quartz crystal microbalance (QCM) and density functional theory (DFT) methods. The QCM data indicated linear adsorption of CO 2 (0-0.3 mmol of CO 2 /g of KGa-2) onto the kaolinite surface up through the gaseous state (0.186 g/cm 3 ). However, in the supercritical region, the extent of CO 2 adsorption increases dramatically, reaching a peak (0.9-1.2 mmol of CO 2 /g of KGa-2) near 0.40 g/cm 3 , before declining rapidly. DFT studies of interactions of CO 2 with kaolinite surface models confirm that surface adsorption is favored up to ∼0.34 g/cm 3 of CO 2 , showing distorted T-shaped CO 2 -CO 2 clustering, typical of supercritical CO 2 aggregation over the surface at higher densities. Beyond this point, the adsorption energy gain for any additional CO 2 becomes smaller than the CO 2 interaction energy (∼0.2 eV) in the supercritical medium, resulting in the desorption of CO 2 from the kaolinite surface.
Original language | English |
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Pages (from-to) | 142-145 |
Number of pages | 4 |
Journal | Environmental Science and Technology Letters |
Volume | 1 |
Issue number | 2 |
DOIs | |
State | Published - Feb 11 2014 |
Externally published | Yes |