July 19, 2011
Journal Article

In Situ Infrared Spectroscopic Study of Forsterite Carbonation in Wet Supercritical CO2


Carbonation reactions are central to the prospect of CO2 trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the long-term partner fluid: water-containing supercritical carbon dioxide (‘wet’ scCO2). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg2SiO4) for 24 hr with wet scCO2 at 50°C and 180 atm, using water concentrations corresponding to 0%, 55%, 95%, and 136% saturation. Results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO2 showed no detectable carbonation reaction. At 55% and 95% water saturation, a liquid-like thin water film was detected on the forsterite particles; less than 1% of the forsterite transformed, mostly within the first 3 hours of exposure to the fluid. At 136% saturation, where an (excess) liquid water film approximately several nanometers thick was intentionally condensed on the forsterite, the carbonation reaction proceeded continuously for 24 hr with 10% to 15% transformation. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO2.

Revised: May 31, 2012 | Published: July 19, 2011


Loring J.S., C.J. Thompson, Z. Wang, A.G. Joly, D.S. Sklarew, H.T. Schaef, and E.S. Ilton, et al. 2011. In Situ Infrared Spectroscopic Study of Forsterite Carbonation in Wet Supercritical CO2. Environmental Science & Technology 45, no. 14:6204-6210. PNNL-SA-74249. doi:10.1021/es201284e