Solubility of CO2 in water from -1.5 to 100°C and from 0.1 to 100 MPa:: evaluation of literature data and thermodynamic modelling

Experimental measurements of the solubility of CO2 in pure water at pressures above I MPa have been assembled from 25 literature studies and tested for their accuracy against simple thermodynamic criteria. Of the 520 data compiled, 158 data were discarded. Possible reasons for the observed discrepancies between datasets are discussed. The 362 measurements that satisfy the acceptance criteria have been correlated by a thermodynamic model based on Henry's law and on recent high-accuracy equations of state. The assumption that the activity coefficients of aqueous CO2 are equal to unity is found to be valid up to solubilities of approximately 2 mol%. At higher solubilities the activity coefficients show a systematic trend from values greater than unity at low temperatures, to values progressively lower than unity at high temperatures. An empirical correction function that describes this trend is applied to the basic model. The resulting corrected model reproduces the accepted experimental solubilities with a precision of better than 2% (1 standard deviation) over the entire P-T-x range considered, whereas the data themselves scatter with a standard deviation of approximately 1.7%. The model is available as a computer code at <www.geo.unibe.ch/diamond>. In addition to calculating solubility, the code calculates the full set of partial molar properties of the CO2-bearing aqueous phase, including activity coefficients, partial molar volumes and chemical potentials. (C) 2003 Elsevier Science B.V. All rights reserved.