pH of CO2 saturated water and CO2 saturated brines: Experimental measurements and modelling

Reza K. Haghi, Antonin Chapoy*, Luís M. C. Peirera, Jinhai Yang, Bahman Tohidi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Citations (Scopus)
829 Downloads (Pure)


In this work, both spectroscopic and electrometric methods were employed to measure the pH of water saturated with carbon dioxide at pressures up to 6 MPa, temperature ranges from 293.15 to 353.15 K and salinities up to 3 mol kg−1. Furthermore, a model was developed to predict the changes in the pH due to the solubility of CO2 in the aqueous phase at high pressure and high temperature conditions as well as the effect of NaCl. The pH model was developed by coupling the Cubic-Plus-Association Equation of State (CPA EoS) and the Pitzer equations. The former was used to determine the solubility of acid gases in aqueous solutions while the latter was employed to calculate activity coefficients for each ion species. The predictive capability of the pH model was evaluated against the data gathered from the literature and data measured in this work. The model allowed a prediction of the pH with an overall average absolute deviation (AAD) to measured data of 0.03 and 0.06 pH units in the CO2-H2O system using electrometric and spectroscopic techniques, respectively, and between 0.04 and 0.10 pH units in the CO2-H2O-NaCl systems by employing the spectroscopic technique.

Original languageEnglish
Pages (from-to)190-203
Number of pages14
JournalInternational Journal of Greenhouse Gas Control
Early online date21 Oct 2017
Publication statusPublished - Nov 2017


  • Carbon dioxide
  • pH
  • Sodium chloride
  • Water

ASJC Scopus subject areas

  • Pollution
  • Energy(all)
  • Industrial and Manufacturing Engineering
  • Management, Monitoring, Policy and Law


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