A thermodynamic model for predicting carbon dioxide solubility in aqueous sodium chloride solutions using an association equation of state

Authors

  • Wei Xiong National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China; Institute of Marine Natural Gas Hydrates, Southwest Petroleum University, Chengdu 610500, China (Email: 18328068580@163.com)
  • Yu-Long Zhao National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
  • Lie-Hui Zhang National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
  • Shao-Mu Wen PetroChina Southwest Oil & Gas Field Company, Chengdu 610051, China
  • Yong Hu PetroChina Southwest Oil & Gas Field Company, Chengdu 610051, China
  • Hong-Bin Liang School of Petroleum Engineering, Chongqing University of Science & Technology, Chongqing 401331, China
  • Xin Huang Research Institute of Natural Gas Technology, PetroChina Southwest Oil & Gasfield Company, Chengdu 610100, China
  • Yong-Chao Wang National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
  • Xiang-Yu Liu National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
  • Cheng Cao National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China
  • Tao Zhang National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China

Abstract

An activity coefficient-fugacity coefficient type thermodynamic model, i.e., CPA-P, based on the cubic-plus-association equation of state (CPA EoS) and Pitzer’s activity model, is presented to study the phase behavior of carbon dioxide (CO2)-water (H2O) and CO2-H2O-sodium chloride (NaCl) systems at 273.15 to 573.15 K, 0.1 to 350 MPa, and 0-6 molality of NaCl. This model involves the hydrogen-bond interactions between H2O and CO2 molecules. The vapor-liquid equilibrium condition results in the extended Henry’s law for CO2 and Raoult’s law for H2O. Moreover, the properties of pure water are calculated by the IAPWS-95 EoS to improve the accuracy of the CPA-P model. The activity coefficients of CO2 and the osmotic coefficient of H2O are calculated by Pitzer’s approach in aqueous electrolyte solution. The average absolute relative deviations (AARDs) of the CPA-P predictions for CO2 solubility in pure water and aqueous NaCl solutions are 3.53% and 3.50%, respectively.

Document Type: Article

Cited as: Xiong, W., Zhao, Y.-L., Zhang, L.-H., Wen, S.-M., Hu, Y., Liang, H.-B., Huang, X., Wang, Y.-C., Liu, X.-Y., Cao, C., et al. A thermodynamic model for predicting carbon dioxidesolubility in aqueous sodium chloride solutions using an association equation of state. Sustainable Earth Resources Communications, 2026, 2(3): 92-114.https://doi.org/10.46690/serc.2026.03.01

DOI:

https://doi.org/10.46690/serc.2026.03.01%20

Keywords:

CCS, solubility, CPA equation of state, Henry’s law, CO2-brine mixtures

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Published

2026-08-28

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Xiong, W., Zhao, Y.-L., Zhang, L.-H., Wen, S.-M., Hu, Y., Liang, H.-B., … Zhang, T. (2026). A thermodynamic model for predicting carbon dioxide solubility in aqueous sodium chloride solutions using an association equation of state. Sustainable Earth Resources Communications, 2(3), 92–114. https://doi.org/10.46690/serc.2026.03.01

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Vol. 2 No. 3 (2026): September

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Copyright (c) 2026 Wei Xiong, Yu-Long Zhao, Lie-Hui Zhang, Shao-Mu Wen, Yong Hu, Hong-Bin Liang, Xin Huang, Yong-Chao Wang, Xiang-Yu Liu, Cheng Cao, Tao Zhang

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