The PVTx properties of aqueous electrolyte solutions containing Li+, Na+, K+, Mg2+, Ca2+, Cl− and SO42− under conditions of CO2 capture and sequestration

- A density model based on Pitzer theory is developed for binary sulfate-water systems.
- A predictive PVTx model is proposed for aqueous mixed chloride and sulfate solutions.
- Densities of CO2-bearing electrolyte solutions are calculated under CCS conditions.

Based on the Pitzer electrolyte theory, an accurate density model of binary sulfate-water systems (Li2SO4-H2O, Na2SO4-H2O, K2SO4-H2O and MgSO4-H2O) has been established. Corresponding model parameters are obtained by the least square method. Compared with reliable experimental data of the Li2SO4-H2O, Na2SO4-H2O, K2SO4-H2O and MgSO4-H2O systems, the average density deviations are 0.046%, 0.036%, 0.051%, 0.038%, respectively, which are within or close to experimental uncertainties. Combined a simple mixing rule with the density models of binary sulfate-water systems and previous chloride-water systems (LiCl-H2O, NaCl-H2O, KCl-H2O, MgCl2-H2O and CaCl2-H2O), a predictive density model is proposed for aqueous mixed electrolyte solutions containing Li+, Na+, K+, Mg2+, Ca2+, Cl− and SO42− under conditions of CO2 capture and sequestration (CCS) (generally less than 473 K and 300 bar). Compared to experimental density data of multi-component water-salt systems, the average density deviation of each system is usually less than 0.1%. The model can be used to calculate the apparent molar volume at infinite dilution and the volumetric properties of CO2-bearing multi-component electrolyte solutions under the CCS conditions. A computer code for the volumetric properties of multi-component aqueous electrolyte solutions can be obtained from the corresponding author.