VLE Modeling of Aqueous Solutions of Unloaded and Loaded Hydroxides of Lithium, Sodium and Potassium

Abstract

This work focuses on equilibrium modeling of CO2 solubility in aqueous solutions of unloaded (as hydroxides) and loaded (as carbonates) hydroxides containing Li+, Na+ and K+ counter ions. Due to the ionic nature of the LiOH/NaOH/KOH-CO2-H2O solutions, the electrolyte-Non-Random-Two-Liquid (e-NRTL) model, described by Chen and Evans [1], is applied to correct the non-idealities in the liquid phase. The special feature of the equilibrium model employed in this work is the simultaneously regression of Vapor-Liquid Equilibrium (PCO2, Ptotal) and apparent Henry's law constant data selected from literature and Ptotal data for LiOH measured in this work. This approach will give better prediction for the molecular CO2 activity coefficients and the liquid phase activities calculated by use of the resulting e-NRTL model will be consistent with the apparent Henry's law constant. The equilibrium model developed in this work is based on and represented 112 data points for Li+ with 2.7% total AARD, 432 selected data points for Na+ with total 7.2% AARD and 354 selected data points for K+ with total 9.9% AARD. The total pressure data over aqueous LiOH solutions were measured for a range of concentrations (0.25 – 8.5wt. %) and temperatures (40 – 90°C) using an ebulliometer.