Osmotic and Activity Coefficients of Aqueous Lithium Sulfate Solutions within the Temperature Range 293.15–498.15 K to 40 MPa

Comprehensive equations for the thermodynamic properties of aqueous Li2SO4 solutions applicable to high temperatures and pressures have been generated by using the literature data for the volumetric properties in conjunction with the osmotic/activity coefficients at 0.1 MPa for temperatures up to 373.15 K and vapor saturation pressures above 373.15 K. The composition dependence has been represented by the equations of Pitzer, which combine a theoretical form and Debye–Hückel terms with empirically evaluated parameters for short-range interactions. In particular, the volume equations have been integrated to yield the osmotic and activity coefficients. The pressure derivatives of the Pitzer ion-interaction parameters of osmotic/activity coefficients provided the values of relative apparent molar enthalpies of this electrolyte solution. The set of equations generated here gives rise to osmotic coefficients, activity coefficients, and relative apparent molar enthalpies of aqueous Li2SO4 solutions to 1.0 mol·kg–1, 40 MPa, and 498.15 K. Analyses of the results provided important information regarding the ion-association behavior of the system under consideration.