A Volumetric Pitzer Model for Aqueous Solutions of Zinc Sulfate up to Near-Saturation Concentrations at Temperatures from 293.15 to 393.15 K and Pressures up to 10 MPa

Abstract

Literature data for the volumetric properties of aqueous solutions of zinc sulfate have been compiled and compared with extensive recently available measurements. A semi-empirical Pitzer model has been derived from these data that reproduces the apparent molar volumes and compressibilities of zinc sulfate solutions with good accuracy to near-saturation concentrations (m ≲ 3.0 mol·kg-1) over the temperature range 293.15 ≤ T/K ≤ 393.15 and at pressures up to 10 MPa, using standard volumes, V°, obtained by additivity of ionic values from the literature. By including the dependence of V° on the compressibility of pure water, the model was able to predict apparent molar volumes with good accuracy even up to 100 MPa at 298 K. Of potential use for engineering applications, imposition of the inequality (∂2Vφ/∂T2)p,m < 0 to the Pitzer model has created the possibility of physically reasonable extrapolations to temperatures well beyond the parameterization range.