Estimation of the Pitzer Parameters for 1–1, 2–1, 3–1, 4–1, and 2–2 Single Electrolytes at 25 °C

摘要

The Pitzer model is one of the most important thermodynamic models to predict theudbehavior of aqueous electrolyte solutions, especially at high ionic strengths. However, most of theudparameters in the Pitzer equations have to be obtained experimentally and this represents an importantuddrawback to this model. Therefore, in order to make the Pitzer equations less dependent on experimentaluddata and more dependent on the properties of the solution, new equations that correlate the Pitzerudequations with the properties of the solution have been successfully developed for 1-1, 2-1, 3-1, 4-1 andud2-2 electrolytes. In particular, these equations were developed for two cases: (i) considers the originaludPitzer equations and (ii) considers some simplifications to the Pitzer equationud(assuming CMX  , BMX (2) and 2 = 0). In particular, for case (ii), the second virial coefficients BMX (0) and BMX (1)udof the Pitzer equations were re-estimated using published experimental data of the osmotic coefficientudobtained from the literature. As a conclusion, both the simplified and the original Pitzer equationsudpresented a very good match with this published experimental data for the osmotic coefficients.udAdditionally, the second virial coefficients BMX (0) and BMX (1) for both cases were successfully correlatedudwith the ionic radius and the ionic charge, and this is confirmed by the very high coefficients ofuddetermination achieved (R2>0.96). However, these new equations are valid only to cases in which noudsignificant ion association occurs, which is also the basic premise of the original Pitzer model.