A consistent Thermodynamic Model for Solid Liquid Equilibrium (SLE) and Vapor Liquid Equilibrium (VLE) in Aqueous Amine Solutions

Abstract

Two thermodynamic models (NRTL/UNIQUAC) were tested to model the SLE and VLE of the aqueous piperazine system. The reported 6 species in solid and liquid phases were represented successfully together with the estimated standard enthalpies and Gibbs energy of formation. The earlier reported experimental data for different SLE and VLE were found to be very useful for this work. The models consistently represent the experimental data. However, efforts are still needed to improve the model and a direct measurement of the solution heat capacity will reduce the number of fitted parameters.

Quasichemical Approach to pH Shifts in Frozen Phosphate Buffers

“…The EUQ model has been extensively employed to reproduce the phase diagrams of various systems including liquid–gas, ,, liquid–solid, ,− , and liquid–liquid systems. − A number of combinations of parameters have been evaluated in terms of the agreements of experimental data with calculated phase behaviors. ,, In this study, the parameters listed in Tables S1 and S2 were used to predict the behavior of the components of phosphate buffers using the EUQ model. The binary phase diagrams of water and one of the phosphate salts were first studied to validate the present calculations.…”

“…Phase Diagrams of Phosphate Solutions and Buffers. The EUQ model has been extensively employed to reproduce the phase diagrams of various systems including liquid− gas, 35,38,39 liquid−solid, 33,[43][44][45]54 and liquid−liquid systems. 40−42 A number of combinations of parameters have been evaluated in terms of the agreements of experimental data with calculated phase behaviors.…”

“…However, the EUQ model has been applied to the explanation of the freezing behavior of aqueous electrolytes and has provided relatively good predictions. An advantage of this approach is that it requires fewer parameters than other equivalent models. − In this method, the original universal quasichemical model is combined with long-range interactions of ions to reasonably represent aqueous electrolyte solutions. Christensen and Thomsen have interpreted the solid–liquid equilibria of phosphate buffers using this model.…”