Thermodynamics of alkali metal orthophosphate water-salt systems. I. Dissociation constants and the H2O – K3PO4 system: Experimental study and modelingстатья
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Дата последнего поиска статьи во внешних источниках: 10 апреля 2024 г.
Аннотация:An approach to thermodynamic modeling of electrolyte systems based on alkali metal orthophosphates is outlined. Updated parameters are proposed for describing the standard properties of HPO42– and PO43– anions with the Helgeson-Kirkham-Flowers equation of state, necessary for calculating the second and third dissociation constants of phosphoric acid. An experimental study and thermodynamic modeling of the H2O – K3PO4 system were carried out.The water activity of aqueous K3PO4 solution was studied in temperature range from 288.15 to 308.15 K. The results were obtained by two independent approaches: dew point and static vapor pressure methods in a wide concentration range.The modeling of the solution was performed within the Pitzer-Simonson-Clegg framework, taking into account the first step of hydrolysis of the phosphate anion. Thus, the model considers the presence of K+, PO43–, HPO42–, OH– ions in the solution. The degree of hydrolysis was calculated using the third basicity constant of phosphoric acid (Kb,3). The model is based on experimental data on water activity, thermochemical properties and solubilities, in the range from 0 to 9.90 mol/kg and from 249 to 433 K. The range of temperatures within which the model performs reliable results is from the eutectic point (248.9 K) to the boiling point at 101.325 kPa.