Influence of the Temperature, Type of Salt, and Alcohol on Phase Diagrams of 2-Propanol + Inorganic Salt Aqueous Two-Phase Systems: Experimental Determination and Correlation

Abstract

The liquid–liquid equilibriums (LLEs) for 2-propanol + tripotassium phosphate + water at 298.15, 308.15, and 318.15 K and 2-propanol + dipotassium hydrogen phosphate + water at 298.15 K were measured. The binodal curves of 2-propanol + potassium sulfate/potassium sulfite + water at 298.15 K were measured and compared. Accordingly, the experimental binodal data were correlated using Merchuk, Hu, and Pirdashti equations, and the tie-line compositions were correlated using Othmer–Tobias and Bancroft equations. The effect of temperature, anion type, and length of alcohol chain on the binodal curve, tie-line length (TLL), slope of tie-line (STL), and phases’ physical properties were studied. It was found that an increase in salt’s hydrophobicity and alcohol’s carbon number in low temperature led to the expanding biphasic region and approaching the binodal curve to the origin. The phase-forming ability of different anions was studied using effective excluded volume (EEV) model, and the relation between the EEV ...