Liquid-Liquid Equilibrium of Alcohols plus Ammonium/Potassium/Sodium Acetate plus Water Systems: Experimental and Correlation

Liquid liquid equilibra of alcohol + acetate salt + water systems namely, 2-butanol + ammonium acetate + water, 1-propanol + sodium/potassium acetate + water, and 2-propanol + sodium/potassium acetate + water systems were successfully determined. The ability of acetate salt to form aqueous two-phase system (ATPS) with alcohol was found to be mainly driven by a high Gibbs energy (i.e., greater than -1000 kJ/mol). The fitting of the experimental binodal data was done by using the Merchuk equations. The tie-line data were satisfactorily correlated by the Othmer-Tobias and Bancroft equations. The salting-out strength of the acetate salts was evaluated based on the effective excluded volume theory and the Setschenow-type equation. The phase-forming abilities of the investigated alcohols were in the order of 2-butanol > 1-propanol > 2-propanol. For 2-propanol + acetate salt + water systems, the salting-out strength of sodium acetate was greater than that of potassium acetate. In contrast, for 1-propanol + acetate salt + water systems, the salting-out strength of potassium acetate was greater than that of sodium acetate. Ethanol was unable to form ATPS with all the investigated acetate salts, whereas ammonium acetate could not form ATPS with either 1-propanol or 2-propanol.