Measurement and Correlation of Phase Diagram Data of Hydrophilic Alcohols (1-Propanol/2-Propanol) + + Salts (Na2SO4/(NH4)2SO4/NH4NO3) + Water Systems

Aqueous two-phase systems (ATPSs) are composed of two immiscible aqueous phases that are in equilibrium. As one of the separation methods, aqueous two-phase extraction (ATPE) has advantages of biocompatibility, process integration capability, and large-scale feasibility1. As far as we know, ATPE has been used for the separation of proteins2, enzymes3–4, organic acids5–6, and so on. Based on the composition of ATPS, they can be classified into the following categories: polymer-based ATPS, ionic liquid (IL)-based ATPS, surfactant-based ATPS, and hydrophilic alcohols-based ATPS. Among the ATPS mentioned above, the weaknesses of the polymer-based ATPS are high price and high viscosity. The ionic liquid (IL)-based ATPS also shares the disadvantage of high cost. In comparison with other ATPSs, the hydrophilic alcohol-based have advantages of low viscosity and low cost simultaneously7. And they have the potential to achieve the desired purification and concentration of the product in a single step8. In addition, the hydrophilic alcohol can be recycled and reused in some way7, which will further cut the process costs. Based on our knowledge, there are only two works in the literature describing phase diagrams of ternary systems composed by 2-propanol+(NH4)2SO4+ +H2O 9 and 2-propanol+Na2SO4/(NH4)2SO4+H2O 10. None of these reports have conducted a systematic study on the phase-formation ability of the sulfate salts in hydrophilic alcohol + salt + water systems. Also, no LLE data have been previously reported in the literature for the 1-propanol + Na2SO4/(NH4)2SO4 + water systems, and aliphatic alcohols + NH4NO3 + water systems. Therefore, the aim of this work is to systematically investigate the liquid–liquid equilibria for ternary systems of [hydrophilic alcohols (1-propanol/2-propanol)+salts (Na2SO4/(NH4)2SO4/ NH4NO3)+water]. The salting-out ability of the salts and the phase-forming ability of the hydrophilic alcohols were discussed by the effective excluded volume (EEV) and salting-out coefficient (Ks) of the mentioned salts. Furthermore, the dependability of the calculation method was tested by the Othmer–Tobias and Bancroft equations. Measurement and Correlation of Phase Diagram Data of Hydrophilic Alcohols (1-Propanol/2-Propanol) + + Salts (Na2SO4/(NH4)2SO4/NH4NO3) + Water Systems