Phase behavior of quaternary aqueous two-phase systems: Influence factors and extraction mechanism study

The liquid-liquid equilibrium for five systems containing sodium carbonate + ethanol + 2-propanol + water (with different ethanol to 2-propanol mass ratios), sodium sulphate  + ethanol + 2-propanol + water, sodium carbonate/sodium dihydrogen phosphate + ethanol + 1-butyl-3-methylimidazolium tetrafluoroborate + water were determined at T = 308.15 K and atmospheric pressure. The binodal curves were correlated by Merchuk equation and another empirical formula while tie-lines were satisfactorily reproduced by a two-parameter equation with two other expressions respectively developed by Othmer-Tobias and Bancroft. Numerous factors were introduced to explore their impacts on the salting-out abilities of the quaternary aqueous two-phase systems. Results have shown that the anion species, ratio of organic components and system types significantly affected the phase behavior of investigated systems. Besides, the optimal system in this work was selected to extract vitamin B6 under laboratory conditions and the influences of pH value, temperature and extraction time on extraction process were investigated as well.