Effect of pH on the phase separation in aqueous solutions containing poly (propylene glycol) and the kosmotropic salt sodium citrate at T = ۲۹۸.۱۵ K

Liquid-liquid extraction utilizing aqueous two-phase systems (ATPS's) has found its platform in several aspects of separation research both in industry and academia. When ATPS's are used for preparative purposes, e.g. for separation, isolation or purification of a product, the knowledge of the mechanism of the phase separation in the used system is important to increase the efficiency of the process or is of purely academic interest [۱]. In this respect, this work is devoted to study the effect of the aqueous medium pH on the two-phase equilibrium behavior of the {poly (propylene glycol) (PPG P۴۰۰) + sodium citrate} ATPS in order to obtain further information about the salting-out effects and the consequent phase separation in PPG-salt ATPS's. The effect of pH on the ATPS-promoting capability of citrate anions in the aqueous PPG solutions was explained based on the structural hydration Gibbs free energy (ǻGhyd) of the citrate anions at different pH values. Furthermore, a local composition NRTL [۲] model was examined to correlate the tie-line data of the investigated system at different pH values.

کلیدواژه ها:

Phase diagram ، Poly (propylene glycol) ، Kosmotropic salt ، Salting-out effect