Phase separation rates of aqueous two‐phase systems: Correlation with system properties

Abstract

The kinetics of phase separation in aqueous two-phase systems have been investigated as a function of the physical properties of the system. Two distinct situations for the settling velocities were found, one in which the light, organic-rich (PEG) phase is continuous and the other in which the heavier, salt-rich (phosphate) phase is continuous. The settling rate of a particular system is a crucial parameter for equipment design, and it was studied as a function of measured viscosity and density of each of the phases as well as the interfacial tension between the phases. Interfacial tension increases with increasing tie line length. A correlation that describes the rate of phase separation was investigated. This correlation, which is a function of the system parameters mentioned above, described the behavior of the system successfully. Different values of the parameters in the correlation were fitted for bottom-phase-continuous and top-phase-continuous systems. These parameters showed that density and viscosity play a role in the rate of separation in both top continuous- and bottom continuous-phase regions but are more dominant in the continuous top-phase region. The composition of the two-phase system was characterized by the tie line length. The rate of separation increased with increasing tie line length in both cases but at a faster rate when the bottom (less viscous) phase was the continuous phase. These results show that working in a continuous bottom-phase region is advantageous to ensure fast separation.

Continuous aqueous two-phase extraction of human antibodies using a packed column

“…The continuous and dispersed phase selection in an LLE process is a relevant issue [23]. In view of that, two different preliminary tests have been performed in order to select which phase, bottom phosphate-rich or top PEG-rich phase, would be the dispersed phase.…”

Towards optimal aqueous two‐phase extraction system flowsheets for protein purification

“…Equation is the constraint on the ATPE system settling rate and tol k is the minimum settling rate allowable for stage k :1.0 × 10 −7 m s −1 for the aqueous polymer mixture system and 5.0 × 10 −7 m s −1 for the aqueous polymer‐salt system , . These values set the maximum practical viscosity of the ATPE systems and the size/residence time of the extraction equipment.…”

Phase separation in a salting-out extraction system of ethanol–ammonium sulfate

“…It has been reported that the phase separation time was closely related to the composition of the system and phase continuity, which influenced the movement and coalescence of the droplets [14]. A mathematical model was also proposed to correlate the physico-chemical properties (viscosity, density and interface tension) and the phase separation rate in PEG-phosphate system [15]. However, to our knowledge, no systematical study has been reported on the separation rate in hydrophilic organic solvent-based SOESs.…”