Phase separation rates of aqueous two-phase systems: correlation with system properties.
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.
Asenjo
J A
JA
Centre for Biochemical Engineering and Biotechnology, Department of Chemical Engineering, Millennium Institute for Advanced Studies in Cell Biology and Biotechnology, University of Chile, Beauchef 861, Santiago, Chile.
Mistry
S L
SL
Andrews
B A
BA
Merchuk
J C
JC
D008956:Models, Chemical; D009038:Motion; D010710:Phosphates / Q000737:chemistry* / Q000302:isolation & purification*; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000302:isolation & purification*; D012212:Rheology / Q000295:instrumentation* / Q000379:methods; D012680:Sensitivity and Specificity; D013500:Surface Tension; D014783:Viscosity; D014867:Water / Q000737:chemistry
D010710:Phosphates; D014867:Water; D011092:Polyethylene Glycols