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.
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.
J A
JA
Asenjo
S L
SL
Mistry
B A
BA
Andrews
J C
JC
Merchuk
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