Further increase in the stirring time resulted
in rupture of liquid emulsion membranes leading to out flow of extracted
alcohol into the external phase. A comparison of stability of
liquid emulsion membrane consisting of hexane and heptane system
indicates that the hexane system was more stable than heptane.
The stability can be inferred from the time at which the
extent of alcohol extraction decreases with an increase in stirring
time. In case of hexane system it was 20 min whereas for heptane
system it was 10 min. It is earlier reported that heptane is more viscous compared to hexane [45], the viscosity of the membrane
phase influences resistance to mass transfer of the solutes, this
might be the reason for reduced extraction of the heptane system
as compared to the hexane system in the first 5 min. Therefore,
mixing time of 20 and 10 min for hexane and heptane system,
respectively was maintained for further experiments.