3.3. Effect of volume ratio of internal aqueous phase to membrane
phase
The effect of volume ratio of the internal to membrane phase on
the liquid emulsion membrane stability was studied by varying the
ratio from 1 to 4. The increase in this ratio from 1 to 3 resulted in
increase in rate of extraction from 46.04% to 50.73% and from
39.02% to 48.37% in case of hexane and heptane systems, respectively
(Fig. 4). This can be attributed to the fact that an increase
in the internal phase volume fraction shifts the internal drop size
distribution toward larger size and decreases the thickness of the
membrane phase resulting in enhanced mass transfer [13,41]. This
results in increase in the capacity of the membrane for enhanced
permeation of the solute. However, there is a limit to which the
size of the droplet can increase with an increase in internal aqueous
phase to membrane phase ratio. Further increase in the ratio
(up to 4.0) results in thinning of membrane phase and reduced
membrane bending moment due to availability of insufficient volume
of organic phase for enclosing all the internal aqueous phase
[3,42]. This increases the leakage and threatens the stability of theliquid membrane. Hence, a volume ratio of 3 was selected for further
studies.