A new model of batch-extraction in emulsion liquid membrane: Simulation of globule-globule interaction and leakage

The present paper seeks to provide an understanding of the possible effect of interaction between emulsion globules, on batch extraction, utilising emulsion liquid membranes. The conventional reversible model of Bunge and Noble (1984) considers an isolated globule, for explaining type-1, reaction-facilitated transport. Their basic approach has been extended here through Monte Carlo simulation of a system of emulsion globules, interacting via coalescence-redispersion. Collision of such an interacting pair results in internal circulation in membrane phase of globules and causes mixing of solute existing therein. This translates into faster solute penetration inside the globule. Hence, solute depletion rate in the external phase is enhanced, over and above that of a diffusion-limited reaction. In experiments, at high stirring speeds involving extraction of weakly basic amines with a strong internal phase acid (Baird et al., 1987), this trend has been observed during the initial period. A further shortcoming of the reversible model is that it overpredicts the maximum extraction achieved in these experiments, which is corrected by introducing leakage of internal drops during redispersion. (C) 1998 Elsevier Science Ltd. All rights reserved.