| Available from UMI in association with The British Library.; Emulsion liquid membrane extraction is an extraction process where separation is achieved by the transport of a solute through an organic liquid film which is interposed between two aqueous phases. By suitable adjustment of the phase volume ratios and conditions, the solute can be simultaneously separated and concentrated: this operation has potential application in process biotechnology where product concentrations are low.; The batch extraction of lactic acid from model and real fermentation broths was carried out in a stirred vessel. The feed and stripping phase solute concentrations were measured, and through mass and volume balances the phase volume and osmotic pressure variations were monitored.; Initially, a liquid membrane emulsion system was formulated in order to realise acceptable levels of kinetics and system stability. The extraction chemistry between lactic acid and Alamine 336 was also elucidated; the experimental results agreed well with a simple stoichiometry.; New quantitative models were developed and tested to describe osmotically-driven water transport; experimental data agreed well with the theory. It was established that the rate of selling was proportional to (a) the osmotic pressure difference between the stripping and feed phases, and (b) the concentration of surface-active material in the organic solvent. It was also shown that swelling can be suppressed by reducing the overall osmotic pressure difference. It was found that a shrinking core model for emulsion swelling described the experimental results well.; There was very good agreement between a facilitated extraction model, which accounted for convective solute transport, and the experimental results. A shrinking core model was necessary to describe solute transport in the emulsion globules. It was found that swelling did not significantly affect the rate of solute depletion from the feed phase. The kinetic model was able to predict the effects of variations in parameters such as the carrier concentration, and the feed and stripping phase concentrations.; Extraction selectivity was examined and it was found that glucose and sucrose, initially in the feed phase, accumulated in the stripping phase. Extraction of lactic acid from fermentation broth was poor in comparison to results obtained from the model systems, because of competition for the carrier by hydrochloric acid used to adjust the pH. (Abstract shortened by UMI.)... |
