Batch and continuous separation of acetic acid from succinic acid in a feed solution with high concentrations of carboxylic acids by emulsion liquid membranes

Separation of acetic acid from succinic acid was carried out in batch and continuous emulsion liquid membrane (ELM) systems where concentrations of the two carboxylic acids in a feed solution were as high as those in an actual fermentation broth producing succinic acid. In the batch ELM system, we investigated the effects of three major operating variables affecting degree of extraction of acetic acid, such as initial volume ratio of emulsion phase to feed phase, initial C9232 concentration in the membrane phase and initial NaOH concentration in the stripping phase, on degrees of extraction of acetic acid and succinic acid, enrichment ratio of acetic acid in the stripping phase, and degree of emulsion swelling. Not only the apparent degree of extraction of acetic acid higher than 95% but also its enrichment ratio of 3.0 or higher was simultaneously obtained under specific operating conditions. The best batch ELM results were applied to the continuous removal of acetic acid from succinic acid in an extraction column of Oldshue–Rushton type. In view of the fact that high degree of extraction of acetic acid as well as high enrichment ratio of acetic acid was still obtained in the continuous ELM system, the developed ELM process seemed quite practical for separation of acetic acid from succinic acid.