An attempt to separate acetic acid from succinic acid in an aqueous solution by emulsion liquid membranes was made in a batch reactor for the first time. In order to find an optimal operating condition under which a high degree of extraction of acetic acid and a high separation factor for acetic acid and succinic acid were simultaneously obtained, we investigated the effects of various experimental variables, such as stirrer speed, concentration of carboxylic acids in the feed phase, organic membrane composition, and concentration of stripping agent in the stripping phase, on degree of extraction of acetic acid, separation factor, and enrichment ratio of acetic acid in the stripping phase. The ELM system containing only a bifunctional polyamine, acting as extractant and emulsifier, in the membrane phase gave a much higher separation factor than that containing both of the polyamine and a commercial amine extractant. Under a specific operating condition, the degree of extraction of acetic acid reached to 99% and its maximal enrichment ratio was higher than 7, while the degree of extraction of succinic acid and its enrichment ratio were very low. (C) 2010 Elsevier B.V. All rights reserved.