FACILITATED TRANSPORT OF 7-AMINOCEPHALOSPORANIC ACID IN A BULK LIQUIDMEMBRANE

7-Aminocephalosporanic acid (7-ACA) was transported from a dilute aque ous solution through a bulk liquid membrane containing Aliquat-336 as a carrier dissolved in butyl acetate as the solvent to another aqueous solution of lower pH. The transport is based on the pH dependant dist ribution coefficient of 7-ACA, which is defined as the ratio of the eq uilibrium concentration of 7-ACA in the organic membrane phase to that in the aqueous phase. Thus, by maintaining a pH gradient between the feed and stripping phases, 7-ACA transport could be facilitated. The c ounter transport of chloride ion favours facilitated transport, but a limiting Cl- concentration exists beyond which the stripping rate is d ecelerated. The results of experiments in a stirred transfer cell coul d be interpreted from a simple mass transfer model developed on the ba sis of the overall rate dependant on diffusion of the 7-ACA anions at the interfaces and membrane liquids.