a b s t r a c tThe removal and recovery of Cephalexin from aqueous solutions by supported liquid membranes (SLMs) with strip dispersion has been studied. Experiments used a Liqui-Cel ® hollow-fiber module as a mircoporous support and an organic membrane solution consisting of Aliquat 336, Isopar L (isoparaffinic hydrocarbon solvent), and 1-decanol. The aqueous strip solution was composed of potassium chloride and citrate buffer. The presence of the strip dispersion, formed by dispersing the aqueous strip solution in the organic membrane solution with a mixer, on the shell-side of the hollow-fiber module ensures SLM stability. Various experimental parameters such as strip dispersion mixing rate, Aliquat 336 concentration in the organic membrane phase, KCl and citrate buffer concentrations in the aqueous strip solution, volume of aqueous strip solution, and feed and strip dispersion flow rates were investigated. High extraction and recovery rates were achieved when maintaining a proper pH in the aqueous strip solution combined with an excess of KCl. Typical results using an Aliquat 336 concentration of 2.5 wt% (48 mM) have shown >99% extraction, recovery rates of 96-98%, and enrichment ratios of 1.6-3.3 from a feed solution containing 15 mM of Cephalexin. Mass transfer resistances were analyzed, showing the resistance from the extraction reaction to be dominant.

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Supported liquid membranes (SLMs) with strip dispersion and carrier, Aliquat 336, were used for the selective recovery of Cephalexin from simulated enzymatic solutions for Cephalexin synthesis. For the Cephalexincontaining feed solution, pH control methods using constant NaOH titration, carbonate buffer, and phosphate buffer were compared. Carbonate buffers with concentrations of 0.05 and 0.10 M gave the highest extraction and recovery, in which recovery for both cases was over 99%. Optimal extraction of Cephalexin from feed solutions containing equimolar concentrations of 7-amino-3-desacetoxicephalosporanic acid (7-ADCA) occurred at a feed solution pH ) 9.5, resulting in a separation factor of 12.1. The recovery of Cephalexin from solutions containing 7-ADCA, phenylglycine amide (PGA), and phenylglycine (PG) was also demonstrated. Improved Cephalexin extraction was achieved at a feed pH ) 8.0 when compared to a feed pH ) 9.5 due to high coextraction of PG at the latter. At a feed pH ) 8.0 and a feed solution composition of 15, 15, 15, and 3 mM for Cephalexin, 7-ADCA, PG, and PGA, respectively, an initial Cephalexin flux of 3.1 g/(m 2 h) was achieved.