EXTRACTION OF CD2-SOLUTION USING METAL-SORBING VESICLES IN A HOLLOW-FIBER CARTRIDGE( AND PB2+ FROM DILUTE AQUEOUS)

Continuous extraction of heavy metal ions from dilute aqueous solution using engineered surfactant vesicles as metal ion sorbents has been i nvestigated. In this experimental process, the metal-sorbing vesicle s olution circulates through the tube-side of a hollow-fiber cartridge, while metal bearing solution circulates through the shell-side. The ve sicle sorbents are stable and rapidly take up and concentrate by order s of magnitude both Cd2+ and Pb2+. A lipophilic metal carrier in the p hosphatidylcholine vesicle wall shuttles heavy metal ions to the aqueo us vesicle core where an encapsulated water-soluble chelating agent, n itrilotriacetate, complexes the ion, thereby providing the driving for ce for metal ion sorption. Two metal carriers have been studied: natur al antibiotic, A23187, and a novel synthetic carrier. Vesicles contain ing the synthetic carrier show selective uptake of Pb2+ over Cd2+ at p H 5.5 from a mixed solution. A pseudo-steady state model simulates the overall extraction process well. The rate of extraction has been foun d to be limited by the rate of diffusion of ions through the hollow fi ber membrane.