ULTRAFILTRATION OF DIVALENT METAL-CATIONS FROM AQUEOUS-SOLUTION USINGPOLYCARBOXYLIC ACID TYPE BIOSURFACTANT

Biosurfactant-based ultrafiltration was used to remove the divalent me tal ions, Cu+2, Zn+2, Cd+2, and Ni+2 ions from aqueous solution contai ning either a single metal species or a mixtures of metal ions, Polyca rboxylic acid type biosurfactant, sodium salt of 2-(2-carboxyethyl)-3- decyl maleic anhydride (DCMA-3Na) derived from spiculisporic acid was added to trap the metal ions through the binding onto the micelles and /or the formation of metal-biosurfactant precipitates, The present stu dy aimed at investigating the permeating flux and the removal efficien cies of divalent metal cations from aqueous solutions using a batch-ty pe stirred ultrafiltration cell. Concerning the flux decline, the memb rane of molecular weight cutoff (MWCO) 1,000 is more vulnerable to the formation of a gel layer and the concentration polarization than that of MWCO 3,000, Formation of metal-biosurfactant precipitates makes th e gel concentration of DCMA-3Na relatively low compared with the case of chemically synthesized surfactant such as SDS and CPC, However, bio surfactant-based ultrafiltration is of practical significance because high rejection efficiencies for cupric, zinc, cadmium ions can be achi eved only with equimolar ratio of DCMA-3Na to the metal ions. DCMA-3Na exhibits the metal binding affinity on the order of Cd+2 > Cu+2 appro ximate to Zn+2 > Ni+2 when one metal species is present, Even under th e competitive binding condition when four metal ions are present in th e mixture, DCMA-3Na shows the same affinity order toward the metal ion s, although small variations in rejection coefficients are observed. ( C) 1998 Academic Press.