NOVEL POLY-GLUTAMIC ACID FUNCTIONALIZED MICROFILTRATION MEMBRANES FORSORPTION OF HEAVY-METALS AT HIGH-CAPACITY

Various sorbent/ion exchange materials have been reported in the liter ature for metal ion entrapment. We have developed a highly innovative and new approach to obtain high metal pick-up utilizing poly-amino aci ds (poly-L-glutamic acid, 14,000 MW) covalently attached to membrane p ore surfaces. The use of microfiltration (0.2-0.6 mu m) membrane-based sorbents containing multiple functional groups is a novel technique t o achieve high metal sorption under convective flow conditions. For ou r studies, both commercial membranes and laboratory prepared cellulose membranes containing aldehyde groups were used for the attachment of poly-amino acids. Cellulose membranes were prepared by converting cell ulose acetate microfiltration membranes to cellulose (using alkali tre atment), subsequent oxidation of hydroxyl groups to aldehyde using sod ium periodate, and attachment of poly-L-glutamic acid via Schiff base chemistry. Extensive experiments (pH 3-6) were conducted (under convec tive flow mode) with the derivatized membranes involving the heavy met als: lead, cadmium, nickel, copper, and selected mixtures with calcium in aqueous solutions. Metal sorption results were found to be a funct ion of derivatization (aldehydes) density of membranes and degree of a ttachment of the polyfunctional groups, number of functional groups pe r chain, membrane surface area, and the type of metals to be sorbed. W e have obtained metal sorption capacities as high as 1.5 g metal/g mem brane. Of course, depending on the desired goals the membrane containi ng metal could be regenerated or stabilized for appropriate disposal. (C) 1998 Elsevier Science B.V.