Reusable biosorbents in capsules from Zoogloea ramigera cells for cadmium removal

A biosorbent was prepared by immobilizing and culturing Zoogloea ramigera c ells in calcium alginate capsules to high density. The biosorbent (the cell and its exopolysaccharide "Zooglan") along with the [calcium] alginate is known to be responsible for cadmium rem ova I. The dry weight of the biosor bent reached 107 g/L after 3 days of cultivation and 220 g/L after 5 days b ased on the core volume of a 2.0-mm diameter capsule used. The biosorbents were completely contained in the core of the capsule where the cells grew p referentially near the shell of the capsules while the polymer distributed homogeneously in the core. The specific cadmium uptake by the capsule bioso rbent was 1.9 mg/g adsorbent at an initial cadmium concentration of 3 mg/L. This is 1.24 times more than the specific cadmium uptake by the 1.8-mm bea ds prepared under a comparable condition. The capsules crosslinked with 1% triethylene tetramine and 1% glutamic dialdehyde solutions were superior to the uncrosslinked capsules in mechanical strength. The crosslinked capsule s maintained their mechanical strength and adsorption/desorption capacity e ven after 30 cycles of repeated use. (C) 1999 John Wiley & Sons, Inc.