well known to have a high affinity to divalent cations. A viscous alginate solution causes gelation upon contact with divalent cations, which can be explained by the egg-box model (Rees and Welsh, 1997) that each divalent metal ion binds to two carboxyl groups on adjacent alginate molecules. So far, adsorption property of alginate has been investigated for many heavy metal ions (Jang et al., 1991 and Jang et al., 1999; Konichi et al., 1993).