BIOSORPTION OF Cd~(2+),Pb~(2+) ONTO LAMINARIA JAPONICA

It's very important to develop highly economical,effective and practical technologies for the removal of heavy metals in the environment.Biosorption of Cd2+ and Pb2+ onto Laminaria japonica was studied by batch adsorption system to investigate the adsorption mechanism.Acid number and acid dissociation constant of carboxylic functional groups(metal-binding site) for Laminaria japonica were determined by conductometric and potentiometric titration.The number and the acid dissociation constant were determined as 1.25 mmol·g-1 and 0.18 mmol·l-1.The Cd2+ and Pb2+ adsorption data were analyzed using two different binding models.The models were based on the monodentate or bidentate binding reactions of bivalent metal ions to acidic sites.The results showed that the biosorption of bivalent metal ions onto Laminaria japonica followed the bidentate adsorption model,and the bidentate binding constants were 5.72×103 and 6.28×104L·mol-1 for Cd2+ and Pb2+ respectively.It was also shown that the adsorption process of Laminaria japonica followed the pseudo-second-order kinetics.We concluded that the biosorption amounts of Cd2+ and Pb2+were more than other seaweed biosorbents.