Molybdate sorption by cross-linked chitosan beads: Dynamic studies

Chitosan, a biopolymer extracted from crustacean shells, exhibits high sorp tion capacities for metal ion recovery. Sorption efficiency and removal rat es are controlled by several diffusion mechanisms. Chitosan gel beads have been prepared and have shown enhanced sorption performance in batch systems . This study shows that, in continuous systems. sorption capacities can rea ch 700 mg/g, a level close to that obtained in batch studies. The effects o f metal concentration, how velocity, and column size are investigated and d emonstrate that, because of diffusion mechanisms, the optimum concentration range is approximately 50 to 100 mg/L. In column systems, the Blot number, though greater than 1, is lower than the Blot number obtained in batch sys tems, indicating that external mass transfer influences mass transfer at th e low superficial velocity investigated in this work (0.5 to 2 m/h).