Removal of selected metal ions from aqueous solutions using chitosan flakes

Commercially available chitosan's potential in the adsorption of heavy meta ls like zinc, copper, cadmium, and lead from aqueous solutions under variab le physicochemical conditions was investigated. The results obtained from e quilibrium and kinetic studies showed that there was significant uptake of these metal ions by chitosan and that chitosan flakes had a maximum sorptio n capacity for copper ions. The order of metal ion adsorption by chitosan d ecreased from Cu2+ to Zn2+ as follows: copper < lead < cadmium < zinc. Ther e was a considerable increase in sorption capacity with an increase in chit osan amount; however, this parallelism diminished when the chitosan mass ex ceeded 0.24 g in 25 mL of metal solution. The sorption of metal ions from v arious salt solutions by chitosan flakes was not improved by agitation. The heavy metal uptake by chitosan was found to be pH-dependent, with a maximu m at pH 6.0 and 7.0. Sorption equilibrium studies were conducted with a con stant sorbent weight and varying initial concentration of metal ions. The e xperimental data of adsorption from solutions containing metal ions were fo und to correlate well with the Langmuir isotherm equation.