Removal of selected metal ions from aqueous solutions using chitosan flakes

Commercially available chitosan's potential in the adsorption of heavy metals like zinc, copper, cadmium, and lead from aqueous solutions under variable physicochemical conditions was investigated. The results obtained from equilibrium and kinetic studies showed that there was significant uptake of these metal ions by chitosan and that chitosan flakes had a maximum sorption capacity for copper ions. The order of metal ion adsorption by chitosan decreased from Cu2+ to Zn2+ as follows: copper < lead < cadmium < zinc. There was a considerable increase in sorption capacity with an increase in chitosan amount; however, this parallelism diminished when the chitosan mass exceeded 0.24 g in 25 mL of metal solution. The sorption of metal ions from various salt solutions by chitosan flakes was not improved by agitation. The heavy metal uptake by chitosan was found to be pH-dependent, with a maximum at pH 6.0 and 7.0. Sorption equilibrium studies were conducted with a constant sorbent weight and varying initial concentration of metal ions. The experimental data of adsorption from solutions containing metal ions were found to correlate well with the Langmuir isotherm equation.