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Background & Aims of the Study:  The increasing levels of toxic heavy metals discharged into the environment have received considerable attention due to the adverse effects on receiving waters. Therefore, the developed adsorbent was assessed for its practical role in removal of metal ions from industrial wastewater. The purpose of the present work is to investigate the removal of Ni(II) and Zn(II) ions by chitosan as an abundant and inexpensive adsorbent.

Materials & Methods: In this study, adsorption of metal cations onto this new adsorbent was studied in terms of pH (2.0-9.0), adsorbent dose (1.0-7.0 g), contact time (15-120 min) and initial dye concentration (100-800 mg.L^-1) in batch mode. The experimental data were fitted with different isotherms and kinetics models.

Results: The results demonstrated that the optimum pH was found to be 5.0 and 6.0 for Ni(II) and Zn(II) and the equilibrium was achieved after 75 and 60 min for Ni(II) and Zn(II) adsorption, respectively. Evaluation of the experimental equilibrium data by Langmuir and Freundlich isotherm illustrated that Langmuir is superior to other model for fitting the experimental data in term of higher correlation coefficient. The results of examination of the time on experimental adsorption data and fitting the data to conventional kinetic model show the suitability of pseudo-second order model. The maximum predicted adsorption capacities for Ni(II) and Zn(II) ions were obtained as 52.6 and 45.4 mg.g^−1, respectively.

Conclusions: The results indicate that the chitosan is one of the best adsorbents for the removal of metal cations from aqueous solution.