Dithiocarbamated chitosan as a potent biopolymer for toxic cation remediation

The biopolymer chitosan was chemically modified with dithiocarbamate, characterized by elemental analysis, IR, (13)C NMR and TG, and applied for lead, copper and cadmium removal. Based on sulfur elemental analysis an amount of 2.66 mmol g(-1) of pendant chain was incorporated in the original biopolymer, as also demonstrated through the appearance of a signal at 201 ppm in the (13)C NMR in the solid state. The TG curve demonstrated that the final product is more stable than the precursor chitosan. The sorption capacity of modified biopolymer was determined through a batchwise methodology, with maximum capacities of 2.24; 1.14 and 0.84 mmol g(-1) for divalent lead, copper and cadmium from aqueous solution, respectively. The highest sorption capacity for lead reflects the soft cation/sulfur interaction. The experimental data were adjusted to the Langmuir, the Freundlich and the Temkin sorption isotherm models using both linear and nonlinear regression analysis.