Effective adsorption Ag(I) onto triethylenetetramine-modified chitosan beads: adsorption equilibrium, kinetic, and thermodynamic studies

The increasing heavy metal pollution caused by industrial wastewater has posed serious environmental concerns, and the removal of heavy metals such as silver becomes an urgent issue to be solved currently. In this research, novel functionalized chitosan beads were prepared by grafting of triethylenetetramine onto chitosan beads. Compared to unmodified chitosan, the triethylenetetramine-modified chitosan (CS-TA) exhibited both higher adsorption capacity and better selectivity for Ag(I) adsorption due to the introduction of amino/amine groups which has a high affinity for Ag(I). The influences of pH, sorbent dose, contact time Ag(I) concentration, and co-existed ions on Ag(I) adsorption were investigated. The adsorption kinetics could be fitted by pseudo-second-order model, whereas the adsorption isotherms could be described by the Langmuir model, indicating that chemisorption is the main mechanism for Ag(I) adsorption. The maximum adsorption capacity reached 419.8 mg/g at pH 5.0 and 298 K. The thermodynamic parameters suggest that the Ag(I) adsorption is endothermic and spontaneous. This work demonstrated that CS-TA exhibited superior performance for Ag(I) removal from aqueous solution due to its good hydrophilicity, high adsorption capacity, and fast kinetic rate, thus it could be potentially applied in wastewater treatment.