Comparison of Co2+ adsorption by chitosan and its triethylene-tetramine derivative: Performance and mechanism

A cross-linked chitosan derivative (CCTS) was synthesized via cross-linking of epichlorohydrin and grafting of triethylene-tetramine. The adsorption performance and capacity of the raw chitosan (CTS) and its derivative were also investigated for removal of Co2+ from aqueous solution. A maximum adsorbed amount of 30.45 and 59.51 mg/g was obtained for CTS and CCTS, respectively under the optimized conditions. In addition, the adsorption kinetics for the adsorption of Co2+ by CTS and CCTS were better described by the pseudo second-order equation. The adsorption isotherm of CCTS was well fitted by the Langmuir equation, but the data of the adsorption of Co2+ onto CTS followed Freundlich and Sips isotherms better. Furthermore, the adsorbent still exhibited good adsorption performance after five regeneration cycles. Finally, Co2+ removal mechanisms, including physical, chemical, and electrostatic adsorption, were discussed based on microstructure analysis and adsorption kinetics and isotherms. Chemical adsorption was the main adsorption method among these mechanisms. (C) 2016 Elsevier Ltd. All rights reserved.