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

• Triethylene-tetramine modified crosslinked chitosan was synthesized.
• The chitosan derivative exhibited good adsorption efficiency for Co2+ removal.
• Co2+ adsorption on CCTS was a chemical adsorption along with physical adsorption.
• Both amine and hydroxyl groups were involved in the adsorption of Co2+.
• The maximum adsorption capacities were 30.45 and 59.51 mg/g for CTS and CCTS.

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.