Selective removal of Hg(II) from aqueous solution by functionalized magnetic-macromolecular hybrid material

•Magnetic hybrid material for mercury recovery from slightly acidic solutions.•Diethylenetriamine grafting on chitosan for improved sorption performance.•Pseudo-second order rate equation for modeling uptake kinetics.•Selectivity for mercury recovery against other base metals.•Mercury can be easily desorbed from sorbent for efficient recycling. A new hybrid material was prepared using chitosan, glycidyl methacrylate and magnetite microparticles. The concentration of amine groups on the sorbent was increased by grafting diethylenetriamine. These materials were tested for the sorption of Hg(II) metal ions. These materials showed high affinity and selectivity for Hg(II) uptake from aqueous solutions: maximum sorption capacity reached 2.6mmolg−1 at pH 4.0. The influence of pH was tested on the selective separation of Hg(II) from a mixture of Hg(II), Co(II), Cu(II), Fe(II), Ni(II), Zn(II) and Mg(II). The effect of counter anions was also studied at different pH values. Sorption may occur by chelation of cationic mercury species on amino groups or by ion exchange of chloroanionic mercury species on protonated amino groups. Uptake kinetics and sorption isotherms were modeled using the pseudo-second order rate equation and the Langmuir equation, respectively. The distribution coefficient was obtained at different temperatures and the thermodynamic parameters have been calculated: the sorption is endothermic, spontaneous and contributes to increase the entropy of the system. Potassium iodide was used for Hg(II) desorption from loaded sorbents: desorption yields 99%, and the sorbent could be efficiently recycled for a minimum of three sorption/desorption cycles.