Preparation of cross-linked magnetic chitosan-phenylthiourea resin for adsorption of Hg(II), Cd(II) and Zn(II) ions from aqueous solutions

Highlights: ► Chitosan was chemically modified through the reaction with phenylisothiocyanate. ► The modified chitosan-phenylthiourea cross-linked with formaldehyde in presence of magnetite to produce modified magnetic resin. ► The resulted resin characterized by various instrumental methods. ► The resin was applied to remove Hg2+, Cd2+ and Zn2+ from aqueous solutions. - Abstract: In this study, cross-linked magnetic chitosan-phenylthiourea (CSTU) resin were prepared and characterized by means of FTIR, 1H NMR, SEM high-angle X-ray diffraction (XRD), magnetic properties and thermogravimetric analysis (TGA). The prepared resin were used to investigate the adsorption properties of Hg(II), Cd(II) and Zn(II) metal ions in an aqueous solution. The extent of adsorption was investigated as a function of pH and the metal ion removal reached maximum at pH 5.0. Also, the kinetic and thermodynamic parameters of the adsorption process were estimated. These data indicated that the adsorption process is exothermic and followed the pseudo-second-order kinetics. Equilibrium studies showed that the data of Hg(II), Cd(II) and Zn(II) adsorption followed the Langmuir model. The maximum adsorption capacities for Hg(II), Cd(II) and Zn(II) were estimated to be 135 ± 3, 120 ± 1 and 52 ± 1 mg/g, which demonstrated the high adsorption efficiency of CSTU toward the studied metal ions.