A new porous magnetic chitosan modified by melamine for fast and efficient adsorption of Cu(II) ions

A new porous magnetic chitosan modified by melamine (MA-CS/Fe3O4) was synthesized. The compositions and surface topographies were characterized by infrared (IR) spectroscopy, X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis and scanning electron microscope (SEM), respectively. The results of adsorption kinetics showed the adsorption behavior could be better described by the pseudo-second-order equation (R > 0.999). The adsorption isotherm was well fitted by the Langmuir equation (R > 0.999), and the values of separation factors were in the range of 0-1.0. The maximum adsorption capacity for Cu(II) was 2.58 mmol g−1 at the optimal experimental conditions, which were pH = 5.5, t = 25 min, C0 = 5.0 mmol L−1. The rate-controlling step was supposed to be chemical adsorption rather than mass transport. The adsorbent still exhibited high adsorption capacity after five regeneration cycles. The adsorption mechanism was due to coordination between Cu(II) and N atoms.