Removal of aqueous Cd(II) and Ni(II) by aminopyridine functionalized magnetic Fe3O4 nanocomposites

Aminopyridine functionalized Fe3O4 nanocomposites (HE-Fe3O4@SiO2-AP and HO-Fe3O4@SiO2-AP) were prepared by the general method and simple one-pot method. They were employed as adsorbents for removing aqueous Cd(II) and Ni(II). The factors that influence the adsorption behavior was tested and the optimum condition was determined. The best adsorption was achieved under pH 6 for the two ions. The uptake of Cd(II) and Ni(II) can achieve saturation at 270 and 260 min. Kinetic process is controlled by film diffusion and follows pseudo-second-order (PSO) model. The adsorption prefers high concentration and temperature. It is a chemical process and can be depicted with Langmuir model. The adsorption mechanism is demonstrated by experimental technique and density functional theory (DFT) simulation. The adsorption is the synergistic effect of the nitrogen atoms of aminopyridine group, the oxygen atom of ether linkage, and hydroxyl oxygen atom. The nitrogen atoms of aminopyridine group play a leading role in the adsorption. The regeneration performance shows the nanocomposites can be regenerated and recycled.