Magnetic nanoparticles surface-modified with tridentate ligands for removal of heavy metal ions from water

In this study, a novel superparamagnetic nanoparticle modified with N2S tridentate ligand was synthesized and applied as an effectual nanosorbent to uptake Pb2+ and Cd2+ ions. To synthesize the amino/thiol magnetic nanoparticles (Fe3O4@SiO2@GLYMON-en), Fe3O4@SiO2 was functionalized by thio-(3-Glycidyloxopropyl)trimethoxysilane (GLYMO(S)) and modified by a ring-opening reaction between GLYMO(S) and ethylenediamine. The physical and surface properties of magnetic nanoparticles (MNPs) were characterized by TEM, FE-SEM, XRD, TGA, VSM, and FT-IR analytical techniques. The structural analysis revealed a core-shell structure of Fe3O4@SiO2@GLYMO(S)-en and confirmed the presence of amino and thiol groups on Fe3O4@SiO2 MNPs. To find the optimal adsorption conditions and minimize the number of experiments, Box Behnken Design (BBD) based on response surface methodology (RSM) was applied. In optimum conditions Fe3O4@SiO2@GLYMO(S)-en adsorbed Pb2+ (93.5 mg/g) and Cd2+ (80.64 mg/g) ions at pH 7, adsorbent dosage 16 mg and contact time 55 min. The data revealed that heavy metal ions removal followed the Pseudo-second-order kinetic model (R-2 = 0.98) and Langmuir isotherm (R-2 = 0.99). The effects of coexisting metal ions on Pb2+ and Cd2+ adsorption were investigated by MNPs. The reusability of Fe3O4@SiO2@GLYMO(S)-en was utilized at five cycles and removal of Pb2+ and Cd2+ conserved above 90%. The results show that the novel MNPs can successfully apply as an efficient and reusable nanosorbent with a high adsorption rate in removing further heavy metal ions from wastewater.