Preparation of core-shell magnetic Fe3O4@SiO2-dithiocarbamate nanoparticle and its application for the Ni2+, Cu2+ removal

A novel magnetic nanoparticles-based dithiocarbamate absorbent (Fe₃O₄@SiO₂-DTC) with core-shell structure was synthesized under mild conditions and used in aqueous solution Ni²⁺ and Cu²⁺ ions treatment. The structure, morphology and magnetic properties of the adsorbent were characterized by X-ray diffraction (XRD), fourier transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Fe₃O₄@SiO₂-DTC exhibited a typical superparamagnetic with a saturation magnetization value of 52.7 emu/g, which could be rapidly separated from aqueous solution under external magnetic field. We investigated the effects of solution pH, adsorption time, and the initial concentration of heavy metal ions on the adsorption of Ni²⁺ and Cu²⁺. The adsorption equilibrium times of Ni²⁺ and Cu²⁺ on Fe₃O₄@SiO₂-DTC were reached at 15 min and 90 min, respectively. The adsorption kinetic data were fitted to the pseudo-second-order model, and the adsorption data were consistent with the Frenudlich isotherm model. When the initial concentration of heavy metal ions was 250 mg/L, the maximum adsorption capacity of Ni²⁺ and Cu²⁺ at room temperature was 235.23 mg/g and 230.49 mg/g, respectively. In addition, we discussed the plausible adsorption mechanism. The results indicated that the adsorption was mainly dominated by chelation.