One-Pot synthesis, characterization and adsorption studies of amine-functionalized magnetite nanoparticles for removal of Cr (VI) and Ni (II) ions from aqueous solution: kinetic, isotherm and thermodynamic studies

BACKGROUND Discharge of heavy metals such as hexavalent chromium (Cr (VI)) and nickel (Ni (II)) into aquatic ecosystems is a matter of concern in wastewater treatment due to their harmful effects on humans. In this paper, removal of Cr (VI) and Ni (II) ions from aqueous solution was investigated using an amino-functionalized magnetic Nano-adsorbent (Fe3O4-NH2). METHODS An amino-functionalized magnetic Nano-adsorbent (Fe3O4-NH2) was synthesized by compositing Fe3O4 with 1, 6-hexanediamine for removal of Cr (VI) and Ni (II) ions from aqueous solution. The adsorbent was characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM), powder X-Ray Diffraction (XRD), and Vibrating Sample Magnetometry (VSM). Also, the effects of various operational parameters were studied. RESULTS According to our finding, Fe3O4-NH2 could be simply separated from aqueous solution with an external magnetic field at 30 s. The experimental data for the adsorption of Cr (VI) and Ni (II) ions revealed that the process followed the Langmuir isotherm and the maximum adsorption capacity was 232.51 mg g(-1) for Cr (VI) at pH = 3 and 222.12 mg g(-1) and for Ni(II) at pH = 6 at 298 °K. Besides, the kinetic data indicated that the results fitted with the pseudo-second-order model (R(2): 0.9871 and 0.9947 % for Cr (VI) and Ni (II), respectively. The results of thermodynamic study indicated that: standard free energy changes (ΔG(ɵ)), standard enthalpy change (ΔH(ɵ)), and standard entropy change (ΔS(ɵ)) were respectively -3.28, 137.1, and 26.91 kJ mol(-1) for Cr (VI) and -6.8433, 116.7, and 31.02 kJ mol(-1) for Ni (II). The adsorption/desorption cycles of Fe3O4-NH2 indicated that it could be used for five times. CONCLUSIONS The selected metals' sorption was achieved mainly via electrostatic attraction and coordination interactions. In fact, Fe3O4-NH2 could be removed more than 96 % for both Cr (VI) and Ni (II) ions from aqueous solution and actual wastewater.