EDTA functionalized magnetic graphene oxide for removal of Pb(II), Hg(II) and Cu(II) in water treatment: Adsorption mechanism and separation property

EDTA functionalized magnetic graphene oxide (EDTA-mGO), a good adsorbent for Pb(II), Hg(II) and Cu(ll), was synthesized in the present work. It was characterized by SEM, FTIR, BET, XRD, XPS, TGA and zeta potential analysis. Contact time, adsorbent dose, pH and initial concentration were optimized to improve the removal efficiency. Most importantly, EDTA-mGO displayed better adsorption performance than EDTA-GO, EDTA-Fe3O4 and mGO. The adsorption of Pb(II), Hg(II) and Cu(II) mainly depend on the metal chelation of EDTA and the electrostatic attractions of abundant functional groups on GO surface. Besides, good magnetic performance of EDTA-mGO makes it easy to achieve the solid-liquid separation. The magnetic separation process only took 25 s. The adsorption kinetic data described well with the pseudo-second-order model and the equilibrium data fitted well to Freundlich and Temkin isotherms. The maximum adsorption capacity was 508.4 mg g(-1) for Pb(II), 268.4 mg g(-1) for Hg(II) and 301.2 mg g(-1) for Cu(II) from Langmuir isotherm. Thermodynamic studies (Delta G < 0, Delta H > 0, Delta S > 0) implied an endothermic and spontaneous adsorption process in nature. Furthermore, the excellent reproducibility indicated that EDTA-mGO has a promising application in water treatment. (C) 2015 Elsevier B.V. All rights reserved.