Magnetic graphene oxide nanocomposite: One-pot preparation, adsorption performance and mechanism for aqueous Mn(Ⅱ) and Zn(Ⅱ)

Excessive discharge of heavy metals by industrial activities has caused severe environmental problem. In this work, a magnetic graphene oxide nanocomposite (MGON) based on graphene oxide-Fe3O4 framework was prepared, characterized and employed as adsorbent to remove aqueous Mn(Ⅱ), Zn(Ⅱ) efficiently. The adsorption performance and mechanism were investigated carefully. Results suggest, the mutual enhancement between GO and Fe3O4 brings synergistic effect on adsorption performance, which enables MGON to outperform either of the two single phase. In particular, MGON efficiently adsorbs 399.67 mg g−1, 372.98 mg g−1 of Mn(Ⅱ), Zn(Ⅱ) in 4 min, 6 min, respectively. What is more, MGON can be readily recovered via magnetic separation for further recycling. The thermodynamic parameters of the adsorptions under 298.15 K are: ΔH = 20.86 kJ mol−1, ΔS = 108.84 J K−1 mol−1, ΔG = −11.59 kJ mol−1 for Mn(Ⅱ) and ΔH = 20.99 kJ mol−1, ΔS = 96.04 J K−1 mol−1, ΔG = −7.64 kJ mol−1 for Zn(Ⅱ), respectively, indicating spontaneous, endothermic and entropy increasing features. Both adsorptions fit well by the Freundlich, pseudo second order, and intra-particle diffusion models. Furthermore, adsorption mechanism is based on the chemical interaction of the oxygen atoms in CO, C-O related groups with Mn(Ⅱ), Zn(Ⅱ). The high adsorption efficiency suggests that MGON has promising application in heavy metal treatment.