Preparation of a novel graphene oxide/Fe-Mn composite and its application for aqueous Hg(II) removal

Abstract A novel graphene oxide/Fe-Mn (GO/Fe-Mn) composite was synthesized (molar ratio of Fe/Mn = 3/1 and mass ratio of Fe/GO = 1/7.5) and investigated for the sorption characteristics and mechanisms of aqueous mercury (Hg 2+ ) as well as the biological effects to wheat and rice. Characterization tests showed that Fe-Mn oxides were impregnated onto GO sheets in an amorphous form through oxygen-containing functional groups (i.e., C O, epoxy C O C, carboxyl O C O, and C O) and π-π interactions. GO/Fe-Mn possessed large surface area, surface enhanced Raman scattering with more sp 3 defects, and greater thermal stability than GO. XPS analysis revealed that Fe 2 O 3 , FeOOH, MnO 2 , MnOOH, and MnO were the dominant metal oxides in GO/Fe-Mn. Pseudo-second-order kinetic model and Sips isotherm model fitted well with the sorption kinetic and isotherm data. The maximum sorption capacity for mercury was 32.9 mg/g. Ligand exchange and surface complexation were the dominant mechanisms for mercury removal. GO/Fe-Mn greatly reduced the bioavailability of mercury to wheat and rice, even promoted the seedling growth. This work suggests that GO/Fe-Mn can be used as an effective and environmental-friendly adsorbent in heavy metal remediation.