Graphene oxide enhanced the reductive sequestration of UO 2 2+ , ReO 4 − , SeO 4 2− and SeO 3 2− by zero-valent iron: batch, column and mechanism investigations

This paper revealed the enhancement role of graphene oxide (GO) in reductive sequestration of UO 2 2+ , ReO 4 − , SeO 4 2− and SeO 3 2− on zero-valent iron (ZVI) using batch, column and X-ray spectroscopic experiments. First, we decorated nanoscale zero-valent iron (NZVI) on GO to obtain NZVI-GO, and the kinetics for adsorption of these radionuclides on NZVI-GO could be well described by the pseudo-second-order model, indicating a chemical interaction process. The isotherms for UO 2 2+ adsorption on NZVI-GO could be fitted better by Freundlich model than that by Langmuir model. Besides, the presence of co-existing dissolved humic acid could significantly promoted the adsorption. In column experiments, the combination of GO to pack with ZVI and sand as reactive medium for removal of these radionuclides prolong the reaction longevity of the column packed with ZVI and sand as reactive medium. It might be the first report from XPS that the GO decoration facilitated NZVI reduced Re(VII), Se(VI) and Se(IV) into Re 0 and Se(-II) with lower oxidation state, which could be not observed in bare NZVI system. So, due to the excellent electron mediation ability and adsorption capacity, GO demonstrated an important role in enhancing reductive sequestration of redox-sensitive radionuclides in a wide range of natural environments.