▎ 摘　　要

Magnetite-reduced graphene oxide (M-rGO) composites with different mass% (from 33% to 93%) magnetite contents were successfully synthesized via an in situ chemical precipitation method. The composites of M-rGO were characterized by SEM, XRD, FTIR, and XPS techniques. Macroscopic, spectroscopic and modeling techniques were used to study the mechanism for U(VI) removal by M-rGO. The results revealed that the high performance of M-rGO toward U(VI) removal resulted from the contribution of both sorption and reduction mechanisms. The reduction of U(VI) to U(IV) by M-rGO increased with increasing content of magnetite (Fe3O4), as evidenced by the XPS analysis. The kinetics model further suggested that the reduction reaction happened after the sorption of U(VI) on M-rGO. U(VI) was adsorbed on M-rGO via outer-sphere and inner-sphere surface complexation with oxygen-containing groups, whereas the inner-sphere surface complexation dominated with the increasing content of Fe3O4 on M-rGO due to the increased sorption sites (i.e., equivalent to FeOH). The findings herein highlight the elucidation of the interaction mechanisms between M-rGO and U(VI), which is of significance in predicting the U(VI) removal properties of M-rGO and designing versatile adsorbents in environmental cleanup.