Nanoscale zero valent iron supported on MgAl-LDH-decorated reduced graphene oxide: Enhanced performance in Cr(VI) removal, mechanism and regeneration

[Display omitted] •LDH was used to modify rGO for better dispersibility and more positive surface.•nZVI NPs are well distributed over LDH/rGO support without significant aggregation.•By synergic effect of LDH and rGO, Fe@LDH/rGO performs robustly in Cr(VI) removal.•Alkaline-driven Cr(III) desorption with NaBH4 reduction can regenerate Fe@LDH/rGO. The scaled application of nanoscale zero-valent iron nanoparticles (nZVI or Fe° NPs) in environmental remediation is challenged by easy surface passivation and particle aggregation. To improve this situation and enhance their performance in Cr(VI) removal from water phase, we present one novel strategy to hybridize nZVI with layered double hydroxide (LDH) decorated reduced graphene oxide (rGO). The as-prepared ternary (Fe@LDH/rGO) composites possess better dispersibility, improved hydrophilicity and more positive surfaces that allows higher removal efficiency and capacity for Cr(VI) oxyanions. Composition proportion are optimized and influences of surroundings (solution pH, Cr(VI) concentration and temperature) are evaluated. Also, we demonstrate that Fe@LDH/rGO can be reused with suitable post-treatments, which combines alkaline solution desorption and NaBH4 revivification possess. Cr desorption and Fe leaching ratio during regeneration should be critical indicators that determine the recovery efficiency. Synergistic effect within this ternary system not only contributes to its superiorities in stability, but also continuous iron corrosion via the formation of micro Fe-C batteries, where rGO acts as cathode and alternative electron conductor. The present work suggests great potentials of Fe@LDH/rGO composites in groundwater remediation.