Enhanced removal of Cr(VI) from wastewater by nanoscale zero valent iron supported on layered double hydroxides

The application of nanoscale zero-valent iron (NZVI) in a promising remediation strategy was challenged by easy aggregation and surface passivation. To enhance their performance of Cr(VI) removal, layered double hydroxides (LDHs) supported NZVI (NZVI@LDH) with different loading amount via an in-situ way was successfully synthesized. The structural characterization and morphology revealed LDHs could stabilize and uniformly disperse NZVI on the surface of LDHs layer, however, superabundant NZVI still leaded to a visibly aggregation. Cr(VI) removal by NZVI@LDH was higher than that of the sum of NZVI and LDHs, revealing a synergistic effect within this system. The results of Cr(VI) removal displayed with the growth of iron loading amount, the removal efficiencies were raised firstly but declined afterwards. Kinetics studies for all samples showed Cr(VI) removal well fitted pseudo-second-order model and isotherm data was well described by Langmuir model. The effects of initial concentration and pH on Cr(VI) removal were also examined. Cr(VI) in the wastewater was reduced by NZVI to Cr(III), NZVI was oxidized into Fe(II) and Fe(III). The excellent removal performance suggested a promising strategy in sewage water remediation.