One-pot formation of magnetic layered double hydroxide based on electrostatic self-assembly to remove Cr(VI) from wastewater

Magnetic ZnAl-LDH composite materials (Fe 3 O 4 @LDH) based on the electrostatic attraction was manufactured by self-assembly method to remove Cr(VI) from wastewater simultaneously. Fe 3 O 4 microspheres with suitable size can be surrounded by the LDH layers in the formation process to separate easily and reduce the dosage of Fe 3 O 4 . The removal behaviors of Cr(VI) from wastewater were investigated and the obtained samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopic (TEM) and molecular simulation. Equilibrium studies indicated that the experimental data was well described by Langmuir models and the removal was a charge-limited process. Compared with other reported papers, the removal capacity for Cr(VI) by this method was larger, revealing a maximum utilization of charges on LDH. By molecular simulation, the relationship among chemical bond, electron transfer and energy was explained microscopically and the removal mechanism was proved that Cr(VI) trapped onto Fe 3 O 4 @LDH involved ion electrostatic interaction. The reusability of Fe 3 O 4 @LDH composite was tested and illustrated that it can be reused for several times.