Self-assembled morphology-controlled hierarchical Fe3O4 @LDH for Cr (VI) removal

The efficient removal of Cr(VI) in water with high solubility and mobility is of great significance because Cr(VI) is one of the most toxic heavy metals, but it also faces some major challenges. The dispersibility and recyclability of nanoadsorbents are closely related to their Cr(VI) removal efficiency. Herein, the self-assembly method was used to synthesize core-shell hybrid nanoparticles, named Fe3O4 @LDH, with a vertically aligned layered double hydroxide (MgAl-LDH) nanosheet shell and a Fe3O4 magnetite core. The obtained Fe3O4 @LDH nanoparticles exhibit a highly porous and well-ordered three-dimensional core-shell structure with a wool-ball-like morphology. The self-assembled morphology of the core-shell structure can be effectively controlled and induced by regulating the Mg2+/Al3+ ratio of the reaction system. The influence mechanism of charge density of LDH brucite-like layers on the self-assembled morphology was proposed. Fe3O4 @LDH nanoparticles exhibit a Cr (VI) adsorption capacity of 108.7 mg/g. The synergetic contribution of the hybrid self-assembly of Fe3O4 and MgAl-LDH leads to more dispersion, better adsorption capability, and faster kinetics. Moreover, because of the super-paramagnetic and highly saturated magnetization (34.53 emu/g) of the Fe3O4 @LDH nanoparticles, they can be used as efficient magnetic adsorbents and easily separated using a magnetic field and reused. The prepared Fe3O4 @LDH nanoparticles are a cost-effective nanoadsorbent for removing Cr(VI) from wastewater and provide a reference for the structural design and construction of nanocomposites.