Magnetite-Coated Boron Nitride Nanosheets for the Removal of Arsenic(V) from Water.

It is widely known that the existence of arsenic (As) in water negatively affects humans and the environment. We report the synthesis, characterization, and application of boron nitride nanosheets (BNNSs) and Fe3O4-functionalized BNNS (BNNS-Fe3O4) nanocomposite for removal of As(V) ions from aqueous systems. The morphology, surface properties, and compositions of synthesized nanomaterials were examined using scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, surface area analysis, zero-point charge, and magnetic moment determination. The BNNS-Fe3O4 nanocomposites have a specific surface area of 119 m2 g-1 and a high saturation magnetization of 49.19 emu g-1. Due to this strong magnetic property at room temperature, BNNS-Fe3O4 can be easily separated in solution by applying an external magnetic field. From the activation energies, it was found that the adsorption of As(V) ions on BNNSs and BNNS-Fe3O4 was due to physical and chemical adsorption, respectively. The maximum adsorption capacity of BNNS-Fe3O4 nanocomposite for As(V) ions has been found to be 26.3 mg g-1, which is 5 times higher than that of unmodified BNNSs (5.3 mg g-1). This closely matches density functional theory simulations, where it is found that binding energies between BNNS-Fe3O4 nanocomposite and As(OH)5 are 5 times higher than those between BNNSs and As(OH)5, implying 5 times higher adsorption capacity of BNNS-Fe3O4 nanocomposite than unmodified BNNSs. More importantly, it was observed that the synthesized BNNS-Fe3O4 nanocomposite could reduce As(V) ion concentration from 856 ppb in a solution to below 10 ppb (>98.83% removal), which is the permissible limit according to World Health Organization recommendations. Finally, the synthesized adsorbent showed both separation and regeneration properties. These findings demonstrate the potential of BNNS-Fe3O4 nanocomposite for commercial application in separation of As(V) ions from potable and waste water streams.