Adsorption Selectivity of Boron Nitride Nanostructures Designed for Environmental Protection

Abstract

Because of the adsorption selectivity of different molecules from gaseous and liquid media, boron nitride (BN) nanostructures with large specific surface area are considered as useful materials in environmental protection, e.g., in water treatment for removal of organic pollutants. Here, we propose a theoretical model explaining the selectivity of boron nitride surfaces to adsorb different molecules. The weakness of interaction between BN hexagonal layers gives the possibility for such kind of reconstruction of the surface layer when B and N atoms are displaced in opposite directions from the surface plane. Bonding in BN is partially ionic, i.e., B and N atoms possess non-zero effective electrical charges of opposite signs. Thus, BN surfaces should be polarized and interact with ions, and induce and/or attract the electrical dipoles of molecules. The adsorption depends on the relation between electrical attraction and Pauli repulsion forces between BN hexagonal surface and molecules, i.e., their characteristics, such as size, charge, dipole moment, and polarizability.

Mean Electric Field of Dielectric Nanoparticle

“…Assuming that surface reconstruction compensates for the binding energy imbalance resulting from the destruction of interlayer bonds, the thickness of the surface dipole layer in h-BN was estimated as 0.14 Å [3]. In this work, this and above theoretical predictions on the reconstruction of ideally flat/cylindrical BN surfaces with hexagonal atomic structure are indirectly supported by experimental finding of intensive radial vibrations visible in the Raman spectra of BN nanotubes.…”

“…The theoretical model of layered binary compounds, namely hexagonal boron nitride h-BN, proposed in [3] can explain the selectivity of their surface to the adsorption of various particles from gases or liquids. The weakness of the interaction between layers compared to the intralayer bonding makes it possible to reconstruct the surface layer in such a way that different atoms are displaced in opposite directions from the surface plane.…”