Quantum chemical study of the defect laden monolayer boron nitride nanosheets for adsorption of pesticides from wastewater

The accumulation of hazardous pesticides and their residues in –water sources has raised serious concerns to find a suitable way to eliminate them. In this study, the adsorption behavior of monolayer boron nitride (BN) nanosheet with B, N and B+N vacancies towards the cadusafos, chlorantraniliprole, fluazolate and lufenuron pesticides is investigated using the first principle density functional theory. The molecular electrostatic potential maps, the density of states plots and the HOMO-LUMO energy distributions based on optimized geometries were obtained. The theoretical infrared spectra confirmed the post-adsorption structural changes in defect-laden BN nanosheets. The pesticides formed a stable complex with defect laden BN nanosheets in aqueous media with the release of energy in the range of 40–130 kJ mol-1. The molecular electrostatic potential provided evidence for the appearance of the electronegative regions in the pesticides post adsorption. The most profound effect of electronegative regions was in the case of the BN/B+N nanosheet. The bandgap values of the nanosheets decreased after the interaction with pesticides. The HOMO-LUMO analysis showed that the molecular orbitals resided near the vacancy sites and thus played an important role in determining the adsorption interaction. The adsorption interactions were physical in nature, dominated by weak Van der Waals forces. The adsorption behavior of the BN/N nanosheet was best among the studied adsorbates towards pesticides. These findings give an account of how the defects in monolayered BN nanosheets can enhance the adsorption of organic (pesticide) molecules and develop viable adsorbents for wastewater treatment.