Removal of arsenic ions using hexagonal boron nitride and graphene nanosheets: A molecular dynamics study

The presence of high concentration of arsenic in conventional water sources can cause serious health and environmental hazards. An urgent need is to find an efficient adsorbent for the removal of arsenic ions (As3+) from contaminated water. In the present study, molecular dynamics simulation is used to understand the adsorption behaviour of As3+ on hexagonal boron nitride (h-BN) and graphene nanosheets. The adsorption of As3+ follows the Langmuir isotherm and the maximum adsorption capacities are found to be 270.1 and 211.7 mg/g for h-BN and graphene nanosheets, respectively. Further, potential of mean force (PMF) of As3+ revealed that the h-BN nanosheet possesses lower contact minima (-1.35 kcal/mol) for arsenic ion compared to graphene nanosheet (-1.2 kcal/mol). These results indicate strong interaction between arsenic ion and h-BN nanosheet. On the other hand, desorption of As3+ on h-BN nanosheet showed higher energy barriers (2.3 kcal/mol) compared to graphene nanosheet (1.5 kcal/mol). Correspondingly, the residence time of As3+ is approximately threefold higher on h-BN nanosheet compared to graphene nanosheet. We also report that the presence of partial charges on B and N atoms in the h-BN sheet influence the adsorption behaviour As3+ ions and the maximum adsorption capacity of h-BN nanosheet with partial charges is found to be 311.7 mg/g. Thus, our study strongly suggests the potential applicability of h-BN nanosheet as an efficient adsorbent for the removal of arsenic ions.