Insights into water permeability and Hg2+ removal using two-dimensional nanoporous boron nitride

Abstract

Industrial wastewater containing Hg²⁺, when discharged into nature, will pose a serious threat to ecological security. In order to separate Hg²⁺ from sewage, we investigate the potential applications of hexagonal boron nitride (h-BN) for Hg²⁺ removal using molecular dynamics simulations. The relationships between water flux and pore size, pore chemistry and applied pressure are analyzed, and the filtration mechanism of Hg²⁺ is also discussed in detail. The calculated thermodynamic data are compared with the measured values in the related literature. The results indicate that water flux is proportional to pore size and applied pressure. The N-edged pore can induce water molecules to pass through the nanopore. The potential barrier and the hydration are beneficial to Hg²⁺ rejection. When the pore diameter is smaller than the second hydration radius of Hg²⁺, the efficiency of Hg²⁺ removal is high. In particular, the Hg²⁺ rejection ratio of B5 is 100%, and water permeability is also 2–3 orders of magnitude higher than that of traditional reverse osmosis membranes. Overall, this work plays a guiding role in the liquid phase separation of heavy metal ions.