Optimizing Structural Parameters for BNNT-Supported Boron Nitride Membranes in Seawater Desalination: A Molecular Dynamics Simulation Investigation

In recent years, the development of high-performance membranes for seawater desalination has attracted significant attention. This work proposes a novel model by employing a boron nitride nanotube (BNNT) as a support in lamellar boron nitride (BN) membranes. The effects of structural parameters as well as the role of nanotubes on seawater desalination performance are explored systematically via nonequilibrium molecular dynamics simulations (NEMD). In addition, the transport mechanism for water molecules and the separation mechanism for ions transmitted through the BN-BNNT membranes are elucidated at the molecular level. Simulation results indicate that the BN-BNNT membrane exhibits a higher water flux rate compared to the BN membrane. Additionally, reducing the gap width from 10 Å to 8 Å leads to a higher ion rejection rate but a significant decrease in water flux rate. The rejection rates for Na⁺ and Cl^- ions are promoted by increasing the interlayer spacing to larger values. This phenomenon can be attributed to the trapping of water molecules and hydration ions in the interfacial regions formed between the BN and BNNT nanosheets. It is possible to simultaneously increase the water flux and interception by inserting nanotubes and adjusting the distance of the interlayer spacing. This study suggests that the stability of lamellar nanomembranes can be enhanced through the incorporation of nanotubes as a support. Simultaneously, it is possible to enhance the rejection rate in such membranes without decreasing the water flux rate by adjusting the relevant structural parameters.