Intrinsic ion transport of highly charged sub-3-nm boron nitride nanotubes

Debate regarding the transport mechanisms of water and ions in highly charged one-dimensional (1D) nanochannel continues because of a lack of available experimental data. Here, we present a nanofluidic platform consisting of approximate to 2.7-nm-diameter boron nitride nanotubes (BNNTs) as a model system, and report the experimental ion transport in these sub-3-nm BNNTs. We elucidate that strong electrostatic interactions between the highly charged tube walls and ions, stemming from the high surface-charge density (378 mC/m(2)) of BNNTs, play important roles in defining the ion transport mechanism in BNNT pores. Experimental analysis of ion transports supported by numerical the Donnan steric pore model with dielectric exclusion (DSPM-DE) and Derjaguin-Landau-Verwey-Over beek (DLVO) model elucidate the relationship of the ionic charge density and surface-charge density of the BNNT wall to electrostatic interaction, steric, and dielectric effects. We also demonstrate that BNNTs exhibit higher NaCl separation (approximate to 90%) than commercial reverse-osmosis (approximate to 80%) and nanofiltration (approximate to 60%) membranes under the same experimental conditions, despite having a larger pore size. Our results establish design criteria for developing highly efficient ion-selective membranes for various practical applications.

Automated summary

This study presents a nanofluidic platform utilizing BNNTs as a model system to investigate ion transport. The results reveal the significant role of strong electrostatic interactions between highly charged BNNTs and ions in defining the ion transport mechanism. Furthermore, the study demonstrates the superior NaCl separation performance of BNNTs compared to commercial membranes.