Continuous water-water hydrogen bonding network across the rim of carbon nanotubes facilitating water transport for desalination

Abstract

The development of membranes featuring carbon nanotubes (CNTs) have provided possibilities of next-generation solar desalination technologies. For solar desalination, the microstructures and interactions between the filter membrane and seawater play a crucial role in desalination performance. Understanding the mechanisms of water evaporation and ion rejection in confined pores or channels is necessary to optimize the desalting process. Here, using non-equilibrium molecular dynamics simulations, we found that continuous water-water hydrogen bonding network across the rims of CNTs is the key factor in facilitating water transport through CNTs. With the continuous hydrogen bonding network, the water flux is two times of that without the continuous hydrogen bonding network. In CNT arrays, each CNT transports water molecules and rejects salt ions independently. Based on these observations, using CNT arrays consisted with densely packed thin CNTs is the most advisable strategy for evaporation desalination, possessing high transport flux as well as maintaining high salt rejection.