Water desalination using nano screw pumps with a considerable processing rate

Abstract

The ability of a nano screw pump (NSP) to reject salt ions while conducting fast water flow makes it an ideal candidate as a desalination device. In this work, the desalinating performances of NSPs due to the influence of screw radius, screw pitch, and the number of the screw pitch were investigated using molecular dynamics (MD) simulations. Our results demonstrate that, on the one hand, a narrow screw pitch blocks the passage of hydrated ions, as extra energy is needed for dehydration. On the other hand, a considerable water flux can be obtained by increasing the screw diameter without losing the capability for salt rejection. The mechanisms of water transport through NSPs can be explained by the synergistic effect of confinement resistance and pitch-dependent water transport modes, while the latter factor plays a more dominant role. Water flux is further improved by decreasing the screw pitch number, which can not only decrease the confinement resistance but also facilitate a faster water transport mode. The excellent desalination properties validate NSP as a promising nanofluidic device for water desalination, purification and separation. This work can also provide useful guidelines for the design of other desalinating nanodevices.