In recent experiments performed by the group of Prof. Zhiping Lai at KAUST, it was found that there can be high-flux water desalination effect in nanoporous carbon composite membrane, involving a salt water-air meniscus intersecting with carbon nanofibers. In order to explain the large flux and the desalination effect, large scale molecular dynamics (MD) simulation is performed to show the formation of pure water droplets from NaCl solution across the contact line region. Here the contact line is defined to be the intersection of the meniscus with the carbon surface. The size distribution of the equilibrium pure water droplets on carbon surfaces is obtained. The pure water droplets are shown to be from the surface freshwater layer, and hence does not involve latent heat as required in membrane distillation. In addition, the diffusion process of the droplets of different size on the carbon surface is monitored so as to obtain the corresponding surface diffusivity. From such information the surface diffusion flux can be obtained by the linear response theory. The simulation results provide the underlying mechanism for the observed high-flux water desalination in nanoporous carbon composite membrane.
Level 0, between bld. 4 and 5
14:00 - 14:30