writer：Jing-Gang Gai*, Xiao-Lei Gong, Wu-Li Kang, Xin Zhang, Wei-Wei Wang
keywords：PA membrane；Hydrates, nanochannels， functional groups
source：期刊
specific source：Desalination 2014, 333(1), 52-58
Issue time：2014年

Desalination by

aromatic polyamide (PA) composite membranes is currently the most important

technology of solving the global freshwater crisis. However, understanding the

main factors influencing

water diffusion in the desalination process remains a major hurdle in designing

new membrane materials. Here, we investigate the key roles of the hydrates, the

nanochannels in a PA membrane and the functional groups of the membrane on

water diffusion by molecular dynamic simulations. Results show that the

membrane can strongly hinder the diffusions of water molecules via both

geometrical obstruction and water–membrane

interaction when the radius of the water diffusion channel in the membrane is

less than 8.75?. Conversely,

the membrane has little influence

on water diffusion. In a dilute NaCl solution, the effect of salt ions on the

overall diffusion behavior of water can be neglected because only a small

quantity of water molecules form hydrates. Almost all Na+ and Cl?, on the contrary,

can form hydrates, which could explain why the PA membrane has a higher

rejection level to salt ions rather than to water in seawater.