Key factors influencing water diffusion in aromatic PA membrane: Hydrates, nanochannels and functional groups
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.