Size effects of pore density and solute size on water osmosis through nanoporous membrane
J. Phys. Chem. B 2012, 116, 13459?13466
Kuiwen Zhao and Huiying Wu
School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dong Chuan Road, Shanghai, 200240, China
The paper investigates the influence of pore density on the osmotic transport of water across nanoporous membranes using molecular dynamics (MD) simulations. The authors looked at the size effects related to the center-to-center distance of each pore and the solute size.
The nanopores were modeled using uniform (6,6) armchair-type carbon nanotubes (CNTs) and were arranged hexagonally on the membrane. The membrane separates the saltwater (1.1 mol/L) and pure water chambers. Water was modeled using TIP3P, with an equilibrium density of 1.009 g/cm3. Pore density values ranged from 2-8 x 1013 pores/cm2, which corresponds to a structure with a minimum of 12 CNTs and a maximum of 30 CNTs.
Results of the simulations show that the effect of pore density and solute size on osmosis is independent of solute concentration and pore diameter. Moreover, a dimensionless relation for the real osmotic flux as a function of pore density and solute size (ionic radius) was established. From this relation, the area ratio was selected as parameter. The authors also showed that solute hydration affects pore density because it increases the effective solute size.
The authors also highlight the importance of this paper in modeling real osmotic processes. They mentioned that by including the effects of pore density, solute size, and solute hydration on the osmotic transport of water, the deviations of real osmotic process from ideal behavior can be reduced.
Contribution and application:
This paper can contribute to the further research of our lab about nanoporous CNT membranes. It shows that consideration about pore density is important specially when our lab will try to simulate a bigger system of multi-pored CNT membrane for desalination.
By: Hannah Ebro