Project title: Flow of fluids through porous media with application to membranes: from the molecular to the continuum scale.

Supervisors: Omar Matar, Erich Müller

Project description:

Nanoporous materials have been the subject of extensive research in recent years. This includes carbon nanotubes (CNTs) or porous graphene sheets used for water desalination or gas separation.[1,2] Finding more efficient and cheaper methods of separating solutes from a solution can make these separation mechanisms more economically viable and accessible which makes it an important area of research. During my PhD project I aim to analyse non-continuum effects in fluid transport through nanopores and how they can be exploited to improve rejection mechanisms.

Continuum-scale fluid flow through simple channels, such as cylindrical pipes, is well described by the Hagen-Poisieulle equation.[3] This continuum description, however, breaks down for channels with small diameters. This is as there are fluid-wall effects on the molecular scale. As the diameter approaches molecular sizes, these effects will start to significantly effect flow behaviour. Several adaptations to the Hagen-Poisieulle equation have been proposed, ranging from explicitly including a slip length[3] to introducing a different viscosity near the wall [4,5].

In my research project I aim to analyse the applicability of porous media for various rejection processes. The value of my research will be in isolating contributing factors to solute rejection, such as fluid-pore interactions, size effects and properties of fluids under confinement. My calculations will be performed in order to assist the understanding of experimental results, which show slightly counter-intuitive behaviour of rejection in porous media.

[1] R. R. Nair et al., Science 335, pp. 1–3 (2012). 
[2] A. T. Nasrabadi and M. Foroutan, Desalination (277), pp. 236–243 (2011). 
[3] M. E. Suk and N. R. Aluru, RSC Advances 3, p. 9365 (2013).
[4] T. G. Myers. Microfluid Nanofluid 10. pp. 1141-45 (2011).
[5] F. Calabro et al., Applied Mathematics Letters 26, pp. 991-4 (2013).