Molecular dynamics simulations in membrane-based water treatment processes: A systematic overview
Journal of Membrane Science, 438, 2013, 112?125
Hannah Ebro1, Young Mi Kim1, Joon Ha Kim1,2,3
1School of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Republic of Korea
2Center for Seawater Desalination Plant, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Republic of Korea
3Sustainable Water Resource Technology Center, Gwangju Institute of Science and Technology (GIST), Gwangju 500-712, Republic of Korea
This paper is a two-part overview on the fundamentals of molecular dynamics (MD) and its applications on membrane-based treatment processes. MD is a computational method used to simulate the motion and interaction of molecules. In classical MD, molecular trajectories are calculated using Newton's equation of motion, a formula that associates change in velocity with applied force. The said forces are determined by virtue of pair interaction; forces arising from bonded and long-range molecular interaction as well as from external effects.
An MD simulation run is a series of iterative step-by-step calculations evaluated over defined time steps. The system is first set to initial conditions and then allowed to equilibriate or "relax" such that it can be considered to be in steady-state. After this period, the system is run for data production. The gathered data can be plotted as an animation in 3D-space for visual observation of transport phenomena on the molecular scale such as separatory processes in membranes. Data from MD can also be used to estimate bulk properties such as viscosity and diffusivity.
The materials mentioned in this paper include carbon and boron nitride nanotubes, polymeric membranes and porous graphene. These materials possess interesting properties on the nanoscale, i.e. presence of pores or channels that facilitate ion rejection and water flux primarily for reverse osmosis. Studies on biological components such as embedding of membrane proteins called aquaporins as water channels, as well as fouling investigation were also covered.
This paper presented exhaustive discussions of MD studies on different materials and also suggested that MD be used to venture into other membrane technologies such as forward osmosis, pressure retarded osmosis and membrane distillation.
Molecular dynamics is a powerful computational technique that has been gaining interest in materials research as it can help further understanding of the behavior and properties of materials. This research can be extended to environmental applications, as was discussed in this paper: water treatment using membranes as an answer to the global water scarcity crisis. MD is expected to become a commonplace procedure in various types of research, as computational power and technology continue to improve. This paper presented valuable information on the usage of MD and on the active areas of research with regards to membrane technology.
John Matthew V. Cajudo