Effect of Molecular Forces on Mass Transfer Rates
We report computer simulations of semi-permeable membranes using the method of molecular dynamics, to study
solutions undergoing osmosis and reverse osmosis. These studies have been carried out at steady state, by periodically
recycling solvent molecules that permeate the semi-permeable membrane. The method has been used to investigate
the effect of a range of molecular forces, state conditions, and membrane morphology on the mass transfer rate
of solvents across the membrane. These results could be used to test the accuracy of continuum, micro-continuum
and statistical mechanical theories for transport across membranes, apart from being of intrinsic fundamental interest.
For further information, one should consult our article "Molecular Modeling of Fluid Separations Using
Membranes: Effect of Molecular Forces on Mass Transfer Rates" (Chem. Eng. J., 1998 in press)
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A schematic diagram of: (a) the membrane structure (b) the simulation system. Periodic boundary conditions lead
to a system infinite in the y and z directions with alternating solution and solvent compartments in the x direction
separated by semi-permeable membranes
Solvent permeation rates across the semi-permeable membrane with solvent recycling every 2500 or 5000 time steps.
Also shown is the case where no recycling is carried out and the system is allowed to reach equilibrium. The points
represent simulation results, while the lines in this and all subsequent figures are to guide the eye only.
Effect of changing the Lennard Jones (LJ) parameters  on the solvent permeation rate across the semi-permeable membrane.
Effect of changing the LJ parameters
on the density profiles of solvent molecules in the x-direction (perpendicular to the semi-permeable membranes).
Effect of changing the LJ parameters
on the mean squared displacement of the solvent molecules in the x-direction (perpendicular to the semi-permeable
membranes)
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