Simulation of osmotic pressure across an amorphous semipermeable membrane

• Published in: Journal of membrane science 2018-10, Vol.563, p.183-190
• Main Authors: Raim, Vladimir, Srebnik, Simcha
• Format: Article
• Language: English
• ISSN: 0376-7388; 1873-3123
• DOI: 10.1016/j.memsci.2018.05.058

Molecular simulations were employed to investigate osmosis for systems far from ideal conditions. Osmotic pressure was calculated for of a fluid mixture separated from a pure fluid by a fictitious semipermeable membrane using Gibbs ensemble Monte Carlo (GEMC) and compared with that of the two phases separated by a physical amorphous polyamide membrane using molecular dynamics. The calculated osmotic pressure for these two simulation set-ups was compared with various predictive models for a range of solute concentrations and solution densities. Both equilibrium-based theories, which are mostly limited in their applicability to near-ideal conditions or low solute concentrations, and non-equilibrium theories that extend to more concentrated solution conditions fared well against the GEMC simulation in their expected range, but did not adequately predict the osmotic pressure calculated according to simulations across the physical membrane for finite system size and under the limiting conditions considered. The discrepancies were particularly large for high solute concentrations and low solution densities. The observed differences are discussed in terms of solution inhomogeneities resulting from particle-membrane interactions. •Molecular simulations are used to study osmotic pressure across membranes for finite system.•Several models are investigated for their prediction of osmotic pressure.•Poor predictions are found for low solution density and high solute concentration.•Membrane-solute interactions reduce the measured osmotic pressure. [Display omitted]