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Effect of size-asymmetric electrolyte on single-file osmosis A. V. Raghunathan and N. R. Alurua

Summary: Effect of size-asymmetric electrolyte on single-file osmosis
A. V. Raghunathan and N. R. Alurua
Department of Mechanical Science and Engineering, Beckman Institute for Advanced Science
and Technology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
Received 23 March 2006; accepted 5 July 2006; published online 10 August 2006
Single-file osmosis through a 0.9 nm diameter semipermeable carbon membrane using various
size-asymmetric electrolyte solutions is investigated using molecular dynamics simulations. In an
uncharged pore, the osmotic flux with a KCl solution is found to be higher than that of in a NaCl
solution, i.e., JKCl JNaCl, for the same concentration gradient of solute. Mean force and hydration
analysis indicate that distinct ion-water and ion-pore molecular interactions cause a differential
cation and anion affinity to the pore, leading to the observed size-asymmetric electrolyte dependence
on osmotic flux. The water orientation in the pore during osmosis is also related to the ion affinity
and exhibits a size-asymmetric electrolyte dependence. 2006 American Institute of Physics.
DOI: 10.1063/1.2335969
Osmosis is defined as the phenomenon in which a sol-
vent is driven by its free energy gradient through a semiper-
meable membrane towards a solute-rich reservoir. Osmosis
is critical to living organisms, as it is the primary mechanism
for water transport in and out of cells and membranes. Os-
mosis is widely encountered in a variety of fields including


Source: Aluru, Narayana R. - Department of Mechanical and Industrial Engineering, University of Illinois at Urbana-Champaign


Collections: Engineering; Materials Science