Colloidal permeability of liquid membranes consisting of hard particles by nonequilibrium simulations

A novel particulate membrane, comprised of a confined fluid of colloidal hard spheres, is presented and studied by means of simulations. Using a fluid of smaller hard spheres as feed, the transport properties of the membrane are studied as a function of the volume fractions of both the feed solution and membrane and the size ratio between both types of particles. Our simulations show that the fluid in the membrane is compressed to the permeate side due to the pressure of the feed. This effect controls the permeability behavior of the membrane: impermeable when the feed pressure is too low, or when the pressure is high enough to induce crystallization of the membrane fluid. Thus, the permeability first increases and then decreases, upon increasing the feed concentration. Finally we focus in systems with high concentrations of the feed and membrane fluids, where completely impermeable membranes are obtained only when the feed spheres are big enough (sigma(f)>0.38 sigma(m)). (C) 2009 American Institute of Physics. [doi:10.1063/1.3253716]