PERVAPORATIVE TRANSPORT OF AQUEOUS-ETHANOL - DEPENDENCE OF PERMEATIONRATES ON ETHANOL CONCENTRATION AND PERMEATE SIDE PRESSURES

The pervaporative transport of aqueous solutions of high ethanol conte nt was studied on polyion complex membranes. It was found that the per meation rate of water became smaller with the decrease in the water co ntent of the feed solution and/or with the increase in the permeate si de pressure. This fact suggested that the permeation rate was dependen t on the activity of water in the membrane, Therefore, on the basis of the solution-diffusion theory, an equation of the permeation rate of water was derived on the assumption that both the activity and the dif fusion constant of water depended on concentration. The permeation rat e was calculated for the membranes of different thickness and under va rious permeate side pressures. It was confirmed that the derived equat ion accurately described the experimental data for permeation rate of water, On the other hand, the permeation of ethanol resulted mostly fr om the volume flow through incomplete parts of the membrane but was ne gligible compared with the permeating water flow.