Salt diffusion through cation-exchange membranes in alcohol–water solutions

The salt flow through several commercial cation-exchange membranes separating two NaCl alcohol–water solutions with the same alcohol concentration, but different NaCl concentration was investigated. Homogeneous (Nafion-115) and heterogeneous (MK-40 and CR65-AZL-412) membranes were used in this work. The integral permeability coefficient was determined from the temporal evolution of the concentration in the dilute solution. The results showed that the integral permeability coefficient depends on both the solution alcohol concentration and the type of alcohol. It is observed that this dependence is function of the membrane structure. In general, for the heterogeneous membranes, the integral permeability coefficient is less sensible to alcohol concentration than for the homogeneous membrane at low and intermediate values of the alcohol percentage in the solutions.