DIFFUSION OF ACETIC-ACID AND WATER THROUGH POLY(VINYLALCOHOL) MEMBRANES - COUPLING EFFECTS

Permeation fluxes of water and acetic acid from water-acetic acid mixt ures were independently monitored as a function of time in differentia l permeation with dual detection. Two successive permeation waves were detected for water permeation and only one for acetic acid permeation in the transient regime. The onset of the second permeation wave for water coincides with that of acetic acid permeate whatever the conditi on. The time delay for the appearance of these waves decreases with in creasing temperature and water content in the binary mixtures. The mea n diffusion coefficient for different permeation waves and their activ ation energy were calculated from the permeation rates in the transien t regime. The results strongly indicated a coupling of acetic acid flu x with the second step of water permeation which probably results from the permeation of water-acetic acid aggregates.