Application of aromatic polyamide membranes for pervaporation and vapor permeation

In this article, three types of aromatic polyamides were prepared by the direct polycondensation of bis[4-(4aminophenoxy) phenyl] diphenyl methane (BAPDM) with various of aromatic diacids such as terephthalic acid (TPAc), 5-tert-butylisophthalic acid (TBPAc), and 4,4N-hexafluoroisopropylidenedibenzoic acid (6FDAc). The pervaporation and vapor permeation performance of the above novel aromatic polyamide membranes for dehydrating an aqueous alcohol solution was investigated. Compared with pervaporation, vapor permeation effectively increases the perm-selectivity of water. Moreover, the effect of aromatic diacids on the polymer chain packing density, pervaporation, and vapor permeation performance was investigated. It was found that the permeation rate can be increased by introduction of a bulky group into the polymer backbone.

A novel BAPDM-based aromatic polyamide membrane has been successfully prepared in this study. The BAPDM based aromatic polyamide membranes exhibited water selectivity during all process runs. Compared with pervaporation, vapor permeation effectively increases the permselectivity of water. The vapor permeation process is more heat sensitive than that of the pervaporation.