PERVAPORATION PROPERTIES OF SELECTIVE LAY ERS BASED ON SULFONATE-CONTAINING POLY(PHENYLENE PHTHALAMIDES) - THE EFFECT OF THE CONFIGURATIONAL CHAIN STRUCTURE AND NATURE OF COUNTERIONS ON PERVAPORATION SEPARATION OF AQUEOUS-ORGANIC MIXTURES

For the membrane based on sulfonate-containing aromatic polyamides, pe rvaporation separation of water from water-alcohol mixtures was invest igated. The selectivity and permeability of the membranes were studied as a function of the composition of the selective layer and the natur e of counterion of the sulfo acid group. The composition of the select ive layer was controlled by varying the ratio between terephthalic and isophthalic acid chlorides in the polymer chain. The selective layer based on polyamides containing equal molar fractions of terephthalic a nd isophthalic components was shown to be characterized by maximum sel ectivity and permeability. The selectivity coefficient depends on the nature of the counterion and increases in the following order: Na+ < K + < Cs+ < N+ (C2H5)(4) less than or equal to poly(ethylenimine). In th e last case, the selectivity coefficient (the ratio between the molar fractions of the water and solvent in the permeate) was equal to 5.5 x 10(3) for the pervaporation separation of water-butanol mixture. The diffusion coefficient of water and its dependence on partial water vap or pressure were found to be determined by a configurational chain str ucture.