Development of polyion complex membranes for the separation of water–alcohol mixtures. III. Preparation of polyion complex membranes based on the k‐carrageenan for the pervaporation separation of water–ethanol

Pervaporation separation of water–ethanol was carried out with polyion complex membranes based on k-carrageenan. The polyion complex membranes were prepared by the ion complex formation between k-carrageenan (anionic polymer) and poly{1,3-bis[4-alkylpyridi-nium]propane bromide}s (cationic polymers) with different numbers of methylene units between two ionic sites within a repeating unit, respectively. The ion complex membranes were characterized with FT-IR, X-ray diffractometry. Dehydration of 90 wt % aqueous ethanol solution was carried out at different temperatures (30, 40, 50, and 60°C). The selectivity and permeability through them were very good over a wide temperature range; in the case of the polyion complex membrane consisting of k-carrageenan and poly{1,3-bis[4-ethylpyridinium]propane bromide}, the permselectivity was 45,000 and permeability was 150 g/m2 h at 30°C. With increasing operating temperature, the permeability was increased highly but the selectivity decreased slightly.