EFFECT OF COAGULATION BATH TEMPERATURE ON STRUCTURE AND GAS SEPARATION PROPERTIES OF CELLULOSE HOLLOW FIBER MEMBRANES

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Cellulose hollow fiber membranes (CHFMs) were prepared by a new dissolving method. The influence of coagulation bath temperature on the morphology and properties such as crystallinity degree, mechanical strength and gas permeation performance of CHFM was systematically investigated. The results showed that with the increase of coagulation bath temperature, the morphology of asymmetric cellulose hollow fiber membranes would become much looser, and more large finger-like pores could be found across the section. At the same time, crystallinity degree almost showed no change and mechanical strength became worse obviously. As a result gas permeation performance of dry CHFMs would increase dramatically with the coagulation bath temperature and show obvious "Knudson-diffusion selective" mechanism. While for wet CHFMs, permeation rates for all gases would decrease sharply and interestingly for CHFMs from coagulation bath temperature of 0 degrees C and 20 degrees C carbon dioxide became the fastest gas because of the permeation mechanism had changed to "solution selective" in wet CHFMs. While for CHFMs from coagulation bath temperature of 40 degrees C and 60 degrees C, this "solution selective" effect cannot be found because of their much looser structure.