Preparation of dual-layer cellulose/polysulfone hollow fiber membrane and its performance for isopropanol dehydration and CO 2 separation

Abstract

Dual-layer cellulose/polysulfone (PSf) hollow fiber membrane used for isopropanol (IPA) dehydration and CO 2 separation was prepared by using co-extrusion technique with a triple-orifice spinneret. N-methylmorpholine-N-oxide monohydrate (NMMO·H 2O) was selected as the cellulose solvent since it can dissolve cellulose through a purely physical process. Scanning electron microscopy (SEM) images show that there is no obvious delamination between the inner and outer layer and no obvious defect can be seen in the outer skin of the fiber. In order to find out the advantage of novel prepared dual-layer membrane over homogeneous cellulose membrane, tests including isopropanol dehydration by pervaporation and CO 2 separation were carried out. For pervaporation experiments, the effects of operation conditions including feed concentration and operation temperature on pervaporation (PV) performance were investigated systemically. The results showed that similar with the flat cellulose membrane, the permeation flux increased obviously with the increase of both water concentration in feed and operation temperature. Under all tested conditions, water contents in permeate maintained higher than 99.90 wt.%, and it reached a maximum value of 99.98 wt.% with a water content of 5 wt.% in feed at 25 °C. Moreover, the water-swollen dual-layer cellulose/PSf hollow fiber membrane showed much higher gas permeation rate and comparable selectivities of CO 2/H 2, CO 2/N 2 and CO 2/CH 4. The CO 2 permeance of dual layer cellulose/PSf hollow fiber membrane was ∼3 GPU, which was five times higher than that of single-layer cellulose hollow fiber membrane. In a word, the performance, especially the permeation rate of new developed dual layer cellulose/PSf hollow fiber membrane was greatly improved by its reduced separation layer, and this could definitely increase its potential for later practical application.