Investigation of post-treatment effect on morphology and pervaporation performance of PEG added PAN hollow fiber membranes

In this study, hydrophilic additive, polyethylene glycol (PEG) was added in polyacrylonitrile (PAN)/N,N-dimethylformamide (DMF) dope solution to fabricate PAN hollow fiber membrane via wet-spinning process to investigate the effect of post-treatment on the morphology and pervaporation performance of PAN hollow fiber membrane. The post-treatment includes two processes, a water bath post-treatment for 4 h at various temperatures and a dry air oven heat-treatment at 120°C for 12 h. The morphology of the hollow fiber membranes were observed with scanning electron microscope (SEM). The results show that after heat-treatment, 200 g/mole molecular weight of PEG 200 is more suitable to add in the PAN dope to fabricate the aqueous isopropanol (IPA) solution dehydration use PAN hollow fiber membrane by comparing with PEG series of additives. The porosity of the outer edge of PAN pristine hollow fiber membrane increases with increasing PEG 200 content in PAN dope solution. After post-treating the PEG-added PAN hollow fiber membrane in water bath, PEG could be leached out from the hollow fiber membrane matrix and the annealed effect might be occurred. Moreover, the pervaporation performance of 90 wt.% aqueous IPA solution through dry-air heat-treated PAN hollow fiber membranes were also investigated. By comparing with water bath post-treated-free PAN hollow fiber membranes, the water bath post-treated hollow fiber membranes have shown lower permeation rate and a little higher water content in permeate.