Separation of Dimethylformamide/H₂O Mixtures Using Pervaporation-Distillation Hybrid Process

Three kinds of commercial PVA composite membranes with different crosslinking degrees (PVA-1, PVA-2 and PVA-3) were used to separate DMF/H₂O mixtures. Their pervaporation performance was investigated at different operation temperatures. The results showed that PVA-1 was the most suitable one for separating DMF/H₂O mixtures. When operation temperature was 60^oC and downstream pressure was lower than 6kPa, flux reached to 0.59 kg·m^-2·h^-1 and separation factor was 33 for PVA-1 membranes. Aspen Plus^® was applied to simulate the normal distillation for retentate from pervaporation unit. Comparing with the two-effect distillation, the cost of concentrating DMF could be reduced 16.2% to 19.2% for DMF aqueous solution with different composition by hybrid processes. The cost would be the lowest for a hybrid process that concentrated the feed into 50wt% by pervaporation firstly, then concentrated retentate to 99.6wt% by two-effect distillation