PDMS/PVDF Hollow Fiber Composite Membrane For Alcohol-Water Separation

Membrane contactor is a kind of novel separator which efficiently integrated membrane process with conventional chemical separation technology, achieving gas/liquid or liquid/liquid mass transfer without dispersion of one phase within another. Distillation in hollow fibers is a novel membrane contactor which will play a more and more important role in the near future. Compared with conventional separation facilities, the separation in membrane contactor has many advantages. For example, because the phases are separated by the membrane, the loading, flooding and channeling constraints of convention packing are eliminated. Furthermore, it has wider operation range, high separation efficiency, independent flow between liquid and gas, linear scale-up and compact structure, etc.In order to improve the performances of the system, PDMS/PVDF composite membrane were prepared. Because PDMS had specific characters, such as good thermostablility, cold-resistant, permeability, acid-proof, alkaline resistant, nontoxicity and hydrophobic nature, PDMS was known as a representative alcohol-permselective membrane material for aqueous solutions with low alcohol concentrations, and chosen as the active layer material in this experiment. Novel PVDF and PDMS/PVDF hollow fiber composite membrane contactors (HFMCs) were used as structured packing for the distillation of ethanol/water and isopropanol/water solutions. The performances of two different membranes were compared. The result showed that both modified and unmodified membrane contactors gave better, more productive separations than traditional packing in distillation. Almost all the contactors could work well above the limit where flooding normally occurs in conventional cases. The modified membrane contactors performed better than unmodified ones, especially in ethanol/water separation, the distillation efficiency increased59%and35%, respectively. The overall mass transfer coefficients of hollow fiber contactors for ethanol/water and isopropanol/water increased rapidly from12.42×10-4cm/s to58.15×10-4cm/s and68.31X10-4cm/s to137.99×10-4cm/s, respectively.