PDMS/PS Hollow Fiber Membrane Contactor For Distillation Of Alcohols-Water

A novel membrane contactor is a high efficiency separation device, integrating with conventional chemical and membrane separation technologies, which achieves gas/liquid or liquid/liquid mass transfer without dispersion of one phase within another. Due to the advantages such as inherent huge interfacial area and independent two fluids flow, hollow fiber membrane contactor performed very well in separation efficiency and operation flexibility. Based on our previous work, the process operated under total reflux. The condensate flowed down along the lumen of hollow fibers while the vapor flowed counter-currently in shell side. Polydimethylsiloxane (PDMS) was selected due to its specific properties, such as strong hydrophobicity, excellent temperature resistance, exceptional chemical stability and permeability. In this research, polysulfone (PS) and polydimethylsiloxane/polysulfone (PDMS/PS) hollow fiber membranes were selected to separate different alcohols-water systems, which were methanol-, ethanol-, isopropanol-water binary solution. We investigated the effect of coated PDMS layer and distinguished separation systems on operating specification and distillation efficiency. It is represented the PS and PDMS/PS hollow fibers could break the restraint of flooding and low limit permit that normally occurred in conventional case. Furthermore, PS hollow fiber membrane offered high separation efficiency with HTU in the range of0.07m and0.3m before and after coating. On the other hand, the modified membrane contactor performed worse than unmodified one in the product concentration, the height of transfer unit (HTU), and the overall mass transfer coefficients, especially, the variation of separation property in distillation of ethanol-water was the sharpest and that was the mildest in isopropanol-water. Addition, PS hollow fibers before and after coating always performed better in isopropanol-water separation than in others. It was found the swelling degree of hollow fibers gradually increased as in methanol, ethanol and isopropanol, while the shortening degree kept the same after dried under normal temperature, and the PDMS layer did not have a notable impact on the hollow fiber membrane distortion.