Polysiloxaneimide membranes for removal of VOCs from water by pervaporation

For the separation of volatile organic compounds (VOCs) from water by perva poration, three polysiloxaneimide (PSI) membranes were prepared by polycond ensation of three aromatic dianhydrides of 4,4'-(hexafluoroisopropylidene)d iphthalic anhydride (6FDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydri de (BTDA), and pyromellitic dianhydride (PMDA) with a siloxane-containing d iamine. The PSI membranes were characterized using H-1-NMR, ATR/IR, DSC, XR D, and a Rame-Hart goniometer for contact angles. The degrees of sorption a nd sorption selectivity of the PSI membranes for pure organic compounds and organic aqueous solutions were investigated, The pervaporation properties of the PSI membrane were investigated in connection with the nature of orga nic aqueous solutions. The effects of feed concentration, feed temperature, permeate pressure, and membrane thickness on pervaporation performance wer e also investigated. The PSI membranes prepared have high pervaporation sel ectivity and permeation flux towards hydrophobic organic compounds. The PSI membranes with 150-mu m thickness exhibit a high pervaporation selectivity of 6000-9000 and a high permeation flux of 0.031-0.047 kg/m(2) h for 0.05 wt % of the toluene/water mixture. (C) 2000 John Wiley & Sons, Inc.