| Pervaporation (PV) is a promising membrane technology for its lower energy consumption, high efficiency and pollution-free. PV has been applied widely in organic solvent dehydration, removal of VOCs from water and separation of organic solvent mixture. Polyelectrolyte complexes (PECs) are ideal materials for pervaporation dehydration due to their ionic crosslinking and excellent hydrophilicity. However, solid PECs are commonly infusible and insoluble due to the ionic crosslinking structures. In this thesis, water dispersible PECs were prepared and then crosslinked by glutaraldehyde (GA). Crosslinked PEC composite flat membranes and crosslinked PEC composite hollow fiber membranes were prepared by dip-coating respectively and their PV performance for dehydration of isopropanol was investigated.Water dispersible PEC of poly(diallyldimethylammonium chloride)(PDDA) and sodium carboxymethyl cellulose (CMCNa) were prepared by "Acid protection-Alkali dispersion". Then, water dispersible PEC was crosslinked via aldolization reaction between CMCNa and GA. Fourier transform infrared spectroscopy (FTIR) spectra, Doppler Broadening Energy Spectroscopy (DBES) and X-ray photoelectron emission microscopy (XPS) results indicated that the crosslinking of PEC colloidal particles was successful and the crosslinking degree increased regularly with increasing GA content. Atomic force microscope (AFM) micrographs showed that special needle-shaped microstructures of PECs were not destroyed by chemical crosslinking, and aggregation of them emerged when GA content was as high as1.5wt%.As for crosslinked PEC composite flat membranes, effects of GA content, feed temperature and feed composition on PV performance were carefully studied. It was found that composite flat membranes exhibited super permeability, high selectivity, high water resistance and good long time stability. Crosslinked PEC flat membrane with0.5wt%GA (CPECM0.5) showed a permeate flux of21.2kg/m2h and water content in permeate of98.1wt%in dehydrating50wt%aqueous isopropanol mixture at70℃. This should be due to both charged water channel structure and chemical crosslinkages of PEC colloidal particles. Water channel structure endowed membrane super permeability and high selectivity, while chemical crosslinkages endowed membrane high water resistance property and long time stability. Crosslinked PEC composite hollow fiber membranes were prepared successfully by dip-coating. Effects of pH of casting PEC dispersion and GA content on PV performance of composite hollow fiber membranes were investigated. Composite hollow fiber membrane prepared under optimum conditions (pH=5.0and GA content1.5wt%) showed the best PV performance (J=1059.4gh-1m-2and α=2036) for dehydrating10wt%aqueous isopropanol mixture at60℃. Pervaporation amplification experiments were performed and a hollow fiber membrane module with0.163m2membrane area was prepared. The hollow fiber membrane module exhibited good PV performance in dehydration of isopropanol. |
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