| Two kinds of monomers, acrylic acid (AA) and sodium styrene sulfonate (SSS), werecopolymerised onto the surface of polypropylene nonwoven fabric (PPNWF) underultraviolet irradiation. The effects of monomer concentration, exposure time, crosslinkerand photosensitizer concentrations on grafting were investigated in detail. The morphology,microstructure and properties of the grafted nonwovens were examined by infraredspectroscopy, scanning electron microscopy, thermal gravimetric analyzer and X-rayphotoelectron spectroscopy. The adsorptive separation of the grafted towards the cationicdye was estimated in the thermodynamic, kinetic, and equilibrium aspects for the dyesolutions at the different temperatures, initial concentrations and pH values. In addition,the adsorption of the grafted with double monomer towards Cu(II) was studied briefly. Themajor results and conclusions are listed as follows:(1) The anionic monomer, AA, was successfully grafted onto the surface of PPNWFunder UV irradiation. The degree of grafting was linearly increased with monomerconcentration. The photo polymerization was complete within20mins. The degree ofgrafting was highest at1.5%of the concentrations of both photosensitizer and crosslinker.(2) PPNWF-g-AA presented good cationic dye adsorption performance. A highgrafting degree resulted in an enhanced dye removal. The dye amount of adsorption of thegrafted was significantly increased at a high initial concentration. The increased dyesolution temperature seemed not conducive to adsorption. The reduced pH and the dosedsodium chloride in the dye solutions caused the low dye removal.(3) The isothermal equilibrium adsorption of the grafted followed the Freundlichisotherm model, and the adsorption dynamic process prefered the Lagergren’spseudo-second order kinetic equation. The adsorption was spontaneous thermodynamically.The adsorption process might be described by a double exponential model to some extent,which implied the spatial nonuniformity of the grafting polymers in the nonwoven. (4) In the process of filtration, the water flux was proportional to the appliedtrans-fabric pressure. The grafting decreased the water flux of nonwoven. The high pHvalue of source solution reduced flux remarkably. The flux of source solution with0.5MNaCl was2230L/m2h, in comparison with the flux840L/m2h of deionized water. The dyeremoval maintained over91%with total permeated volume25liters of the source solutionat dye concentration of10mg/L.(5) During the dye adsorption-desorption cycles, the dye removal was getting high.(6) The polar styrene sulfonate couldn’t be grafted onto the surface of hydrophobicPPNWF, while the presences of both the surfactant sodium dodecyl benzene sulfonate andthe pre-grafted polyacrylic acid increased its grafting.(7) During the adsorption of cationic dye, PPNWF-g-(AA-SSS) demonstrated lessdependence on the pH value of dye solution, as compared to PPNWF-g-AA. Theadsorption rate and the removal rate of PPNWF-g-(AA-SSS) were fastest and highest atpH=9.5respectively, while they were slowest and lowest at pH=2.1respectively.The features and innovations of the thesis are as follows:(1) The anionic monomers, AA and SSS, were photo-grafted onto the surface of PPnonwovens. The dye removal of PPNWF-g-AA maintained over91%with total permeatedvolume25liters of the source solution at dye concentration of10mg/L and at the averagewater flux of30L/m2h. During the dye adsorption-desorption cycles, the dye removal wasgetting high.(2) Sodium styrene sulfonate was only grafted onto the surface of PPNWF-g-AA,accroding to the results of X-ray photoelectron spectroscopy and IR spectroscopy, as wellas the adsorptions of copper ions and cationic dye. |
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