| Polymer organic polymer polyvinylidene fluoride （PVDF） is admired for its excellent performance,such as chemical stability, radiation resistance, fouling resistance, heat resistance and film formingproperties. However, due to the lower PVDF surface energy, the PVDF membrane has a stronghydrophobic, and they are vulnerable to be polluted in the membrane separation process and result in thewater production of the film to reduce. Modification of membrane materials is the fundamental way tosolve the membrane fouling.In order to enhance the PVDF ultrafiltration membranes’ hydrophilic and its anti-pollution capacity inthe water treatment process, this paper adopt phase inversion method to prepare inorganic nanoparticlesand PVDF blends modified ultrafiltration membranes. Pure water flux of these membranes wereinvestigated with a cup ultrafiltration device; pure water contact angle was examined with contact anglemeasurements to characterize membrane hydrophilic change; strength measuring instrument was used tomeasure the mechanical properties of the membrane; the retention efficiency of modified membranes wastested with the bovine serum albumin （BSA） solution; liquid-liquid displacement method was used todetermine the membrane pore size and pore size distribution; The results of pure water flux, mechanicalstrength, contact angle and rejection rate tests showed that pure water flux of the modified membranePVDF1311is167.43L m-2h-1, and the unmodified membrane PVDF21000is93.28L m-h-1, pure water fluxincrease79.5%; the mechanical strength of the modified membrane increase41.6%; modified membranePVDF1311pure water contact angle dropped from78.68°to50.54°, compare to unmodified membrane thehydrophilic has been significantly improved; membrane pore size and pore size distribution of the testsshow that the nano-modified membrane’ average pore size were large than unmodified membranes, theirpore size distribution is more uniform.The membranes’ surface, cross-section morphology and membrane internal pore structure wereanalyzed with scanning electron microscope （SEM） and atomic force microscopy （AFM）. AFM test resultsshow that the average surface roughness of the nano-modified membrane was increased, which result inthe increase of filtration area of the ultrafiltration membrane, thereby increasing the modified pure waterflux; SEM test results show that the modified membrane and unmodified membranes have parallel densecortex and finger-like hole structure, the modified membrane pore are more smooth, the modifiedmembranes’ anti-pollution performance were improved during operation. PVDF’ crystal was tested byFourier transform infrared spectroscopy （FT-IR）, the results showed that the nano-components caused thecasting solution stress change, so that the modified membrane of PVDF α crystalline form was reduced,and the number of β polymorphs was increased; in the infrared spectrum of the modified membrane exceptto the nano-particle’s characteristic absorption peaks has no a new absorption peak was generated,confirming the organic-inorganic blends modified was pure physical blend.In order to investigate the nanoparticles’ thermodynamic effects in the film-forming process of PVDFultrafiltration membrane, cloud point titration was determined. The results show that nano-componentsdecrease the ability to accommodate the non-solvent in the casting solution; smaller non-solventconcentration can be cured film. UV spectrophotometer transmittance decline curve of the casting solutionsystem was measured to investigate the kinetic effects of nano-components in the PVDF film formation process, the results showed that nano-components in the casting solution reduced solvent and non-solventtwo-way transfer resistance, shorten the time from the casting solution immersed in the gelation to the filmwas cured.The PVDF membranes modified by inorganic nano-sized particles and the unmodified PVDFmembranes were used to treat with the waste water of oil filed. The results showed that these two kinds ofmembranes has basically the same pollutant removal rate, the major pollutants in ultrafiltration water, oilcontent <0.8mg L-1, turbidity <1.9NTU, suspended solids <0.4mg L-1, the COD removal rate reached90%, TOC removal rate was more than95%; modified PVDF ultrafiltration membranes’ flux decay rateand flux cleaning recovery rate experiment showed that flux attenuation rate of nano-modified membranewas dropped, flux recovery rate was increased, by adding the nanoparticles into PVDF ultrafiltrationmembrane enhanced its unti-fouling ability. |
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