Polyvinylidene fluoride (PVDF) ultrafiltration membranes have
been extensively applied in wastewater treatment because they
have such advantages as thermal and mechanical stability,
microbiological resistance and low cost over other polymer materials
[9,10]. The hydrophobic PVDF membrane is susceptible to
fouling while treating aqueous solutions containing natural
organic matters, e.g. proteins, which are prone to be easily
absorbed onto the membrane surface or block the surface pores
with elongated time. Accordingly various methods have been proposed
to modify PVDF membranes. In general, these methods consist
basically in (a) introduction of hydrophilic polymers with
different characteristics with PVDF, (b) atom transfer radical polymerization
method and (c) surface chemical modification of PVDF,
including organic substance grafting and inorganic substance
grafting. Ochoa [11] reported that asymmetric ultrafiltration membranes were obtained by introducing PMMA into PVDF solution.
It was observed that the membrane fouling and the sieving
effect of membranes were all related to the hydrophilic extent of
membranes surface. Singh [12] used atom transfer radical polymerization
to modify PVDF membranes with pyridinium exchange
group. Results indicated that it was possible to tune the ion-exchange
capacity and the average pore size in rational ways, by
changing polymerization time. Li [13] studied that oily waste
water was treated by organic–inorganic composite tubular ultrafiltration
membranes prepared by blending PVDF membrane with
inorganic nano-sized alumina particles. Retentions of COD and
TOC through membranes were more than 90% and 98%, respectively.
The results indicated that after UF treatment, both oil content
and suspended solids content were below 1 mg/L. However,
it was clearly found that the permeation water flux was so small
that there existed no applied prospect. Nunes [14] reported that
dense hydrophilic composite ultrafiltration membranes were prepared
by coating a thin layer of polyether-block-polyamide copolymer
on an asymmetric PVDF support. Membranes with molecular
weight cut off (MWCO) of 800–4500 and water permeability of
2.3–9.4 L/(m2 h bar) were obtained. The composite membranes
exhibited lower susceptibility to fouling. Bottino [15] studied sulfonated
polyvinylidene fluoride membranes systematically and
found that the modification process increased the hydrophilicity
and antifouling capability of the membranes. Munari [16] prepared
anisotropic sulfonated PVDF membranes, which exhibited excellent
antifouling ability against protein.
Polyvinylidene fluoride (PVDF) ultrafiltration membranes havebeen extensively applied in wastewater treatment because theyhave such advantages as thermal and mechanical stability,microbiological resistance and low cost over other polymer materials[9,10]. The hydrophobic PVDF membrane is susceptible tofouling while treating aqueous solutions containing naturalorganic matters, e.g. proteins, which are prone to be easilyabsorbed onto the membrane surface or block the surface poreswith elongated time. Accordingly various methods have been proposedto modify PVDF membranes. In general, these methods consistbasically in (a) introduction of hydrophilic polymers withdifferent characteristics with PVDF, (b) atom transfer radical polymerizationmethod and (c) surface chemical modification of PVDF,including organic substance grafting and inorganic substancegrafting. Ochoa [11] reported that asymmetric ultrafiltration membranes were obtained by introducing PMMA into PVDF solution.It was observed that the membrane fouling and the sievingeffect of membranes were all related to the hydrophilic extent ofmembranes surface. Singh [12] used atom transfer radical polymerizationto modify PVDF membranes with pyridinium exchangegroup. Results indicated that it was possible to tune the ion-exchangecapacity and the average pore size in rational ways, bychanging polymerization time. Li [13] studied that oily wastewater was treated by organic–inorganic composite tubular ultrafiltrationmembranes prepared by blending PVDF membrane withinorganic nano-sized alumina particles. Retentions of COD andTOC through membranes were more than 90% and 98%, respectively.The results indicated that after UF treatment, both oil contentand suspended solids content were below 1 mg/L. However,it was clearly found that the permeation water flux was so smallthat there existed no applied prospect. Nunes [14] reported thatdense hydrophilic composite ultrafiltration membranes were preparedby coating a thin layer of polyether-block-polyamide copolymeron an asymmetric PVDF support. Membranes with molecularweight cut off (MWCO) of 800–4500 and water permeability of2.3–9.4 L/(m2 h bar) were obtained. The composite membranesexhibited lower susceptibility to fouling. Bottino [15] studied sulfonatedpolyvinylidene fluoride membranes systematically andfound that the modification process increased the hydrophilicityand antifouling capability of the membranes. Munari [16] preparedanisotropic sulfonated PVDF membranes, which exhibited excellentantifouling ability against protein.
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