Preparation And Characterization Of Hydrophilic PVDF Ultrafiltration Membranes

Membrane separation technology has been widely used in many industries due to its own advantages.Polyvinylidene fluoride(PVDF)has become a kind of widely applicable membrane material in the water treatment because of its good physical and stable chemical properties.Research concerning about the modification of PVDF material and the fabrication technology of PVDF membrane have been paid more and more attentions in recently years,especially the amphiphilic blending technology,which is a kind of simple and easy-to-industrial modification method.In this paper,a series of amphiphilic P(VAc-co-HEMA)copolymers were prepared with different hydrophilicity/hydrophobicity ratios using vinyl acetate(VAc)and hydroxyethyl methacrylate(HEMA)as the hydrophobic segment and the hydrophilic segment,respectively.It was found that the hydrophobicity of PVDF was improved by blending with the amphiphilic copolymer and could be stable in the membrane.The optimal molar fraction of HEMA in the copolymer with PVDF was 8.2%.Using PVP-K30 as the pore-forming agent,it was found that the optimal mixing ratio of amphiphilic copolymer and PVDF in the membrane fabrication was 6/19.Moreover,under the same fabrication conditions,PEG-6000 was also used as the pore-forming agent in the formation of PVDF membrane.It was found that PEG-6000 was more suitable than PVP-K30,the better addition ratio was about 6%in the solvent.The prepared hydrophilic PVDF hollow fiber composite ultrafiltration membrane had a pure water flux of 460 L/m2 h at 0.1 MPa.In addition,the membrane rejection and permeate flux for 1000 ppm BSA reached 78%and 148 L/m2 h,respectively,and the membrane has a molecular weight cut off 200 kDa.Moreover,the prepared PVDF membrane has the feature of acid and oxidation resistance to a certain extent,but poor alkali resistance.