Preparation And Performance Research Of Nanofibrous Composite Membranes Applied In Water Treatment

Due to the increasing population and energy crisis,the target of membrane separation with advantages of high flux and low operating pressure becomes the research focus.Recently,taking advantages of high porous and low permeate pressure,the electrospinning nanofibrous substrates have been widely applied in prearation of thin film nanofibrous composite(TFNC)membranes,used in water treatment filed.Compared with conventional membranes,these TFNC membranes exhibited a high flux at low pressure.Herein,combined with phase inversion and LBL(layer-by-layer)assemble,two kinds of TFNC membrane were fabricated,which were applied in nanofiltration and heavy metal removal,respectively.(1)High flux composite nanofiltration(NF)membranes were prepared using a phase inversion method after casting polyether sulfone(PES)or PES/sulfonated poly ether ether ketone(SPEEK)coatings on layer-by-layer(LBL)modified electrospun polyester(PET)nanofibrous membranes.Due to the macro-voids sublayer of convention membranes substituted by nanofibrous scaffolds,these developed composite membranes possessed a ultrathin phase-inversion layer(?10 um).The factors were investigated including electrospinning condition,chitosan(CHI)/algnate(ALG)concentration,thickness of separation layer,PES concentration,exposed time,coagulating temperature,thermal treatment,and sulfonated poly ether ether ketone(SPEEK)content.With the optimized condition,the obtained membrane exhibited a flux of as high as?70 Lm-2h-1,,which is even higher than the conventional NF membranes with a MgSO4 rejection of?80%.(2)Chitosan(CHI)/alginate(ALG)film composite membranes were prepared by layer-by-layer assembly on the surface on the electrospun polyester(PET)nanofibrous membranes.The separation layer was consisted of layer-by-layer structure of CHI/ALG,possessing multi-adsorptive sites of amino-and carboxyl-groups,indicating its potential application on removing differently charged heavy metal ions.The factors influencing the structure and performance of membrane,including pH,bilayer number,polyelectrolyte concentration,terminating layer and Cu(?)/Cr(?)concentration,have been investigated.With the optimized condition,the obtained membrane exhibited a high efficiency for Cu(?)/Cr(?)removal(100%/90%,100 ppm/40 ppm)under a low operation pressure of 0.08 MPa.After 3 cycles of repeating use,the membrane still remained-70%Cu(?)/Cr(?)removal efficiency,which indicates a stable recycle property.