Preparation Of Polyaminocyclophosphazene Composite Nanofiltration Membrane And Its Antibacterial Properties

With the advantages of low operation cost,relatively high flux,high retention to multivalent ions and low molecular organics,nanofiltration(NF)membranes have been widely utilized in drinking water treatment,seawater pre-treatment,industrial wastewater treatment and dye removal.However,the fouling of NF membrane,especially biofouling,is still a serious problem,which shortens the life of membrane and increases the cost.Therefore,it is one of the most challenging tasks to prepare antibacterial NF membrane using a simple and environmental friendly method.Introducing antibacterial agents to NF membrane via surface modification is the most common method to inhibit bacteria propagation and alleviate biofouling.However,the introduced modification layer usually causes negative effect to the intrinsic permselectivity of NF membrane.In view of the above problems,a new method of preparing novel antibacterial composite NF membrane was proposed.In this paper,a novel positive-charged polyamine-based cyclophosphazene nanofiltration membrane(PEI/HCCP)was prepared via the interfacial polymerization using the branched polyethyleneimine(PEI)as an aqueous monomer,hexachlorocyclotriphosphazene(HCCP)as an organic phase monomer,on the surface of polysulfone ultrafiltration membrane by chlorine substitution reaction.At the same time,a PEI/TMC composite membrane was set as a reference.The optimal membrane formation conditions were determined by analysis of monomer concentration,reaction time,curing conditions and so on.Surface chemical structure,surface morphology,surface hydrophilicity and charge property of the PEI/HCCP composite membrane were characterized by attenuated total reflectance-Fourier transform infrared(ATR-FTIR),scanning electron microscopy(SEM),atomic force microscopy(AFM),contact angle measurement and zeta potential analyzer.The permselectivity and dye rejection were tested by cross-flow filtration test.The results show that when the PEI content was 5 wt%,the HCCP content was lwt%,the reaction time was 5 min and heat treatment temperature was 100? for 15 min,the PEI/HCCP composite membrane obtained the best performance.The rejection to different ions is in the order of MgCl2(97%)>MgSO4(88%)>NaCl(87%)>Na2SO4(58%),and the permeation flux is about 55 L/m2h when tested at 25?,1.5MPa.In addition,Gram-negative E.coli and Gram-positive S.aureus were used as the bacterial model to evaluate the antibacterial properties of the membranes using shake flask method.The morphology of the bacteria on the membrane surface and the changes of the membrane surface were observed by SEM.We see that the PSf membrane does not show obvious antibacterial property.The bacteria killing ratio of PEI/TMC composite membrane was 35%-60%,while the PEI/HCCP composite membrane was nearly 100%.Moreover,the bacteria could be completely eliminated by 1.5 h contacting with PEI/HCCP composite membrane.The bacteria present normal morphology on polysulfone membrane surface,while the structure was destroyed on the surface of PEI/HCCP composite membrane,which further proved that the PEI/HCCP composite membrane has good antibacterial property.