Preparation of forward osmosis membrane modified by tannic acid-iron(Ⅲ)and its antifouling performance
The active layer of cellulose triacetate(CTA)forward osmosis membrane was modified by surface coating.Firstly,a metal-polyphenol precursor layer was constructed by self-assembly of tannic acid(TA)and iron ions(Fe3+)on the membrane surface,and then the hydrophilic functional layer of tannic acid/diethylenetriamine(TA/DETA)was further coated.Finally,the Ag/polyvinylpyrrolidone(PVP)antibacterial functional layer was in-situ formed on the membrane surface by the reductive property of TA,and the TA/Fe3+-TA/DETA-Ag/PVP modified membrane was prepared.The change of membrane water flux during dynamic fouling experiment was investigated using a cross flow forward osmosis device.The surface morphology and the composition of the original membranes and fouled membranes were analyzed by scanning electron microscopy(SEM)and infrared spectroscopy(FTIR).The distribution of bacteria and pollutants on the fouled membrane surface was characterized by confocal laser scanning microscope(CLSM).And the cleaning efficiency of original CTA membrane and modified membrane was compared.The results showed that the water contact angle of TA/Fe3+-TA/DETA-Ag/PVP modified membrane decreased from 78.79° to 33.05°,and the hydrophilicity was significantly improved.After the 15 days dynamic fouling experiment,the flux of original CTA membrane and TA/Fe3+-TA/DETA-Ag/PVP modified membrane decreased to 52.14%and 72.81%of their initial flux,respectively.Compared with CTA membrane,the amount of live bacteria and organic contaminants on the surface of TA/Fe3+-TA/DETA-Ag/PVP modified membrane was substantially reduced.After hydraulic cleaning and osmotic backwashing,the flux recovery of TA/Fe3+-TA/DETA-Ag/PVP modified membrane was up to 80.37%,which was much higher than 49.88%of CTA membrane,and the TA/Fe3+-TA/DETA-Ag/PVP modified membrane exhibited a better antifouling performance.
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