The Preparation Of PES/PAN Blending Membrane And Study On Its Antifouling Property In MBR

In the paper,the blending membrane was prepared by immersion precipitation phase inverse method with polyethersulfone(PES) and polyacrylonitrile(PAN) as membrane materials,lithium chloride(LiCl) and polyvinylpyrrolidone(PVP) as additives.The effects of different contents of PES,PAN and additives on membrane strength,elongation and viscosity of membran ecasting solution were preliminarily discussed.By the determination of membrane poresize,porosity,pure water flux,BSA rejection rate and scanning electron microscope(SEM) analysis,the effects of serial main factors in the process of membrane preparation on the membrane structure and performance were studied.According to the analysis of the orthogonai experiment results,the optimum PES/PAN blending membrane preparation programs was:PES/PAN(mass ratio)was 8: 2,the total mass fraction was 16%,additives were LiCl and PVP,LiCl/PVP(mass ratio) was 2:8, the total mass fraction was 8%.when the press was 0.2MPa,the pure water flux of the PES/PAN membrane was 302.57L·m^-2·h^-1,which was nearly 1 time higher than the PES membrane prepared under the same condition,but BSA rejection rate was 86.4%with little change.In the experiment,the printing and dyeing wastewater was confected on the basic of the practical water quality of one banner and tent factory in ShangHai.The PES/PAN blending membrane was used to treat the printing and dyeing wastewater in a MBR.On the basic of the orthogonal experiment,the influence of membrane preparation factors on membrane flux and MBR effluent quality were further analyzed,then the optimal membrane preparation method was confirmed.When the MBR effluent quality treated by the membrane prepared by the best method meet the optimal standard of "water quality standards of regenerated and miscellaneous sewage for urban"(GB/T18920-2002),the membrane flux should reach the maximum value as much as possible.Membrane preparation method of the PES/PAN blending membrane was:PES/PAN (mass ratio) was 8:2,the total mass fraction was 15%,additives were LiCl and PVP,LiCl/PVP (mass ratio) was 2:8,the total mass fraction was 10%,membrane casting solution temperature was 40℃,evaporation time was 90s,coagulation bath was solution including 5%DMAc, coagulation bath temperature was 40℃,residence time in coagulation bath was 5min.when the press was 0.2MPa,the pure water flux of the PES/PAN membrane prepared under the above conditions was 505.89 L·m^-2·h^-1,nearly 1 time higher than that of the self-made PES membrane, nearly 2 times higher than commercial PES membrane.The COD_cr,turbidity,chroma and ammonia nitrogen removal efficiency of wastewater in aeration tank were respectively 71.8%, 80.6%,78.6%,19.7%by PES/PAN membrane,slightly lower than PES membrane.When the quality of MBR effluent treated by the PES/PAN membrane meet the reuse standard,the membrane flux basically reach the maximum,the PES/PAN membrane had practical applying value.Under the operational condition of 25℃and 90KPa,the PES/PAN blending membrane, self-made PES membrane,commercial PES membrane were continuously used in a MBR for 24h,it was found that the PES/PAN membrane flux was generally higher than PES membrane, membrane flux variation in unit time of PES/PAN membrane,self-made PES membrane, commercial PES membrane were respectively 0.2559L·m^-2·h^-1·min^-1,0.3366L·m^-2·h^-1·min^-1, 0.3539L·m^-2·h^-1·min^-1,flux of PES/PAN membrane was decreased most slowly,the anti-fouling performance of PES/PAN membrane was better than that of PES membrane.After three kinds membranes were continuously ran in a MBR for 15d,polluted membranes were took out.After chemical cleaning for polluted membranes,PES/PAN membrane,self-made PES membrane, commercial PES membrane were respectively 83.75%,63.58%,61.32%,the pure water flux recovery rate of PES/PAN membrane was the maximum,the anti-fouling performance of PES/PAN membrane was better than that of PES membrane.After 24h in MBR,analyses with scanning electron microscopy(SEM) also indicated that PES membrane was polluted more serious than PES/PAN membrane,the antifouling performance of PES/PAN membrane improved,its utilization period was longer and PES/PAN membrane had practical applying value.