MWCNTs预涂覆及预吸附处理缓解低压膜腐殖酸污染的机制研究
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摘要
以腐殖酸(Humic Acid,HA)为研究对象,采用多壁碳纳米管(Multiwalled Carbon Nanotubes,MWCNTs)对聚偏氟乙烯(Polyvinylidene Fluoride,PVDF)平板超滤膜进行预涂覆改性处理,并与等量MWCNTs分散状态时吸附处理HA对膜污染的缓解效果进行了对比,考察了MWCNTs在处理HA过程中缓解膜污染的机制.同时,分析了MWCNTs投量和溶液离子变化对MWCNTs吸附及截留作用缓解膜污染的影响.结果表明,MWCNTs预涂覆与吸附相比,能够更有效地缓解膜污染,其中,分散剂为乙醇的MWCNTs预涂覆层对膜污染的缓解效果最好.增加MWCNTs投量不能无限地提高其对HA的吸附及截留效果;添加Na~+会造成MWCNTs对HA的吸附及截留效果变差;添加Ca~(2+)能够提高MWCNTs对HA的吸附及截留效果.膜表面污染照片及膜电镜观测结果表明,乙醇分散MWCNTs在超滤膜(UF)表面形成的预涂覆层呈均匀的层状结构,HA被拦截在MWCNTs层的多孔结构内,不易进入PVDF膜膜孔,反洗时易脱附,可逆性高;纯水分散MWCNTs在超滤膜表面形成的预涂覆层易于团聚,HA容易透过MWCNTs涂覆层进而堵塞PVDF膜膜孔,可逆性低;MWCNTs预吸附处理后形成MWCNTs和HA的包裹体,不经微滤膜滤除,会在PVDF膜表面产生复合污染.
Polyvinylidene fluoride(PVDF) flat ultrafiltration membranes was modified with multi-walled carbon nanotube(MWCNTs) to remove humic acid(HA). To understand the mechanism of MWCNTs on membrane fouling control in the removal of HA, the adsorption and the interception performances of the pre-deposited MWCNTs(MWCNTs layer) were systematically compared. Besides, the effects of MWCNTs dosage and solution ions were further analyzed. The results reveal that MWCNTs deposition was benefit for fouling control. The MWCNTs layer formed by using ethanol as dispersant had the optimal efficiency on fouling alleviation. Increasing the MWCNTs dosage can′t increase the adsorption and retention of HA indefinitely. The addition of Na~+ will reduce, but Ca~(2+) can improve the adsorption and retention of HA by MWCNTs. The fouling membrane surface was observed with optical and scanning electron microscope. The results demonstrate that the pre-deposited MWCNTs dispersed with ethanol had a uniform layer structure. HA was retained in the porous structure of the MWCNTs layer and was difficult to enter the PVDF membrane pores. HA was easily desorbed easy desorption of HA during backwash improves the membrane′s reversibility. However, MWCNTs despersed with water were prone to aggregate. HA was tend to adhere on the PVDF membrane surface or enter into the pores of PVDF membrane, which reduced membrane reversibility. After pre-adsorption of HA by MWCNTs, complex pollution of MWCNTs/HA would form on the surface of PVDF membrane, if not removed by microfiltration.
Polyvinylidene fluoride(PVDF) flat ultrafiltration membranes was modified with multi-walled carbon nanotube(MWCNTs) to remove humic acid(HA). To understand the mechanism of MWCNTs on membrane fouling control in the removal of HA, the adsorption and the interception performances of the pre-deposited MWCNTs(MWCNTs layer) were systematically compared. Besides, the effects of MWCNTs dosage and solution ions were further analyzed. The results reveal that MWCNTs deposition was benefit for fouling control. The MWCNTs layer formed by using ethanol as dispersant had the optimal efficiency on fouling alleviation. Increasing the MWCNTs dosage can′t increase the adsorption and retention of HA indefinitely. The addition of Na~+ will reduce, but Ca~(2+) can improve the adsorption and retention of HA by MWCNTs. The fouling membrane surface was observed with optical and scanning electron microscope. The results demonstrate that the pre-deposited MWCNTs dispersed with ethanol had a uniform layer structure. HA was retained in the porous structure of the MWCNTs layer and was difficult to enter the PVDF membrane pores. HA was easily desorbed easy desorption of HA during backwash improves the membrane′s reversibility. However, MWCNTs despersed with water were prone to aggregate. HA was tend to adhere on the PVDF membrane surface or enter into the pores of PVDF membrane, which reduced membrane reversibility. After pre-adsorption of HA by MWCNTs, complex pollution of MWCNTs/HA would form on the surface of PVDF membrane, if not removed by microfiltration.
引文
Ajmani G S,Goodwinb D,Marshb K,et al.2012.Modification of low pressure membranes with carbon nanotube layers for fouling control[J].Water Research,46(17):5645-5654
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Cai Z,Benjamin M M.2011.NOM fractionation and fouling of low-pressure membranes in microgranular adsorptive filtration[J].Environmental Science & Technology,45(20):8935-8940
Costa A R,Pinho M N,Elimelech M.2006.Mechanisms of colloidal natural organic matter fouling in ultrafiltr ation[J].Journal of Membrane Science,81(1):716-725
Filloux E,Gallard H,Croue J.2012.Identification of effluent organic matter fractions responsible for low-pressure membrane fouling[J].Water Research,46(17):5531-5540
GallagherM J,Huang H,Schwab K J,et al.2013.Generating backwashable carbon nanotube mats on the inner surface of polymeric hollow fiber membranes[J].Journal of Membrane Science,446:59-67
Hamad J Z,Dua R,Kurniasari N,et al.2014,Irreversible membrane fouling abatement through pre-deposited layer of hierarchical porous carbons[J].Water Research,65:245-256
Hong S K,Elimelech M.1997.Chemical and physical aspects of natural organic matter(NOM) Fouling of Nanofiltration Membranes[J].Journal of Membrane Science,132(2):159-181
侯娟,邵嘉慧,何义亮.2010.溶液环境对荷电超滤膜和传统中性超滤膜去除天然有机物的影响[J].环境科学,31(6):1518-1524
Hyung H,Kim J.2008.Natural organic matter(NOM) adsorption to multi-walled carbon nanotubes:effect of NOM characteristics and water quality parameters[J].Environmental Science & Technology,42(12):4416-4421
Katsoufidou K,Yiantsios S G,Karabelas A J,et al.2005.A Study of ultrafiltration membrane fouling by humic acids and flux recovery by backwashing:experiments and modeling[J].Journal of Membrane Science,266(1):40-50
Kuberkar V T,Davis R H.2000.Modeling of fouling reduction by secondary membranes[J].Journal of Membrane Science,168(1/2):243-258
Lohwacharin J,Takizawa S.2009.Effects of nanoparticles on the ultrafiltration of surface water[J].Journal of Membrane Science,326(2):354-362
Lu C,Su F.2007.Adsorption of natural organic matter by carbon nanotubes[J].Separation and Purification Technology,58(1):113-121
Madaeni S S,Zinadini S,Vatanpour V,et al.2011.Convective flow adsorption of nickel ions in PVDF membrane embedded with multi-walled carbon nanotubes and PAA coating[J].Separation and Purification Technology,80(1):155-162
Platkowska-Siwiec A,Bodzek M.2011.The influence of membrane and water properties on fouling during ultrafiltration[J].Journal of Desalination and Water Treatment,35(1/3):235-241
Shao J H,Hou J,Song H.2011.Comparison of humic acid rejection and flux decline during filtration with negatively charged and uncharged ultrafiltration membranes[J].Water Research,5(2):473-482
Tian J Y,Ernst M,Cui F,et al.2013.Effect of different cations on UF membrane fouling by NOM fractions[J].Chemical Engineering,23:547-555
Upadhyayula V K K,Deng S,Mitchell M C,et al.2009.Application of carbon nanotube technology for removal of contaminants in drinking water:A review[J].Science of The Total Environment,408(1):1-13
王利颖,石洁,王凯伦,等.2017.纳米管改性PVDF中空纤维超滤膜处理二级出水抗污染性能研究[J].环境科学,38(1):220-228
Wang X,Lu J,Xing B,et al.2008.Sorption of organic contaminants by carbon nanotubes:Influence of adsorbed Organic Matter[J].Environmental Science & Technology,42(9):3207-3212
Yang S,Hu J,Chen C,et al.2011.Mutual effects of Pb(II) and humic acid adsorption on multiwalled carbon nanotubes/polyacrylamide composites from aqueous solutions[J].Environmental Science & Technology,45(8):3621-3627
Yang X,Lee J,Yuan L,et al.2013.Removal of natural organic matter in water using functionalised carbon nanotube buckypaper[J].Carbon,59(4):160-166
Ajmani G S,Chob H,Talia E,et al.2014.Static and dynamic removal of aquatic natural organic matter by carbon nanotubes[J].Water Research,59: 262-270
Cai Z,Benjamin M M.2011.NOM fractionation and fouling of low-pressure membranes in microgranular adsorptive filtration[J].Environmental Science & Technology,45(20):8935-8940
Costa A R,Pinho M N,Elimelech M.2006.Mechanisms of colloidal natural organic matter fouling in ultrafiltr ation[J].Journal of Membrane Science,81(1):716-725
Filloux E,Gallard H,Croue J.2012.Identification of effluent organic matter fractions responsible for low-pressure membrane fouling[J].Water Research,46(17):5531-5540
GallagherM J,Huang H,Schwab K J,et al.2013.Generating backwashable carbon nanotube mats on the inner surface of polymeric hollow fiber membranes[J].Journal of Membrane Science,446:59-67
Hamad J Z,Dua R,Kurniasari N,et al.2014,Irreversible membrane fouling abatement through pre-deposited layer of hierarchical porous carbons[J].Water Research,65:245-256
Hong S K,Elimelech M.1997.Chemical and physical aspects of natural organic matter(NOM) Fouling of Nanofiltration Membranes[J].Journal of Membrane Science,132(2):159-181
侯娟,邵嘉慧,何义亮.2010.溶液环境对荷电超滤膜和传统中性超滤膜去除天然有机物的影响[J].环境科学,31(6):1518-1524
Hyung H,Kim J.2008.Natural organic matter(NOM) adsorption to multi-walled carbon nanotubes:effect of NOM characteristics and water quality parameters[J].Environmental Science & Technology,42(12):4416-4421
Katsoufidou K,Yiantsios S G,Karabelas A J,et al.2005.A Study of ultrafiltration membrane fouling by humic acids and flux recovery by backwashing:experiments and modeling[J].Journal of Membrane Science,266(1):40-50
Kuberkar V T,Davis R H.2000.Modeling of fouling reduction by secondary membranes[J].Journal of Membrane Science,168(1/2):243-258
Lohwacharin J,Takizawa S.2009.Effects of nanoparticles on the ultrafiltration of surface water[J].Journal of Membrane Science,326(2):354-362
Lu C,Su F.2007.Adsorption of natural organic matter by carbon nanotubes[J].Separation and Purification Technology,58(1):113-121
Madaeni S S,Zinadini S,Vatanpour V,et al.2011.Convective flow adsorption of nickel ions in PVDF membrane embedded with multi-walled carbon nanotubes and PAA coating[J].Separation and Purification Technology,80(1):155-162
Platkowska-Siwiec A,Bodzek M.2011.The influence of membrane and water properties on fouling during ultrafiltration[J].Journal of Desalination and Water Treatment,35(1/3):235-241
Shao J H,Hou J,Song H.2011.Comparison of humic acid rejection and flux decline during filtration with negatively charged and uncharged ultrafiltration membranes[J].Water Research,5(2):473-482
Tian J Y,Ernst M,Cui F,et al.2013.Effect of different cations on UF membrane fouling by NOM fractions[J].Chemical Engineering,23:547-555
Upadhyayula V K K,Deng S,Mitchell M C,et al.2009.Application of carbon nanotube technology for removal of contaminants in drinking water:A review[J].Science of The Total Environment,408(1):1-13
王利颖,石洁,王凯伦,等.2017.纳米管改性PVDF中空纤维超滤膜处理二级出水抗污染性能研究[J].环境科学,38(1):220-228
Wang X,Lu J,Xing B,et al.2008.Sorption of organic contaminants by carbon nanotubes:Influence of adsorbed Organic Matter[J].Environmental Science & Technology,42(9):3207-3212
Yang S,Hu J,Chen C,et al.2011.Mutual effects of Pb(II) and humic acid adsorption on multiwalled carbon nanotubes/polyacrylamide composites from aqueous solutions[J].Environmental Science & Technology,45(8):3621-3627
Yang X,Lee J,Yuan L,et al.2013.Removal of natural organic matter in water using functionalised carbon nanotube buckypaper[J].Carbon,59(4):160-166