【作者】 李旭辉；

【导师】 于水利；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2010， 硕士

【摘要】 膜污染是限制膜技术在给水处理中广泛应用的瓶颈之一。近年来,很多研究表明天然有机物的亲疏水性和分子量分布对膜污染影响重大。本文针对天然有机物特性对膜污染的影响进行了研究。将地表原水中的天然有机物进行树脂分离,得到强疏水性、弱疏水性和亲水性有机物组分。发现各组分比例分别为55.46%、23.62%和23%,前两种组分分子量主要分布在0.5³ kDa,后一种组分分子量主要分布在3¹00 kDa。膜过滤三种组分有机物试验表明,强疏水性有机物,弱疏水性有机物,亲水性有机物对膜污染的程度依次减弱。过滤60 min后原膜比通量分别为60.6%、70.8%和82.0%,而改性膜比通量为75.1%、77.6%和86.0%。原膜对三种组分的DOC截留率依次为15.8%、10.5%和5.2%,改性膜为28.6%、11%和16.3%,说明膜对有机物的截留率与膜通量下降程度没有正相关性,同时改性膜对三种有机组分的去除率高于原膜,但其通量下降率却小于原膜,说明改性膜亲水性的提高有利于膜的水处理能力及抗污染性能的增强。进一步采用腐殖酸、富里酸、牛血清蛋白和聚乙二醇作为天然有机物的模型物质进行了过滤试验。结果表明,有机物的亲疏水性和分子量分布是影响膜污染的主要因素,膜通量恢复率和膜总污染指数呈负相关,膜截留率和有机物的亲疏水性及分子量大小密切相关。通过静态试验研究了膜对腐殖酸的吸附性能。结果表明,膜吸附量随着腐殖酸初始浓度、离子强度和温度增大而增大。膜吸附过程符合Langmuir等温模型,吸附等温线方程为q=18.622·0.047C/（1+0.047C）。吸附过程热力学计算表明,膜吸附腐殖酸是增熵自发过程。膜吸附过程动力学研究表明,吸附过程可通过颗粒内扩散动力学方程较好的描述。对膜过滤地表原水进行了研究。在试验条件下,得出膜通量和水中溶解性有机碳含量之间的关系为J=J0t^{-0.0152exp（0.3735（DOC））}。改性膜对浊度和UV₂₅₄的去除效果均优于原膜。最后,采用水力反冲洗、乙醇、盐酸及氢氧化钠溶液对地表原水污染的膜进行了清洗,结果表明,0.1%盐酸浸泡1 h和0.01 M氢氧化钠溶液浸泡2 h膜通量恢复效果较好。更多还原

【Abstract】 Membrane fouling has been one of the bottlenecks and limiting factors, which is blocking and confining the wide application of membrane technology in the water treatment. In recent years, a great many of studies indicate that hydrophobicity and molecular weight distribution （MWD） of natural organic matter （NOM） have a significant effect on membrane fouling. In this paper, the effect of characteristics of NOM on membrane fouling was investigated.NOM in surface water was isolated into strongly hydrophobic organic, weakly hydrophobic organic and hydrophilic fractions by resins. It was found that the percentages of strongly hydrophobic, weakly hydrophobic and hydrophilic fractions were 55.46%、23.62% and 23% respectively, MWD of strongly hydrophobic and weakly hydrophobic fractions was mainly 0.5³ kDa, hydrophilic fractions was 3¹00 kDa. Filtration tests of the three organic fractions showed that, strongly hydrophobic organics show the highest fouling potential, which followed by weakly hydrophobic and hydrophilic organics, 60 minutes later, flux declines with unmodified membrane was 60.6%, 70.8% and 82.0% of the initial flux, while flux declines with modified PVDF membrane was 75.1%, 77.6% and 86.0%. DOC rejection of unmodified membrane was 15.8%, 10.5% and 5.2%, rejection of modified membrane was 28.6%, 11% and 16.3%, showing that the extent of flux decline may not be associated with the extent of organics rejected. Moreover, the removal ratio of three organic fractions using modified membrane was higher than that of using unmodified membrane, while the flux decline was lower that of unmodified membrane, indicating that the enhancement of hydrophilic property was favorable for the improvements of membrane treatment capacity and anti-fouling characteristics. Further filtration studies about model substance of NOM, Humic acid （HA）, Fulvic acid （FA）, bovine serum albumin （BSA） and polyethylene glycol （PEG） were conducted. Results showed that hydrophobicity and MWD of NOM are the main factors affecting membrane fouling, there was a negative correlation between membrane flux recovery ratio and membrane total fouling index （Ft）, also there was close relation between membrane reject ratio and hydrophilicity/hydrophobicity and MWD of organic matters. Static adsorption experiment was performed to study properties of HA adsorption onto membrane surface. The results showed that adsorption was higher at higher concentration, adsorption increases as ionic strength increases, low temperature decreases adsorption. Langmuir isotherm model fits membrane adsorption well, adsorption isothermal equation was q=18.622·0.047C/（1+0.047C）. Adsorption thermodynamics indicated that adsorption of HA on membrane was entropy increase and spontaneous process. Kinetics tests of membrane adsorption indicated that adsorption can be well describled by Intra-particle diffusion equation.Filtration of raw surface water was disscussed. Under conditions of this study, the quantitative relationship between membrane flux and dissolved organic carbon （DOC） in water was determined as J=J0t^{-0.0152exp（0.3735（DOC））}. The removal ratio of turbidity and UV₂₅₄ using modified membrane was higher than that of using unmodified membrane. Inaddition, membrane which was fouled by raw surface water was cleaned by hydraulic backwash, ethanol, hydrochloric acid and sodium hydroxide solution. Results showed that effectiveness of membrane flux recovery by hydrochloric acid （0.1%） soaking 1 h and sodium hydroxide （0.01 M） solution soaking 2 h is better.更多还原