超滤动态膜的类型及其数学模型

总结了超滤过程中形成动态膜的种类,并针对不同种类动态膜在合理假设的基础上,推导出各种变量之间的函数关系。     

有机物极性对超滤膜过滤性能的影响

为研究有机物极性对超滤膜过滤性能的影响,用超滤膜过滤有机物含量相当,有机物极性成分不同的5种水样,基于滤饼堵塞过滤模型和中间堵塞过滤模型对试验结果拟合。研究表明,超滤膜对不同极性有机物去除率由高到低为:VHA>SHA>NEU>CHA,在膜的浓水、正冲水、反洗水及化学清洗废液中,疏水性有机物的比例也相对较高。疏水性有机物浓度由高到低的水样1、水样2、水样3、水样4和水样5,过滤结束时通量分别为起始通量的91%,80%,69%,56%和45%,滤饼层过滤阻力系数kp和膜孔吸附系数kc均随水样中疏水性有机物含量的升高而增大,说明疏水性有机物在膜表面沉积和在膜孔的吸附性能都比亲水性有机物强,疏水性有机物是造成超滤膜有机污染的主要因素。     

小截留分子量共混超滤膜的研究(Ⅱ)——PVDF与PVAc共混前后超滤膜性能的比较

以聚偏氟乙烯 (PVDF)和聚醋酸乙烯酯 (PVAc)共混 ,采用相转化法制备亲水性小截留分子量共混超滤膜 .本文对PVDF和PVAc共混前后超滤膜性能进行了比较 ,结果表明 ,在相同截留率的前提下共混超滤膜的水通量得到提高且在经济性上也有较大的改善     

纳米Al2O3改性PVDF超滤膜的制备及其抗污染性

为改善聚偏氟乙烯(PVDF)超滤膜的水通量和抗污染性能,以无机纳米氧化铝粒子作为添加剂与PVDF共混,采用相转换法流延成膜.用接触角测定仪测得膜与水的接触角用以表征膜的亲水性的变化;用扫描电镜(SEM)和透射电镜(TEM)观察膜的表面孔分布和断面孔的结构及纳米颗粒在膜中的分散情况;采用万能电子试验机(W-56)强度测定仪测定膜的机械性能;利用杯试超滤装置对改性膜的抗污染性能进行研究,并对污染膜上的污染物进行了气相色谱和质谱分析.结果表明,纳米Al2O3的加入量(质量百分比)为2%时,改性膜具有较好的水通量、强度和抗污染性能;纳米Al2O3的加入没有改变膜的微观结构.改性膜在保持PVDF有机膜原有特性的基础上,通过改善PVDF膜的表面亲水性而使其通量和抗污染性能得到增强.     

聚丙烯腈超滤膜的流动特性研究

研究了多孔性聚丙烯腈管式超滤膜的流动特性．考察了不同浓度的ＮａＣｌ,ＫＣＩ,ＭｇＣｌ２, ＮａＳＯ４和ＭｇＳＯ４等电解质溶液对ＵＦ膜的流动特性随区差的变化关系．结果显示,在几种电解质 溶液中．ＵＦ膜的透过流量随压差变化表现出良好的线性关系．这种关系不随电解质种类、浓度和 压差变化．实验过程中ＵＦ膜的微孔结构稳定．使用过程中膜孔因堵塞造成膜污染的机会很小．     

纳米无机添加剂对聚偏氟乙烯膜的疏水性影响

使用非溶剂致相分离法制备聚偏氟乙烯(PVDF)膜,考察了不同铸膜液浓度下PVDF膜的疏水性,研究添加疏水性纳米粒子对PVDF膜疏水性的影响.结果表明:PVDF膜的疏水性随着铸膜液中PVDF含量的升高而降低,疏水性随着纳米颗粒添加量的增大而升高;当铸膜液中PVDF质量分数为10%,纳米SiO2质量分数为2.5%时,PVDF膜的接触角可达136°;当铸膜液中PVDF质量分数为10%,纳米TiO2质量分数为15%时,PVDF膜的接触角可达141°.     

PVDF/纳米Al2O3共混超滤膜的制备及其性能

为提高聚偏氟乙烯超滤膜的亲水性,增强其在水处理中的抗污染能力,以无机纳米氧化铝粒子作为共混剂与聚偏氟乙烯(PVDF)共混,采用相转化法流延工艺制得共混超滤膜.用透射电镜观察纳米氧化铝粒子在膜中的分布;用扫描电镜对膜表面、断面孔结构及孔径进行观测.改性前后超滤膜的测试结果表明,纳米A l2O3的加入改善了PVDF超滤膜的强度、通量、亲水性和抗污染性.     

溶剂结构对CA超滤膜性能的影响

通过研究12种有机溶剂的溶解度参数对CA超滤膜水含量的影响,发现用溶解度参数较大并能与水产生强烈的亲合作用的二甲基甲酰胺DMF作溶剂时,所得的超滤膜孔径较大;用CA-DMF-Licl系统制取了截留分子量(MWCO)为156000的超滤膜,并且较详细地研究了影响膜性能的因素,结果表明在探作压力为0.05MPa时,膜的f=93％～98％,J=96％～120mL/cm~2·h;当用醋酸、二(口恶)烷、四氢呋喃、环氧丙烷组成混合溶剂或用醋酸、二(口恶)烷分别与丙酮配制成混合溶剂时,可得到MWCO为35000的超滤膜。     

SPES/PVDF Binary Membrane as an Alternative Proton Exchange Membrane in Vanadium Redox Flow Battery Application

SPES/PVDF blends were employed to prepare the ion exchange membranes for vanadium redox flow battery(VRB) application for the first time. The addition of the highly crystalline and hydrophobic PVDF effectively limited the swelling behavior of SPES. The vanadium ion permeability of SPES/PVDF membranes was one order of magnitude lower than that of Nafion 117 membrane and pristine SPES membrane. Single cells with SPES/PVDF composite membranes showed significantly lower capacity loss, higher coulombic efficiency and higher energy efficiency than that with Nafion117 and pristine SPES membranes. The blend membrane with 40 wt% of PVDF(denoted as S_(0.6) P_(0.4)) showed energy efficiency of 83.2% at 30 mA?cm~(-2), which was superior to that of the Nafion117 and SPES membranes. In the self-discharge test, S_(0.6) P_(0.4) membrane showed twice longer duration in open circuit decay than that with Nafion 117 membrane. With all the good properties and low cost, the SPES/PVDF membranes are expected to have excellent commercial prospects as ion exchange membranes for VRB system.     

应用前表面三维荧光表征有机膜污染物质的方法

一直以来膜污染都是膜过滤技术中亟待解决的问题,新型的膜污染表征定量技术的开发有助于对膜污染过程的深入了解,并为膜污染控制提供参考.本研究开发了采用前表面荧光法对有机膜污染物质进行直接测量的表征方法.以牛血清蛋白(BSA)为标准污染物进行聚偏二氟乙烯膜(PVDF)的超滤实验,结合使用平行因子分析法,对超滤过程中膜表面累积的污染物进行定量,并评估其准确性.实验证实前表面三维荧光法能够准确地定量黏附在膜表面的BSA污染物,表征结果表明,在膜污染初期BSA的黏附相对较慢,随着过滤进行,膜表面形成滤饼层,黏附作用逐渐加快,造成膜阻力的增大也越来越快.用前表面三维荧光法定量有机膜污染物质,操作简便且准确直观,有望为膜污染的深入研究及膜污染的在线检测提供技术支撑.     

小截留分子量共混超滤膜的研究(Ⅰ)——PVDF与PVA_c的混溶性

以聚偏氟乙烯 (PVDF)和聚醋酸乙烯酯 (PVAc)共混 ,采用相转化法制备亲水性小截留分子量共混超滤膜 .本工作的第一阶段 ,用稀溶液粘度法研究PVDF和PVAc的混溶性 ,结果表明这两种聚合物可以任意的共混比混溶     

小截留分子量共混超滤膜的研究（I）—PVDF与PVAc的混溶性

以聚偏氟乙烯（PVDF）和聚醋酸乙烯酯（PVAc)共混,采用相转化法制备亲水性小截留分了量共混超滤, 本工作的第于阶段,用烯溶液粘度法研究了PVDF和PVAc的混溶性,结果表明这两种聚合物可以任意的共混比混溶。     

絮凝时间对混凝-超滤工艺的膜污染特性影响

为了考察混凝条件对混凝-超滤工艺中有机物去除效果和膜污染的影响,采用静态超滤试验装置对引黄水库水进行了试验研究。研究了絮凝时间对有机物去除效果、絮体特性和超滤膜过滤特性的影响,分析了膜污染的影响因素。试验结果表明：溶解性有机污染物质( DOC、UV254)的去除作用主要发生在快速混合和凝聚过程,后续的絮凝反应过程对溶解性有机污染物质的去除效果没有影响。絮凝反应时间对絮体特性和膜污染特性的影响显著,过短或过长的絮凝时间均会产生不利影响,絮凝时间10 min时絮凝指数处于最佳范围,絮体二维分形维数最小,膜比通量最大,膜总阻力最小,滤饼层阻力最小,膜孔阻力趋于稳定。混凝剂投加量为20 mg/L、絮凝10 min时,絮体特性和超滤膜过滤性能均达到最佳。欠投药和过投药都会对混凝效果、絮体特性和膜阻力特性产生显著影响。     

PVDF膜在碱液下的性能衰减

为了研究聚偏氟乙烯(PVDF)膜在碱液下的性能变化,采用单侧浸润方法对PVDF膜的接触角、临界水入口压力、气体渗透通量、孔径和孔隙率进行了分析.结果表明,当在浓度为1.5 mol/L的碱液中浸润300 h后,PVDF膜表面疏水性下降,膜孔被润湿,传质阻力增大.PVDF膜的疏水性随着碱液浓度的增加而降低.当PVDF膜的浸润时间为150~250 h时,PVDF膜的气体渗透通量和孔径的变化幅度最大.浸润300 h后,PVDF膜的孔隙率增加,传质系数降低,传质阻力增加.随着碱液浓度的增加,PVDF膜的结构性能变化得更为明显.     

PVDF/TiO_2自组装膜的制备及其性能研究

采用溶胶-凝胶相转化法和自组装法制备PVDF/TiO2自组装膜,并利用SEM、接触角、FT-IR和XRD进行了表征;通过纯水通量、孔隙率、膜阻力分析和腐植酸(HA)过滤去除实验,考察了PVDF/TiO2自组装膜的性能,探究了PVDF/TiO2自组装膜在臭氧条件下的催化臭氧化反应机理。结果表明:SEM直观显示膜上存在TiO2粒子;与PVDF原膜相比,纯水的接触角由43.92°减小至25.46°,膜的亲水性显著提高;FT-IR分析,PVDF/TiO2自组装PVDF膜上存在Ti-O键,羟基数量显著增加;XRD表明膜上存在金红石矿型TiO2粒子;自组装后PVDF膜纯水通量由152.5 L·m-2·h-1提高到215.3 L·m-2·h-1,孔隙率由90.2%下降至88.6%,PVDF/TiO2自组装膜对HA具有较强的吸附去除能力,PVDF/TiO2自组装膜对HA的去除率达到75%。     

Effect of slurry conditioning on flocculant-aided filtration of coal tailings studied by low-field nuclear magnetic resonance and X-ray micro-tomography

The present work aimed to study the effect of slurry conditioning on flocculant-aided filtration of coal tailings by the analysis of filtration kinetics and filter cake structure. Laboratory filtration tests of the coal tailings showed that both the shear rate and agitation time have significant effects on filtration rate and cake moisture. Moderate agitation at the shear rate of 92 s⁻¹ was favorable for fast filtration, but high cake moisture was encountered. The low-field ¹H nuclear magnetic resonance (NMR) measurements of the filter cake showed that the slurry conditioning has a significant effect on the residual water in large pores and a negligible effect on the residual water in small pores. The X-ray micro-tomography (XRM) measurements indicated that the filter cake formed at the shear rate of 92 s⁻¹ has more macro-pores and higher porosity than that formed at the shear rate of 53 s⁻¹, hence more residual water was entrapped in filter cake. The slurry conditioning in the presence of flocculant will change the structure of filter cake and affect the filtration performance. There was a paradox between fast filtration rate and low filter cake moisture. The findings enable better understanding of the effect of slurry conditioning on flocculant-aided filtration of coal tailings.     

聚偏氟乙烯多孔膜的结晶行为

为了分析聚偏氟乙烯(PVDF)多孔膜的结晶行为,以聚乙烯吡咯烷酮和无水LiCl为添加剂,采用浸没沉淀相转化法制备PVDF多孔膜.利用傅里叶红外光谱仪、X射线衍射仪和差示扫描量热仪研究了PVDF多孔膜的结晶行为,同时分析了膜结构和结晶行为的关系.结果表明,添加剂的加入促进了β晶型的形成,增大了PVDF膜的结晶度,并可以改变PVDF膜孔结构,但结晶行为对PVDF膜力学性能的影响因为大量膜孔的生成而被忽略.     

超声凝胶对复合超滤膜结构与性能的影响研究

将纯纳米TiO2和改性TiO2粒子分别添加到聚偏氟乙烯(PVDF)超滤膜铸膜液中,在超声辅助下进行凝胶成膜,制备出了不同结构与性能的PVDF复合超滤膜.采用红外光谱(FT-IR)、扫描电镜(SEM)、接触角测定、膜渗透测定等手段考察了超声波作用下不同改性复合膜结构与性能的变化(包括膜微观结构、表面接触角、膜通量、截留率).结果表明:超声凝胶作用提高了改性复合膜表面的粗糙度,使其亲水性得以强化;加速了凝胶过程溶剂与非溶剂之间的微相分离,使膜结构由海绵结构向指状多孔结构转变;在KH570-纳米TiO2与甲基丙烯酸甲酯(MMA)-丙烯酸(AA)-纳米TiO2改性复合超滤膜中,后者改性膜亲水性强化效果较为显著,且在截留率基本保持稳定的前提下,膜通量可达到85 mL/(cm2.h).     

Composite Polymer Electrolyte Membranes based on Nafion and Modified PVDF Electrospun Nanofiber Mats

We fabricated the nanofiber composite membranes by impregnating Nafion into the modified polyvinylidene fluoride(PVDF) electrospinning nanofiber mat for proton exchange membrane fuel cells applications.The hydrophobic PVDF nanofibers mat became to the hydrophilic state by alkali treatment for the full embedding of Nafion into the PVDF network.The fabricated composite membranes exhibit significantly enhanced thermal stabilities,swelling resistance,and observably improved mechanical property compared to the pristine Nafion membrane.When the content of PVDF nanofiber mat is 15.1wt% in the membrane,the proton conductivity of the nanofiber composite membrane is nearly equal to that of pristine Nafion membrane with the same condition.The experimental results show that the prepared composite membrane can be used as a promising polyelectrolyte membrane for fuel cell applications.     

Composite nanofiltration membranes synthesized from PAMAM and TMC by interfacial polymerization

A novel NF membrane prepared with poly(amidoamine) (PAMAM) dendrimer and trimesoyl chloride (TMC) by interfacial polymerization on polysulfone (PSF) ultrafiltration membrane was investigated. Field emission scanning electron microcopy (FESEM) ,atomic force micrograph(AFM) and contact angle(CA) of pure water on PA and PSF substrate were employed to characterize the chemical and physical properties of membranes. The PAMAM concentration,retention of salt solutions and organics were studied on the performance of the NF membrane. From the analyses of SEM and AFM,the polyamide active skin layers of the composite membranes are dense,rough,and finely dispersed nodular structures,packed tightly by the spherical globules. The contact angle of PA nanofitration membrane decreased after polymerization. The higher PAMAM concentration can result in lower flux and higher rejection. The salt rejection of PA membranes decreases in the order K2SO4 > Na2SO4 > MgSO4 > MgCl2 > CaCl2 > NaCl,which indicates that the resulting membranes is nagatively charged. The pH increases from 3 to 10 in the feed resulting in the decrease of the flux and the increase of the rejection for Na2SO4 solution. The molecular weight cut off (MWCO) of the composite NF membrane is nearly 860 kg/mol. The resulted PA membrane can be used to separate small organics and salt solutions.