聚砜中空纤维超滤膜制备及性能

以聚砜(PSU)为成膜聚合物,聚乙烯吡咯烷酮(PVP)为成孔添加剂,二甲基乙酰胺为溶剂,采用干–湿法纺丝工艺和浸没沉淀相转化法制备了PSU中空纤维膜,研究了添加剂含量、凝固浴温度、干纺程对中空纤维膜结构与性能的影响。结果表明,随着添加剂PVP含量的增大,在PSU中空纤维膜表皮层形成贯通膜孔,皮层变薄,孔径变大,指状孔发达,水通量提高,截留率下降;凝固浴温度升高对膜水通量起到一定的抑制作用,凝固浴温度为30℃时,制得的膜具有较高的水通量和卵清蛋白截留率,以及较高的孔隙率;干纺程的大小对膜性能有重要影响,当干纺程为11 cm时,膜纯水通量为200 L/(m~2·h),截留率为90%,综合性能较好。     

基于仿生矿化的PTFE中空纤维膜亲水改性研究

由于聚四氟乙烯(PTFE)材料具有强疏水性和极低的表面能,使得PTFE中空纤维膜润湿性差,难以处理水性溶液,限制了其应用过程和领域,因此开展PTFE中空纤维膜亲水化改性研究具有重要的现实意义。利用仿生矿化技术对PTFE中空纤维膜进行表面改性,研究了不同矿化工艺对膜亲水性能的影响,并对改性前后PTFE中空纤维膜的官能团、水通量、气通量、孔径及孔径分布进行了表征。研究表明,仿生矿化能够提高PTFE中空纤维膜的亲水性和水通量,同时由于碳酸钙分子进入膜孔内部,使孔径分布更加均匀,平均孔径和气通量减小。     

硅藻土/α-Al_2O_3中空纤维膜的制备与表征

文中采用相转化烧结的方法制备了硅藻土/α-Al_2O_3中空纤维膜,研究了硅藻土百分含量和烧结温度对制备的中空纤维膜性能的影响,该中空纤维膜具有较高的纯水通量和较高的机械强度,在硅藻土百分含量为10%,烧结温度为1 250℃,烧结时间为2 h的条件下,制备的硅藻土/α-Al_2O_3中空纤维膜抗弯强度为15.83 MPa,在操作压力为0.15 MPa时,纯水通量为3 227.18 L/(m~2·h),平均孔径范围为0.27～0.40μm,泡压范围为0.22～0.43 MPa。在大肠杆菌的去除试验中,去除率达到99.99%以上,能够有效去除饮用水中的大肠杆菌,可用于饮用水的微滤除菌应用。     

UHMWPE/EVA中空纤维膜的制备及性能研究

通过在超高相对分子质量聚乙烯(UHMWPE)纺丝液中添加不同含量的乙烯-醋酸乙烯酯共聚物(EVA),采用热致相分离法制备了UHMWPE/EVA中空纤维膜,实现对UHMWPE中空纤维膜的亲水改性,并通过扫描电子显微镜、接触角测量仪、差示扫描量热仪、万能材料试验机等对中空纤维膜的结构与性能进行了表征,采用自制UHMWPE/EVA中空纤维膜过滤装置对中空纤维膜的过滤性能及防污性能进行了评价。结果表明:随着EVA含量的增加,UHMWPE/EVA中空纤维膜的断面结构变得致密,熔点及结晶度下降,接触角减小,亲水性提高,但其拉伸强度有所下降;随着EVA含量的增加,UHMWPE/EVA中空纤维膜的孔隙率增大,但随着EVA添加质量分数(相对UHMWPE质量)进一步增大到20%,孔隙率则随之下降;当加入EVA质量分数(相对UHMWPE质量)15%时,UHMWPE/EVA中空纤维膜的纯水通量和截留率以及水通量回复率均达到最大值,即其纯水通量为435.77 L/m~2·h,对牛血清蛋白及碳素墨水的截留率分别为68.5%和93.95%,水通量回复率达94.66%;UHMWPE/EVA中空纤维膜中,EVA的最佳添加量其质量分数(相对UHMWPE质量)为15%。     

熔融纺丝拉伸法制备PP/PPOH中空纤维膜的研究

根据片晶分离致孔的机理,利用羟基化改性聚丙烯(PPOH)与聚丙烯(PP)共混,通过熔融纺丝拉伸法制备具有一定亲水性的PP/PPOH中空纤维膜,探究了热处理温度及热拉伸温度对PP/PPOH中空纤维膜的结构与性能的影响。结果表明：当热处理温度为130℃时,PP/PPOH初纺中空纤维膜的结晶度高,力学性能较好,纯水通量为102.4 L/(m²·h);当热处理温度为130℃、热拉伸温度为130℃时,PP/PPOH中空纤维膜的结晶度最高,达39.4%,拉伸强度达93.1 MPa,表面微孔结构完善,纯水通量最高,达118.4 L/(m²·h)。     

推压成型工艺对PTFE初生中空纤维力学性能的影响

聚四氟乙烯(PTFE)初生中空纤维是拉伸制备PTFE中空纤维膜的先驱体,其力学性能直接影响制膜工艺和产品性能。系统考察了推压成型温度、速度和压力条件对PTFE初生纤维力学性能的影响,并通过纤维表面微观结构分析,探究其力学性能变化的内在因素。结果表明,较高的推压成型温度和压力、较低的速度,有利于制备综合力学性能较优的PTFE初生中空纤维;纤维表面树脂初级粒子纤维化是影响其力学性能的内因;相比,推压成型温度和压力变化对树脂粒子纤维化影响较大。当推压成型温度、速度和压力分别控制为50~80℃,9~15 mm/min和38~42MPa时,纤维综合力学性能较好。     

聚醚砜中空纤维膜的制备

讨论了在二次成形聚醚砜(PES)中空纤维膜的制备中,PES浓度和不同的填充液对中空纤维膜结构和性能的影响。结果发现:随着PES浓度的增大,中空纤维膜的水通量呈下降的趋势,确定了二次成形PES中空纤维膜制备中PES最佳浓度为24%;不同填充液与溶剂之间的相互扩散速率不同,得到了具有不同结构的聚醚砜中空纤维膜。随着填充液压力的提高,纤维的内径、外径增加,壁厚减小,水通量增大,一般填充液压力为0.020MPa。     

介孔Al_2O_3/PVDF复合中空纤维膜的制备及其性能

为了提高PVDF中空纤维膜在处理含油废水过程中的亲水性能、抗压实性能和抗污染性能,实验以介孔Al2O3为无机添加粒子,采用溶液纺丝法制备出介孔Al2O3/PVDF复合中空纤维膜。通过扫描电子显微镜和傅里叶红外光谱观察介孔Al2O3/PVDF复合中空纤维膜的形貌和成分,结果证明介孔Al2O3成功地添加到PVDF中空纤维膜中。通过接触角,纯水和含油废水通量的测试,结果表明介孔Al2O3的添加改善了PVDF膜的亲水性能、抗压实性能和抗污染性能。     

壳聚糖对聚氨酯成膜动力学及膜性能的影响

在聚氨酯(PU)中添加壳聚糖(CS)微粉,通过湿法成膜的方法制备了PU/CS共混膜。采用成膜动力学测试仪测试PU/CS共混膜的成膜速率,研究了CS用量对成膜动力学的影响;用扫描电镜(SEM)对PU/CS共混膜的结构进行表征,并研究了CS用量对PU水通量、孔隙率和吸湿率的影响。结果表明:CS可显著提高PU的成膜速率,使其膜孔数量增加、孔径变大。当CS用量为1.5%时,成膜动力学斜率值由10.98增加到17.50;水通量由1.75 L/(m~2·h)增加到9 L/(m~2·h);透气度由1.045 L/(cm~2·min)增加到2.720 L/(cm~2·min);孔隙率由35.98%增加到54.35%;吸湿率由33.3%增加到58.4%;接触角由77.1°减小到71.3°,此时PU/CS共混膜的综合性能最好。     

后处理对改性聚氨酯系中空纤维膜压力响应行为的影响

采用熔融纺丝制得改性聚氨酯系中空纤维膜,通过测试水通量随压力的变化研究了拉伸、热处理温度和热处理时间对改性聚氨酯系中空纤维膜压力响应行为的影响。结果表明,所得膜可发生明显的压力响应行为,且拉伸倍数越大,膜的强度越大,压力响应行为越精确;随热处理温度升高,膜的支撑性变差,压力响应行为变弱;随热处理时间延长,膜形变回复率变低,压力响应行为减弱。     

Fabrication and characterization of novel foaming polyurethane hollow fiber membrane

Foam-like materials had attracted great interest as promising absorbent. In this study, thermoplastic polyurethane(TPU) block sponge was synthesized. Polyester(PET) braid tubular reinforced polyurethane(PU) spongy hollow fiber membrane was prepared by a concentric circular spinning method. The method was woven from an outer coated water-blown PU separation layer and inner PET braid tubular. We have developed a simple and useful preparation technique for the PU spongy hollow fiber membrane. For the first time, the PU spongy hollow fiber membrane was prepared using a coating and controlled foaming technique. The influence of toluene isocyanate index on the physical properties, morphology, and structure of flexible PU sponge was discussed in terms of water contact angle(CA), pure water flux(PWF), Fourier Transform Infrared Analysis(FTIR),pressure-responsive property, and pull-out strength. The morphologies of the membranes were investigated by scanning electron microscopy. We have characterized the foams from an intuitive point of view and demonstrated that the dimensional morphology of the membrane was closely related to isocyanate index. The result showed that the surface cell size of the PU sponge hollow fiber membrane gradually decreased with an increase of the isocyanate index. Due to the elasticity of PU at room temperature, the pressure responsive characteristic of the membrane was prepared. When isocyanate index was 1.05, the interface bonding strength of PU spongy hollow fiber membranes reached as high as 0.37 MPa, porosity and PWF were 71.5% and 415.5 L·m~(-2)·h~(-1),respectively.     

内压超滤膜丝单双端给水的纯水通量分布

强调了研究内压中空超滤膜丝纯水通量分布特性对于研究超滤工艺的意义,给出了单端给水方式与双端给水方式内压膜丝沿程通量的变化规律,分析了单端与双端给水内压膜丝沿程通量的压力特性及温度特性,比较了长膜丝与短膜丝沿程通量特性的差异,明确了内压中空超滤膜丝双端给水方式所具有的多项技术优势,为中空超滤膜组件及膜系统的运行分析提供参考。     

气态膜吸收法脱除水中氨的传质效果

利用聚丙烯中空纤维气态膜对氨/水分离过程及影响因素进行研究,考察膜两侧液体流速、浓度、温度等工艺条件对传质系数和氨脱除率的影响。研究结果表明：气态膜-化学吸收法对氨/水有很好分离效果;原料液温度和流速的影响较为显著,传质系数随温度升高而升高,而提高原料液的流速,膜通量增加,氨的脱除率却下降,压力降升高;氨的初始浓度对膜通量影响较大,膜通量随初始浓度升高而增大;吸收液中反应物浓度相对于透过氨浓度过量时,吸收液的浓度、流速对传质过程影响较小。     

膜生物反应器中影响膜透水率的几个因素

本文研究了影响膜 -好氧生物反应器中中空纤维膜透水率的几个因素 ,如组件长度、操作压力、膜面流速、活性污泥浓度和温度。中空纤维膜内 ,压力沿料液流动方向呈抛物线型分布 ,所以在膜内径和膜面流速一定的情况下 ,存在一个最佳的膜组件长度 Llin使得膜利用率最高 ,且最省能 ;操作压力对膜透水率的影响分为三个区域 ,各个区域膜的主要过滤阻力不同 ,不同污泥浓度时 ,为了使中空纤维膜内腔不堵塞 ,膜面流速必须高于某一范围 ,膜透水率随温度呈正比例关系变化。     

Study on a new air-gap membrane distillation module for desalination

A new air-gap membrane distillation (AGMD) module for desalination with internal latent-heat-recovery which consisted of parallel hollow fiber membranes and heat exchange hollow fibers was successfully developed. The influences of feed flow rate, feed temperature and feed initial concentration on AGMD process were investigated. The vapor pressure polarization coefficient (η) was introduced to measure the reduction in the effective driving force for mass transfer with regard to the driving force imposed. Among all AGMD experiments, the maximum water vapor permeate flux (J_D) of 5.30 kg/m² h and the gained output ratio (GOR) of 5.70 were obtained. A theoretical model based on the mass and energy balances of the hot feed side was established to calculate the temperature and the local water vapor permeate flux distributions along the hollow fiber membrane, which showed that the temperature drop and local water vapor permeate flux drop were much larger at the upper part than those at the lower part of the membrane module in the hot feed side.     

Transient Simulation of Hollow‐Fiber Membrane Filtration with Nonuniform Permeability Distribution

Transient simulation of filtration in hollow‐fiber membranes with nonuniform permeability distribution was conducted. The diversity of permeability distributions caused different initial flux and transmembrane pressure distributions. Manipulating the permeability distribution enables a hollow‐fiber membrane to achieve its maximum volumetric flow rate. During solid‐liquid separation, the inter‐adjustment between flux and cake distributions improved their uniformities simultaneously. The reciprocal of the volumetric flow rate of the membranes all increased linearly with water production. Severely nonuniform permeability distribution caused low water production. The numerical results could be applicable to account for the non‐ideal performance of industrial hollow‐fiber membrane modules.     

烧结温度对TiO2/不锈钢中空纤维复合膜结构和性能的影响

不锈钢中空纤维膜基膜孔径大,直接涂覆分离层容易产生表面缺陷。在二氧化钛悬浮液中加入聚乙烯醇作为黏结剂,通过真空辅助抽滤法在不锈钢中空纤维基膜表面形成一层均匀的分离层。通过高温烧结得到了TiO₂/不锈钢中空纤维复合膜,考察了烧结温度对于TiO₂/不锈钢中空纤维复合膜表面分离层形貌和结构的影响。不同烧结温度时,TiO₂/不锈钢中空纤维复合膜的表面形貌有所差异;随着烧结温度的升高,不锈钢复合膜的孔径和纯水通量均先升高再下降。当烧结温度为500℃时,表面涂层均匀,孔径分布集中,水通量较高。最后,以SPT-500膜测试了水包油乳液分离效果,分离效率达到99%以上,且具有良好的抗污染性能。     

Preparation of a heterogeneous hollow‐fiber affinity membrane modified with a mercapto chelating resin

A high‐quality, heterogeneous hollow‐fiber affinity membranes modified with mercapto was prepared through phase separation with blends of a chelating resin and polysulfone as membrane materials, poly(ethylene glycol) as an additive, N,N‐dimethylacetamide as a solvent, and water as an extraction solvent. The effects of the blending ratio and chelating resin grain size on the structure of the hollow‐fiber affinity membrane were studied. The effects of the composition of the spin‐cast solution and process parameters of dry–wet spinning on the structure of the heterogeneous hollow‐fiber affinity membrane were investigated. The pore size, porosity, and water flux of the hollow‐fiber affinity membrane all decreased with an increase in the additive content, bore liquid, and dry‐spinning distance. With an increase in the extrusion volume outflow, the external diameter, wall thickness, and porosity of the hollow‐fiber affinity membrane all increased, but the pore size and water flux of the hollow‐fiber affinity membrane decreased. It was also found that the effects of the internal coagulant composition and external coagulant composition on the structure of the heterogeneous hollow‐fiber affinity membrane were different. The experimental results showed that thermal drawing could increase the mechanical properties of the heterogeneous hollow‐fiber affinity membrane and decrease the pore size, porosity, and water flux of the heterogeneous hollow‐fiber affinity membrane, and the thermal treatment could increase the homogeneity and stability of the structure of the heterogeneous hollow‐fiber affinity membrane. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007