影响聚醚砜超滤膜性能的因素

通过对聚醚砜(PES)超滤膜的水通量，尿素去除率和肌肝去除率的测定，研究了铸膜液中聚醚砜质量分数，凝固浴质量分数，大分子添加剂PVP的含量，小分子添加剂PEG的含量对聚醚砜超滤膜的影响。     

外凝固浴对聚醚砜中空纤维水通量的影响

制备了聚醚砜（PES）中空纤维膜，并研究了外凝固浴组成对膜水通量的影响。结果表明，纯水通量随外凝固浴中二甲基乙酰胺（DMAc）含量提高而增加。     

凝固浴温度对PVDF/PES-C共混膜结构及性能的影响

以邻苯二甲酸二丁酯(DBP)和N,N-二甲基乙酰胺(DMAc)为混合稀释剂,采用热致相分离法(TIPS)制备了聚偏氟乙烯(PVDF)/酚酞型聚醚砜(PES-C)共混膜,考察了不同凝固浴温度对膜结构和性能的影响。采用扫描电镜观察了膜的结构,测试了膜的纯水通量。运用DSC和XRD方法检测了膜的结晶性能。将制备的膜在膜生物反应器(MBR)中运行测试了膜的污水通量和出水指标。随凝固浴温度的升高,共混膜的最高熔融温度上升,膜中α晶型的含量增加。在凝固浴温度为25℃时,膜形成了较为致密的皮层结构和较为疏松的支撑层结构,此时共混膜的纯水通量和污水通量达到最大值,且MBR出水COD和NH4+-N含量达到排放要求。     

双向拉伸法制备聚醚砜中空纤维

采用双向拉伸的方法制备了聚醚砜中空纤维,探讨了工艺条件对聚醚砜中空纤维取向度和水通量的影响。结果表明:随着纺丝速度的提高,纤维的取向度上升,水通量下降;在总拉伸倍数不变的前提下,随着凝固浴拉伸倍数的提高,纤维的取向度和水通量都减小;随着填充液压力的提高,纤维的取向度下降,水通量增加;随着凝固浴中二甲基亚砜含量的提高,纤维的取向度先增大后减小,出现了一个最大值,水通量先减少后增加,出现了一个最小值。     

凝固浴质量分数对聚醚砜中空纤维膜结构和性能的影响

采用干喷湿纺法纺制成聚醚砜中空纤维膜,研究了凝固浴质量分数与PES中空纤维结构和性能之间的关系。结果表明：在凝固浴质量分数10％～40％的范围内,中空纤维膜的水通量先减少再增加;中空纤维的取向度则先增大后减小;膜表面孔的数量及孔径都有一个先减后增的现象。     

聚电解质复合纳滤膜的制备及其截盐性能研究

采用静电诱导法，通过铸膜液中带负电的磺化聚醚砜(SPES)和凝固浴中带正电的聚乙烯亚胺(PEI)在相分离时形成的相互吸引作用，在聚醚砜(PES)膜表面形成聚电解质分离层，再经过交联处理和热处理制得聚醚砜复合纳滤膜。结果表明，当铸膜液中SPES/PES比例为4/17，凝固浴中加入的PEI分子量为10 000 g/mol时，所制得的纳滤膜在较低测试压力(0.3 MPa)下对硫酸镁(MgSO₄)和硫酸钠(Na₂SO₄)的截留率分别为91.1%、85.7%，对其溶液的渗透性能分别为71.4 L/(m²·h·MPa)、75.9 L/(m²·h·MPa)。     

聚醚砜质量分数对聚偏氟乙烯/聚醚砜共混膜性能和结构的影响

用与聚醚砜共混的方法来改善聚偏氟乙烯膜的抗收缩性能,以二甲基乙酰胺作溶剂,聚乙烯吡咯烷酮为添加剂,研究了聚醚砜(PES)质量分数对聚偏氟乙烯/聚醚砜共混膜的收缩率、水通量、截留率及形态结构的影响。聚醚砜的加入可以有效地降低共混膜的收缩率,在w(PES)=1.5%时,共混膜的水通量取得极大值,截留率取得极小值。     

二氧化硅填充聚醚砜超滤膜

本文通过在聚醚砜中引入活性炭粉和无定型二氧化硅粒子，以N，N-二甲基甲酰胺为溶剂，以水为凝固浴，利用相转化湿法成膜机理，制得了一系列不同粒子含量的聚醚砜超滤平板膜。通过扫描电子显微镜对膜结构进行了观察和对比研究，并对膜的纯水通量和鸡蛋卵清蛋白的截留进行了测试，结果发现：二氧化硅的加入，改变了铸膜液的浊点组成；产生了大量的界面空隙，即界面孔：增加了膜孔的贯通性；提高了膜的亲水性；使膜的通量大大提高，并且保持了很好的截留率。而活性炭粉填充聚醚砜超滤膜的综合性能远远差于二氧化硅填充聚醚砜超滤膜。     

PES/fMWNT共混超滤膜的制备及其抗污染研究

采用非溶剂致相分离法(NIPS)制备聚醚砜/羧基化碳纳米管共混膜,以N,N-二甲基乙酰胺(DMAc)和N-甲基吡咯烷酮(NMP)为溶剂,聚乙二醇(PEG4000)为致孔剂。研究了碳纳米管添加量和管径对膜结构和膜性能的影响。结果表明,共混膜的拉伸强度、杨氏模量随着碳纳米管含量的增加先增大后减小,但随着碳纳米管的管径增加而减小。当碳纳米管含量为1. 0%,管径为20～30 nm时,聚醚砜/碳纳米管共混膜的接触角从纯聚醚砜膜的78. 16°降到64. 30°,纯水通量达到50. 39 L/(m~2·h),是纯聚醚砜通量的4倍,对牛血清蛋白(BSA)截留率保持在95%以上,通量恢复率从54. 29%增加到84. 59%,抗污染性能较纯聚醚砜膜明显提高。     

PVDF/PES-C共混膜的结构与性能

以邻苯二甲酸二丁酯(DBP)和N,N-二甲基乙酰胺(DMAc)为混合稀释剂,采用热致相分离法(TIPS)制备了聚偏氟乙烯(PVDF)和酚酞型聚醚砜(PES-C)共混膜,采用扫描电镜观察了膜的截面结构,测试了膜的纯水通量。通过膜生物反应器处理生活污水,检验了膜的污水处理性能。与PVDF膜相比,共混膜具有一个较薄的致密的皮层和较为疏松的支撑层,共混膜的纯水通量约为纯聚偏氟乙烯膜的两倍。同时共混膜的污水通量较高,COD和NH4+-N的去除率与PVDF膜相比约增加10%,共混膜的通量衰减系数较小,具有更好的抗污染性能。     

Effect of coagulation bath temperature on formation mechanism of poly(vinylidene fluoride) membrane

Effects of coagulation bath temperature on the membrane formation mechanism and the morphologies of the formed membranes were studied. The binodal and spinodal lines in the phase diagrams of water/DMAc/Poly(vinylidene fluoride) (PVDF) were calculated based on the thermodynamics equations of membrane formation, and the gel phase boundaries of the systems at 25°C and 60°C were determined via cloud point measurement. The obtained ternary phase diagrams of water/DMAc/PVDF contain three regions: the one‐phase region, the liquid–liquid two‐phase region, and the gel region. In the phase diagrams, the liquid–liquid demixing line (binodal) is located inside the gelation line. At low temperature, there exists a wide region between gelation line and binodal line. Gelation could occur in the absence of liquid–liquid demixing, and becomes the dominant membrane formation mechanism. At high temperatures (60°C), however, the gelation line approaches the binodal line, which results in a much smaller gelation zone. The kinetics of the solvent out‐flux and water influx were enhanced, liquid–liquid demixing is the dominant mechanism. The membrane formation mechanisms at different temperature were confirmed by the light transmission measurements during membrane forming process and the morphologies of the membranes examined by SEM imaging. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

Trade-off between thermodynamic enhancement and kinetic hindrance during phase inversion in the preparation of polysulfone membranes

Polysulfone membranes were prepared via the diffusion-induced phase inversion process from casting solutions consisting of polysulfone, dimethyformamide, and polyvinyl pyrrolidone as a polymeric additive. The effect of PVP added in casting solutions was analyzed by measuring the prepared membranes' morphology and water permeability. Variations in a casting solution's thermodynamic and kinetic properties caused by PVP addition suggest that the thermodynamic variation works in favor of the enhancement of demixing in the casting solution, but the rheological variation induces the opposite trend, or the delay of demixing. When prepared by the immersion coagulation into a water bath, the solidified membranes' structural and functional properties indicate that the coagulation of cast solutions was affected by the trade-offrelationship between thermodynamic enhancement and kinetic hindrance. With a small amount of PVP in the casting solution, the thermodynamic driving force played a major role on solution demixing, inducing the demixing enhancement, corresponding to the acceleration of phase separation due to the PVP's nonsolvent effect. Consequently, the PVP acts as a phase separation enhancer, resulting in both macropore enlargement and permeate flux increase. With more addition of PVP, however, the macropore structure and the water permeability were suppressed rather than enlarged or increased. These phenomena reflect that the demixing of the cast solution was delayed, with the kinetic hindrance offsetting the thermodynamic effect for phase separation enhancement.     

MORPHOLOGY AND TRANSPORT STUDY OF PHASE INVERSION POLYSULFONE MEMBRANES

Two different types of polysulfone (PS) membranes were prepared by the phase inversion process utilizing water or isopropanol as nonsolvent. The Flory-Huggins theory for a ternary system nonsolvent/solvent/polymer is applied to describe the'thermodynamic equilibria of the components. The calculated ternary phase equilibria show that demixing of a PS binary solution with n-methylpyrrolidone (NMP) will be fast in a water coagulation bath and will be delayed in an isopropanol bath. The prepared membranes were characterized by SEM, gas adsorption-desorption technique, and permeability measurements. The membrane, which is precipitated by fast demixing in a water bath, has nodular structures in the skin region and includes finger-like cavities in the sublayer. The membrane coagulated by isopropanol has a very dense and thick skin structure, which is formed by delayed demixing. The membrane coagulated by isopropanol showed considerably lower pore volume and surface area compared to that observed with water coagulation method.     

混凝试验中效果评判的新方法

通过对两类不同的水源进行混凝试验,发现用混凝后水的浊度来评判混凝效果的方法,对一般水质的水源是有效的,但对某些特殊水质的水源如低温低浊水,或对混凝处理后水质要求较高的场合如反渗透进水,就无法准确找出最佳的混凝剂和混凝条件.因此,提出了用测量矾花(絮凝体)大小及生长速度和泥渣虚度的指标来评判混凝试验效果的新方法,与常用的以混凝后水的浊度来评判混凝效果相比,用此方法更能准确地评判混凝试验效果的优劣.     

Poly(vinyl chloride) Asymmetric Membrane Modified with Poly (ethylene glycol): Effect of Additive Concentration on the Morphology and Performance

Asymmetric membranes of polyvinyl chloride modified with polyethylene glycol as pore former have been prepared by nonsolvent-induced phase separation method using N,N-dimethylacetamide/water as solvent/nonsolvent system. The phase diagram of polyvinyl chloride/polyethylene glycol/N,N-dimethylacetamide/water system showed that polyethylene glycol favors the demixing process. The prepared membrane is characterized by scanning electron microscopy, ATR-FTIR, equilibrium water content, porosity, pure water flux, and contact angle. The addition of polyethylene glycol favored the formation of finger-like structure of polyvinyl chloride membrane initially, and at higher polyethylene glycol concentration, a spongy structure is obtained. The prepared membrane possesses high water flux, excellent thermal stability, and sufficient mechanical strength suitable for ultrafiltration operation.     

Synthesis and characterization of polyethersulfone membranes

Phase inversion method was used to prepare polyethersulfone (PES) ultrafiltration (UF) membranes. Polyethylene glycol (PEG); N, N-dimethyl formamide (DMF) and water were utilized as pore-forming additive, solvent and non-solvent, respectively. Effects of PES and PEG concentrations in the casting solution, PEG molecular weight (MW) and coagulation bath temperature (CBT) on morphology of the prepared membranes were investigated. Taguchi experimental design was applied to run a minimum number of experiments. 18 membranes were synthesized and their permeation and rejection properties to pure water and human serum albumin (HSA) solution were studied. It was found out that increasing PEG concentration, PEG MW and CBT, accelerates diffusional exchange rate of solvent (DMF) and non-solvent (water) and consequently facilitates formation of macrovoids in the membrane structure. The results showed that, increasing PES concentration, however, slows down the demixing process. This prevents instantaneous growth of nucleuses in the membrane structure. Hence, a large number of small nucleuses are created and distributed throughout the polymer film and denser membranes are synthesized. A trade-off between water permeation and HSA rejection was involved, with membranes having higher water permeation exhibited lower HSA rejection, and vice versa. Hence, optimizing preparation variables to achieve high pure water permeation flux along with reasonable HSA rejection was inevitable. Analysis of variance (ANOVA) showed that all parameters have significant effects on the response (water flux and HSA rejection). However, CBT and PES concentration were more influential factors than PEG concentration and MW on the responses.     

凝固浴组成和温度对PVDF疏水微孔膜结构与性能的影响

利用非溶剂相转化法(NIPS),以聚偏氟乙烯(PVDF)/磷酸三乙酯(TEP)-N,N-二甲基乙酰胺(DMAc)为铸膜液体系,乙醇水溶液为凝固浴制备高性能的PVDF疏水微孔膜。考察了凝固浴中乙醇(EtOH)含量及凝固浴温度对PVDF成膜分相速率、膜结构和膜疏水性的影响。实验结果表明,在20℃的凝固浴温度下,凝固浴中乙醇含量的升高减慢了铸膜液体系的分相速率,提高了PVDF膜的孔隙率;在凝固浴中添加60%(wt)的乙醇,可形成表面荷叶状结构和截面对称的海绵状结构,膜表面的接触角为130.3°,呈很强的疏水性,并具有较优的膜强度。     

纳滤/反渗透/石灰混凝法深度处理垃圾渗滤液

采用纳滤-反渗透法深度处理垃圾渗滤液T-MBR生化出水,考察了纳滤膜和反渗透膜对COD、总氮、硬度、重金属的去除效果,以及压力和运行时间对通量的影响。对纳滤的浓缩水进行石灰混凝处理,考察石灰投加量对COD、硬度的去除效果。结果表明,纳滤和反渗透可以有效去除COD、总氮、硬度、重金属等,出水各指标稳定达到垃圾渗滤液排放限值,通量在较长时间内能够保持稳定。回收率为80%的纳滤浓缩水经过石灰混凝后,当石灰投加量为3 g.L-1时,COD去除率为31%,硬度去除率达到89%。混凝后的上清液回到纳滤系统继续处理,系统的水总回收率为86%。     

聚丙烯腈超滤膜的制备

为了得到高性能的超滤膜,采用相转化法,以聚丙烯腈(PAN)为原料,N-甲基-吡咯烷酮(NMP)为溶剂,制备了聚丙烯腈超滤膜.采用纯水通量以及膜对牛血清蛋白(BSA)的截留率作为评价标准,并使用扫描电镜对膜结构进行表征.研究了聚合物质量分数、添加剂种类、凝胶浴温度、凝胶浴种类对膜性能的影响.研究发现:在一定范围内提高聚合...     

Demixing kinetics of phase systems employed for liquid-liquid extraction and correlation with system properties

The kinetics of phase demixing in liquid-liquid extraction for model systems comprising PEG 4000/potassium phosphate and t-butanol/ammonium sulfate was studied. The kinetics of demixing depicts the entire demixing pattern of phases of the phase system during and after extraction and hence the study is essential prior to design of large scale gravity phase separators. With an increase in composition, both the systems showed increase in demixing rate (decrease in demixing time). At high tie line length (TLL) and phase volume ratio <1, with salt rich phase as continuous phase, both PEG 4000/potassium phosphate and t-butanol/ammonium sulfate systems showed reduction in demixing time by 59% and 50%, respectively as compared to that at low TLL. An empirical equation proposed in the literature for rate of phase demixing was used to correlate the experimental data. The agreement was better for t-butanol/ammonium sulfate system when compared to PEG 4000/potassium phosphate system.