聚丙烯膜表面磷脂自组装/交联改性及其表面性能

发展了一种基于分子自组装/交联的聚丙烯微孔膜(PPMM)表面改性方法,以含不饱和长烷基链的两亲性天然卵磷脂为改性剂,首先通过分子自组装在PPMM表面形成类磷脂组装层,再采用紫外线原位聚合交联方法在PPMM表面构建稳定的类磷脂仿生修饰层,进而赋予PPMM表面优异的亲水性和生物相容性。分别采用FTIR/ATR和XPS分析确证了改性前后膜表面基团及化学成分的变化。通过水接触角测定、荧光标记蛋白质吸附和酶联免疫吸附(ELISA)实验,考察了类磷脂仿生修饰前后膜表面亲水性和抗蛋白质吸附性能,发现类磷脂仿生修饰后PPMM表面水接触角由130°下降至30°,抗蛋白质吸附性能也得到明显改善;自组装/交联改性PPMM经多次水洗后仍能保持良好的亲水性和抗蛋白质吸附性能,表明膜表面所形成的类磷脂仿生修饰层具有良好的稳定性。     

N,O-羧甲基壳聚糖/聚砜复合纳滤膜的制备及性能研究

以聚砜(PsF)超滤膜为基膜、N,O-羧甲基壳聚糖(NOCC)水溶液为活性层铸膜液、戊二醛(GA)为交联剂,采用涂敷和交联的方法制备了复合纳滤膜.测试了膜表面的流动电势(E)随操作压力(△P)的变化,实验结果表明在电解质溶液中,NOCC/PSF复合NF膜表面荷负电.对其结构和形貌进行了表征,并研究了有机小分子添加剂对复合膜截留性能的影响.NOCC/PSF复合NF膜对几种无机盐的截留顺序为Na2S04＞NaCl＞MgSOa＞MgCl2,呈现出荷负电纳滤膜的截留特征.     

Zeta电位法表征γ-球蛋白对超滤膜污染研究

研究聚偏氟乙烯(PVDF)超滤膜截留γ-球蛋白的过程中,溶液质量浓度、pH值和膜面流速的变化对膜吸附污染的影响,结合截留率和膜表面Zeta电位的变化,从宏观和微观角度分析膜的污染情况.结果表明:PVDF膜在中性溶液中呈荷负电性;膜对γ-球蛋白的截留率随着溶液质量浓度的增大而升高,同时膜表面Zeta电位向荷正电性移动,膜污染越严重;将溶液向酸性或碱性调节以及加快膜面流速后截留效果虽有不同,但污染后的膜表面Zeta电位都更接近新膜.     

自组装改性纳滤膜研究

荷电纳滤膜可以在膜表面吸附不带电或者携带异种电荷的微粒。本文采用荷负电的聚哌嗪酰胺纳滤膜和强正电载体聚乙烯亚胺(PEI)进行改性试验,PEI胶体通过自组装在膜表面形成致密层。针对不同的PEI质量分数、相对分子质量和反应时间,确定了优化条件。结果表明,经过改性的聚哌嗪酰胺纳滤膜对NaCl、NaF、MgCl2等无机盐的截留性能和膜的水通量均有所提高。     

膜特征对锂资源提取过程的影响

可再生能源领域的发展吸引了众多学者对锂电池行业的关注,高效绿色提锂技术成为研究的重点。膜分离技术由于在连续操作中具有操作方便、运行易控、耗能低等特点在锂资源提取中展现出广阔的应用前景。本文基于锂资源提取的膜分离技术,归纳并讨论膜孔和膜表面特征对锂离子分离的影响。文章指出,离子在膜孔中的传输是其分离的基础,离子尺寸和离子在膜孔中传输形态影响其传输速率。膜孔的尺寸和形态是影响锂离子分离的关键因素,不同尺寸、形态和膜孔内电荷在分离过程中表现出不同的分离效果。基于膜表面特征,文章概括了现有荷正电膜、荷负电膜及表面亲疏水性在锂离子分离中的性能差异。最后,文章探究了膜分离技术在锂资源提取中存在的挑战和机遇,推进膜分离技术在锂资源提取方向的理论研究和实际应用。     

中空纤维膜在阳极电泳漆超滤系统中的应用

本报道了荷负电中空纤维膜用于阳极电泳漆超滤系统的试验结果。结果表明，此荷负电中空纤维膜具有优良的抗污染性能；透水率高；能满足阳极电泳漆超滤系统要求；有可能取代醋酸纤维素管式膜而应用于阳极电泳漆超滤系统。     

氨基酸型两性离子超滤膜对染料分子的回收

通过特定化学反应对截留相对分子质量30×103再生纤维素(RC)膜进行表面修饰,得到3种氨基酸(甘氨酸、丝氨酸和赖氨酸)改性的两性离子超滤膜,选取3种分子量相近而所带电荷量不同的染料分子(亚甲基蓝、甲基橙和直接黄12),以考察两性离子超滤膜回收水中染料分子的可能。研究比较了染料荷电量、膜的接枝基团及离子强度对以上3种染料截留率的影响。结果表明,相较于中性膜,两性膜仅对荷负电染料截留能力增强;赖氨酸改性膜尽管荷电性呈中性,但仍有与其他改性膜相近的去除效果,在膜通量约为50 L/(m2·h)时,对直接黄12的截留率可达80%左右,这归因于赖氨酸基团形成了更致密的水化层;此外,离子强度的增加屏蔽了膜与荷负电染料的静电排斥,最终导致截留率降低。     

荷电中空纤维膜对肝素钠的分离特性

在紫外辐照下,引发聚砜（PSF）中空纤维膜与2-丙烯酰胺-2-甲基丙磺酸（AMPS）的表面化学接枝反应,制备得到荷负电型PSF-g-AMPS膜,研究了该荷电膜对肝素钠的分离浓缩特性。实验结果表明,紫外光引发膜接枝过程中辐照时间、接枝单体浓度、肝素钠溶液的pH值影响着膜的渗透通量及截留效果。在辐照时间为2 min、AMPS单体浓度为1%条件下得到的荷电膜在0.1MPa压力下对肝素钠具有最佳的截留效果。溶液pH=9的条件下,膜对肝素钠具有较高的截留率,而在pH=5条件下具有较高的渗透通量。荷负电膜与带阴离子基团肝素钠的静电排斥效应使得膜对肝素钠的截留率提高,而接枝链的亲水性使得膜的渗透通量得以提高。     

氯碱离子膜中的全氟羧酸层及其运行机理研究

基于离子膜烧碱的电解原理,分析了羧酸层树脂的微观结构,认为钠离子和水分子是以水合离子在电驱动下通过膜通道的方式进行迁移的。膜的离子交换基团负责离子簇的形成,并赋予膜以离子透过能力即电导性。结合加工过程解释了离子通道的形成过程,提出曲折贯通的离子通道是羧酸层导电的前提,而阴极侧负电性和弱酸本性导致的动态非完全解离则是阻拦氢氧根的主要屏障。展望了新一代氯碱膜的开发前景,认为在疏水性微孔膜阴极侧制造荷负电的表面是可行的方案。     

荷正电微孔陶瓷膜对水中达旦黄的吸附性能

采用浸渍-烧结工艺制备纳米Y_2O_3涂层的荷正电微孔陶瓷膜,通过FT-IR、SEM、ζ电位等分析了膜的组成结构,并对负电染料达旦黄进行吸附性能实验,考察了荷电膜对达旦黄吸附效果的影响因素。结果表明,荷电膜的平均孔径为0.6μm,表面均匀分布着纳米Y_2O_3粒子,膜等电点在p H=8.3左右;对质量浓度为10 mg/L的达旦黄溶液,在pH为3~8时,荷电膜能够有效吸附达旦黄,去除率均达到90%以上。通过正负电荷之间的静电吸附作用,荷正电微孔陶瓷膜对达旦黄有良好的吸附去除性能,预示着荷电膜在工业染色废水处理中具有很好的应用前景。     

聚电解质涂层/纳米纤维膜复合滤膜的制备

以静电纺丝法制备的PAN纳米纤维多孔膜为基膜,以层层自组装成膜技术制备的壳聚糖-海藻酸钠聚电解质涂层为表面选择性涂层,成功制备了聚电解质涂层/纳米纤维膜复合滤膜。用扫描电镜(SEM)对复合膜的微观形态进行表征。在操作压力为0.7MPa的条件下,分别过滤纯水以及质量浓度为1000mg/L的NaCl和500mg/L的MgSO4溶液,测试结果表明:盐离子截留率随聚电解质涂层层数的增加而增加,但同时复合膜的水通量随之明显降低。当聚电解质涂层层数为10时,水通量均在18L/m·2h左右,对MgSO4截留率为64.22%,对NaCl截留达到52.45%。     

Surface characterization and performance evaluation of commercial fouling resistant low-pressure RO membranes

This paper describes the characterization and evaluation of various RO/NF membranes for the treatment of seasonally brackish surface water with high organic contents (TOC ≈21 mg/L). Twenty commercially available RO and NF membranes were initially evaluated by performing controlled bench-scale flat-sheet tests and surface characterization. Based on the results, four low pressure RO membranes were selected for use in the pilot study. The surface characterization revealed that each of four selected membranes had unique surface characteristics to minimize membrane fouling. Specifically, the LFC1 membrane featured a neutral or low negative surface to minimize electrostatic interactions with charged foulants. The X20 showed a highly negatively charged surface, and thus, was expected to perform well with feed waters containing negatively charged organics and colloids. The BW30FR1 exhibited a relatively neutral and hydrophilic surface, which could be beneficial for lessening organic and/or biofouling. The SG membrane had a smooth surface that made it quite resistant to fouling, particularly for colloidal deposition. In the large-scale pilot study using single element, all of the four membranes experienced a gradual increase in specific flux over time, indicating no fouling occurred during the pilot study. The deterioration of permeate water quality such as TDS was also observed over time, suggesting that the integrity of the membranes might be compromised by the monochloramine used for biofouling control.     

Improving the antifouling properties of ceramic membranes via chemical grafting of organosilanes

For enhanced antifouling surface properties, the alumina membranes were modified through a simple silanization process. Three organosilanes presenting neutral, positive, and negative charges were allowed to graft onto alumina membranes. A small decrease in the pore size and the successful chemical binding of organosilanes were confirmed, respectively. The membrane filtration test using humic acid (HA) was conducted to evaluate the effect of surface charges on fouling resistance. The neutral and negatively charged membranes achieved remarkable flux behaviour due to no charge interaction and electrostatic repulsion force, respectively. Especially, the negatively charged membranes presented the lowest flux decline, the highest flux recovery, and the lowest membrane fouling.     

二氧化钛调控基膜结构对氧化石墨烯复合膜性能的影响

以聚醚砜(PES)超滤膜为基膜，通过聚多巴胺(PDA)表面改性后压力沉积不同量的二氧化钛(TiO₂)纳米粒子作为基底，再沉积氧化石墨烯(GO)片层制得TiO₂/GO复合分离膜，重点考察基膜表面形貌对GO膜分离性能的影响。通过扫描电子显微镜、接触角测试仪、固体表面Zeta电位分析仪、X射线衍射分析仪等对有无TiO₂沉积层的GO复合膜进行表征，并考察TiO₂沉积量对GO复合膜分离性能的影响。结果表明，TiO₂纳米粒子以团簇状态均匀分布在改性的超滤膜表面，随TiO₂沉积量的增加，团簇密度增大，GO沉积后表层的峰谷结构更为明显，但表层的层间距并无明显改变。TiO₂/GO复合膜的水通量随TiO₂沉积量的增加而明显增大，TiO₂的沉积对GO沉积量低的复合膜通量的影响更明显，当 GO沉积量为4.11 μg/cm²，TiO₂沉积量为20.55 μg/cm²时，复合膜的水通量较无TiO₂的复合膜提高了108.38%。复合膜对无机盐溶液的截留性能主要基于膜表面所带负电的道南排斥作用，TiO₂/GO复合膜对刚果红的截留率在99%以上，对甲基橙的截留率可达82%，TiO₂层的加入并未降低复合膜的截留效果。     

Dehydration of C2–C4 alcohol/water mixtures via electrostatically enhanced graphene oxide laminar membranes

The dehydration of alcohol/water mixtures using pervaporation membranes requires less energy than is required by conventional separation technologies. In this paper, we report electrostatically enhanced graphene oxide (GO) membranes for the highly efficient pervaporation dehydration of C₂–C₄ alcohol/water mixtures. Positively charged molecules were introduced as the interlayer of negatively charged GO layers via layer-by-layer assembly, thereby creating an electrostatic attraction that drives the assembly of GO nanosheets into ordered interlayer channels. The effects of the feed temperature, water concentration, and continuous operation on the membrane transport behavior were systematically investigated. In the dehydration of 90 wt% alcohol/water mixtures at 70°C, the membrane exhibited ethanol/water, isopropanol/water, and n-butanol/water fluxes of 2.35, 2.98, and 4.69 kg/(m² hr), respectively, as well as separation factors for the same mixtures of 3,390, 5,790, and 4,680, respectively. This excellent alcohol/water dehydration performance outperforms those of state-of-the-art polymeric membranes and GO-based membranes.     

Novel charged chitosan composite nanofiltration membranes containing chiral mesogenic group

To improve the performance of nanofiltration (NF) membranes, a chiral mesogenic compound, a positively charged compound, and a negatively charged compound were grafted to chitosan, respectively. Series of novel composite NF membranes were prepared by over‐coating the polysulfone ultrafiltration membrane with the mixture of chitosan and modified chitosan. The chiral mesogenic compound, the positively charged compound, the negatively compound and their chitosan derivatives were characterized by infrared spectrophotometer, differential scanning calorimetry, polarized optical microscope; the structure of the membrane was characterized by scanning electron microscopy. The performance of composite NF membranes was strictly related to the novel compounds grafted to chitosan and its composition. The rejection reached the maximum of 95.7% for CaCl₂ with P_2‐7 composite NF membrane, corresponding flux was 3155 Lm^?2h^?1. The rejection reached the maximum of 93% for Na₂SO₄ with P_3‐5 composite NF membrane, corresponding flux was 3879 Lm^?2h^?1. Comparing with conventional NF membranes, the membranes were used in low pressure with high flux, especially for the separation of high‐valence ions from solution. The membranes were typical charged NF membranes. POLYM. ENG. SCI., 57:22–30, 2017. © 2016 Society of Plastics Engineers     

Charged membranes for ultrafiltration treatment of synthetic waste water containing peptone

Continuous ultrafiltration of synthetic waste water containing peptone was carried out by using positively and negatively charged polyacrylonitrile membranes. The filtration experiments were operated in cross-flow mode under 10 kPa of applied pressure. The filtration properties of the charged membranes were compared with those of uncharged polyacrylonitrile ultrafiltration membranes having similar molecular sieve characteristics and membrane structure to the charged ultrafiltration membranes. During the continuous filtration, the filtration rate decreased and the operation pressure increased because of the formation of a peptone gel layer on the membrane surface. It was found that, for the positively charged membrane, the decrease in the filtration rate of the charged membranes was smaller than that of the uncharged membrane. In addition, the positively charged membrane maintained the initial operation pressure during the filtration. The reduction of fouling in the positively charged membrane was discussed by analyzing the gel components on the membrane surface.     

Development of polyethersulfone/polylactic acid-blended nanocellulose membranes for enhanced removal of methylene blue dye

Herein, adsorptive polyethersulfone/polylactic acid (PES/PLA) blends membranes with systematic concentrations of cellulose nanofibers (CNFs) (0.5–2.5 wt%) were developed via a modified phase inversion process for the enhanced removal of cationic methylene blue (MB) dye. To the best of our knowledge, this is the first time that such adsorptive membranes have been produced for potential use in wastewater treatment. The fabricated membranes were characterized for surface and cross-sectional morphology (scanning electron microscope), surface roughness (atomic force microscope), functionality (Fourier-transform infrared spectroscopy), thermal stability (thermal gravimetric analysis), wettability (contact angle measurements), antifouling behavior (flux recovery studies), and dye adsorption and reusability (adsorption and desorption tests). CNF incorporated membranes showed improved wetting properties, with contact angle decreasing from 76° in the pristine membranes to 48° in 2.5 wt% PES/PLA membranes. The membrane bulk porosity increased from 60.3% to 79.23%, while the pure water flux increased from 210.8 to 399.12 Lm⁻² h⁻¹. At optimal conditions, CNF-modified membranes removed >98% of MB compared with 8% removal by the pristine membranes. After five cycles of adsorption and desorption, the membrane with 2 wt% CNFs achieved over 70% dye removal showing excellent reusability properties. Adsorption followed pseudo-second-order and Freundlich models. The adsorption was attributed to electrostatic interactions between the negatively charged membrane surfaces and the positively charged dye molecules as well as through hydrogen bonding. Therefore, this work revealed that CNF-modified PES/PLA membranes can be used as adsorbents for the enhanced removal of organic pollutants in water treatment applications.     

Fabrication and characterization of silane-functionalized Na-bentonite polysulfone/polyethylenimine nanocomposite membranes for dye removal

In this study, tetraethoxysilane (TEOS)-functionalized Na-bentonite incorporated into polysulfone/polyethylenimine (PSF/PEI) membranes were fabricated by phase inversion method for the efficient removal of methylene blue dye. For the preparation of PSF/PEI nanocomposite membranes, silane-functionalized Na-bentonite and pure Na-bentonite were used at three different concentrations (0.5, 1, and 2 wt%). The prepared membranes were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscopy, porosity, hydrophilicity, and water permeability measurements. Antifouling behaviors and methylene blue dye rejections of the PSF/PEI nanocomposite membranes were also tested. The obtained results showed that the addition of pure Na-bentonite and silane-functionalized Na-bentonite both increased the water permeability of the membranes. The PSF/PEI membrane containing 2 wt% silane-functionalized Na-bentonite showed the highest water flux of 105 L m⁻² h⁻¹, while the lowest water flux of 1.2 L m⁻² h⁻¹ was recorded for pure PSF membrane. Filtration results demonstrated that the antifouling capacity was significantly increased due to the negatively charged surface of the newly generated silane-functionalized Na-bentonite PSF/PEI membranes. In summary, TEOS-functionalized Na-bentonite can be used to fabricate PSF/PEI nanocomposite membranes with effective filtration ability, antifouling capacity with lower decay ratio, higher flux recovery ratio, and 99% methylene blue dye removal performance.     

Foulants analyses for NF membranes with different feed waters: coagulation/sedimentation and sand filtration treated waters

Two different NF membranes were operated to remove natural organic matter (NOM) originating from Dongbok Lake in Korea. Coagulation/sedimentation and sand filtration treated waters as membrane feed waters were used. The tested NF membranes were autopsied to compare the fouling propensity from different feed waters using pure water and a NaOH solution. Organic/inorganic foulants onto membrane surface were analyzed in terms of molecular weight (MW) distribution, structure, and IR analysis, and fouled membranes were also characterized in terms of pore size distribution, surface charge, and SEM–EDS analysis. Polysaccharides and/or N-acetyl aminosugar groups with MW ranging from 30,000 to 50,000 g/mol were identified using HP-SEC and IR analysis. Inorganic foulants (i.e., Si and Al) were also fouled onto the membrane surface and/or pores, and it is effectively removed by caustic cleaning, not pure water. Caustic cleaning was proven to be effective to remove both fouled NF membranes as a basis of flux recovery, and it could efficiently desorb the hydrophobic NOM constituents or protein-like substances from the relatively hydrophilic and less negatively charged NF membranes.