交联壳聚糖渗透蒸发膜的制备及其在偏二甲肼/水体系分离中的应用

采用壳聚糖为原料,聚酯无纺布为支撑层,用戊二醛交联制备了高选择性、高通量的交联壳聚糖渗透蒸发复合膜.考察了料液浓度、料液温度、膜厚等对偏二甲肼/水体系分离性能的影响.结果表明:在料液温度为10℃,膜厚度为25 μm,进料液中偏二甲肼的质量分数为50％时,改性复合膜的分离因子最高达到5.25,渗透通量可达167 g/(m...     

静电纺丝聚砜支撑层制备正渗透复合膜

采用静电纺丝法制备了聚砜(PSf)纳米纤维作为正渗透复合膜的支撑层,在此基础上通过界面聚合反应制备了正渗透膜。考察了纺丝液自身性质,PSf含量以及溶剂N,N-二甲基甲酰胺(DMF)与N-甲基-2-吡咯烷酮(NMP)比例对PSf支撑层微观结构及其性能影响。结果表明,纺丝液的PSf质量分数为20%,NMP/DMF体积比为3/7时得到的纺丝纤维均匀无瑕疵,平均纤维直径为396 nm,平均孔径为1.34μm,孔隙率为75.77%。经界面聚合反应在PSf支撑层表面形成聚酰胺活性层,经测试其水通量为42.17 L/(m~2·h),比3种商品膜水通量提高了3倍以上。     

高通量二氧化硅复合膜的制备及其渗透汽化性能研究

二氧化硅复合膜展现出的耐酸性和稳定性在渗透汽化领域有着广阔的应用前景。本文采用真空抽吸浸渍法制备二氧化硅复合膜的支撑层,得到高通量二氧化硅复合膜。本文对支撑层真空抽吸的最优条件进行探究,并采用扫描电镜对膜层的表面、截面形貌结构进行表征。结果表明,当支撑层溶胶质量浓度为2%,真空抽吸时间为10 s,真空抽吸压力为0.10 MPa时制备出致密的二氧化硅复合膜,其膜层厚度为6~7 μm。将本文制备的二氧化硅复合膜应用于异丙醇水溶液渗透汽化中,该膜显示出优异的分离性能,其中异丙醇的渗透通量为6.42 kg/(m²·h)。     

PSF支撑层结构对PDMS复合膜渗透汽化性能的影响

以4种不同结构的聚砜(PSF)作为支撑层,制备PDMS/PSF渗透汽化复合膜,考察其用于乙醇/水体系的分离性能,以研究支撑层结构对渗透汽化复合膜分离性能的影响。采用SEM和EDX分析复合膜表层结构,结果表明,支撑层结构几乎不影响复合膜的选择性,但对膜通量有较大影响,特别是支撑层的表面结构对复合膜性能的影响比断面结构更明显。     

CTAB改性膨润土填充PEBAX/PVDF膜渗透汽化降低汽油噻吩含量

用十六烷基三甲基溴化铵(CTAB)对膨润土进行柱撑改性,并对改性前后的膨润土进行吸附实验及红外测定。将改性后膨润土置于填充聚醚共聚乙酰胺(PEBAX)聚合物溶液中,以聚偏氟乙烯(PVDF)超滤膜为支撑膜,制备复合膜,考察复合膜在模拟汽油(噻吩/正庚烷)中的溶胀性能,并进行渗透汽化实验,研究膜的分离性能。利用SEM考察膜的形貌结构。结果发现:30℃下,溶胀度随噻吩质量分数的增加而升高,15 min后达溶胀平衡,并且在填充量为20%时最大。渗透汽化结果表明:在料液温度为30℃,噻吩质量分数为1 100μg/g时,CTAB填充量为20%的PEBAX/PVDF复合膜的渗透通量和硫富集因子分别为2.81 kg/(m2·h)和4.65。     

用于反渗透复合膜的海绵状结构支撑膜制备研究

通过调节铸膜液中聚砜浓度和非溶剂含量,浸没沉淀法制备海绵状结构的支撑膜,并在支撑膜上界面聚合制备聚酰胺反渗透复合膜。分别对支撑膜及反渗透复合膜的结构和性能进行表征,考察聚砜浓度对支撑膜结构和性能的影响,以及不同结构支撑膜对反渗透复合膜结构和性能的影响。结果显示,随着聚砜浓度的增加,支撑膜表面孔径和孔隙率下降,断面结构变致密,耐压性增强。在不同支撑膜上制备的反渗透复合膜具有不同的通量和脱盐率。综合考虑支撑膜及反渗透复合膜的性能,以聚砜浓度为15%制备的海绵状结构支撑膜更适于作为制备反渗透复合膜的支撑层。     

PDMS涂覆的Al2O3中空纤维膜在ABE/水体系分离中的应用

通过浸渍-提拉的方法制备了PDMS涂覆的Al2O3中空纤维膜,并系统地研究了其用于ABE/水体系的分离过程。首先对制备出的膜进行了形貌表征,SEM电镜照片表明,所用的Al2O3中空纤维支撑体具有非对称结构,海绵孔位于膜壁的中间而指状孔在其两侧。制备出的PDMS涂覆的Al2O3中空纤维复合膜表面致密完好没有缺陷,其厚度小于10μm,说明PDMS层被均匀地涂在支撑体外表面。然后在不同的模拟体系(丙酮-水、丁醇-水、乙醇-水)中,系统地考察了复合膜的性能。实验表明,复合膜具有优异的渗透汽化性能(通量和分离因子)。最后将该复合膜用于ABE-水体系的分离,考察了膜在操作过程中的渗透汽化性能和稳定性,同时将二元体系与四元体系过程对比,讨论渗透汽化对ABE体系的分离作用。     

一步法制备含氨基化合物的非对称CO_2分离膜

采用一步相分离法,制备以聚醚砜(PES)为主体材料,二乙醇胺(DEA)为添加剂和氨基载体的膜,用于CO_2分离。考察了PES浓度、DEA浓度、膜厚度对CO_2/N_2分离性能的影响,同时考察了膜性能的长时间稳定性。当涂膜液中DEA/PES的质量比为12/26、刮刀与无纺布的距离为300μm、进料气压力为0.11 MPa(表压)时,膜的CO_2渗透速率可达274 GPU,CO_2/N_2分离因子可达50。测试温度低于40℃时,DEA/PES膜的CO_2渗透速率和CO_2/N_2分离因子保持稳定。另外,对CO_2/N_2分离性能较好的DEA/PES膜(质量比为12/27)进行CO_2/CH_4分离性能测试,在1 MPa(表压)下性能优于商品膜。上述结果表明,本文研制的DEA/PES膜制备步骤简单,易于规模化制备,性能较优,在CO_2分离领域具有良好的应用前景。     

聚酰胺复合正渗透膜的制备及其脱盐性能研究

通过溶液相转化法制备四种基膜,然后采用界面聚合法制备不同基膜的聚酰胺复合正渗透(FO)膜,并对其结构与性能进行表征。结果表明,正渗透膜基膜表面开孔率高、孔径分布均匀,且纯水通量大;在基膜中引入聚酯(PET)筛网使其厚度增大、孔隙率和纯水通量降低。基膜材料为聚砜(PSF)时,复合膜聚酰胺分离层较为疏松,以聚偏氟乙烯(PVDF)为基膜材料,形成的分离层较为致密且具有典型峰谷结构,从而使反向盐通量更小。四种复合膜的正渗透纯水通量均大于10 L/m2·h,最高达20 L/m2·h。120 min连续正渗透脱盐实验表明,复合膜截盐率及其稳定性优于商用膜,尤其PET筛网支撑PVDF基复合膜的截盐率基本稳定在97. 5%左右,表现出良好的运行可靠性。     

聚酰胺复合正渗透膜的制备及其脱盐性能研究

通过溶液相转化法制备四种基膜,然后采用界面聚合法制备不同基膜的聚酰胺复合正渗透(FO)膜,并对其结构与性能进行表征。结果表明,正渗透膜基膜表面开孔率高、孔径分布均匀,且纯水通量大;在基膜中引入聚酯(PET)筛网使其厚度增大、孔隙率和纯水通量降低。基膜材料为聚砜(PSF)时,复合膜聚酰胺分离层较为疏松,以聚偏氟乙烯(PVDF)为基膜材料,形成的分离层较为致密且具有典型峰谷结构,从而使反向盐通量更小。四种复合膜的正渗透纯水通量均大于10 L/m2·h,最高达20 L/m2·h。120 min连续正渗透脱盐实验表明,复合膜截盐率及其稳定性优于商用膜,尤其PET筛网支撑PVDF基复合膜的截盐率基本稳定在97. 5%左右,表现出良好的运行可靠性。     

温度对正向渗透的影响机制与数值模拟

正向渗透(FO)是一种以溶液自身渗透压作为推动力的膜分离技术。温度对溶液、膜的性质以及溶液与膜之间的相互作用有很大影响,进而影响FO的水通量。利用数值模拟与试验研究了温度对FO性能的影响。结果表明,当膜两侧等温时,FO水通量随着温度的升高而增大;当膜两侧不等温时,原液(FS)一侧温度的影响比提取液(DS)一侧更大,主要是因为温度升高降低了溶液黏度,强化了过膜扩散过程,而温度对DS渗透压的影响不明显。在不同温度条件下,FO水通量和热通量随流量的增大而增大,主要是由于流速的增大压缩膜表面的流体边界层,强化了传质和传热过程。     

界面聚合中空纤维正渗透膜的制备和表征

以聚砜为原料,通过浸没沉淀法制备中空纤维基膜,然后采用界面聚合法制备出中空纤维正渗透膜。考察了制膜参数、基膜结构和FO性能三者之间的关系。结果表明基膜的厚度为影响FO性能的主要因素之一。基膜的厚度越厚,FO过程中渗透效率越低。制得PSF中空纤维正渗透膜的厚度为0.129 mm,断裂拉伸力为2.48 N,FO通量为10.3 L·m^-2·h^-1,逆向盐扩散性能为0.15 g·L^-1。     

Studies on Concentration of Simulated Ammonium-diuranate Filtered Effluent Solution by Forward Osmosis Using Indigenously Developed Cellulosic Osmosis Membranes

In this study, we discuss the preparations of cellulosic membranes from cellulose acetate (CA), cellulose triacetate (CTA) and cellulose acetate blend (CAB) [blending of CA and CTA] systems and their potential for concentration of simulated ammonium-diuranate (ADU) effluent solution (only uranium and ammonium nitrate) by FO. The membranes are prepared using casting solution of polymers in mixed solvent systems with gelling in ice-cold water followed by annealing in 80°C hot water. Prepared membranes are characterized in terms of separation performance (tested under brackish water reverse osmosis test condition), water contact angle and surface average roughness. The performance of the membranes are evaluated in terms of volume reduction factor using solution of 40,000 ppm of NH₄NO₃ and 20 ppm uranium as feed and 320000ppm of NH₄NO₃ as draw solution. It is found that the volume reduction factor increases in the order of CTA<CAB<CA membranes. The effect of different draw solutions on volume reduction for the same system using CA membrane is also evaluated. Almost no leaching of uranium is found to the draw solution side for all the membranes. Possibility of using the FO process in a simpler way (as membrane pouch) to concentrate this simulated ADU filtered solution has been ascertained.     

An agent-based simulation with NetLogo platform to evaluate forward osmosis process (PRO Mode)

Forward osmosis (FO), as an emerging technology, is influenced by different factors such as operating conditions, module characteristics, and membrane properties. The general aim of this study was to develop a suitable (flexible, comprehensive, and convenient to use) computational tool which is able to simulate osmosis through an asymmetric membrane oriented in pressure retarded osmosis (PRO) mode in a wide variety of scenarios. For this purpose, an agent-based model was created in NetLogo platform, which is an easy-to-use application environment with graphical visualization abilities and well suited for modeling a complex system evolving over time. The simulation results were validated with empirical data obtained from literature and a great agreement was observed. The effect of various parameters on process performance was investigated in terms of temperature, cross-flow velocity, length of the module, pure water permeability coefficient, and structural parameter of the membrane. Results demonstrated that the increase in all parameters, except structural parameter of the membrane and the length of module led to the increase of average water flux. Moreover, nine different draw solutes were selected in order to assess the influence of net bulk osmotic pressure difference between the draw solution (DS) and feed solution (FS) (known as the driving force of FO process) on water flux. Based on the findings of this paper, the performance of FO process (PRO mode) can be efficiently evaluated using the NetLogo platform.     

Developing thin‐film‐composite forward osmosis membranes on the PES/SPSf substrate through interfacial polymerization

A new scheme has been developed to fabricate high‐performance forward osmosis (FO) membranes through the interfacial polymerization reaction on porous polymeric supports. p‐Phenylenediamine and 1,3,5‐trimesoylchloride were adopted as the monomers for the in‐situ polycondensation reaction to form a thin aromatic polyamide selective layer of 150 nm in thickness on the substrate surface, a lab‐made polyethersulfone (PES)/sulfonated polysulfone (SPSf)‐alloyed porous membrane with enhanced hydrophilicity. Under FO tests, the FO membrane achieved a higher water flux of 69.8 LMH when against deionized water and 25.2 LMH when against a model 3.5 wt % NaCl solution under 5.0 M NaCl as the draw solution in the pressure‐retarded osmosis mode. The PES/SPSf thin‐film‐composite (TFC)‐FO membrane has a smaller structural parameter S of 238 μm than those reported data. The morphology and topology of substrates and TFC‐FO membranes have been studied by means of atomic force microscopy and scanning electronic microscopy. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Effect of cellulose triacetate membrane thickness on forward‐osmosis performance and application for spent electroless nickel plating baths

Cellulose triacetate (CTA) forward‐osmosis (FO) membranes were prepared via the phase inversion method. The influence of thickness on the performance and morphology of CTA FO membranes was discussed in detail. When the thickness of the membrane was 50.0 ± 0.5 μm (CTA4), the prototype CTA membranes displayed a water flux of 20.2 L m^?2 h^?1 and a reverse salt transport of 14.6 g m^?2 h^?1 using 1 mol/L NaCl as the draw solution and deionized water as the feed solution during the FO process at 25 °C. In addition, the high‐performance CTA4 FO membranes have been used to process spent electroless nickel plating baths where the water flux could reach 13 L m^?2 h^?1 and NiSO₄·6H₂O crystals occurred in the feed solution of the spent electroless nickel plating baths. The recovery rates of NiSO₄·6H₂O and water from the spent electroless nickel plating baths were 44.54% and 53.53%, respectively. This study focused on improving membrane design for the FO process and finding a new method of waste liquor or wastewater treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45049.     

Synthesis and characterization of PES/PSF/PEG by immersion precipitation for Mediterranean seawater desalination by FO membrane

In the present study, a simple, inexpensive, nontoxic, and environmentally friendly polyethylene glycol (PEG) polymer was used to enhance the hydrophilicity of the forward osmosis (FO) membrane using various PEG concentrations as a pore forming agent in the casting solution of polyethersulfone/polysulfone (PES/PSF) blend membranes. A nonwoven PES/PSF FO blend membrane was fabricated via the immersion precipitation phase inversion technique. The membrane dope solution was cast on polyethylene terephthalate (PET) nonwoven fabric. The results revealed that PEG is a pore forming agent and that adding PEG promotes membrane hydrophilicity. The membrane with 1 wt% PEG (PEG1) had about 27% lower contact angle than the pristine blend membrane. The PEG1 membrane has less tortuosity (which reduces from 3.4–2.73), resulting in a smaller structure parameter (S value) of 277 μm, due to the presence of open pores on the bottom surface structure, which results in diminished ICP. Using 1 M NaCl as the draw solution and distilled water as the feed solution, the PEG1 membrane exhibited higher water flux (136 L m⁻² h⁻¹) and lower reverse salt flux (1.94 g m⁻² h⁻¹). Also, the selectivity of the membrane, specific reverse salt flux, (J_s/J_w) showed lower values (0.014 g/L). Actually, the PEG1 membrane has a 34.6% higher water flux than the commercial nonwoven-cellulose triacetate (NW-CTA) membrane. By means of varied concentrations of NaCl salt solution (0.6, 1, 1.5, and 2 M), the membrane with 1 wt% PEG showed improved FO separation performance with permeate water fluxes of 108, 136, 142, and 163 L m⁻² h⁻¹. In this work, we extend a promising gate for designing fast water flux PES/PSF/PEG FO blend membranes for water desalination.     

Molecular design of the cellulose ester-based forward osmosis membranes for desalination

This work has investigated the fundamental science of phase inversion and formation mechanism of cellulose ester membranes at the interface between polymer and casting substrate. It also explores the desired membrane preparation conditions for forward osmosis (FO) applications. With the aid of positron annihilation lifetime spectroscopy (PALS), the similarity in physicochemical properties between the polymer and the substrate was found to play a significant role in determining the porosity of the bottom interfacial layer. The structure of the dense interfacial layer was also strongly dependent on membrane thickness and solvent composition. Experimental results surprisingly reveal that the original pore size of the as-cast membrane plays a critical role determining the final performance of the subsequent annealed membrane independently of annealing temperature and time. In addition, since a threshold pore size exists during annealing above which pores become difficult to downsize, we have found that a thin dense selective layer integrated in an asymmetric membrane may not always be the best option for FO. A balanced membrane structure consisting of a thin porous support and a thin dense selective layer has been developed for FO, which shows a low internal concentration polarization (ICP) and a relatively high water flux when seawater was employed as the feed.     

三乙酸纤维素正渗透膜的制备与性能

以三乙酸纤维素（CTA）为膜材料,1,4-二氧六环、丙酮为溶剂,甲醇、乳酸为添加剂,采用相转换法制备了三乙酸纤维素正渗透膜。研究了不同1,4-二氧六环/丙酮配比、添加剂乳酸含量、挥发时间、膜厚度、热处理温度条件下正渗透膜性能的变化规律。研究表明,当采用纯水为原料液,0.56mol/L CaCl2为汲取液时,优化制备的CTA正渗透膜的水通量达到14.10L/(m2?h),溶质反扩散量为0.031mol/(m2?h);采用0.1mol/L NaCl为原料液,4mol/L葡萄糖为汲取液时,优化制备的CTA正渗透膜的水通量保持在5L/(m2?h)以上,对NaCl的截留率大于99%。CTA正渗透膜相比于HTI膜,具有较高的亲水性、水通量、截留率,稳定性更好。     

正渗透膜过程中临界通量的影响因素

临界通量是膜过程中一种重要的污染特性指标.采用阶梯汲取液浓度递增法测定不同污染物、架桥离子浓度及膜面流速对正渗透(FO)膜过程临界通量的影响.结果表明,海藻酸钠(SA)、腐殖酸(HA)及二氧化硅(SiO2)污染时FO膜临界通量值分别为29.32,46.35和32.17 L/(m2·h);随 Ca2+浓度由0 mmol/...