Impact of Organic Solvents on Physicochemical Properties of Nanofiltration and Reverse‐Osmosis Membranes

Polymeric membranes subjected to the permeation of n‐hexane were characterized and the influence of pretreatment with ethanol on the properties of the membranes was studied to assess membrane performance and stability. The results suggest that the selectivity of the membrane depends not only on the pore size, but also to a great extent on the interaction between solvent and polymer. An increase in membrane roughness and contact angle was observed for all membranes after pretreatment with ethanol and n‐hexane permeation. Moreover, the surface free energy decreased after solvents exposure, indicating an increase in membrane surface hydrophobicity and polymer swelling. The studied membranes show feasibility of use for the recovery of solvents, if suitable process parameters are selected.     

Reproducible Measurement Results in Organic Solvent Nanofiltration with Ceramic Membranes

Ceramic membranes are still quite innovative to organic solvent nanofiltration. Nevertheless, flux and rejection results obtained in filtration measurements seem to depend largely on the experimental procedure, membrane production batch and setup. Therefore, an experimental approach is described, which proved to provide reproducible and reliable results that may be used as data set to derive parameters in model development.     

Performance of Nanofiltration Membranes for Solvent Purification in the Oil Industry

The extraction stage of edible oil in the oil industry is commonly performed by using toxic solvents (e.g. hexane) and processes with high energy consumption (e.g. distillation, evaporation) to recover the solvent, which represents around 70–75 wt% in the oil–solvent mixture. In this paper, a membrane-based extraction method using nanofiltration (NF) membranes is presented. Commercial nanofiltration membranes made of different polymers (Desal-DK-polyamide NF from GE-osmonics^®, NF30 polyethersulfone NF from Nadir^®, STARMEM^TM122 polyimide from MET^® and SOLSEP NF030306 silicone base polymer SOLESP^®) were selected and tested to recover the solvent from soybean oil/solvent (10–20–30% w/w oil) mixtures at various separation pressures and constant temperature in a dead-end filtration set up. The selection of the solvent was made in order to compare solvents obtainable from renewable resources, such as ethanol, iso-propanol and acetone, with solvents traditionally used in the industry (i.e. cyclohexane and n-hexane). The structural stability of the membranes towards the different solvents used in this work was verified visually, by the variation of the membrane area and by means of permeate flux assessments. Desal-DK and NF30 showed poor filtration performance and even visible defects after exposure to acetone but a good performance was obtained for the nanofiltration membranes STARMEM^TM122 and SOLSEP NF030306 with ethanol, iso-propanol and acetone. For example, considering a mixture with 30% edible oil in acetone, STARMEM^TM122 shows a flux and oil rejection of 16.8 L m^?2 h and 70%, respectively. For the same conditions, SOLSEP NF030306 exhibited a flux of 4.8 L m^?2 h with 78% rejection, which shows the potential application of nanofiltration membranes in the oil industry.     

Silane‐Crosslinked Asymmetric Polythiosemicarbazide Membranes for Organic Solvent Nanofiltration

Crosslinked polythiosemicarbazide (PTSC) membranes with a positively charged surface are fabricated via a reaction with (3‐glycidyloxypropyl)trimethoxysilane. The integrally asymmetric ultrafiltration membranes discussed here can be easily prepared by water‐induced phase separation using a PTSC solution in dimethylsulfoxide (DMSO). The crosslinked PTSC membranes are stable in DMSO, N,N‐dimethylformamide, and tetrahydrofuran and they reject molecules of molecular weights (MW) above 1300 g mol^?1. The influence of the crosslinking agent on the surface charge, membrane solvent resistance, and membrane performance is discussed. The crosslinked asymmetric PTSC membranes totally reject Direct Red dye (MW 1373 g mol^?1), while the pristine PTSC membrane does not show any rejection for this dye. This finding suggests that an inorganic‐type‐network is formed during the crosslinking reaction, which tunes the pore size of the prepared membranes.     

Performance of Alumina Membranes from New Nanosynthesis in Ultrafiltration and Nanofiltration

Starting from simple inorganic or organic raw materials in aqueous or alcoholic solvents, a synthesis process has been developed for (i) the preparation of sol–gel-derived alumina (Al₂O₃) membranes or (ii) the manufacture of membranes by the deposition of precalcined nanocorundum (α-Al₂O₃) powders. Because of the equiaxed shape of the synthesized constituent particles, the permeability of the membranes is a factor of 3–5 greater than in previous products. In contrast to the case for known porous transitional Al₂O₃, the equiaxed shape of the particles in this case is enabled for any of the transitional phases and for the final corundum by a synthesis method that avoids the intermediate crystallization of platelet-shaped boehmite. By this means, nanoporous Al₂O₃ components with pore sizes of ∼1 nm or up to 5 nm can be derived preferentially by sol–gel processing, whereas both sol–gel and nanopowder techniques are used to manufacture ultrafiltration α-Al₂O₃ membranes with a high chemical and thermal stability and with average pore sizes of 10–60 nm. Compared with the sol–gel approach, powder processing decreases the drying and sintering shrinkage and, thus, the frequency and size of flaws, improving the cutoff characteristics of the membranes. For catalytic applications, the porous ceramic microstructures also can be applied on larger metal substrates.     

新型纳滤膜材料研究进展

简单阐述了纳滤膜的特点及应用范围,重点分类介绍了近年来一系列新型纳滤膜材料及其性质与研究成果,包括有机高分子膜材料、有机-无机矿物膜和无机陶瓷膜材料三大类,分别列举各类材料的典型膜,对各种膜的性能参数和主要制备方法进行了对比总结,并对膜材料今后的发展前景作了展望。     

Performance of Nanofiltration Membranes in Ethanol

Abstract

Several nanofiltration membranes were tested for flux and rejection of selected solutes in ethanol. The membranes were initially conditioned with pure solvent containing increasing concentrations of ethanol. Flux decreased with increase in ethanol concentration and increased at higher temperatures and pressures. The type of solute had an influence on membrane rejection profiles. The DK membrane showed increasing rejection of polyethylene glycols (PEG) dissolved in ethanol from 29% at a molecular weight (MW) of 200 to 80% at MW 1000. However, the MW of sugars and lipids had little or no effect on rejection with the DK membrane; their rejection averaged 87%. In contrast, the TFC‐SR1 membrane showed higher rejections with higher MW compounds: lipid rejection increased from 19% to 71%, sugars from 35% to 85%, and lipids from 77% to 89%. The TFC‐SR2 membrane was much more open and showed the lowest rejections of all these compounds. Flux generally showed opposite trends, with the DK showing the lowest flux and the SR2 the highest.     

Development of High Performance Nanofiltration Membranes with Hydrophilic Surface for the Removal of Cadmium from Contaminated Water

In present research, novel asymmetric polysulfone (PSF) membranes with high hydrophilicity and noticeable rejection of cadmium, as one of the major environmental problems, were prepared from PSF/PEG400/NMP system via immersion precipitation. Pure water was used as gelation media. The variation effect of the coagulation bath temperature (CBT) and addition of PEG400 on morphology, wettability, and permeability of the prepared membranes were studied by scanning electron microscopy (SEM), contact angle measuring, and the experimental set up. The results demonstrated that both the hydrophilicity and the rejection properties of the prepared membranes were significantly enhanced by a small addition of PEG400 in the casting solution along with using the lowest level of CBT. Also, it was found out that the addition of PEG400 in the casting solution along with increasing the CBT resulted in the formation of membranes with high permeability and sub-layer porosity and thin top layer.     

Performance of Nanofiltration Membranes in the Treatment of Synthetic and Real Seawater

Abstract

Nanofiltration membranes (NF) are being employed in pretreatment unit operations in both thermal and membrane seawater desalination processes and as partial demineralization to seawater. In order to predict NF membrane performance, a systematic study on the filtration performance of selected commercial NF membranes against seawater is presented in this paper. Two commercial nanofiltration membranes (NF90 and NF270) have been investigated in details to study their performance in filtering the salt mixture, synthetic and real seawater in a cross‐flow NF membrane process at a pressure range from 4 to 9 bars. The Spiegler‐Kedem model was used to fit the experimental data of rejection with the permeate flux in order to determine the fitting parameters of the reflection coefficient (σ) and the solute permeability (P_s). The results showed that the rejection increases with pressure for NF90 and slightly increases with pressure for NF270. Also, the NF90 membrane has shown to be able to reject both monovalent and divalent of all investigated mixtures and seawater with very reasonable values but at a relatively low flux. Moreover, it reduced the salinity of investigated seawater from 38 to 25.5 g/L using one stage of the NF membrane at 9 bars. This makes NF90 more suitable for the application in the pretreatment of desalination processes. On the other hand, NF270 can reject monovalent ions at relatively low values and divalent ions at reasonable values. It has also reduced the seawater salinity to 33.6 g/L, but at a very high permeate flux. The SKM model fitted the experimental data of divalent ions in salt mixture and seawater.     

无机/有机复合分离膜研究与应用进展

无机/有机复合分离膜既具有聚合物膜的高选择性、高渗透性的优势，又具有无机膜的耐高温、抗腐蚀的优点。开发新型的无机/有机复合分离膜是膜材料领域的热点之一。介绍了无机/有机复合分离膜的特点、结构、制法以及提高复合分离膜渗透性能和选择性的途径。最后对复合分离膜的应用进展作了阐述。     

Estimation of Separation of Electrolytes and Organic Compounds by Nanofiltration Membranes Using an Irreversible Thermodynamic Modei

Nanofiltration separation has become a popular technique for removing large organic molecules and inorganic substances from water. It is achieved by a combination of three mechanisms: electrostatic repulsion, sieving and diffusion. In the present work, a modei based on irreversible thermodynamics is extended and used to estimate rejection of inorganic salts and organic substances. Binary systems are modeled, where the feed contains an ion that is much less permeable to the membrane as compared with the other ion. The two modei parameters are estimated by fitting the modei to the experimental data. Variation of these parameters with the composition of the feed is described by an empirical correlation. This work attempts to describe transport through the nanofiltration membranes by a simple model.     

Role of Organic Acids in Flux Enhancement of Polyamide Nanofiltration Membranes

A novel thin‐film composite (TFC) nanofiltration membrane containing hydrophilic organic additives was fabricated via interfacial polymerization. Three organic acids, i.e., lactic, maleic, and citric acid, served as aqueous‐phase additives and their role in membrane structure and nanofiltration membrane flux enhancement was investigated. Fourier transform‐infrared (FT‐IR) analysis confirmed the presence of organic acids in the polyamide (PA) layer. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses were applied to investigate the membrane morphology. The more carboxylic functional groups present in the additive resulted in higher hydrophilicity and porosity and flux was enhanced significantly compared to the neat PA membrane, while salt rejection was influenced only to a minor extent.     

用不可逆过程热力学模型估算通过纳米过滤膜电解质和有机化合物的分离

Nanofiltration separation has become a popular technique for removing large organic molecules and inorganic substances from water. It is achieved by a combination of three mechanisms: electrostatic repulsion,sieving and diffusion. In the present work, a model based on irreversible thermodynamics is extended and used to estimate rejection of inorganic salts and organic substances. Binary systems are modeled, where the feed contains an ion that is much less permeable to the membrane as compared with the other ion. The two model parameters are estimated by fitting the model to the experimental data. Variation of these parameters with the composition of the feed is described by an empirical correlation. This work attempts to describe transport through the nanofiltration membranes bv a simple model.     

耐溶媒纳滤膜在盐酸林可霉素母液回收中的应用

采用Hydrochem公司的SeLROTM耐溶媒纳滤膜及M104防爆型中试设备浓缩盐酸林可霉素丙酮母液至30万U/ml,将浓缩液重结晶,获得盐酸林可霉素成品.根据检验结果,盐酸林可霉素符合CP2000标准,另外可提高收率2%～4%,效益十分可观,应用前景广阔.     

抗污染纳滤膜的制备及性能研究

以哌嗪为水相单体,海藻酸钠为其亲水性表面活性剂,以含有均苯三甲酰氯的IsoparG为油相,聚砜超滤膜为底膜,通过界面聚合反应制备一种网络结构的抗污染纳滤膜.利用扫描电子显微镜,原子力显微镜和红外光谱仪等检测方法对纳滤复合膜进行了性能和结构方面的表征.结果 表明:在0.75 MPa、3.785 L/min、25℃恒温条件...     

溶剂的性质对聚砜／磺化聚砜合金膜性能的影响

介绍了溶剂的性质对聚砜 /磺化聚砜 (PSF/SPSF)合金分离膜膜性能的影响     

Treatment of Oily and Salty Mining Water by Ceramic Nanofiltration Membranes

Ceramic nanofiltration membranes were successfully tested and piloted for the treatment of oily and salty water from oil sand mining in Alberta, Canada. The membranes showed a stable behavior over two years operation. The complete removal of suspended solids as well as the reduction of multivalent ions enable the use of recycle water from tailing ponds to prepare boiler feed water. In high salt concentration like waste water from potash mining a dependency of salt retention on the salt composition and concentration was observed. High MgSO₄ retention even at high salt concentration was achieved.     

PVDF有机膜改性技术的研究进展

综述了目前PVDF有机膜的改性技术及其研究进展,PVDF有机膜的改性技术总体分为物理改性和化学改性。经过改性后的膜在一定程度上能够有效增强亲水性和抗污染能力,但成膜后的稳定性有待进一步提高。指出今后应加强在不同的环境因素中对PVDF有机膜的改性及应用研究。     

纳滤膜对无机盐水溶液脱盐性能的研究

选择了NE和HL两种纳滤膜对NaCl、KCl、Na2SO4、MgCl2、CaCl2及MgSO4等6种无机盐水溶液体系进行分离实验;考察纳滤膜分离性能随操作压力、料液浓度、无机盐种类等变化的影响及纳滤膜脱盐的稳定性,得到纳滤膜一些脱盐的规律。