耐溶剂纳滤膜的制备与应用研究进展

有机溶剂纳滤(organic solvent nanofiltration,OSN)是近年来快速发展起来的一项新型纳滤膜分离技术,具有广阔的应用前景。耐溶剂纳滤(solvent-resistant NF,SRNF)膜的制备是OSN技术发展的关键,也是目前的研究热点之一。本文侧重阐述了SRNF膜在制备及应用方面的进展,着重介绍了相转化法、界面聚合法、自组装法及有机-无机杂化法等SRNF膜制备方法。相转化法是目前国内外SRNF膜制备研究常用的方法,但该法所制备的膜皮层较厚,通量明显偏小;界面聚合法SRNF膜制备的相关研究目前较少,但由于其皮层非常薄,因此是SRNF膜制备发展的一大趋势;自组装膜有较好的耐溶剂性能;加入无机物可以提高耐有机溶剂性,有机-无机杂化法的膜制备是SRNF膜制备的趋势之一。同时简单介绍了SRNF膜的应用,并对未来SRNF膜研究的方向提出了建议。     

有机溶剂纳滤传递模型及最新膜材料研究进展

有机溶剂纳滤（organic solvent nanofiltration, OSN）是一种高效节能、操作简便的新型膜分离技术,在化工、制药、能源和环境等相关领域具有广阔的应用前景,因此受到了膜技术领域内研究者们的重点关注。本文首先简述了有机溶剂纳滤的应用背景,其次从有机溶剂纳滤传递模型与膜材料两个方面,总结归纳了近年来在有机溶剂纳滤领域取得的研究进展。总结了基于无机陶瓷、高分子聚合物、多孔有机聚合物、有机-无机杂化材料以及石墨烯类二维材料等用于制备新型OSN膜的研究进展,并结合传输模型讨论分析了有机溶剂分子在膜内的传输行为及膜的分离性能。最后简述了有机溶剂纳滤技术在化工及相关行业中的应用现状,并指出了这些关键有机溶剂纳滤膜材料在有机溶剂纳滤应用中存在的优势和挑战,提出了基于这些关键材料的特点进行设计和优化OSN膜性能的建议供参考,以期促进有机溶剂纳滤膜的研究和应用。     

Enrichment of carotene from palm oil by organic solvent nanofiltration

Palm oil is one of the richest sources of natural plant carotene with typical concentration of about 0.5–0.7 g/L. Unfortunately, during physical refining of palm oil, most of the carotenes were destroyed by high temperatures and this represents a loss of potential source of natural carotene. Various techniques have been developed to extract and recover carotenes from palm oil, however these processes often require high energy usage, and usually renders the oil useless for further consumption. Recently, organic solvent nanofiltration (OSN) has become an important method for molecular separation particularly for the separation of low molecular weight bioactive compounds. This work presents the application of OSN membranes for the separation of carotene from a crude palm oil/solvent system. Several commercial OSN membranes (DuraMem and PuraMem series) fabricated from polyimide were evaluated for their separation abilities. PuraMem 280 showed the best selectivity performance, with the concentration of carotene in permeate oil increased from 0.60 to 0.79 g/L when hexane was used as the solvent. Runs by using DuraMem 150, DuraMem 300 and DuraMem 500 showed low or no selectivity between carotene and triglyceride in all solvents. It was found that the rejection of carotene depends strongly on the type of solvents. A coupled solution diffusion and film theory was also utilized to model carotene transport through OSN membrane. It was demonstrated that OSN can serve as an alternative for the direct carotene recovery from palm oil and can be potentially applied for other minor compounds recovery from vegetable oils.     

Nanofiltration membrane cascade for continuous solvent exchange

This paper proposes a continuous process for solvent exchange, a key unit operation for organic synthesis in pharmaceutical manufacturing. This process comprises a counter-current membrane cascade using organic solvent nanofiltration (OSN) membranes. The effect of process parameters, such as number of stages and flow rate ratio of replacing solvent to initial solvent, on solvent exchange performance are tested through simulations and experiments. Experimental results show 47.8%, 59.2%, and 75.3% solvent exchange for single-stage, two-stage and three-stage cascades, values which are close to the 50.0%, 66.6%, and 75.0% predicted by simulations. In general, the feasibility of OSN membrane cascades for continuous solvent exchange is demonstrated in this work.     

Molecularly imprinted organic solvent nanofiltration membranes – Revealing molecular recognition and solute rejection behaviour

A new class of organic solvent nanofiltration (OSN) membranes featuring molecular recognition sites has been fabricated by a phase inversion molecular imprinting technique. Polybenzimidazole (PBI) was employed as a functional polymer for molecular imprinting for the first time. Apart from acting as a functional polymer, PBI exhibits excellent chemical and solvent stability and can be used as a nanofiltration membrane, acting both as shape-specific adsorbent and size-exclusion membrane. The molecularly imprinted organic solvent nanofiltration (MI-OSN) membranes fabricated in this study showed both nanofiltration membrane performance, and excellent molecular recognition ability. The model system comprised roxithromycin pharmaceutical, 2-aminopyrimidine building block and N,N-dimethylaminopyridine catalyst, which are retained, adsorbed and permeated through the MI-OSN membrane, respectively. The effect of both dope solution concentration and applied pressure on the molecular recognition behaviour of MI-OSN membranes has been investigated by employing Sips and Freundlich adsorption isotherms, as well as examining the physical morphology of the membranes. The rate of adsorption was investigated, revealing that the adsorption follows second-order kinetics and is not limited by diffusion. The imprinted membrane exhibited fourfold higher flux whilst maintaining the same rejection performance in comparison to the control membrane. It is shown that increasing the transmembrane pressure across the MI-OSN membrane irreversibly suppresses the molecular recognition whilst maintaining the rejection and flux performance.     

有机溶剂纳滤膜的润湿性对渗透和分离性能的影响

有机溶剂纳滤是一种绿色、高效、节能的新型膜分离技术,在回收和处理有机溶剂中具有广泛的应用前景。本文采用浸渍法分别将聚合物聚二甲基硅氧烷（PDMS）、嵌段聚醚酰胺（PEBAX2533）和聚乙烯醇（PVA）与聚砜（PS）超滤基膜复合,制备了3种不同润湿性的聚合物耐溶剂纳滤膜,研究了PDMS/PS、PEBAX/PS和PVA/PS复合膜对甲醇、乙醇、异丙醇、正己烷、正庚烷的渗透性能,考察了3种聚合物膜对伊文思蓝/甲醇溶液的有机溶剂纳滤性能。结果表明,有机溶剂在不同润湿性复合膜的渗透和传递性能与溶剂本身的溶度参数、分子量、黏度和极性等有很密切的相关性,溶剂的分子量、黏度、分子动力学直径越小,在同一极性复合膜中渗透通量越大;对伊文思蓝/甲醇溶液的有机溶剂纳滤分离表明,PDMS/PS和PEBAX/PS复合膜的截留率均可达90%以上,通量分别为 58.0L/(m²·h·MPa)和72.2L/(m²·h·MPa);PVA/PS复合膜的截留率为85.1%左右,通量为57.5L/(m²·h·MPa)。     

Investigation of OSN properties of PDMS membrane for the retention of dilute solutes with potential industrial applications

Few commercially available membranes can be used for organic solvent nanofiltration (OSN). Applying OSN in chemical industries is nevertheless of high interest to cut with energy consumption linked to solvent recycling and soluble catalysts recovery. A commercial membrane, PERVAP4060, was used to investigate the retention of dilute solutes in toluene feeds and to mimic metathesis medium. The studied solutes were R-BINAP a neutral polyaromatic molecule used in metathesis chemistry, tetraoctylammonium bromide (ToABr), a charged molecule used as a homogeneous catalyst and n-hexadecane. Retention of polar ToABr (95%) was higher than that of neutral R-BINAP (80%). The transfer mechanism, either pore flow or solution-diffusion, was discussed. All the results obtained suggested that the transport is governed by the solution-diffusion mechanism. The measured retentions could be explained in terms of solubility affinities and diffusion coefficients. The stability and performances of PERVAP4060 were well established, showing the strong potential for industrial applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48359.     

Potenziale und Herausforderungen in der Implementierung der organophilen Nanofiltration in der Spezialchemie

Organic solvent nanofiltration (OSN) is a suitable tool for process intensification. For specialty chemicals production within a multi‐purpose environment, there are some specific concerns regarding membranes and equipment design that have to be considered. Process development for OSN to date is hampered by a lack of system characteristics and detailed transport models. Here, we present a systematic investigation with different membrane materials and solvents in order to define guidelines for a fast membrane selection.     

Hybrid separations combining distillation and organic solvent nanofiltration for separation of wide boiling mixtures

Membrane assisted hybrid separations offer tremendous potential for process intensification which aims at increasing resource efficiency as well as decreasing operating and capital costs. Design of such processes is challenging due to large number of degrees of freedom but also due to large experimental effort necessary for membrane screening and for characterising membranes in whole operating range. To address these issues, this paper elaborates a four-step design method for combination of organic solvent nanofiltration (OSN) and distillation in a hybrid separation of wide boiling mixtures. The design method is applied in a case study which is the separation of small amounts of heavy boiler from a mixture containing a mid- and a light-boiler. In the first step, different process options are generated based on heuristics and engineering judgement and screened for feasibility. In the second step, the options are evaluated based on quantitative metrics using rigorous models. In this step the unknown key parameters are identified, and their influences on the process performance are quantified in a detailed a priori process analysis. If hybrid separations with OSN show to be promising when compared to stand-alone distillation, experiments are conducted to (i) identify the best membrane for the operating window in which the hybrid process operates and (ii) to perform model validation and parameterisation in the third step. In the last (fourth) step, an optimisation is performed to identify the best (cost optimal) process using the experimental data gained in step three.     

High-flux and solvent-selective membranes with aromatic functionalities and dual-layer structures

Efficient separation of aromatic-aliphatic hydrocarbon mixtures has long been an important topic in chemical industries. Organic nanofiltration (OSN) has been revealing great promise in separating solvent mixtures that has not been effectively resolved by the state-of-the-art technologies. Herein, novel OSN membranes are designed for the separation of toluene and n-heptane. Polyamide active layer with diaminonaphthalene as the aqueous phase monomer is prepared by interfacial polymerization for the first time. The addition of polydimethylsiloxane gutter layer, as well as the combination of spin coating technique and macroporous substrate, renders the membranes with loose and defect-free architectures. The as-designed membranes achieve a rather high selectivity of toluene over n-heptane (>4) together with ultra-high toluene permeance (>180 L m^?2 h^?1 bar^?1). These membranes also present excellent stability in the long-term operation.     

Homogeneous Catalyst Recycling and Separation of a Multicomponent Mixture Using Organic Solvent Nanofiltration

In homogeneous catalysis, the application of organic solvent nanofiltration (OSN) has become a well‐known alternative to common recycling methods. Even though some OSN membranes are commercially available, their classification and the scope of application have to be determined for the specific solvent mixture. The commercial membrane Evoniks DuraMem® 300 was tested in a mixture of ethanol, ethyl acetate, and cyclohexane with magnesium triflate as possible catalyst. The cross permeate fluxes were measured for two transmembrane pressures and the hydrodynamic radii of the components were determined. Some of the components in the ternary mixture are retained, which makes the membrane also suitable for fractioning thereof.     

Recent advances in acid-resistant zeolite T membranes for dehydration of organics

Zeolite membranes offer outstanding potentials in separation of many molecular mixtures due to their molecular sieving selectivity and the high thermal and mechanical stability that allow them to operate at harsh conditions.Development of durable and high separation performance membranes with lower fabrication and operation cost are highly demanded for industrial applications. Zeolite T membrane possesses good acid-resistance with excellent hydrophilic properties as compared to NaA zeolite membrane and can be extended to industrial organic dehydrations under an acidic environment. In the present review the research advances in development of zeolite T membranes for the dehydration of organic mixtures in acidic conditions are summarized. Especially the low temperature synthesis, and epitaxial growth of the zeolite membrane with high performance are well addressed, besides emphasis is particularly placed on ensemble synthesis of hollow fiber zeolite T membrane module and its future prospects for industrial separations.     

Synthesis and optimization of high-performance amine-based polymer for CO2 separation

Membrane technology features inspiring excellence from numerous separation technologies for CO₂ capture from post-combustion gas. Polyvinylamine (PVAm)-based facilitated transport membranes show significantly high separation performance, which has been proven promising for industrial scale-up. However, commercialized PVAm with low molecular weight and excessive crystallinity is not available to prepare high-performance membranes. Herein, the synthesis process of PVAm was optimized by regulating polymerization and acidic hydrolytic conditions. The membranes based on PVAm with a molecular weight of 154 kDa and crystallinity of 11.37% display high CO₂ permeance of 726 GPU and CO₂/N₂ selectivity of 55 at a feed gas pressure of 0.50 MPa. Furthermore, we established a PVAm synthesis reactor with an annual PVAm solution (1%(mass)) capacity of over 7000 kg and realized the scaled-up manufacture of both PVAm and composite membranes.     

Rejection of salt mixtures from high saline by nanofiltration membranes

Nanofiltration (NF) membranes have recently been employed as pretreatment unit operations in seawater desalination processes and as partial demineralization to seawater. The present paper investigates the performance of selected commercial NF membranes to reject salts of high concentrations at salinity levels representative of brackish and sea water. Two commercial nanofiltration membranes (NF90 and NF270) have been investigated in detail to study their performance in filtering aqueous solutions containing different salt mixtures in a cross-flow NF membrane process within the pressure range from 4 to 9 bar. Spiegler-Kedem model (SKM) was used to fit the experimental data of rejection with the permeate flux. The results showed that NF90 membrane was shown to have a distinct ability to reject both monovalent and divalent ions of all investigated mixtures with very reasonable values but with relatively low flux. This will make 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, but at very high permeate flux. The SKM model only fitted well the experimental data of divalent ions in salt mixture. Based on the evaluation of the overall performance of NF90 and NF270 membranes, their distinct ability to reject salts at high salinity from seawater is considered an advantage in the field of pretreatment of seawater feed to desalination units.     

富氮膜分离过程的理论分析和实验研究

本文对用中空纤维膜从空气中富集氮气的过程进行研究,较好地揭示了过程中各参数及膜性能与分离结果的关系.改变实验条件可得到浓度为85%～99.6%的富氮气体,回收率为78%～23%.实验对理论模型进行了验证,结果表明,在实验浓度范围内采用柱塞流逆流模型和全混柱塞流模型的计算值与实验值基本吻合,模型可以满足工业模拟和设计要求.     

Artificial particulate fouling of hyperfiltration membranes — II analysis and protection from fouling

An artificial fouling method was used to study the effect of suspended particulates on the performance of standard asymmetric cellulose acetate membranes in flat cells. Using a modified filtration theory developed here, membrane and cake resistances to permeation were individually monitored as a function of applied pressure, membrane curing temperature, and feed type. The membranes behaved according to the solution-diffusion model.A new previously unreported method of membrane protection — the protective cover method — for submicron colloidal solutions, resulted in as high as 78% increased fluxes and 43% decreased salt rejections, over the unprotected membrane. This development is applicable where low salt rejection and high fluxes are desired such as in industrial and municipal wastewater renovation.     

Development of bipolar membrane-based processes

Recently, a bipolar membrane-based process has become one of the most attractive fields in the world from both academic and industrial points of view. The intention of this paper is to give a brief overview and technical advantages as well as some experimental results by using bipolar membranes in the areas of environmental engineering, chemical production, bioengineering, energy sources, etc.     

Polyaromatics

The polyaromatics are an important group of industrial polymers. For the highest performance applications the polyaryletherketones and polyarylethersulphones have proved very effective and have been successfully commercialised. Both polymer types, but mainly polyetheretherketone (Victrex PEEK), have been subjected to intense academic and industrial research in respect of their physical and chemical properties, thermal stability, irradiation resistance and their application in engineering and composite matrices. The synthesis of these polyaromatics has been widely studied but the nucleophilic polycondensation route is proving to be the only commercially viable one. Block copolymers have been synthesised, using transetherification to randomise polyaryletherketone-co-sulphone backbones as well as by utilising the reactive polymer end-groups, and studied in considerable detail to establish structure–property relationships. Such end-groups on arylethersulphone-type polymers have also been used effectively in the development of tough, solvent-resistant and easily processable thermoset–thermoplastic blends for use, in particular, as composite matrices. Pendant functionality has been studied as a route to improved properties and solvent resistance and is used commercially in the manufacture of polymers for membranes.     

Potential use of nanofiltration like-forward osmosis membranes for copper ion removal

The discharge of industrial effluent containing heavy metal ions would cause water pollution if such effluent is not properly treated. In this work, the performance of emerging nanofiltration(NF) like-forward osmosis(FO)membrane was evaluated for its efficiency to remove copper ion from water. Conventionally, copper ion is removed from aqueous solution via adsorption and/or ion-exchange method. The engineered osmosis method as proposed in this work considered four commercial NF membranes(i.e., NF90, DK, NDX and PFO) where their separation performances were accessed using synthetic water sample containing 100 mg·L~(-1) copper ion under FO and pressure retarded osmosis(PRO) orientation. The findings indicated that all membranes could achieve almost complete removal of copper regardless of membrane orientation without applying external driving force.The high removal rates were in good agreement with the outcomes of the membranes tested under pressuredriven mode at 1 MPa. The use of appropriate salts as draw solutes enabled the NF membranes to be employed in engineered osmosis process, achieving a relatively low reverse solute flux. The findings showed that the best performing membrane is PFO membrane in which it achieved N 99.4% copper rejection with very minimum reverse solute flux of 1 g·m~(-2)·h~(-1).     

Comparative behavior of PVA/PAN and PVA/PES composite pervaporation membranes in the pervaporative dehydration of caprolactam

Flat‐sheet composite membranes were developed by the traditional phase inversion technique using poly;(vinyl alcohol) (PVA). PVA composite pervaporation (PV) membranes were prepared with crosslinked PVA selective layer and porous polyacrylonitrile (PAN) and polyether sulfone (PES) substrate layer material as supports for separating heat sensitivity substance ε‐caprolactam (CPL) from CPL/water mixtures. Glutaraldehyde was used as crosslinking agent. The effect of the composition of glutaraldehyde on membrane stability and structure were investigated. The operating parameters, such as feed concentration and operating temperature, remarkably affected PV performance of the composite membranes. The composite membranes with PVA casted on PAN (PVA/PAN) showed superior PV performance than that casted on PES (PVA/PES). This study has also shown that the type of porous support plays an important role in the PV performance. As a result, this work has presented the information needed of the behavior of PV membranes for dehydration applications of industrial caprolactam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 4005–4011, 2007