Two dimensional nanomaterial‐based separation membranes

Two dimensional nanomaterials including graphene, hexagonal boron‐nitride, molybdenum disulfide, etc., provide immense potentials for separation applications. However, the tradeoff between selectivity and permeability in choosing 2D nanomaterial‐based membrane is inevitable, limiting the progress on separation efficiency for mass industrial applications. To target these issues, versatile strategies such as the rational design of predefined interlayer channels, membrane nanopores, and reasonable functionalization, as well as new mechanisms have been emerged. In this review, we introduce the recent progress on separation mechanisms of 2D nanomaterial‐based membranes with different structures (including the interlayer channels type and the membrane nanopores type) and their inner surface functionalization. Moreover, the interface designs are discussed, in terms of employing dynamic liquid–liquid/liquid–gas interfaces, to advance the selectivity and permeability of the membranes. We further discuss the variety of separation applications based on 2D nanomaterial‐based membranes. The authors hope this review will inspire the active interest of many scientists in the area of the development and application of membrane science.     

Recent progress on the smart membranes based on two-dimensional materials

Inspired by the biosystems, the artificial smart membrane to control the mass transport and molecular conversion has attracted increasing attention in the fields of membrane separation, desalination, nanofiltration, healthcare and environmental remediation. However, the trade-off limitations in polymeric membranes greatly hinder the development of smart membranes with high permeability and manipulability. Recently, inspired by the unique physical/chemical properties of two-dimensional(2 D) mater...     

Nuclear magnetic resonance of polymer electrolyte membrane fuel cells

In this review, the contribution of NMR spectroscopy to the development of the proton exchange membrane fuel cell (PEMFC) is discussed, with particular emphasis on its use in the characterization of structure and transport in proton exchange membranes (PEMs). Owing to copious amount of information available, results of the past decade will be the main focal point. In addition, its use as a screening tool for the PEM materials will be discussed. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.201000010     

Membrane Distillation and Related Operations—A Review

Abstract

Membrane contactors represent an emerging technology in which the membrane is used as a tool for inter phase mass transfer operations: the membrane does not act as a selective barrier, but the separation is based on the phase equilibrium. In principle, all traditional stripping, scrubbing, absorption, evaporation, distillation, crystallization, emulsification, liquid‐liquid extraction, and mass transfer catalysis processes can be carried out according to this configuration. This review, specifically addressed to membrane distillation (MD), osmotic distillation (OD), and membrane crystallization (MCr), illustrates the fundamental concepts related to heat and mass transport phenomena through microporous membranes, appropriate membrane properties, and module design criteria. The most significant applications of these novel membrane operations, concerning pure/fresh water production, wastewater treatment, concentration of agro food solutions, and concentration/crystallization of organic and biological solutions, are also presented and discussed.     

Transport across artificial membranes–an analytical perspective

Biosensors that make use of transport processes across lipid membranes are very rare even though a stimulus, the binding of a single analyte molecule, can enhance the sensor response manifold if the analyte leads to the transport of more than one ion or molecule across the membrane. Prerequisite for a proper function of such membrane based biosensors is the formation of lipid bilayers attached to a support that allow for the insertion of membrane peptides and proteins in a functional manner. In this review, the current state of the art technologies to obtain lipid membranes on various supports are described. Solid supported membranes on transparent and electrically conducting surfaces, lipid bilayers on micromachined apertures and on porous materials are discussed. The focus lies on the applicability of such membranes for the investigation of transport phenomena across lipid bilayers facilitated by membrane embedded peptides, channel proteins and transporters. Carriers and channel forming peptides, which are easy to handle and rather robust, are used frequently to build up membrane based biosensors. However, channel forming proteins and transporters are more difficult to insert functionally and thus, there are yet only few examples that demonstrate the applicability of such systems as biosensor devices.      

Fabrication and analytical applications of hybrid mesoporous membranes.

Recently, a hybrid mesoporous membrane composed of surfactant-templated mesoporous silica inside a porous anodic alumina membrane has been developed. Since this membrane allows the use of columnar silica-mesopores (silica-nanochannels) as nanofluidic channels, separation of molecules can be realized by mass transport through the silica-nanochannel with molecular dimensions. Here, we review the methods to fabricate the hybrid mesoporous membranes, their structural features, and the analytical applications of hybrid mesoporous membranes.     

Laminar Graphene Oxide Membranes Towards Selective Ionic and Molecular Separations: Challenges and Progress

Resolution of resources and environmental crises requires an efficient separation technologies, consequently, scientists and engineers are working vigorously for ideal separation materials. Laminar graphene oxide (GO) is a two‐dimensional (2D) material offers considerable interest in this field due to its single atomic layer thickness, good stability, chemical inertness, and variety of functional groups. Recently, GO have emerged as a novel membrane material for molecular and ionic separation of gases, solvent, water, and desalination applications. This tutorial review aims to discuss the various approaches used to control the stacking of GO‐based membrane with emphasis of advantages and drawbacks associated with each approach. Further, attention will also be given to describe the recent progress in GO based membranes for ionic and molecular separations. Meanwhile, challenges and opportunities will also be discussed in detail. We hope this review expected to provide a compact source of information that will be of great interest to chemists, material scientists, physicists, and engineers working or planning to work in GO based membranes for separation applications.     

Poly(ether ether ketone) derivative membranes—a review of their preparation, properties and potential

The present paper gives an overview of the properties and performance of membranes of a poly(ether ether ketone) derivative with a cardo group in the chain, known in the literature as PEEKWC or PEK-C. This is one of the typical examples of a new polymer, emerged in the last two decades, with the potential to be applied as a membrane material in a wide range of application fields. Due to the presence of the cardo group in the backbone, the polymer is soluble in several common organic solvents, in contrast to the traditional poly(ether ketone) (PEK) and poly(ether ether ketone) (PEEK). It is therefore more versatile and its solubility allows the use of nonsolvent-induced phase inversion techniques to prepare membranes with a wide range of different morphologies and transport characteristics. The present review will show the current state of the art and will testify that PEEKWC offers interesting perspectives in especially the fields of gas separation, biomedical applications and—in its sulfonated form-in fuel cells. Examples of successful application in microfiltration, ultrafiltration, nanofiltration, pervaporation, membrane contactors, catalytic membranes and some other applications, such as packaging and molecular imprinting will also be shown.     

Cargo-towing synthetic nanomachines: towards active transport in microchip devices

This review article discusses the use of synthetic catalytic nano motors for cargo manipulations and for developing miniaturized lab-on-chip systems based on autonomous transport. The ability of using chemically-powered artificial nanomotors to capture, transport and release therapeutic payloads or nanostructured biomaterials represents one of the next major prospects for nanomotor development. The increased cargo-towing force of such self-propelled nanomotors, along with their precise motion control within microchannel networks, versatility and facile functionalization, pave the way to new integrated functional lab-on-a-chip powered by active transport and perform a series of tasks. Such use of cargo-towing artificial nanomotors has been inspired by on-chip kinesin molecular shuttles. Functionalized nano/microscale motors can thus be used to pick a selected nano/microscale chemical or biological payload target at the right place, transport and deliver them to a target location in a timely manner. Key challenges for using synthetic nanomachines for driving transport processes along microchannel networks are discussed, including loading and unloading of cargo and precise motion control, along with recent examples of related cargo manipulation processes and guided transport in lab-on-a-chip formats. The exciting research area of cargo-carrying catalytic man-made nanomachines is expected to grow rapidly, to lead to new lab-on-a-chip formats and to provide a wide range of future microchip opportunities.     

New replication technique for the fabrication of thin polymeric microfluidic devices with tunable porosity

In this article we present a new versatile replication method to produce thin polymeric microfluidic devices with tunable porosity. This method is based on phase separation of a polymer solution on a microstructured mold. Compared to existing microfabrication techniques, such as etching and hot embossing, our technique offers four advantages: (a) simple and cheap process that can be performed at room temperature outside clean room facilities; (b) very broad range of applicable materials (including materials that could not be processed before); (c) ability to make thin flexible chips; (d) ability to introduce and tune porosity in the chip. By introducing porosity, the channel walls can be used for selective transport of gasses, liquids and solutes. A proof-of-concept will be given, by showing fast CO2 transport through the channel walls of a porous polymer chip. Furthermore, it will be demonstrated that the gas permeation performance of chips can be enhanced dramatically by a decrease in chip thickness and incorporation of porosity. We expect that the development of porous chips can lead to the on-chip integration of multiple unit operations, such as reaction, separation, gas liquid contacting and membrane emulsification.     

Potential of membrane-mimetic polymers in membrane technology

Development of new generations of membranes with high degrees of permeabilities and controllable mass transport properties requires a fundamental understanding of the relationship between molecular structures and permeabilities. Initiation of interdisciplinary research in biology, biophysics, polymer and colloid chemistry is proposed to provide the insight to membrane transport processes at the molecular level. Mother nature's most talented transporter — the biological membrane — should inspire this endeavor. Following a survey of the properties of, and recognized transport mechanisms in, biomembranes, membrane-mimetic chemistry is introduced to serve as a bridge between biological and polymeric membranes. Surfactant aggregates — micelles, monolayers, organized multilayers (Langmuir—Blodgett films), bilayer lipid membranes (BLMs), vesicles and polymerized vesicles — are shown to be the media in membrane-mimetic chemistry. Properties of these organized surfactant assemblies are summarized. Emphasis is placed on the control of molecular transport in membrane-mimetic systems. Perspectives and prospectives of biomimetic membranology are discussed.     

Template-synthesized nanotubes for chemical separations and analysis

We have developed a new class of synthetic membranes that consist of a porous polymeric support that contains an ensemble of gold nanotubes that span the thickness of the support membrane. The support is a commercially-available microporous polycarbonate filter with cylindrical nanoscopic pores. The gold nanotubes are prepared by electroless deposition of Au onto the pore walls, that is, the pores acts as templates for the nanotubes. We have shown that by controlling the Au deposition time, Au nanotubes that have effective inside diameters of molecular dimensions (<1 nm) can be prepared. These nanotube membranes can be used to cleanly separate small molecules on the basis of molecular size. Furthermore, use of these membranes as a novel electrochemical sensor is also discussed. This new sensing scheme involves applying a constant potential across the Au nanotube membrane and measuring the drop in the transmembrane current upon the addition of the analyte. This paper reviews our recent progress on size-based based transport selectivity and sensor applications in this new class of membranes.     

Direct reconstitution of plasma membrane lipids and proteins in nanotube-vesicle networks

We demonstrate here that nanotube-vesicle networks can be constructed directly from plasma membranes of cultured cells. We used a combination of dithiothreitol (DTT) and formaldehyde to produce micron-sized plasma membrane vesicles that were subsequently shaped into networks using micromanipulation methods previously used on purely synthetic systems. Only a single cell is required to derive material sufficient to build a small network. This protocol covers the advantages of reconstitution in vesicles, such as full control over the solution environment, while keeping the proteins in their original surroundings with the proper orientation. Furthermore, control of membrane protein and lipid content in the networks is achievable by employing different cell types, for example, by overexpression of a desired protein or the use of specialized cell-types as sources for rare proteins and lipids. In general, the method provides simple accessibility for functional studies of plasma membrane constituents. Specifically, it provides a direct means to functionalize nanotube-vesicle networks with desired proteins and lipids for studies of transport activity both across membranes (protein-mediated) and across nanotubes (diffusion), and substrate conversion down to the single-molecule limit. Nanotube-vesicle networks can adopt different geometries and topologies and undergo shape changes at will, providing a flexible system for changing the physical and chemical environment around, for example, a membrane protein. Furthermore, the method offers unique possibilities for extracting membrane and protein material for nanotechnological sensor and analytical devices based on lipid membrane networks.     

离子液体支撑液膜分离CO2

支撑液膜是一种在湿法冶金、生物技术以及气体分离等多个领域都有应用的重要膜分离技术。本文回顾了支撑液膜技术分离CO2的研究进展,按照液膜相的不同,分类介绍了常规载体支撑液膜和离子液体支撑液膜,指出了常规载体支撑液膜分离CO2的局限性,重点介绍了离子液体支撑液膜分离CO2的发展,分析了气体在离子液体支撑液膜中的传质机理以及常规离子液体结构、含量和支撑膜材料等对分离效果的影响;讨论了离子液体的功能化方法以及功能化离子液体支撑液膜分离CO2的渗透率、选择性和液膜稳定性;介绍了两种新的离子液体支撑液膜改进方法:聚离子液体膜与凝胶化离子液体支撑液膜。最后指出了今后用于CO2分离的离子液体支撑液膜的发展方向。     

Proton transport through hydrated chitosan‐based polymer membranes under electric fields

Proton transport is essential in many areas of chemistry and biology and is especially important in the fields of proton exchange membrane fuel cells and biocompatible, protonic semiconductors. These devices make use of membranes to control the flow of protons for either the generation of energy or to more closely couple electronics and biology. In the present study, we make use of ab initio molecular dynamics simulations, including the effect of applied electric fields, to gain atomistic insight into the intrinsic conductivity of chitosan‐based polymers and demonstrate that chitosan does not act as a significant source of friction for the transport of protons while increasing the number of free ions. Published 2017.^? J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1103–1109     

Recent developments in the field of bending rigidity measurements on membranes

This review gives a brief overview of experimental approaches used to assess the bending rigidity of membranes. Emphasis is placed on techniques based on the use of giant unilamellar vesicles. We summarize the effect on the bending rigidity of membranes as a function of membrane composition, presence of various inclusions in the bilayer and molecules and ions in the bathing solutions. Examples for the impact of temperature, cholesterol, some peptides and proteins, sugars and salts are provided and the literature data are discussed critically. Future directions, open questions and possible developments in this research field are also included.     

Recent advances in polymeric facilitated transport membranes for carbon dioxide separation and hydrogen purification

Membrane and membrane process have been widely considered as one of the best candidates for mitigating CO₂ emissions from the combustion or utilization of fossil fuels. Various amine-containing polymers constitute an important class of membranes, where the highly selective CO₂ transport is achieved by the facilitated transport mechanism. In this review, the amine–CO₂ chemistry is discussed in conjunction with the mechanism of the reaction-mediated CO₂ transport. A wide variety of amine-containing polymers are discussed based on two synthesis motifs: (a) polyamines with amino groups covalently bound to the polymer backbone and (b) small molecule amines embedded in a polymer matrix. This review concludes with the remarks on the facilitated transport membranes for post-combustion carbon capture (CO₂/N₂) and hydrogen purification (CO₂/H₂).     

Membrane electrochemistry

Electrochemistry and biomembranes are interface science in that both are concerned with the phenomena at, as well as across, the interfaces. Membrane electrochemistry may be defined as the application of electrochemistry to biomembrane studies. Additionally, transport processes within the membrane are involved in biomembranes. Since biomembranes are diverse and are usually not amenable to probing by electrochemicophysical techniques, model membrane systems have been developed for their investigation.

The introduction of experimental bilayer lipid membranes (BLM) technique and its modifications have been instrumental in the development and testing of membrane transport concepts (carriers vs channels) and electronic processes in membranes. Instead merely viewing a biomembrane as a physical barrier containing carriers or channels to carry out ionic processes, an ultrathin lipid or biological membrane can also be considered as a complete ‘electrochemical cell’ with one membrane/solution interface reducing (as a cathode) and the other membrane/solution interface oxidizing (as an anode). It is now possible to understand energy transduction (charge generation, separation, and redox reactions) in terms of ultrathin lipid membranes separating two aqueous solutions.

In this paper, we shall discuss the basic principles of electrochemistry as they are applied to membrane studies. Emphasis will be on experimental bilayer lipid membranes (BLM) which have been extensively investigated as models of biomembranes.     

Two‐Dimensional Membranes: New Paradigms for High‐Performance Separation Membranes

Two‐dimensional (2D) materials with atomic thicknesses have aroused great interest as promising building blocks for the preparation of ultrathin 2D membranes. These 2D membranes can exhibit unprecedentedly high separation permeance owing to their ultrasmall membrane thicknesses and superior selectivity because of their size‐selective nanopores and/or nanochannels. Until now, a large number of 2D membranes with good performance have been reported, highlighting the potential of these novel membranes for efficient liquid and gas separations. Summarized in this review are the latest advances in 2D membranes, with a special focus on industrially attractive separation processes, fabrication methods of laminar membranes, choices of membrane materials, designs of membrane structures, and unique membrane transport properties. Opportunities and challenges of 2D membranes for commercial applications are also briefly discussed.