电渗析膜离子分离实验制备

… membranes (IEMs). Among IEMs for the assembly of reverse electrodialysis stacks, pore-filling ion exchange membranes … In our study, we fabricated multiwall carbon nanotube (MWCNT…

… cation exchange membrane (CEM) of sulfonated polybenzimidazole (S-PBI) was fabricated by … AFM were used to characterize membrane properties and the results showed that the ion …

… However, there are few reports in the literature on the fabrication and properties of ion-exchange membranes from the sulfonated polyphosphazenes. The difficulty associated with …

… Some studies of proton exchange membranes used in fuel cells have involved the … of ion exchange membranes (IEMs) used in electrodialysis (ED) has been rarely studied. Co-ion …

Abstract Composite cation exchange membranes (CEMs) based on sulfonated polyether sulfone (SPES) with low sulfonation degree (DS) have been prepared in our previous studies. The results provided an approach for the preparation of CEM with low cost, environment-friendly technology, and ideal properties. On the basis of the previous research, the first purpose of this study was aimed to explore more suitable hydrophilic additives to further improve CEM properties. Hydrophilic polyethylene glycol (PEG) and polyvinylpyrrolidone (PVP) with different molecular weight (Mw) were used as hydrophilic additives, while SPES was still used as the matrix material. The results showed that PEG was not a suitable additive for CEMs due to the low MW, while stability was clearly improved with increased PVP MW. Hence, for researchers, there is no need to waste time on PEG as a hydrophilic agent of CEM prepared with this method in the future. The second purpose of this study, which was the further optimization of the CEM performance, was achieved in the research of suitable hydrophilic additives. The results of stability and electrodialysis showed that SPES blended with PVP K90 was the best prepared CEM. The third purpose was the investigation of mechanism of synergistic effects between sulfonated groups and hydrophilicity on membrane properties. In this part, an innovative concept of effective DS was put forward. This innovative concept will directly impact on ion transport mechanism, and have a very important influence on the preparation idea of CEM. In conclusion, this study is of great significance for selection of CEM materials, improvement of membrane stability and further study of ion transport mechanism.

… counter-ions, cation exchange membranes (CEMs) and anion exchange membranes (AEMs… the scale-up of the membrane fabrication. The incorporation of nanomaterial fillers provides …

Abstract A novel preparation method of cation exchange membranes (CEM), based on sulfonated materials with low sulfonation degree (DS), has been proposed in previous studies. For the preparation of CEMs, these studies have provided an approach with low cost, environment-friendly technology, and ideal properties, and proved the value and feasibility of the new method. Based on this, more work remained to be done to further modify the properties of CEMs prepared with this method. One purpose of this study, which was for the basic needs of good CEM practicability, was to improve CEM stability based on sulfonated polyether sulfone (SPES). This purpose was achieved satisfactorily by the proper design, and proved forcefully by stability testing, including thermostability, mechanical stability, and resistance to acid and base, etc. The other purpose, which was designed due to the special membrane surfaces, was to investigate CEM anti-scaling properties during electrodialysis (ED) processes. Compared with commercial CEMs, one clear different characteristic of CEM prepared by this method was flatter and smoother membrane surfaces, which should be an advantage for anti-scaling of salts during an ED process. From this, experiment of the second part was designed to specifically explore anti-scaling factors, but an unexpected result obtained. It was the higher hydrophilicity of these CEMs rather than their smoother surface that played an important role in anti-scaling behavior. The obtained result should be an innovative and significant discovery of this work. It will directly impact on anti-scaling research of both CEM and anion exchange membranes (AEMs). Hence, this work was a meaningful bridge for expanding previous research of CEM preparation into anti-scaling applications of ion exchange membranes.

In the present work a novel heterogeneous cation exchange membrane (CEM) composed of poly vinyl chloride (PVC) and 2-acrylamido-2-methylpropane sulfonic acid based hydrogel (…

… The fabricated nanocomposite IEMs exhibit improved conductivity while … pristine membranes, the conductivity-permselectivity tradeoff line of the fabricated nanocomposite membranes is …

Electrodialysis related processes are effectively applied in desalination of sea and brackish water, waste water treatment, chemical process industry, and food and pharmaceutical industry. In this process, fundamental component is the ion exchange membrane (IEM), which allows the selective transport of ions. The evolvement of an IEM not only makes the process cleaner and energy-efficient but also recovers useful effluents that are now going to wastes. However ion-exchange membranes with better selectivity, less electrical resistance, good chemical, mechanical and thermal stability are appropriate for these processes. For the development of new IEMs, a lot of tactics have been applied in the last two decades. The intention of this paper is to briefly review synthetic aspects in the development of new ion-exchange membranes and their applications for electrodialysis related processes.

… were fabricated using PANI/GO … into electrodialysis heterogeneous cation-exchange membranes, and the literature is silent on the characteristics and functionality of electrodialysis IEMs …

Salinity gradient power is a renewable, non-intermittent, and neutral carbon energy source. Reverse electrodialysis is one of the most efficient and mature techniques that can harvest this energy from natural estuaries produced by the mixture of seawater and river water. For this, the development of cheap and suitable ion-exchange membranes is crucial for a harvest profitability energy from salinity gradients. In this work, both anion-exchange membrane and cation-exchange membrane based on poly(epichlorohydrin) and polyvinyl chloride, respectively, were synthesized at a laboratory scale (255 cm2) by way of a solvent evaporation technique. Anion-exchange membrane was surface modified with poly(ethylenimine) and glutaraldehyde, while cellulose acetate was used for the cation exchange membrane structural modification. Modified cation-exchange membrane showed an increase in surface hydrophilicity, ion transportation and permselectivity. Structural modification on the cation-exchange membrane was evidenced by scanning electron microscopy. For the modified anion exchange membrane, a decrease in swelling degree and an increase in both the ion exchange capacity and the fixed charge density suggests an improved performance over the unmodified membrane. Finally, the results obtained in both modified membranes suggest that an enhanced performance in blue energy generation can be expected from these membranes using the reverse electrodialysis technique.

Sustainable chemistry principles underscore the pivotal role of solvent-free processes in the fabrication of anion exchange membranes (AEMs). This study presents an eco-friendly, …

… (CA) blend heterogeneous cation exchange membranes were prepared by … and cation exchange resin powder as functional groups agent. CA was employed in membrane fabrication to …

… Ion exchange membranes (IEMs) have a wider application in water purification, electrolytic process, and ion separation. The improvement of IEMs performance through sulfonation …

… a lab-scale electrodialysis cell at constant applied voltage. The prepared membranes DMEA-… the commercial anion exchange membranes Neosepta AMX under the identical conditions. …

Abstract Anion exchange membrane (AEMs) fouling is a serious problem influencing membrane performance during electrodialysis process(ED), which would increase power consumption and reduce water recovery. In this paper, an aliphatic anion-exchange membrane was prepared from quaternized polyvinyl alcohol (QPVA) via dual cross-linking through annealing treatment and condensation reaction to restrain the membrane water swelling. The Wu% of QPVA membrane could be reduced to 22.87 ± 0.81%. Due to the hydrophilia (59.86 ± 0.21°), negative ζ-potential surface and aliphatic matrix of QPVA, no transition time appeared under our experiment condition, indicating the QPVA membrane was scarcely fouled by SDBS. And the existence of SDBS in dilute solution generated slightly effect on the QPVA membrane resistance and only 7.47 ± 0.21% reduction of the desalination rate in ED process. Furthermore, only distilled water was used as solution or reaction media, without any harmful organic solvents, presenting an environmentally friendly route for the preparation of water-based anion-exchange membrane. So, the excellent anti-fouling performance along with green preparation of QPVA showed its remarkable prospect for desalination purpose in ED process.

Reverse electrodialysis (RED) technology represents a promising electro-membrane process for renewable energy harvesting from aqueous streams with different salinity. However, the performance of the key components of the system, that is, the ion exchange membranes, is limited by both the presence of multivalent ions and fouling phenomena, thus leading to a reduced generated net power density. In this context, the behavior of anion exchange membranes (AEMs) in RED systems is more severely affected, due to the undesirable interactions between their positively charged fixed groups and, mostly negatively charged, foulant materials present in natural streams. Therefore, controlling both the monovalent anion permselectivity and the membrane surface hydrophilicity is crucial. In this respect, different surface modification procedures were considered in the literature, to enhance the above-mentioned properties. This review reports and discusses the currently available approaches for surface modifications of AEMs, such as graft polymerization, dip coating, and layer-by-layer, among others, mainly focusing on preparing monovalent permselective AEMs with antifouling characteristics, but also considering hydrophilicity aspects and identifying the most promising modifying agents to be utilized. Thus, the present study aimed at providing new insights for the further design and development of selective, durable, and cost-effective modified AEMs for an enhanced RED process performance, which is indispensable for a practical implementation of this electro-membrane technology at an industrial scale.

… In this article, the fabrication of anion exchange membranes from brominated poly(2,6-… The prepared membranes were characterized in terms of ion exchange capacity (IEC), water …

Anion exchange membranes are highly versatile and nowadays have many applications, ranging from water treatment to sensing materials. The preparation of anion exchange membranes (AEMs) from brominated poly(2,6-dimethyl-1,6-phenylene oxide) (BPPO) and methyl(diphenyl)phosphine (MDPP) for electrodialysis was performed. The physiochemical properties and electrochemical performance of fabricated membranes can be measured by changing MDPP contents in the membrane matrix. The influence of a quaternary phosphonium group associated with the removal of NaCl from water is discussed. The prepared membranes have ion exchange capacities (IEC) 1.09–1.52 mmol/g, water uptake (WR) 17.14%–21.77%, linear expansion ratio (LER) 7.96%–11.86%, tensile strength (TS) 16.66–23.97 MPa and elongation at break (Eb) 485.57%–647.98%. The prepared anion exchange membranes were employed for the electrodialytic removal of 0.1 M NaCl aqueous solution at a constant applied voltage. It is found that the reported membranes could be the promising candidate for NaCl removal via electrodialysis.

Abstract In this study, a chloromethylated polysulfone with controlled degree of chloromethylation (DCM) was synthesized for the preparation of anion exchange membranes (AEMs). The reported method avoided using the hazardous chemicals chloromethyl ether but achieved the same high DCM (up to 1.95) under mild experimental conditions. Various process parameters, including reaction time and temperature, solvent type and volume, and catalyst feeding mode and volume, were discussed to demonstrate how a relatively high DCM could be achieved through this process. AEMs with varied DCM were prepared and their performances were characterized. The reported AEM-1.95 possessed better properties as a result of the high molality of chloromethyl groups, such as higher ion exchange capacity and ionic conductivity, better thermal stability and alkaline stability, as well as better mechanical properties. Additionally, electrodialysis (ED) experiments were conducted to determine the feasibility of AEMs in practical applications. Results showed that the AEM prepared by higher DCM exhibited better desalination properties and lower energy consumption. The desalination rate of AEM-1.95 could be up to 94.5% and the energy consumption was only 7.5 kWh/kg. All the results demonstrate that the proposed route for efficient and non-toxic fabrication of CMPSF with high DCM exhibits significantly potential and may be a promising candidate for the preparation of AEMs with high performances.

… Membranes with thinner film thickness achieve the highest power density because of their … a reverse electrodialysis stack using tailor-made anion-exchange membranes prepared in a …

A membranous copolymer crosslinked with divinylbenzene reacted with N,N,N′,N′-tetra-methylethylenediamine, N,N,N′,N′-tetramethyl-1,3-propanediamine, and N,N,N′,N′-tetramethyl-1,6-hexanediamine to prepare highly crosslinked anion exchange membranes. More than 80% of both tertiary amino groups of the diamines reacted with chloromethyl groups of the membrane to form crosslinkage. After formation of the high crosslinkage of the membrane was confirmed with dialysis of a neutral molecule, electrochemical properties of the obtained membranes (mainly, relative transport number between two anions in electrodialysis) were evaluated: nitrate ions to chloride ions, sulfate ions to chloride ions, fluoride ions to chloride ions, and bromide ions to chloride ions. Though larger anions, in general, were difficult to permeate through the membranes due to high crosslinkage, the number of methylene groups of the diamines (which means the increase in hydrophobicity of anion exchange groups) also affected the relative transport number between two anions. The lower the hydration of anions, the higher the relative transport number of the anions through the membranes with the hydrophobic anion exchange groups. © 1996 John Wiley & Sons, Inc.

… Organic–inorganic hybrid anion-exchange membranes were prepared from quaternized chitosan, anion-exchange silica precursor and poly(vinyl alcohol) by the sol–gel method in …

Abstract In the current study, the indirect recycling of discarded reverse osmosis modules as i) membrane support for the preparation of anion exchange membranes and ii) polypropylene components for the assembly of an electrodialysis stack have been investigated for the first time. In such a way, 51% of the discarded module could be recycled into an electrodialysis system composed of 54% of recycled components. Recycled anion exchange membranes have been prepared by casting and phase inversion methods using discarded reverse osmosis membranes, preconditioned as support. The influence of casting thickness and solvent evaporation time in membrane properties has been studied. Besides, a complete membrane characterization has been carried out (SEM, water content, ion exchange capacity, permselectivity, electrical resistance, diffusion coefficients and mechanical properties) to select the optimal membrane preparation conditions, obtaining recycled anion exchange membranes with a high permselectivity (87%, similar to the commercial membranes). Finally, the technical viability of the recycled membranes has been tested by brackish water desalination experiments in the assembled electrodialysis stack, achieving 84.5% of salt removal. This study could open an alternative within the recycling of discarded reverse osmosis membranes, avoiding their disposal in landfills and moving membrane technology into a circular economy.

… capacity, striking water uptake and excellent dimensional stability were prepared via … anion exchange membranes, and the membrane properties were evaluated by AFM, ion exchange …

… membrane and electrodialysis method, are reviewed. The studies are classified (1) to prepare the composite of the cation-exchange membrane … to change cation-exchange groups from …

… Chronopotentiometry study of prepared membranes confirmed their homogeneous and … splendid alkaline, oxidative and hydrolytic stabilities is a good candidate for electrodialysis. …

… electrodialysis (ED). Herein, mechanically stable ionic liquid-based pore-filling anion-exchange membranes (… The prepared PFAEM exhibited a dramatically greater flux of HCrO 4 − (…

… on ion exchange membranes which can separate ions with the same charge by electrodialysis are re… 13 shows Pgy of anion exchange membranes which were prepared by different …

… to that of a commercial membrane. As an ideal ion exchange membrane should have a high … between counter ions, the selectivity of the membrane was investigated in two ways: the …

Abstract Blue energy (or salinity gradient energy) is a renewable, carbon-neutral, and continuous electrical energy source that can be obtained via the reverse electrodialysis (RED) technique. The viability of this technology strictly depends on the performance and cost of the ion-exchange membranes (IEMs) that compose the RED units; designing the optimal membrane represents a critical challenge due to the complex relation between the performance, properties, and structure of the membrane. In this work, we present our findings on an electrospun cation-exchange membrane based on polyvinyl chloride (PVC), a strongly acidic cation exchange resin, with sodium dodecyl sulfate (SDS) as an additive. We contrast it with a similar membrane produced with the more conventional casting solution technique. The electrospinning technique provides thinner and more homogeneous membranes than those synthesized via casting. The membranes were characterized using morphological, spectroscopic, and analytical methods. Scanning electron microscopy images depicted an intertwined nanofiber mesh within the membrane. We also synthesized the same electrospun cation exchange membrane without SDS; this membrane presented 63% less swelling, and a significant increase in the fixed charge density (CDfix) (119.6 meq/g) when compared to its casting solution counterpart (34 meq/g). This suggests an enhanced permselectivity, and thus better performance for blue energy generation in RED units.

Abstract In this work, novel monovalent selective cation exchange membranes (CEMs) with different mixtures of polyvinylidene fluoride (PVDF) and sulfonated PVDF (S-PVDF) were synthesized. The selected composite membranes were modified by surface polymerization of polyaniline (PANi) to improve their monovalent cation selectivity. PANi was doped with p-toluene sulfonic acid (pTSA) or l -valine (2-amino-3-methylbutanoic acid) and the selectivity of each CEM was determined. Membrane properties, such as chemical composition, water uptake, ion exchange capacity, permselectivity, contact angle and crystallinity were measured. The influence of the applied voltage was also studied. The newly developed membranes were used for electrodialytic concentration of NaCl from synthetic reverse osmosis (RO) brine. Doped membranes with pTSA (SNaMg = 0.13, SNaCa = 3.59) and valine (SNaMg = 0.09, SNaCa = 0.8) have a higher selectivity for sodium than the composite ones (SNaMg = 0.63, SNaCa = 6.82). Moreover, the increase of applied voltage results in an increase of the selectivity for monovalent ions.

Cation exchange membranes (CEMs) play a significant role in the transition to a more sustainable/green society. They are important components for applications such as water electrolysis, artificial photosynthesis, electrodialysis and fuel cells. Their synthesis, however, is far from being sustainable, affecting safety, health and the environment. This review discusses and evaluates the possibilities of synthesizing CEMs that are more sustainable and green. First, the concepts of green and sustainable chemistry are discussed. Subsequently, this review discusses the fabrication of conventional perfluorinated CEMs and how they violate the green/sustainability principles, eventually leading to environmental and health incidents. Furthermore, the synthesis of green CEMs is presented by dividing the synthesis into three parts: sulfonation, material selection and solvent selection. Innovations in using gaseous SO3 or gas–liquid interfacial plasma technology can make the sulfonation process more sustainable. Regarding the selection of polymers, chitosan, cellulose, polylactic acid, alginate, carrageenan and cellulose are promising alternatives to fossil fuel-based polymers. Finally, water is the most sustainable solvent and many biopolymers are soluble in it. For other polymers, there are a limited number of studies using green solvents. Promising solvents are found back in other membrane, such as dimethyl sulfoxide, Cyrene™, Rhodiasolv® PolarClean, TamiSolve NxG and γ-valerolactone.

Abstract Reverse electrodialysis (RED) is one of the most promising membrane-based processes for renewable energy generation from mixing two solutions of different salinity. However, the presence of Mg2+ in natural water has been shown to drastically reduce open circuit voltage (OCV) and output power of RED. To alleviate this challenge, commercial cation exchange membranes (CEM) supplied by Fujifilm Manufacturing Europe B.V. (The Netherlands) were chemically modified by polypyrrole (PPy)/chitosan (CS) composites under controlled Pyrrole (Py) concentration (0.025–1 M) and polymerization time (0–8 h). The modified membranes were physically characterized by FTIR, SEM and EDX along with the determination of key electrochemical properties like ion exchange capacity, ionic conductivity, monovalent selectivity and swelling degree. The monovalent selectivity (Na+ vs Mg2+) of the modified membranes, evaluated based on flux of ions by diffusion dialysis, indicated up to 3-fold improvement compared to pristine membranes inline with the enhanced OCV (up to 20%) during RED test in multi-ion solution. This was obtained without significant change in membrane and interface resistances as depicted by electrochemical impedance spectroscopy. The modified membranes displayed power densities in the range of 0.6–1.5 W/m2MP (MP: membrane pair) with more than 42% improvement compared to pristine membranes during RED test with multi-ion solutions. Although there is a gap for further improvement, these findings highlight a promising use of conducting polymers to design a highly selective and conductive membrane for RED.

Abstract A new type of magnetic mixed matrix cation exchange membrane was prepared by incorporating cobalt ferrite nanoparticles for chromium ions removal via electrodialysis. The CoFe2O4 nanoparticles were synthesized via a simple chemical precipitation method. The synthesized nanoparticles and mixed matrix lab-made membranes were characterized by XRD, FT-IR, EDX, SEM and SOM. The images showed a uniform particle distribution and a relatively uniform surface for the prepared membranes. Utilizing CoFe2O4 nanoparticles in the membrane matrix led to increase of the membrane electrical conductivity and surface hyrophilicity. The membrane potential, charge density, permselectivity, transport number, ion exchange capacity and water content in the membrane were enhanced by using CoFe2O4 nanoparticles loading ratios up to 2 wt% and then decreased again for concentrations above 2 wt%. The sodium flux was also increased sharply by using cobalt ferrite nanoparticles in the membrane matrix. The magnetic PVC-CoFe2O4 membrane showed more dialytic rate in chromium ions removal compared to pristine PVC membrane which could be linked to strong affinity of magnetic nanoparticles in heavy metal ions adsorption.

In this study, a series of PAN-based poly(acrylonitrile-co‑sodium styrene sulfonate-co-2-acrylamido-2-methyl-1-propanesulfonic acid) terpolymer cation exchange membrane (CEM) …

The selective separation of metal species from various sources is highly desirable in applications such as hydrometallurgy, water treatment, and energy production but also challenging. Monovalent cation exchange membranes (CEMs) show a great potential to selectively separate one metal ion over others of the same or different valences from various effluents in electrodialysis. Selectivity among metal cations is influenced by both the inherent properties of membranes and the design and operating conditions of the electrodialysis process. The research progress and recent advances in membrane development and the implication of the electrodialysis systems on counter-ion selectivity are extensively reviewed in this work, focusing on both structure–property relationships of CEM materials and influences of process conditions and mass transport characteristics of target ions. Key membrane properties, such as charge density, water uptake, and polymer morphology, and strategies for enhancing ion selectivity are discussed. The implications of the boundary layer at the membrane surface are elucidated, where differences in the mass transport of ions at interfaces can be exploited to manipulate the transport ratio of competing counter-ions. Based on the progress, possible future R&D directions are also proposed.

… , ion exchange membranes (IEMs) are key factors to the success of future RED energy generation. This research presents the synthesis and … cation exchange membrane (CEM) by using …

… extensive interests in the field of ion exchange membranes. Herein, different mass … cation exchange membranes (CEMs), and the electrodialysis (ED) properties of these membranes …

Abstract Lithium is in demand since decades due to high applicability in batteries for electronic devices, which is expected to increase by 8 to 11% every year and Lithium ion battery market is estimated to grow to € 180 billion by 2024. Land deposits and seawater are two major sources of lithium but availability in sea water is higher than land. So an efficient technology is required to recover the lithium from sea water. Electrodialysis (ED) may be an alternate approach to recover the lithium from sea by selective ion exchange membranes. Here, Lithium selective ion exchange membranes have been synthesized by modification of sulfonated poly (ether ether ketone) (SPEEK) with lithium selective nanomaterial. Synthesized membranes were characterized for their chemical, structural and morphological structures and uniform dispersion of lithium selective nanomaterials. Composite membrane shows better lithium exchange capacity with excellent lithium conductivity as compared to SPEEK membrane. The adsorption of lithium (15.2 mg/g) found to be five times higher than that of Mg while recovery of lithium was 64% using electrodialysis process by NC-4 composite membrane. Selectivity factor for composite membrane were 4.82, 3.0 and 2.17 for Li/Mg, Li/K and Li/Na, respectively. The selective composite membranes can be suitable for Li-ion recovery from sea brine/bittern on large scale.

… membrane performance through BMED for the dissociation of NaCl. We also performed the bipolar membrane electrodialysis (… Among the bipolar membranes, BPM with 40 % less AEL …

… The work reported herein describes the study of desalination of synthetic … bipolar ion exchange membranes (with PVA as the intermediate layer) using bipolar membrane electrodialysis …

Lab-scale wastewater treatment studies, including urine recovery, often rely on oversimplified synthetic wastewater, thereby compromising the reliability of results and data. Here, we systematically evaluate how using full-component versus simplified synthetic urine formulations affects the performance and engineering-economic assessment of bipolar membrane electrodialysis. Our findings reveal that simplification fundamentally alters fouling mechanisms. While urea alone causes significant damage to anion exchange membranes through hydrogen bonding aggregation, natural organic co-components in real urine mitigate fouling via inhibitory interactions—a mechanism confirmed by molecular dynamics simulations and experimental characterization. After seven batches, the full-component formulations showed 29.3% less performance decay and 10–14% higher urea recovery than the simplified formulation. Moreover, the complete removal of organic components disrupts ion-organic co-aggregation pathways on cation exchange membranes, shifting fouling toward mineral crystallization on bipolar membranes. Simplification also distorts the engineering-economic assessment, overestimating cleaning costs by 15.9% and underestimating membrane lifespan by 12.5%. These findings necessitate identifying key wastewater constituents and ensuring experimental integrity to bridge lab-industry gaps, advocating designs comprehensively addressing multi-component interactions.

In recent years, energy conversion and storage technologies have been a research hotspot. Bipolar membrane reverse electrodialysis (BMRED) is a safe and sustainable way to …

… bipolar membranes (BPMs) with low water-dissociation overpotential (η wd ) may enable new electrochemical technologies for electrolysis, fuel cells, acid–base synthesis, … electrolysis (…

… The synthesis of new bipolar membranes based on polysulfone and polyvinyl alcohol polymers have shown promising results in terms of current efficiency and energy consumption (…

During electrodialysis the ion exchange membranes are affected by such factors as passage of electric current, heating, tangential flow of solution and exposure to chemical agents. It can potentially cause the degradation of ion exchange groups and of polymeric backbone, worsening the performance of the process and necessitating the replacement of the membranes. This article aims to review how the composition and the structure of ion exchange membranes change during the electrodialysis or the studies imitating it.

… modified … modification of the AEM with a negatively charged layer, as theoretically expected. The permselectivity between monovalent anions was not affected by the surface modification…

… an increase in membrane electrical resistance, leading to shortened membrane life and … antifouling potential for an anion exchange membrane (AEM) by surface modification with poly(…

… tions during electrodialysis can result in a change of the transport characteristics of ion-exchange membranes. … The most reliable method for preparing of ionexchange membranes with …

… ionic species from aqueous solutions. In this study selectivity of an anion exchange membrane … monovalent anions in electrodialysis, a hybrid surface modification on a heterogeneous …

Abstract Monovalent permselective cation-exchange membrane (CEM) CR671 was developed by coating polyethyleneimine onto the normal grade CEM CR67. Pilot-scale electrodialysis of brackish groundwater demonstrated excellent monovalent permselectivity of the modified CR671 as compared to the normal grade CR67. Advanced analytical approaches were employed to characterize the physicochemical and electrochemical properties of the CEMs to elucidate the mechanisms of permselectivity. Ion-exchange capacities of the CR671 and CR67 were measured to be 2.0 and 2.1 meq/g dry membrane, respectively. Zeta-potential analysis revealed that the CR671 surface was positively charged as a result of polyethyleneimine coating. Electrochemical impedance spectroscopy (EIS) data indicated larger impedance for the CR671 and fitted well to the Maxwell-Wagner model, which provided an equivalent electric circuit for the CEMs, as well as indication of the existence of polyethyleneimine layer. The time constants of different ions transporting through polyethyleneimine modification layer were calculated based on the EIS responses. The results revealed the polyethyleneimine modification layer led to longer transport time for Ca2+ ions through the CR671 than for Na+ ions, supporting the pilot-scale testing results that the CR671 improved the Na+ removal by selectively rejecting Ca2+ ions. However, the difference in ion transport time became less significant with increasing ionic strength of the feed water. The EIS results suggest the monovalent permselectivity decreased during treatment of higher salinity water, supporting the finding that the CR671 exhibited higher monovalent permselectivity during electrodialysis of brackish groundwater than reverse osmosis concentrate in which the salt concentration was 5.7 times higher than the brackish groundwater. This study demonstrates that ion transport time constant is a better indicator for permselectivity of modified ion-exchange membranes than electrical resistance measured by EIS.

The fouling, in particular the organic fouling of anion exchange membranes (AEMs), is a serious problem in electrodialysis (ED). In this paper, we attempted to improve the antifouling …

In this paper, the consequences of traditional chemical cleaning on anion-exchange membrane structure and properties are thoroughly assessed. A homogeneous anion-exchange …

… modified membrane … membrane AMX. At the same time, electroconvection becomes the dominant mechanism for the transfer of salt ions through the modified heterogeneous membrane…

… of ion-exchange membranes (IEMs) used in electrodialysis (ED) for food industry applications constitutes a major challenge. In this regard, four used membranes (… was not modified. A …

Surface modification has been proven to be an effective approach for ion exchange membranes to achieve separation of counterions with different valences by altering interfacial construction of membranes to improve ion transfer performance. In this work, we have fabricated a series of novel cation exchange membranes (CEMs) by modifying sulfonated polysulfone (SPSF) membranes via codeposition of mussel-inspired dopamine (DA) and 4'-aminobenzo-15-crown-5 (ACE), followed by glutaraldehyde cross-linking, aiming at achieving selective separation of specific cations. The as-prepared membranes before and after modification were systematically characterized in terms of their structural, physicochemical, electrochemical, and electrodialytic properties. In the electrodialysis process, the modified membranes exhibit distinct perm selectivity to K+ ions in binary (K+/Li+, K+/Na+, K+/Mg2+) and ternary (K+/Li+/Mg2+) systems. In particular, at a constant current density of 5.0 mA·cm-2, modified membrane M-co-0.50 shows significantly prominent perm selectivity [Formula: see text] in the K+/Mg2+ system and M-co-0.75 exhibits remarkable performance in the K+/Li+ system [Formula: see text], superior to commercial monovalent-selective CEM (CIMS, [Formula: see text], [Formula: see text]). Besides, in the K+/Li+/Mg2+ ternary system, K+ flux reaches 30.8 nmol·cm-2·s-1 for M-co-0.50, while it reaches 25.8 nmol·cm-2·s-1 for CIMS. It possibly arises from the effects of pore-size sieving and the synergistic action of electric field driving and host-guest molecular recognition of ACE and K+ ions. This study can provide new insights into the separation of specific alkali metal ions, especially on reducing influence of coexisting cations K+ and Na+ on Li+ ion recovery from salt lake and seawater.

… due to the presence of competing ions like Mg 2+ and Na + . … to modify cation exchange membranes (CEM, CR671) to enhance Li + transport selectivity and capacities. The modification …

… ionexchange membrane by a dc current is determined by geometric factors, such as, the typical size of the ion-permeable ‘‘gates’’ at the membrane … In the present study we modify this …

In this study, novel pore-filled anion-exchange membranes (PFAEMs) modified with polypyrrole (PPy) and reduced graphene oxide (rGO) were developed to improve the energy harvesting performance of reverse electrodialysis (RED). The surface-modified PFAEMs were fabricated by varying the contents of PPy and rGO through simple spin coating and chemical/thermal treatments. It was confirmed that the PPy and PPy/rGO layers introduced on the membrane surface did not significantly increase the electrical resistance of the membrane and could effectively control surface characteristics, such as structural tightness, hydrophilicity, and electrostatic repulsion. The PPy/rGO-modified PFAEM showed excellent monovalent ion selectivity, more than four times higher than that of the commercial membrane (AMX, Astom Corp., Tokyo, Japan). This means that the PPy/rGO layer can effectively reduce the permeation of multivalent ions with a high charge intensity and a relatively large hydration radius compared to monovalent ions. The results of evaluating the performance of the surface-modified PFAEMs by applying them to a RED cell revealed that the decrease in potential difference occurring in the membrane was reduced by effectively suppressing the uphill transport of multivalent ions. Consequently, the PPy/rGO-modified membrane exhibited a 5.43% higher power density than the AMX membrane.

Selective electrodialysis (ED) is a promising membrane-based process to separate Li+ from Mg2+, which is the most critical step for Li extraction from brine lakes. This study theoretically compares the ED-based Li/Mg separation performance of different monovalent selective cation exchange membranes (CEMs) and nanofiltration (NF) membranes at the coupon scale using a unified mass transport model, i.e., a solution-friction model. We demonstrated that monovalent selective CEMs with a dense surface thin film like a polyamide film are more effective in enhancing the Li/Mg separation performance than those with a loose but highly charged thin film. Polyamide film-coated CEMs when used in ED have a performance similar to that of polyamide-based NF membranes when used in NF. NF membranes, when expected to replace monovalent selective CEMs in ED for Li/Mg separation, will require a thin support layer with low tortuosity and high porosity to reduce the internal concentration polarization. The coupon-scale performance analysis and comparison provide new insights into the design of composite membranes used for ED-based selective ion–ion separation.

Abstract The advances of electrodialysis (ED) have been restricted by the trade-off between perm-selectivity and ion flux of ion exchange membranes. This article lucidly explains the fabrication of novel PVA-based hybrid membranes modified with cationic and anionic layers. Cationic layer is composed of quaternized poly (2, 6-dimethyl-1, 4-phenylene oxide), while anionic layer is sulfonated poly (2, 6-dimethyl-1, 4-phenylene oxide). Interestingly, the perm-selectivity of Li+/Mg2+ via ED was observed up to 5.16 with a feed concentration of 0.1 mol L−1 LiCl/MgCl2 at 2.12 mA cm−2 current density. Electrochemical impedance spectroscopy was used to get further insight about the membrane and solution interfaces such as the influence of a base membrane and the deposited layers, which showed the perm-selective behavior of the modified membranes. The observed high perm-selectivity of modified membranes will step forward the ED applications for production of salts and treatment of saline water comprising monovalent and divalent cations.

… However, the separation efficiency for small organic ions should be … membrane selectivity and transport mechanism of small organic ions from mixed salts by ion-exchange membranes …

… mechanisms governing multi-ion transport in electrodialysis is essential. In … -ionic (Na + and K + ) mass transport in electrodialysis was developed including ion-water and ion-membrane …

… presence of multivalent ions is inevitable, … Membranes with selectivity for monovalent ions may overcome this limitation. Standard ion exchange membranes have low monovalent-ion …

… (PEI), on the membrane surface. This technique is well known … ions [14], [15], [16]. PEI electrodeposition on the cation-exchange membrane was performed directly in the electrodialysis …

… Selective electrodialysis (SED) with acid blocking AEM and monovalent selective cation-exchange membrane (… effect of the two selective ion-exchange membranes by comparing the …

… of electrodialysis (ED) and nanofiltration (NF) for the separation of monovalent and multivalent ions … Selective anion or cation exchange membranes have significantly different transport …

In recent years, the utilization of the selective ion transport through porous membranes for osmotic power generation (blue energy) has received a lot of attention. The principal of power generation using the porous membranes is same as that of conventional reverse electrodialysis (RED), but nonporous ion exchange membranes are conventionally used for RED. The ion transport mechanisms through the porous and nonporous membranes are considerably different. Unlike the conventional nonporous membranes, the ion transport through the porous membranes is largely dictated by the principles of nanofluidics. This owes to the fact that the osmotic power generation via selective ion transport through porous membranes is often referred to as nanofluidic reverse electrodialysis (NRED) or nanopore-based power generation (NPG). While RED using nonporous membranes has already been implemented on a pilot-plant scale, the progress of NRED/NPG has so far been limited in the development of small-scale, novel, porous membrane materials. The aim of this review is to provide an overview of the membrane design concepts of nanofluidic porous membranes for NPG/NRED. A brief description of material design concepts of conventional nonporous membranes for RED is provided as well.

Pore-filling ion-exchange membranes have been produced via complex, low energy efficient, and toxic processes, including repetitive impregnation to fully fill the porous substrates with polymer ele...

… Reverse electrodialysis (RED) is a technology for extracting salinity gradient … membranes. Conventionally, non-conductive spacers are used to separate these ion exchange membranes …

… Here, we report the fabrication of nanoporous carbon membranes via the thermal crosslinking of core–rim structured monomers, that is, polycyclic aromatic hydrocarbons. The …

Abstract Reverse electrodialysis (RED) emerged as a promising membrane-based technology due to an increased interest in salinity gradient energy. We report on the fabrication and characterization of ion-exchange membranes wave-patterned with non-conductive materials and supported by thin (16-μm-thick) pore-filling membranes. These membranes, which are double-sided or single-sided, are designed to secure stable electrolyte channels based on wave lines with mirror images. Cross-flow RED stacks were evaluated as functions of cell pairs and flow rates. The non-conductive material increases the membrane resistance for anion and cation exchange, maintaining permselectivity approximately constant. The gross power density of a flat stack is higher than that of a single-sided patterned membrane stack; however, the latter exhibits superior net power density, particularly at high flow rates. The pressure drop of the single-sided wave-patterned membrane is significantly lower (∼3 × ) than that of the flat membrane. The maximum gross power density was 1.39 W/m2 for 10-cell pairs, and the optimum cell pairs were 30, with the highest net energy efficiency of 9.4%. The net energy efficiency can be maximized by optimizing the design and operating conditions of the RED stack and net power density, via the addition of an ionic conductivity function to the patterned structure.

Abstract The impact of fouling on the performance of Reverse Electrodialysis operated with highly concentrated brine is a poorly investigated area. In this work, the fouling propensity and stability of Ion Exchange Membranes (IEMs), developed by Fujifilm Manufacturing Europe BV (The Netherlands), is investigated under the condition of seawater and brine. The fouling propensity of the IEMs was depicted by the determination of the Gibbs energy barrier of based-on the Classical Nucleation along with the Theoretical modeling of heterogeneous nucleation as a function of electrochemical (contact angle, permittivity, charge density) and morphological (roughness) membrane properties validated by CaCO3 precipitation. Results indicate that Cation Exchange Membranes (CEM) are more susceptible to the scaling due to the reduced energy barrier of heterogeneous nucleation. FTIR-ATR analysis on six months-aged membranes samples indicated a partial modification in the chemical structure of Anion Exchange Membranes (AEM) induced by the organic fouling associated with humic substances. The tensile tests demonstrated substantial mechanical stability of IEMs. Lab-scale RED tests operated with artificial brine over 30 days showed a significant increase in pressure drop through feed channels due to significant colloidal fouling along with a 23% reduction of maximum gross power density with consequent decrease of net power density.

… reverse-electrodialysis cells (MRCs) can be limited by the internal resistance of the reverse electrodialysis … These spacers can be relatively thick compared to the membrane, and thus …

Ion exchange membranes (IEMs) have consolidated applications in energy conversion and storage systems, like fuel cells and battery separators. Moreover, in the perspective to address the global need for non-carbon-based and renewable energies, salinity-gradient power (SGP) harvesting by reverse electrodialysis (RED) is attracting significant interest in recent years. In particular, brine solutions produced in desalination plants can be used as concentrated streams in a SGP-RED stack, providing a smart solution to the problem of brine disposal. Although Nafion is probably the most prominent commercial cation exchange membrane for electrochemical applications, no study has investigated yet its potential in RED. In this work, Nafion 117 and Nafion 115 membranes were tested for NaCl and NaCl + MgCl2 solutions, in order to measure the gross power density extracted under high salinity gradient and to evaluate the effect of Mg2+ (the most abundant divalent cation in natural feeds) on the efficiency in energy conversion. Moreover, performance of commercial CMX (Neosepta) and Fuji-CEM 80050 (Fujifilm) cation exchange membranes, already widely applied for RED applications, were used as a benchmark for Nafion membranes. In addition, complementary characterization (i.e., electrochemical impedance and membrane potential test) was carried out on the membranes with the aim to evaluate the predominance of electrochemical properties in different aqueous solutions. In all tests, Nafion 117 exhibited superior performance when 0.5/4.0 M NaCl fed through 500 µm-thick compartments at a linear velocity 1.5 cm·s−1. However, the gross power density of 1.38 W·m−2 detected in the case of pure NaCl solutions decreased to 1.08 W·m−2 in the presence of magnesium chloride. In particular, the presence of magnesium resulted in a drastic effect on the electrochemical properties of Fuji-CEM-80050, while the impact on other membranes investigated was less severe.

Abstract The utilization of large amounts of volatile organic solvents and the complicated process required for industrial manufacturing of ion-exchange membranes necessitate the development of simple, rapid, and environmentally friendly fabrication methods such as those based on photopolymerization. We employed hydrolytic sol–gel reactions between ammonium- and acrylamide-functionalized silane coupling agents to synthesize water-soluble siloxane resins that exhibit high condensation levels (>80%) and comprise oligomers with molecular weights below 2000 Da. These resins were then mixed with a hydrophilic monomer bearing ammonium and acrylamide groups, and porous polyethylene substrates were impregnated with the resulting mixtures and then irradiated with ultraviolet light. The hydrophilicity, mechanical strength, and other properties of the resulting membranes depended on the resin composition, indicating that the substrate pores were efficiently filled with the prepared resins and further suggesting that the membrane performance could be effectively altered by varying the resin composition. Moreover, the obtained membranes exhibited chemical stability in the pH range between 0 and 11 and in hot water at 60 °C. The reverse electrodialysis stack consisting of these membranes showed higher power density than a stack of commercial membranes. Therefore, it can be concluded that without employing volatile organic solvents for reverse electrodialysis, the developed technique is well-suited for the fabrication of ion-exchange membranes.

… ion exchange membranes. In this study, the fouling characteristics of anion exchange membranes were investigated according to their electric resistances, hydrophobicities, exchange …

Abstract This paper concerns the mechanisms of aging of ion-exchange membranes (IEMs) during their use in electrodialysis (ED) of food industry solutions containing polyphenols (PPs), as well as their cleaning. The study focuses on anion-exchange membranes (AEMs); their behavior is compared with that of cation-exchange membranes (CEMs). First, physicochemical static characteristics, structural, morphological and tensile strength parameters are determined for new AEMs and two batches of used AEMs at different duration of their use in industry, subjected to regular “Cleaning In Place”. Second, non-aggressive and economic ex-situ static cleaning methods involving the application of NaCl at 35 g L−1, a reconstituted seawater and a water-ethanol mixture acidified with H2SO4 were examined. During the cleaning process, the evolution of physicochemical parameters, such as ion-exchange capacity (IEC), electrical conductivity (κm) and contact angle (θ), were followed. It is shown that the application of NaCl solution has a negligible effect on IEC and κm; when soaking the membranes in the reconstituted seawater, κm even slightly decreases; however, there is a significant increase in these parameters when soaking the membranes in the acidified water-ethanol solution. As for the mechanism of fouling, PPs are the main responsible constituents. Apparently, they form dense colloidal nanoparticles not permeable for ions within membrane meso- and macropores, not penetrating into micropores. A modification of the microheterogeneous model under this assumption allows an adequate description of membrane conductivity and explains the fact that the membrane pore size increases with the duration of membrane utilization, while the apparent volume fraction of the inter-gel solution (f2app) decreases. CEMs are found less prone to fouling. The soaking of CEMs in the water-ethanol solution leads to an increase in IEC and f2app by 33% and 60%, respectively, as well as to doubling κm and decreasing θ by 23%, after a 120 h. treatment.

… the nature and to characterize the morphology of CEM fouling during conventional electrodialysis … The integrity of the membranes was analyzed by means of membrane parameters and …

… Observation of properties for the virgin and fouled membranes is of importance since … anion exchange membranes were characterized in terms of their electric resistances, exchange …

… ions via the ion exchange membranes (IEMs) [1]. Because of the advantages such as high water recovery rate, long operation life of membrane … fouling of anion exchange membrane (…

… The aim of this work was to study the effect on the fouling of anion-exchange membranes (… solution to be treated by conventional electrodialysis. It appeared that after demineralization of …

… Ion transport resistance is an important characteristic of ion exchange membranes. It is not a constant but is influenced by among other things the salt concentration in the external …

… ion-exchange membranes (IEMs) in real scenario remains unclear. In this study, we employed interface characterization … both anion-exchange membranes (AEMs) and cation-exchange …

Abstract The structural degradation of an anion-exchange membrane used on the separation of phosphate from sulfate ions at overlimiting current density conditions was investigated. To this, the chemical structure changes, apparent counterion transport number, limiting current density, the apparent fraction of surface conductive regions, degree of hydrophobicity, membrane resistance and conductivity, morphology and thermal degradation profile were studied for the original and used samples of the anion-exchange membrane. The results showed that the degradation of the membrane fixed ion groups and structural polymer backbone affected the ionic transport conditions, reducing its apparent permselectivity and fraction of conductive regions. Also, the increase in the hydrophobicity degree together with the formation of cavities observed in the membrane surface may be responsible for the alteration of membrane conductivity, leading to a higher limiting current density value and a decrease in the plateau length.

… properties of ion exchange membrane. In this paper several cation exchange membranes (CEMs… studied by the correlation analysis and linear regression. The results demonstrated that …

… research trends, electrodialysis enables separation of ions or … different types of ion-exchange membranes on the basis of … on an extensive scale, characterization of the materials of the …