Applications Of Ion-exchange Membranes Research Articles

Ultra-Thin Ion Exchange Membranes by Low Ionomer Blending for Energy Harvesting.

Exploring the utilization of ion exchange membranes (IEMs) in salinity gradient energy harvesting, a technique that capitalizes on the salinity difference between seawater and freshwater to generate electricity, this study focuses on optimizing PVDF to Nafion ratios to create ultra-thin membranes. Specifically, our investigation aligns with applications such as reverse electrodialysis (RED), where IEMs facilitate selective ion transport across salinity gradients. We demonstrate that membranes with reduced Nafion content, particularly the 50:50 PVDF:Nafion blend, retain high permselectivity comparable to those with higher Nafion content. This challenges traditional understandings of membrane design, highlighting a balance between thinness and durability for energy efficiency. Voltage-current analyses reveal that, despite lower conductivity, the 50:50 blend shows superior short-circuit current density under salinity gradient conditions. This is attributed to effective ion diffusion facilitated by the blend's unique microstructure. These findings suggest that blended membranes are not only cost-effective but also exhibit enhanced performance for energy harvesting, making them promising candidates for sustainable energy solutions. Furthermore, these findings will pave the way for advances in membrane technology, offering new insights into the design and application of ion exchange membranes in renewable energy.

Engineered cellulose nanofibers membranes with oppositely charge characteristics for high-performance salinity gradient power generation by reverse electrodialysis

Reverse electrodialysis (RED) using nanofluidic ion-selective membrane may convert the salinity difference between seawater and river water into electricity. However, heterogeneous modification reactions of cellulose commonly leads to the inhomogeneous distribution of surface charges, thereby hampering the improvement of cellulose-based nanofluidic membranes for energy conversion. Herein, RED devices based on cellulose nanofibers (CNF) membranes with opposite charge characteristics were developed for the generation of salinity gradient power. Anion-CNF membrane (A-CNF) with varying negative charge densities was synthesized using 2,2,6,6-Tetramethylpiperidine 1-oxy radical (TEMPO) oxidation modification, whereas cation-CNF membrane (C-CNF) was prepared through etherification. By mixing artificial seawater and river water, the output power density of CNF RED device is up to 2.87 W m−2. The output voltage of 30 RED units connected in series may reach up to 3.11 V, which can be used to directly power tiny electronic devices viz. LED lamp, calculator, etc. The results of this work provide a feasible possibility for widespread application of ion exchange membranes for salinity gradient energy harvesting.

Circular Design and Functionalized Upcycling of Waste Commodity Polystyrene via C-H Activation Using Microwave-Assisted Multicomponent Synthesis.

The inefficient reuse and recycling of plastics-and the current surge of medical and take-out food packaging use during the pandemic-have exacerbated the environmental burden. This impels the development of alternative recycling/upcycling methods to pivot toward circularity. We report the use of the Mannich three-component coupling reaction for the modification of polystyrene (PS) recovered with a 99.1% yield from waste food containers to form functionalized nitrogen and oxygen-rich PS derivatives. A series of functionalized PS with increasing moles of formaldehyde (F) and morpholine (M) (0.5 × 10-2, 1.0 × 10-2, and 2.0 × 10-2 mol) was achieved using a sol-gel-derived Fe-TiO2 catalyst in a solvent-free, microwave-assisted synthesis. Modified polymers were characterized with viscometry, 1H NMR, 13CNMR (DEPT) FTIR, XPS, UV, and TGA. Functionalization scaled with an increasing ratio, validating the 3CR approach. Further functionalization was constrained by a competing oxidative degradation; however, the varying hydrogen bond density due to nitrogen and oxygen-rich species at higher ratios was shown to compensate for molecular weight loss. The integration of the N-cyclic quaternary ammonium cations exhibited the potential of functionalized polymers for ion-exchange membrane applications.

Characterization and applications of ion-exchange membranes and selective ion transport through them: a review

Characterization and applications of ion-exchange membranes and selective ion transport through them: a review

Hydroxide ion-conducting metal–organic frameworks for anion-exchange membrane applications

Metal–organic frameworks are promising materials for ion-exchange membrane applications. This review paper examines their current status and potential to meet the rigorous ion-conductivity requirements, while identifying promising approaches for improvement.

Novel application of ion exchange membranes for preparing effective silver and copper based antibacterial membranes

Ion exchange membranes (IEMs) are widely used in water treatment applications such as electrodialysis. However, the exploration of IEMs as effective antibacterial food contact materials (e.g., food packaging membranes) against pathogenic bacteria to ensure food safety has not been reported. Here, we report a simple but effective method to prepare high performance antibacterial membranes via ion exchange coupled with in-situ reduction. The general membrane properties are characterized using SEM, EDS, FTIR, XPS, XRD, DSC, TGA, water uptake, etc. The distribution of silver and copper in the membranes are generally in line with the distribution of sulfur, indicating that the antibacterial ions are introduced into the membranes via ion exchange and are bonded with the sulfonate groups in the membranes. The antibacterial performance is investigated using zone of inhibition tests and continuous bacteria growth inhibition tests. All of the prepared membranes show obvious antibacterial activities compared to the bare cation exchange membranes. The diameters of inhibition zone against Staphylococcus aureus (S. aureus) are all larger than those of Escherichia coli (E. coli), indicating that the prepared membranes are more efficient in inhibiting S. aureus compared to E. coli. Furthermore, the silver-based membrane shows more sustainable antibacterial activities compared to the copper-based membrane. Especially, the results clearly reveal that the silver-based membrane is capable of killing bacteria instead of just inhibiting the growth of bacteria. We have shown for the first time that membranes derived from IEMs have the potential as food contact materials to inhibit the growth of pathogenic bacteria so as to eliminate the risk of bacterial infections and meanwhile delay food spoilage due to bacteria growth.

Ammonium sulfate production from wastewater and low-grade sulfuric acid using bipolar- and cation-exchange membranes

Conventional electrodialysis can be used to recover ammonia from dewatering centrate (i.e., down-stream wastewater from digested sludge dewatering). However, ionic impurities of the recovered ammonia solution are still a limiting factor for broad applications of ion-exchange membranes (IEMs) in wastewater treatment and resource recovery. In this study, an electrodialysis stack with bipolar membranes (BPMs) and cation exchange membranes (CEMs) but without anion exchange membranes (AEMs) was examined under various operation conditions to demonstrate high-purity ammonium sulfate production using low-grade sulfuric acid and dewatering centrate. Two significant benefits of removing AEMs from the bipolar membrane electrodialysis (BMED) are no more membrane fouling problems on AEMs and complete exclusion of impurity anions (e.g., chloride ions) in the recovered ammonium sulfate solution. A higher applied voltage condition (30 V over 7 pairs of CEM and BPM) resulted in a substantially high ammonia recovery (88.4%) and concentration (4.34 g-N/L) in 90 min. The ammonia recovery and concentration were also improved by increasing the flow rate through the BMED stack. The lowest electric energy consumption in the membrane stack was 9.6 kW h/kg-N, indicating energy efficient production of high-purity ammonium sulfate from wastewater. The amount of divalent cation scales accumulated in the BMED stack was linearly proportional to the average electric current, implying that the scaling problem can be controlled by reducing the applied voltage. Even with the scale accumulation, the electric current generation (i.e., separation performance) was hardly affected during the experiment. These findings demonstrated the strong potential of AEM-lacking BMED for practical ammonia separation from wastewater with reduced impurities.

Fabrication of hydrophilic cation exchange membrane with improved stability for electrodialysis: An excellent anti-scaling performance

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.

A Limiting Case of Constant Counterion Electrochemical Potentials in the Membrane for Examining Ion Transfer at Ion-Exchange Membranes and Patches.

Ion passage through ion-exchange membranes is vital in electrodialysis desalination, batteries and fuel cells, and water splitting. Simplified models of ion transport through such membranes frequently assume complete exclusion of co-ions (ions with the same sign of charge as the fixed charge in the membrane) from the membrane. However, a second assumption of constant counterion electrochemical potentials across the membrane leads to simple analytical expressions for ion fluxes and transmembrane potentials. Moreover, linear corrections to account for a small membrane electrical resistance yield analytical expressions with a wider applicability. For bi-ionic potential measurements and current-induced concentration polarization at low salt concentrations, these analytical solutions match the fluxes and potentials obtained numerically without the limiting assumptions. This gives confidence in both the limiting assumptions (under appropriate conditions) and the numerical solutions. At low ion concentrations, the analytical solutions may enable rapid characterization of membrane coatings or boundary layers in solution, and such boundary layers are important in many applications of ion-exchange membranes. In fact, the assumption of complete co-ion exclusion is sometimes more limiting than the constraint of constant electrochemical potentials of counterions across the membrane. Remarkably, this limiting case readily yields the ion accumulation and depletion regions above "ion-exchange patches" that reside beneath a solution with an applied electric field. Such regions are important for sample preconcentration in microfluidic devices.

Ion exchange membranes in ion chromatography and related applications

This review is a broad survey of ion exchange membranes (IEMs) in chosen areas of analytical chemistry. The coverage is comprehensive in ion chromatography (IC) applications, this includes in-line water purification for IC use, chemical and electrodialytic eluent suppression, eluent generation, eluent purification, pH modification, buffer generation, use in ion exclusion chromatography, charge-based detection, as well as suppressor-detector combinations. The use of IEMs in sample treatment using ion transfer devices and Donnan dialysis preconcentration are discussed. Introduction of reagents through an IEM, whether through a concentration gradient large enough to overcome the Donnan barrier or active electrodialysis, does not involve volumetric dilution. Reagent introduction in this fashion, enabling conductometric detection of otherwise non-ionized weak electrolytes, is discussed. Several important applications of IEMs, in which ion exchange plays little or no role, are discussed; these include (a) diffusion-based gas collection and analysis, (b) evaporative concentration in a flow system, (c) drying of gas streams and (d) sensing of moisture in gases and liquids. An important area that is not covered is ion-sensing with IEMs and/or ionophores.

Application of ion exchange membranes in enhancing algal production alongside desalination of saline water in microbial fuel cell

AbstractIn the present world scenario the demand for fresh water and clean energy is driving the need to convert a microbial fuel cell (MFC) into an algal-based microbial desalination cell (MDC) that can support algal growth along with desalination of saline water. In this study, the performance of a five-chambered MDC fed with saline water having two different salt concentrations, namely 2.5 g/L and 5.0 g/L in desalination chamber, as well as MDC operated without algae in catholyte was investigated. The algal-based MDC operated with 5 g/L of total dissolved solid (TDS) in desalination chamber exhibited the best performance results among all other combinations giving a maximum power density of 45.52 mW/m2 and a desalination efficiency of 71 ± 2 %. Also, a chemical oxygen demand (COD) removal efficiency of 78 % and coulombic efficiency of 12.24 % was achieved with 5 g/L NaCl concentration in desalination chamber. Based on this experimental performance evaluation, it can be inferred that algal-based MDC can provide a promising and sustainable approach for wastewater treatment with the capability of simultaneous desalination, algal production and electrical energy recovery.

Single Layer 2D Crystals for Electrochemical Applications of Ion Exchange Membranes and Hydrogen Evolution Catalysts

AbstractThe isolation of graphene is considered as the beginning of a new generation of 2D materials and 2D crystals. Because of their particular layered structure, with planar topology and a thickness from single to few atomic layers, which provide them with unique properties, 2D material are expected to have important applications in the next generation of energy systems. Electrochemical energy storage devices such as batteries or supercapacitors have already incorporated these materials as electrodes, electrocatalysts, etc. However, most of the applications reported so far use graphene based materials such as graphene oxide (GO) or reduced graphene oxide (rGO), or different 2D materials in a bulk feature. This review aims to provide an overview of the recent progress in using single layer and few layer 2D materials in electrochemical applications of ion exchange membranes and hydrogen evolution catalysts and their efficacy in these systems.

The Stability Challenges of Oxygen Evolving Catalysts: Towards a Common Fundamental Understanding and Mitigation of Catalyst Degradation.

This Review addresses the technical challenges, scientific basis, recent progress, and outlook with respect to the stability and degradation of catalysts for the oxygen evolution reaction (OER) operating at electrolyzer anodes in acidic environments with an emphasis on ion exchange membrane applications. First, the term "catalyst stability" is clarified, as well as current performance targets, major catalyst degradation mechanisms, and their mitigation strategies. Suitable in situ experimental methods are then evaluated to give insight into catalyst degradation and possible pathways to tune OER catalyst stability. Finally, the importance of identifying universal figures of merit for stability is highlighted, leading to a comprehensive accelerated lifetime test that could yield comparable performance data across different laboratories and catalyst types. The aim of this Review is to help disseminate and stress the important relationships between structure, composition, and stability of OER catalysts under different operating conditions.

Investigations on electrochemical properties of membrane systems in ion-exchange membrane transport processes by electrochemical impedance spectroscopy and direct current measurements

Electrochemical impedance spectroscopy (EIS) and direct current method (DC) are two powerful techniques to investigate the electrochemical properties in ion exchange membrane transport processes. This work investigated the resistance of membrane systems obtained by EIS and DC with different solution velocity and temperature. Analysis of experimental data from EIS revealed that EIS can be used to analyze each sublayer of ion exchange membrane systems separately and quantitatively and that the resistance of interfacial layers was related to Donnan exclusion. The Bode plots of EIS data were corrected for ohmic resistance to determine the evident constant phase element (CPE) behavior in the data, and the effects of flow velocity and temperature on ohmic-resistance-corrected Bode plots were also analyzed. With the comparison of data obtained from EIS and DC, the sum of pure membrane resistance, diffusion boundary layer resistance and electrical double layer resistance determined by EIS equaled to the overall resistance of membrane systems determined by DC. The results confirmed the linear relationship between the overall conductivity of membrane systems from DC and the pure membrane conductivity from EIS. These results are of major importance for applications of ion exchange membranes in various electro-membrane processes and applications of EIS on characterization of membrane transport properties.

The removal of boron from the aquatic environment–state of the art

Boron is emitted into the environment in a natural (weathering of rocks) and anthropogenic (wastewaters coming from industry, agriculture) way. It is a micronutrient for plants and animals, as well as a useful component in many branches of commercial activities. However, an excess of boron is toxic for both plants and animals. Extremely narrow is the range between permissible and harmful doses both to people and plants. It is often necessary to remove it from water and wastewater. The acceptable content of boron in drinking water and wastewater discharge into the environment is 1 mg/L. Removal of boron from the aquatic environment can be carried out in the following ways: ion exchange and adsorption onto boron-selective resins; reverse osmosis, in multistage configurations with RO and sorption; hybrid systems combining sorption onto fine resins with membrane filtration and polymer-enhanced ultrafiltration; processes with application of ion exchange membranes. The work presents a comprehensive review of the literature on boron removal with above-mentioned methods. The fundamentals of each process and the effect of experimental parameters are discussed.

International experts meet in Germany to discuss trends in anion exchange membranes

Alkaline membranes and their applications were the main topic of the Workshop on Ion Exchange Membrane Applications, held in June 2014 in Bad Zwischenahn, Germany. The workshop saw 35 experts from nine nations listen to 19 talks given by membrane specialists from academic research facilities and professionals from industry. To give an impression of the workshop programme, this article presents four excerpts from the scientific talks.

Ion-Exchange Membranes in the Chemical Process Industry

Ion-exchange membranes play an important role today in deionization of aqueous solutions, in electrochemical synthesis, and in energy conversion and storage. Some of the applications of ion-exchange membranes are mature and well established processes such as the water desalination by electrodialysis or the electrolytic chlorine–alkaline synthesis. Other applications of ion-exchange membranes are still in an early state of their development, such as the redox flow battery. In this publication the principles of state-of-the-art ion-exchange membrane processes and their applications are briefly described. Their advantages and limitations are discussed, and their commercial relevance is indicated. More recently developed products and processes are also addressed. Their basic functions are described, and their present and potential future applications are discussed. Research needs for a further improvement of ion-exchange membranes and their applications are pointed out.

Degradation of Imidazolium- and Quaternary Ammonium-Functionalized Poly(fluorenyl ether ketone sulfone) Anion Exchange Membranes

Imidazolium and quaternary ammonium-functionalized poly(fluorenyl ether ketone sulfone)s were synthesized successfully with the same degree of cationic functionalization and identical polymer backbones for a comparative study of anion exchange membranes (AEMs) for solid-state alkaline membrane fuel cells (AMFCs). Both anion exchange membranes were synthesized using a new methyl-containing monomer that avoided the use of toxic chloromethylation reagents. The polymer chemical structures were confirmed by ¹H NMR and FTIR. The derived AEMs were fully characterized by water uptake, anion conductivity, stability under aqueous basic conditions, and thermal stability. Interestingly, both the cationic groups and the polymer backbone were found to be degraded in 1 M NaOH solution at 60 °C over 48 h as measured by changes of ion exchange capacity and intrinsic viscosity. Imidazolium-functionalized poly(fluorenyl ether ketone sulfone)s had similar aqueous alkaline stability to quaternary ammonium-functionalized materials at 60 °C but much lower stability at 80 °C. This work demonstrates that quaternary ammonium and imidazolium cationic groups are not stable on poly(arylene ether sulfone) backbones under relatively mild conditions. Additionally, the poly(arylene ether sulfone) backbone, which is one of the most common polymers used in ion exchange membrane applications, is not stable in the types of molecular configurations analyzed.

REMOVED: Practical Applications of Ion-exchange Membranes and Recent Developments

This article has been removed: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been removed at the request of the Executive Publisher. This article has been removed because it was published without the permission of the author(s).

Recent Patented Applications of Ion-Exchange Membranes in the Agrifood Sector

Recent Patented Applications of Ion-Exchange Membranes in the Agrifood Sector