Journal articles on the topic 'Separation Processes, Reactive electrochemical membranes'
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Song, Hyeon-Bee, Do-Hyeong Kim, and Moon-Sung Kang. "Thin-Reinforced Anion-Exchange Membranes with High Ionic Contents for Electrochemical Energy Conversion Processes." Membranes 12, no. 2 (February 8, 2022): 196. http://dx.doi.org/10.3390/membranes12020196.
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Ion-exchange membranes (IEMs) are a core component that greatly affects the performance of electrochemical energy conversion processes such as reverse electrodialysis (RED) and all-vanadium redox flow battery (VRFB). The IEMs used in electrochemical energy conversion processes require low mass transfer resistance, high permselectivity, excellent durability, and also need to be inexpensive to manufacture. Therefore, in this study, thin-reinforced anion-exchange membranes with excellent physical and chemical stabilities were developed by filling a polyethylene porous substrate with functional monomers, and through in situ polymerization and post-treatments. In particular, the thin-reinforced membranes were made to have a high ion-exchange capacity and a limited degree of swelling at the same time through a double cross-linking reaction. The prepared membranes were shown to possess both strong tensile strength (>120 MPa) and low electrical resistance (<1 Ohm cm2). As a result of applying them to RED and VRFB, the performances were shown to be superior to those of the commercial membrane (AMX, Astom Corp., Japan) in the optimal composition. In addition, the prepared membranes were found to have high oxidation stability, enough for practical applications.
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Skolotneva, Ekaterina, Marc Cretin, and Semyon Mareev. "A Simple 1D Convection-Diffusion Model of Oxalic Acid Oxidation Using Reactive Electrochemical Membrane." Membranes 11, no. 6 (June 7, 2021): 431. http://dx.doi.org/10.3390/membranes11060431.
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In recent years, electrochemical methods utilizing reactive electrochemical membranes (REM) have been recognized as the most promising technologies for the removal of organic pollutants from water. In this paper, we propose a 1D convection-diffusion-reaction model concerning the transport and oxidation of oxalic acid (OA) and oxygen evolution in the flow-through electrochemical oxidation system with REM. It allows the determination of unknown parameters of the system by treatment of experimental data and predicts the behavior of the electrolysis setup. There is a good agreement in calculated and experimental data at different transmembrane pressures and initial concentrations of OA. The model provides an understanding of the processes occurring in the system and gives the concentration, current density, potential, and overpotential distributions in REM. The dispersion coefficient was determined as a fitting parameter and it is in good agreement with literary data for similar REMs. It is shown that the oxygen evolution reaction plays an important role in the process even under the kinetic limit, and its contribution decreases with increasing total organic carbon flux through the REM.
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Gu, Liankai, Yonghao Zhang, Weiqing Han, and Kajia Wei. "Membrane Fouling and Electrochemical Regeneration at a PbO2-Reactive Electrochemical Membrane: Study on Experiment and Mechanism." Membranes 12, no. 8 (August 22, 2022): 814. http://dx.doi.org/10.3390/membranes12080814.
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Membrane fouling and regeneration are the key issues for the application of membrane separation (MS) technology. Reactive electrochemical membranes (REMs) exhibited high, stable permeate flux and the function of chemical-free electrochemical regeneration. This study fabricated a micro-filtration REM characterized by a PbO2 layer (PbO2-REM) to investigate the electro-triggered anti-fouling and regeneration progress within REMs. The PbO2-REM exhibited a three-dimensional porous structure with a few branch-like micro-pores. The PbO2-REM could alleviate Humic acid (HA) and Bisphenol A (BPA) fouling through electrochemical degradation combined with bubble migration, which achieved the best anti-fouling performance at current density of 4 mA cm−2 with 99.2% BPA removal. Regeneration in the electro-backwash (e-BW) mode was found as eight times that in the forward wash and full flux recovery was achieved at a current density of 3 mA cm−2. EIS and simulation study also confirmed complete regeneration by e-BW, which was ascribed to the air–water wash formed by bubble migration and flow. Repeated regeneration tests showed that PbO2-REM was stable for more than five cycles, indicating its high durability for practical uses. Mechanism analysis assisted by finite element simulation illustrated that the high catalytic PbO2 layer plays an important role in antifouling and regeneration.
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Kim, Nayeong, and Xiao Su. "Redox-Mediated Electrodialysis for Resource Recovery and Energy-Efficient Desalination." ECS Meeting Abstracts MA2022-02, no. 27 (October 9, 2022): 1057. http://dx.doi.org/10.1149/ma2022-02271057mtgabs.
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In the chemical and biochemical manufacturing industry, separation processes are amongst the most energy-demanding processes. Electrochemical separations have been growing in interest as promising candidates for both downstream processing for resource recovery and producing clean water due to their energy-efficient, environmentally benign, and modular features.1 Leveraging a sustainable redox reaction, we developed a redox-mediated electrodialysis system for energy-efficient desalination coupled with resource recovery of valuable resources such as lithium, and even biomolecules.2, 3 Our proposed redox-mediated electrodialysis system utilizes a reversible redox reaction as a driving force of salt removal at a much lower voltage than a water-splitting reaction (>1.2 V). As the redox materials are reduced or oxidized, all charged species migrate across the membranes to balance the charge in the electrolyte compartment. As the redox materials circulate in the cathode and anode compartments, they sustainably regenerated without additional regeneration steps, one of the major bottlenecks for industrializing the electrosorption system. We demonstrated the redox-mediated electrochemical system for resource recoveries such as simultaneous lithium recovery from brine3 and valorization of whey proteins and lactose from whey waste.2 Especially for the valorization of whey waste, our system treated 99% of salt from the whey solution within a single step and recovered > 98% of various whey proteins (e.g., valuable protein contents such as beta-lactoglobulin, alpha-lactalbumin, and lactose). The preliminary techno-economic analysis confirmed the economic potential of redox-mediated ED with 51−73% lower energy consumption compared to conventional ED. Overall. we envision the system can become a breakthrough in tackling the environmental challenges coupled with the limited resources. Kim, N.; Jeon, J.; Chen, R.; Su, X., Electrochemical separation of organic acids and proteins for food and biomanufacturing. Chemical Engineering Research and Design 2022, 178, 267-288. Kim, N.; Jeon, J.; Elbert, J.; Kim, C.; Su, X., Redox-mediated electrochemical desalination for waste valorization in dairy production. Chemical Engineering Journal 2022, 428, 131082. Kim, N.; Su, X.; Kim, C., Electrochemical lithium recovery system through the simultaneous lithium enrichment via sustainable redox reaction. Chemical Engineering Journal 2021, 420, 127715.
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Miller, Dean, Matthew Liu, and William Abraham Tarpeh. "Evaluating Molecular Catalyst-Mediated Nitrate Reduction for Reactive Separation and Recovery of Ammonia." ECS Meeting Abstracts MA2022-01, no. 40 (July 7, 2022): 1799. http://dx.doi.org/10.1149/ma2022-01401799mtgabs.
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The current state of centralized nitrogen (N) management has destabilized global environmental cycles via Haber-Bosch (HB) ammonia-N manufacturing which contributes 1.2% of global anthropogenic CO2-eq emissions.1 The majority of this N that is discharged to wastewaters goes untreated, leading to harmful algal blooms that threaten coastal and river ecosystems, which already costs the U.S. an estimated $210 billion per year in health and environmental damages.2 Furthermore, the production of HB ammonia, and the subsequent discharge of wastewater nitrogen, is expected to substantially increase in the next three decades as the human population climbs to 9 billion people.3 Simultaneously removing nitrogen pollutants and recovering value-added products can preserve national water quality and supplement supply chains of nitrogen consumables with renewably sourced electricity. The electrochemical nitrate reduction reaction (NO3RR) can be leveraged in reactive separation processes to convert wastewater nitrates to commodity products, such as ammonia. Engineering catalytic NO3RR processes that operate at feasible rates and faradaic efficiencies is challenging because the majority of nitrate-rich wastewaters (e.g., fertilizer runoff) are dilute in nitrate concentration (< 5 mM).4 Molecular catalysts are uniquely suited to reduce nitrate at low concentrations in real wastewaters due to their strong substrate recognition (reactant selectivity) and product selectivity. In this study, we benchmarked the performance of the molecular catalyst Co-DIM (a Co-N4 macrocycle complex and the only known molecular NO3RR catalyst selective for ammonia5) in a reactive separations process for the treatment of real, nitrate-rich wastewaters. We first demonstrated by cyclic voltammetry (CV) and controlled-potential electrolysis (CPE) that selective Co-DIM-mediated NO3RR is feasible in nitrate-rich secondary effluent (municipal wastewater after biological nitrification). We then employed Co-DIM in electrochemical stripping (ECS): a membrane-separated cell that facilitates reactive separation of produced ammonia.6,7 From real secondary effluent (28 mg NO3-N/L), we achieved greater than 60% nitrate removal with a faradaic efficiency of 25% and ammonia selectivity of 98%. However, the energy consumed for ECS per unit mass of N is 16 times the combined energy requirement for conventional wastewater N removal and HB ammonia synthesis. By introducing a mixed feed of ammonia- and nitrate-rich wastewater and performing electrodialysis (ED) to concentrate the reactant nitrate before ECS, the energy requirement for N removal and ammonia recovery was decreased by three times while the ED process became the dominant energy consumer in the overall process. Additionally, the increase in nitrate removal could not be explained by an increase in nitrate concentration alone. The ED process changes the concentrations and relative ratios of competing anions and buffering species, which can inhibit or promote the molecular electrocatalytic activity. We therefore explored a matrix of anion identities and concentrations by rotating-disk voltammetry and CPE to elucidate plausible inhibition and promotion mechanisms associated with catalyst activation and NO3RR catalysis. This study therefore (1) benchmarks current and future efforts to reactively separate ammonia from real nitrate-rich wastewater with a molecular catalyst and (2) highlights molecular and process-level improvements to realize a circular nitrogen economy. References 1 C. Smith, A. K. Hill and L. Torrente-Murciano, Energy Environ. Sci., 2020, 13, 331–344. 2 D. J. Sobota, J. E. Compton, M. L. McCrackin and S. Singh, Environ. Res. Lett., 2015, 10, 025006. 3 J. W. Erisman, M. A. Sutton, J. Galloway, Z. Klimont and W. Winiwarter, Nature Geoscience, 2008, 1, 636–639. 4 Unesco, Ed., Wastewater: the untapped resource, UNESCO, Paris, 2017. 5 S. Xu, D. C. Ashley, H.-Y. Kwon, G. R. Ware, C.-H. Chen, Y. Losovyj, X. Gao, E. Jakubikova and J. M. Smith, Chem. Sci., 2018, 9, 4950–4958. 6 W. A. Tarpeh, J. M. Barazesh, T. Y. Cath and K. L. Nelson, Environ. Sci. Technol., 2018, 52, 1453–1460. 7 M. J. Liu, B. S. Neo and W. A. Tarpeh, Water Research, 2020, 169, 115226.
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Belhadj Ammar, Rihab, Takoua Ounissi, Lassaad Baklouti, Christian Larchet, Lasâad Dammak, Arthur Mofakhami, and Emna Selmane Belhadj Hmida. "A New Method Based on a Zero Gap Electrolysis Cell for Producing Bleach: Concept Validation." Membranes 12, no. 6 (June 10, 2022): 602. http://dx.doi.org/10.3390/membranes12060602.
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Commercial bleach (3.6 wt% active chlorine) is prepared by diluting highly concentrated industrial solutions of sodium hypochlorite (about 13 wt% active chlorine) obtained mainly by bubbling chlorine gas into dilute caustic soda. The chlorine and soda used are often obtained by electrolyzing a sodium chloride solution in two-compartment cells (chlorine-soda processes). On a smaller scale, small units used for swimming pool water treatment, for example, allow the production of low-concentration bleach (0.3 to 1 wt% active chlorine) by use of a direct electrolysis of sodium chloride brine. The oxidation and degradation reaction of hypochlorite ion (ClO−) at the anode is the major limiting element of this two-compartment process. In this study, we have developed a new process to obtain higher levels of active chlorine up to 3.6%, or 12° chlorometric degree. For this purpose, we tested a device consisting of a zero-gap electrolysis cell, with three compartments separated by a pair of membranes that can be porous or ion-exchange. The idea is to generate in the anode compartment hypochlorous acid (HClO) at high levels by continuously adjusting its pH to a value between 4.5 and 5.5. In the cathodic compartment, caustic soda is obtained, while the central compartment is supplied with brine. The hypochlorous acid solution is then neutralized with a concentrated solution of NaOH to obtain bleach. In this work, we studied several membrane couples that allowed us to optimize the operating conditions and to obtain bleach with contents close to 1.8 wt% of active chlorine. The results obtained according to the properties of the membranes, their durability, and the imposed electrochemical conditions were discussed.
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Ramirez-Nava, Jonathan, Mariana Martínez-Castrejón, Rocío Lley García-Mesino, Jazmin Alaide López-Díaz, Oscar Talavera-Mendoza, Alicia Sarmiento-Villagrana, Fernando Rojano, and Giovanni Hernández-Flores. "The Implications of Membranes Used as Separators in Microbial Fuel Cells." Membranes 11, no. 10 (September 28, 2021): 738. http://dx.doi.org/10.3390/membranes11100738.
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Microbial fuel cells (MFCs) are electrochemical devices focused on bioenergy generation and organic matter removal carried out by microorganisms under anoxic environments. In these types of systems, the anodic oxidation reaction is catalyzed by anaerobic microorganisms, while the cathodic reduction reaction can be carried out biotically or abiotically. Membranes as separators in MFCs are the primary requirements for optimal electrochemical and microbiological performance. MFC configuration and operation are similar to those of proton-exchange membrane fuel cells (PEMFCs)—both having at least one anode and one cathode split by a membrane or separator. The Nafion® 117 (NF-117) membrane, made from perfluorosulfonic acid, is a membrane used as a separator in PEMFCs. By analogy of the operation between electrochemical systems and MFCs, NF-117 membranes have been widely used as separators in MFCs. The main disadvantage of this type of membrane is its high cost; membranes in MFCs can represent up to 60% of the MFC’s total cost. This is one of the challenges in scaling up MFCs: finding alternative membranes or separators with low cost and good electrochemical characteristics. The aim of this work is to critically review state-of-the-art membranes and separators used in MFCs. The scope of this review includes: (i) membrane functions in MFCs, (ii) most-used membranes, (iii) membrane cost and efficiency, and (iv) membrane-less MFCs. Currently, there are at least 20 different membranes or separators proposed and evaluated for MFCs, from basic salt bridges to advanced synthetic polymer-based membranes, including ceramic and unconventional separator materials. Studies focusing on either low cost or the use of natural polymers for proton-exchange membranes (PEM) are still scarce. Alternatively, in some works, MFCs have been operated without membranes; however, significant decrements in Coulombic efficiency were found. As the type of membrane affects the performance and total cost of MFCs, it is recommended that research efforts are increased in order to develop new, more economic membranes that exhibit favorable properties and allow for satisfactory cell performance at the same time. The current state of the art of membranes for MFCs addressed in this review will undoubtedly serve as a key insight for future research related to this topic.
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Choi, DongWoong. "Electrochemical Analysis of Polymer Membrane with Inorganic Nanoparticles for High-Temperature PEM Fuel Cells." Membranes 12, no. 7 (June 30, 2022): 680. http://dx.doi.org/10.3390/membranes12070680.
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In order to solve the challenge that battery performance rapidly deteriorates at a high temperature condition of 100 °C or higher, ZrO2-TiO2 (ZT) with various Zr:Ti ratios synthesized by a sol-gel method were impregnated in a Nafion membrane. Through material characterization, a unique ZT crystal phase peak with a Zr-O-Ti bond was identified, and the band range associated with this bond and intrinsic functional group region could be identified. These prepared powders were blended with 10% (w/w) Nafion-water dispersion to prepare composite Nafion membranes (NZTs). The water uptake increased and the ion exchange capacity decreased as the TiO2 content increased in the NZTs in which particles were uniformly distributed. These results were superior to those of the conventional Nafion 112. The electrochemical properties of all membranes was measured using a polarization curve in a single cell with a reaction area of 9 cm2, and the operating conditions in humidified H2/air was 120 °C under 50% relative humidity (RH) and 2 atm. The composite membrane cell with nanoparticles of a Zr:Ti ratio of 1:3 (NZT13) exhibited the best electrochemical characteristics. These results can be explained by the improved physicochemical properties of NZT13, such as optimized water content and ion exchange capacity, strong intermolecular forces acting between water and nanofillers (δ), and increased torsion by the fillers (τ). The results of this study show that the NZT membrane can replace a conventional membrane under high-temperature and low-humidity conditions. To examine the effect of the content of the inorganic nanomaterials in the composite membrane, a composite membrane (NZT-20, NZT-30) having an inorganic nano-filler content of 20 or 30% (w/w) was also prepared. The performance was high in the order of NZT13, NZT-20, and NZT-30. This shows that not only the operating conditions but also the particle content can significantly affect the performance.
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McHugh, Patrick J., Arindam K. Das, Alexander G. Wallace, Vaibhav Kulshrestha, Vinod K. Shahi, and Mark D. Symes. "An Investigation of a (Vinylbenzyl) Trimethylammonium and N-Vinylimidazole-Substituted Poly (Vinylidene Fluoride-Co-Hexafluoropropylene) Copolymer as an Anion-Exchange Membrane in a Lignin-Oxidising Electrolyser." Membranes 11, no. 6 (June 2, 2021): 425. http://dx.doi.org/10.3390/membranes11060425.
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Electrolysis is seen as a promising route for the production of hydrogen from water, as part of a move to a wider “hydrogen economy”. The electro-oxidation of renewable feedstocks offers an alternative anode couple to the (high-overpotential) electrochemical oxygen evolution reaction for developing low-voltage electrolysers. Meanwhile, the exploration of new membrane materials is also important in order to try and reduce the capital costs of electrolysers. In this work, we synthesise and characterise a previously unreported anion-exchange membrane consisting of a fluorinated polymer backbone grafted with imidazole and trimethylammonium units as the ion-conducting moieties. We then investigate the use of this membrane in a lignin-oxidising electrolyser. The new membrane performs comparably to a commercially-available anion-exchange membrane (Fumapem) for this purpose over short timescales (delivering current densities of 4.4 mA cm−2 for lignin oxidation at a cell potential of 1.2 V at 70 °C during linear sweep voltammetry), but membrane durability was found to be a significant issue over extended testing durations. This work therefore suggests that membranes of the sort described herein might be usefully employed for lignin electrolysis applications if their robustness can be improved.
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Zhan, Zhigang, Hao Song, Xiaoxiang Yang, Panxing Jiang, Rui Chen, Hesam Bazargan Harandi, Heng Zhang, and Mu Pan. "Microstructure Reconstruction and Multiphysics Dynamic Distribution Simulation of the Catalyst Layer in PEMFC." Membranes 12, no. 10 (October 14, 2022): 1001. http://dx.doi.org/10.3390/membranes12101001.
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Due to the complexity of both material composition and the structure of the catalyst layer (CL) used in the proton-exchange membrane fuel cell (PEMFC), conjugated heat and mass transfer as well as electrochemical processes simultaneously occur through the CL. In this study, a microstructure model of CL was first reconstructed using images acquired by Nano-computed tomography (Nano-CT) of a real sample of CL. Then, the multiphysics dynamic distribution (MPDD) simulation, which is inherently a multiscale approach made of a combination of pore-scale and homogeneous models, was conducted on the reconstructed microstructure model to compute the corresponded heat and mass transport, electrochemical reactions, and water phase-change processes. Considering a computational domain with the size of 4 um and cube shape, this model consisting of mass and heat transport as well as electrochemical reactions reached a stable solution within 3 s as the convergence time. In the presence of sufficient oxygen, proton conduction was identified as the dominant factor determining the strength of the electrochemical reaction. Additionally, it was concluded that current density, temperature, and the distribution of water all exhibit similar distribution trends, which decrease from the interface between CL and the proton-exchange membrane to the interface between CL and the gas-diffusion layer. The present study not only provides an in-depth understanding of the mass and heat transport and electrochemical reaction in the CL microstructure, but it also guides the optimal design and fabrication of CL components and structures, such as improving the local structure to reduce the number of dead pores and large agglomerates, etc.
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Zuo, Yuxin, Ying Yu, Haoqin Shi, Jiale Wang, Chuncheng Zuo, and Xiaowei Dong. "Inhibition of Hydrogen Evolution by a Bifunctional Membrane between Anode and Electrolyte of Aluminum–Air Battery." Membranes 12, no. 4 (April 6, 2022): 407. http://dx.doi.org/10.3390/membranes12040407.
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The hydrogen evolution reaction of the anode is a severe barrier that limits the further commercial application of Al–air batteries. Therefore, this study introduces a bifunctional membrane for the inhibition of hydrogen evolution in Al–air batteries. The reference to Al2O3@PAN as “bifunctional” means that it has both hydrophobic and anti-corrosion functions. Al2O3 can effectively inhibit the migration of hydroxide ions, and PAN is an excellent hydrophobic material. The bifunctional membrane is placed between the aluminum anode and the electrolyte, which can prevent the invasion of excess water and hydroxide ions, thereby inhibiting the hydrogen evolution corrosion of the anode. Electrochemical tests have confirmed that the corrosion inhibition rate of a bifunctional membrane containing 1.82 wt. % Al2O3@PAN is as high as 89.24%. The specific capacity of Al–air batteries containing this membrane can reach 1950 mAh/g, and the utilization rate of the aluminum anode has reached 61.2%, which is helpful in reducing the waste of aluminum resources. The results prove that the bifunctional membrane has excellent anti-corrosion properties. Bifunctional membranes can also be used to prevent the corrosion of metals in other fields.
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Randall, Corey R., Joseph Dura, Lianfeng Zou, Melodie Chen-Glasser, and Steven C. DeCaluwe. "Using Neutron Reflectometry to Quantify the Carbon-Nafion Interface for Proton Exchange Membrane Fuel Cell Applications." ECS Meeting Abstracts MA2022-01, no. 35 (July 7, 2022): 1409. http://dx.doi.org/10.1149/ma2022-01351409mtgabs.
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Due to its chemical stability in acidic environments and high ionic conductivity, Nafion has proven to be an essential material in proton exchange membrane fuel cell (PEMFC) designs. Nafion functions as both a membrane – separating the two electrodes – and as a conductive binder in each catalyst layer (CL). Nano-thin films of Nafion ionomer allow protons to reach carbon-supported Pt catalysts. In addition to protons, oxygen and water also move through the nano-thin Nafion ionomer to and from reactive Pt sites. These physical transport processes directly impact PEMFC performance. Therefore, measuring and determining ways to improve upon each of these processes is critical in the development of high performance PEMFCs. In regards to thick Nafion membranes, conductivity and diffusion measurements can be readily performed in most laboratories. Nano-thin Nafion films on the other hand prove more challenging to study due to experimental limitations. Nevertheless, neutron reflectometry (NR) has been reported in literature as a capable technique to provide simultaneous quantitative structural and composition profiles for thin-film Nafion [1-5]. Results for Nafion at native silicon oxide interfaces show complex multi-layered structures forming distinct water-rich and water-poor regions [1-3]. Despite these advancements in our understanding of thin-film Nafion, it is still unclear how these observed structures may impact PEMFC performance. This is because silicon does not interface with Nafion in PEMFC CLs. Instead, carbon and Pt are the primary and secondary materials that interface with the thin-film ionomer. In the latter case, thin-film Nafion at Pt interfaces has been briefly studied in literature and shows significantly less structure than Nafion at silicon oxide interfaces [4,5]. Beyond the limited number of studies for Pt-Nafion interfaces, carbon-Nafion interface studies are even more scarce in literature [5]. This is likely because carbon black (i.e. the electron conductor in PEMFC CLs) is too rough to be used with NR. Therefore, to confidently assume the structure of Nafion at carbon black interfaces, trends from NR work on other carbon-based samples need to be compiled and compared, while considering their bonding structures and surface chemistries. In this work, we extend the understanding of thin-film Nafion at carbon interfaces by testing four different carbon-based substrates. Using thin-film Nafion (< 100 nm) deposited on each carbon sample, NR was performed in both dry and humidified environments. Fitting the data to these experiments, results suggest a variety of polymer structures at the carbon-Nafion interface. These include complex multi-layered structures, similar to those at silicon oxide interfaces, as well as simple homogenous films with little-to-no interfacial structure. During this presentation, the implications of these results on species transport in PEMFC CLs will be discussed. Additionally, PEMFC performance predictions that incorporate learnings from this study will be made using an extended model from our earlier work [6]. [1] S.C. DeCaluwe, A.M. Baker, P. Bhargava, J.E. Fischer, and J.A. Dura, “Structure-property Relationships at Nafion Thin-film Interfaces: Thickness Effects on Hydration and Anisotropic Ion Transport,” Nano Energy, vol. 46, pp. 91–100, 2018. [2] J.A. Dura, V.S. Murthi, M. Hartman, S.K. Satija, and C.F. Majkrzak, “Multilamellar Interface Structures in Nafion,” Macromolecules, vol. 42, no. 13, pp. 4769–4774, 2009. [3] U.N. Shrivastava, H. Fritzsche, and K. Karan, “Interfacial and Bulk Water in Ultrathin Films of Nafion, 3M PFSA, and 3M PFIA Ionomers on a Polycrystalline Platinum Surface,” Macromolecules, vol. 51, no. 23, pp. 9839–9849, 2018. [4] V.S. Murthi, J. Dura, S. Satija, and C. Majkrzak, “Water Uptake and Interfacial Structural Changes of Thin Film Nafion Membranes Measured by Neutron Reflectometry for PEM Fuel Cells,” ECS Transactions, vol. 16, no. 2, 2019. [5] D.L. Wood, J. Chlistunoff, J. Majewski, and R.L. Borup, “Nafion Structural Phenomena at Platinum and Carbon Interfaces,” Journal of the American Chemical Society, vol. 131, no. 50, pp. 18096–18104, 2009. [6] C.R. Randall and S.C. DeCaluwe, “Physically Based Modeling of PEMFC Cathode Catalyst Layers: Effective Microstructure and Ionomer Structure–Property Relationship Impacts,” Journal of Electrochemical Energy Conversion and Storage, vol. 17, no. 4, Jan. 2020.
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Yang, Kai, and Mohan Qin. "The Application of Cation Exchange Membranes in Electrochemical Systems for Ammonia Recovery from Wastewater." Membranes 11, no. 7 (June 30, 2021): 494. http://dx.doi.org/10.3390/membranes11070494.
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Electrochemical processes are considered promising technologies for ammonia recovery from wastewater. In electrochemical processes, cation exchange membrane (CEM), which is applied to separate compartments, plays a crucial role in the separation of ammonium nitrogen from wastewater. Here we provide a comprehensive review on the application of CEM in electrochemical systems for ammonia recovery from wastewater. Four kinds of electrochemical systems, including bioelectrochemical systems, electrochemical stripping, membrane electrosorption, and electrodialysis, are introduced. Then we discuss the role CEM plays in these processes for ammonia recovery from wastewater. In addition, we highlight the key performance metrics related to ammonia recovery and properties of CEM membrane. The limitations and key challenges of using CEM for ammonia recovery are also identified and discussed.
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Dao, Khanh-Chau, Yung-Pin Tsai, Chih-Chi Yang, and Ku-Fan Chen. "Simultaneous Carbamazepine and Phosphate Removal from a Moving-Bed Membrane Bioreactor Effluent by the Electrochemical Process: Treatment Optimization by Factorial Design." Membranes 12, no. 12 (December 12, 2022): 1256. http://dx.doi.org/10.3390/membranes12121256.
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Pharmaceutical and personal care products are frequently used in various fields and released into water bodies from the outlets of wastewater treatment plants. These products can harm the environment and human health even at low concentrations. Carbamazepine (CBZ), the most persistent pharmaceutical, has frequently been found in surface waters that bypassed the secondary treatments of conventional activated sludge. In addition, the treatment of phosphate in wastewater by the electrochemical process has recently attracted much attention because of its ability to remove, recover, and prevent environmental problems associated with eutrophication. This study proposes using the electrochemical process as an advanced oxidation process to simultaneously treat CBZ and phosphate from the moving-bed membrane bioreactor effluent. The study includes a long-term survey of CBZ treatment efficiency and common parameters of synthetic wastewater in the moving-bed membrane bioreactor system. Afterward, the electrochemical process is applied as an advanced oxidation process for the simultaneous removal of CBZ and phosphate from the moving-bed membrane bioreactor. Under the investigated conditions, CBZ has proven not to be an inhibitor of microbial activity, as evidenced by the high extent of chemical oxygen demand and nutrient removal. Using a factorial design, the electrochemical process using Pt/Ti as anode and cathode under optimal conditions (reaction time—80 min, bias potential—3 V, and electrode distance—1 cm) resulted in as high as 56.94% CBZ and 95.95% phosphate removal, respectively. The results demonstrated the ability to combine an electrochemical and a moving-bed membrane bioreactor process to simultaneously remove CBZ and phosphate in wastewater.
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Navarro, Andreu Bonet, Adrianna Nogalska, and Ricard Garcia-Valls. "A 3D Printed Membrane Reactor System for Electrochemical CO2 Conversion." Membranes 13, no. 1 (January 10, 2023): 90. http://dx.doi.org/10.3390/membranes13010090.
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Nowadays, CO2 electroreduction is gaining special interest as achieving net zero CO2 emissions is not going to be enough to avoid or mitigate the negative effects of climate change. However, the cost of CO2 electroreduction is still very high because of the low efficiency of conversion (around 20%). Therefore, it is necessary to optimize the reaction conditions. Thus, a miniaturized novel membrane reactor was designed and manufactured in this study, with a shorter distance between the electrodes and a reduced volume, compared with CNC-manufactured reactors, using novel stereolithography-based 3D printing. The reduced distance between the two electrodes reduced the electrical resistance and therefore lowered the overpotential necessary to trigger the reaction from −1.6 V to −1.2 V, increasing the efficiency. In addition, the reduction in the volume of the reactor increased the catalyst area/volume ratio, which also boosted the concentration of the products (from FE 18% to FE 21%), allowing their better identification. Furthermore, the smaller volume and reduced complexity of the reactor also improved the testing capacity and decreased the cost of experimentation. The novel miniaturized reactor can help researchers to perform more experiments in a cost/time-effective way, facilitating the optimization of the reaction conditions.
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Leonardi, Marco, Giuseppe Tranchida, Roberto Corso, Rachela G. Milazzo, Salvatore A. Lombardo, and Stefania M. S. Privitera. "Role of the Membrane Transport Mechanism in Electrochemical Nitrogen Reduction Experiments." Membranes 12, no. 10 (October 2, 2022): 969. http://dx.doi.org/10.3390/membranes12100969.
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The electrochemical synthesis of ammonia through the nitrogen reduction reaction (NRR) is receiving much attention, since it is considered a promising alternative to the Haber–Bosch process. In NRR experiments, a Nafion membrane is generally adopted as a separator. However, its use is controversial since ammonia can be trapped in the membrane, to some extent, or even pass through it. We systematically investigate the interaction of a Nafion membrane with ammonia and with an electrolyte and compare it with Zirfon as a possible alternative separator. We show that Nafion containing ammonia can easily release it when immersed in a 0.1 M Na2SO4 ammonia-free electrolyte, due to the cation exchange mechanism (Na+-NH4+). Since Na2SO4 is a commonly adopted electrolyte for NRR experiments, this may cause serious measurement errors and non-reproducible results. The same experiments performed using the polysulfone Zirfon separator clearly show that it is immune to interactions with ammonia, because of its different ion conduction mechanism. The findings provide a deeper understanding of the choice of membrane and electrolyte to be adopted for NRR tests, and may allow one to obtain more accurate and reliable results.
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Padaki, Mahesh, Chitrakar Hegde, and Arun Mohan Isloor. "Synthesis, Characterization & Impedance Studies of some New Nano Filtration Membranes." Materials Science Forum 657 (July 2010): 26–34. http://dx.doi.org/10.4028/www.scientific.net/msf.657.26.
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In the recent years membrane technology has gained significant attention from polymer chemists all around the world due to their attractive features such as efficiency, low costs, low energy costs and as effective solutions to longstanding problems in the chemical industries. Membrane technologies have been widely applied in the separation of liquids and even gases. Many separation problems can be solved economically by nanofiltration alone or in combination with other separation processes. This study aimed to synthesize polysulfone based nanofiltration membranes using DIPS (diffusion induced phase separation) technique. Newly synthesized polymer membranes were subjected to Infra red spectral and water uptake studies. Membranes were also characterized using electrochemical spectroscopy for their proton conducting property. Their surface morphology is visualized by SEM.
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Rynkowska, Edyta, Kateryna Fatyeyeva, and Wojciech Kujawski. "Application of polymer-based membranes containing ionic liquids in membrane separation processes: a critical review." Reviews in Chemical Engineering 34, no. 3 (April 25, 2018): 341–63. http://dx.doi.org/10.1515/revce-2016-0054.
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Abstract The interest in ionic liquids, particularly in polymerizable ionic liquids, is motivated by their unique properties, such as good thermal stability, negligible vapor pressure, and wide electrochemical window. Due to these features ionic liquids were proposed to be used in the membrane separation technology. The utilization of conventional ionic liquids is, however, limited by their release from the membrane during the given separation process. Therefore, the incorporation of polymerizable ionic liquids may overcome this drawback for the industrial application. This work is a comprehensive overview of the advances of ionic liquid membranes for the separation of various compounds, i.e. gases, organic compounds, and metal ions.
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Matei, Ecaterina, Cristina Ileana Covaliu-Mierla, Anca Andreea Ţurcanu, Maria Râpă, Andra Mihaela Predescu, and Cristian Predescu. "Multifunctional Membranes—A Versatile Approach for Emerging Pollutants Removal." Membranes 12, no. 1 (January 3, 2022): 67. http://dx.doi.org/10.3390/membranes12010067.
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This paper presents a comprehensive literature review surveying the most important polymer materials used for electrospinning processes and applied as membranes for the removal of emerging pollutants. Two types of processes integrate these membrane types: separation processes, where electrospun polymers act as a support for thin film composites (TFC), and adsorption as single or coupled processes (photo-catalysis, advanced oxidation, electrochemical), where a functionalization step is essential for the electrospun polymer to improve its properties. Emerging pollutants (EPs) released in the environment can be efficiently removed from water systems using electrospun membranes. The relevant results regarding removal efficiency, adsorption capacity, and the size and porosity of the membranes and fibers used for different EPs are described in detail.
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Cascaval, Dan, and Anca-Irina Galaction. "New extraction techniques on bioseparations: 1. Reactive extraction." Chemical Industry 58, no. 9 (2004): 375–86. http://dx.doi.org/10.2298/hemind0409375c.
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The complexity of downstream processes for biosynthetic products constitutes a particularity of industrial biotechnologies, especially because of the biosynthetic product high dilution in fermentation broth, their chemical and thermal liability and the presence of secondary products. For these reasons, new separation techniques have been developed and applied to bioseparations. Among them, reactive extraction, pertraction (extraction and transport through liquid membranes) and direct extraction from broths have considerable potential and are required for the further development of many biotechnologies. This review is structured on two parts and presents our original results of the studies on the separation of some biosynthetic products (antibiotics, carboxylic acids, amino acids, alcohols) by reactive extraction in the first part, and by pertraction and direct extraction from broths without biomass filtration in the second. For all the analyzed cases, these extraction techniques simplify the technologies by reducing material and energy consumption, by avoiding product inhibition, by increasing the separation selectivity, therefore decreasing the overall cost of the product.
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Blaga, Alexandra Cristina, Alexandra Tucaliuc, and Lenuta Kloetzer. "Applications of Ionic Liquids in Carboxylic Acids Separation." Membranes 12, no. 8 (August 9, 2022): 771. http://dx.doi.org/10.3390/membranes12080771.
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Ionic liquids (ILs) are considered a green viable organic solvent substitute for use in the extraction and purification of biosynthetic products (derived from biomass—solid/liquid extraction, or obtained through fermentation—liquid/liquid extraction). In this review, we analyzed the ionic liquids (greener alternative for volatile organic media in chemical separation processes) as solvents for extraction (physical and reactive) and pertraction (extraction and transport through liquid membranes) in the downstream part of organic acids production, focusing on current advances and future trends of ILs in the fields of promoting environmentally friendly products separation.
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Lee, Chi-Yuan, Fang-Bor Weng, Chin-Yuan Yang, Chun-Wei Chiu, and Shubham-Manoj Nawale. "Real-Time Monitoring of HT-PEMFC." Membranes 12, no. 1 (January 15, 2022): 94. http://dx.doi.org/10.3390/membranes12010094.
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During the electrochemical reaction of a high temperature proton exchange membrane fuel cell (HT-PEMFC), (in this paper HT-PEMFC means operating in the range of 120 to 200 °C) the inhomogeneity of temperature, flow rate, and pressure in the interior is likely to cause the reduction of ion conductivity or thermal stability weight loss of proton exchange membrane materials, and it is additionally likely to cause uneven fuel distribution, thereby affecting the working performance and service life of the HT-PEMFC. This study used micro-electro-mechanical systems (MEMS) technology to develop a flexible three-in-one microsensor which is resistant to high temperature electrochemical environments; we selected appropriate materials and process parameters to protect the microsensor from failure or damage under long-term tests. The proposed method can monitor the local temperature, flow rate, and pressure distribution in HT-PEMFC in real time.
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Aryal, Utsav Raj, Majid Aziz, and Ajay Krishna Prasad. "(Invited) Electrochemical Gas Separation." ECS Meeting Abstracts MA2022-02, no. 27 (October 9, 2022): 1031. http://dx.doi.org/10.1149/ma2022-02271031mtgabs.
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Electrochemical gas separators are electrically powered systems that selectively remove a targeted gas species from a mixture of gases by virtue of electrochemical reactions. Electrochemical separation is an attractive option owing to its higher efficiency and lower cost compared to incumbent technologies like pressure swing adsorption, cryogenic processes, and selective permeation. This work focuses on two specific electrochemical separation processes – (1) separation of hydrogen from a mixture of gases to help develop the hydrogen distribution infrastructure, and (2) nitrogen separation from air for aircraft fuel tank inerting. Reductions in CO2 emission since the beginning of this century by the US electric power sector are mainly attributed to the replacement of coal by natural gas in power plants. Nevertheless, the combustion of natural gas still contributes heavily to global warming and climate change. It is imperative to find alternatives to combustion-based energy technologies and nurture the growth of renewable energy systems. In this scenario, hydrogen is a leading candidate as a carbon-free fuel with high energy density and is expected to play a key role in future energy systems. However, hydrogen faces serious obstacles in its distribution due to the lack of a nationwide hydrogen pipeline network. Developing a dedicated hydrogen pipeline network will be quite expensive, therefore, it is worthwhile to examine whether existing natural gas pipelines could be effectively deployed for hydrogen distribution. This would be accomplished by directly injecting a prescribed amount of hydrogen at the point of production into a natural gas pipeline. Such a mixture of hydrogen and methane is labeled as hythane. While this enables the convenient transport of hydrogen across large distances, the process can only be completed by separating hydrogen from methane at the destination point. Electrochemical hydrogen separation (ECHS) systems built around proton-selective polymer electrolyte membranes (PEMs) represent an effective platform to separate and simultaneously compress hydrogen in a continuous operation. Furthermore, ECHS ensures that the resulting gas is not contaminated by lubrication oil as observed in conventional systems. In ECHS, the hythane mixture enters the anode compartment wherein the hydrogen is selectively dissociated to protons and electrons. The protons are then driven across the PEM by an externally applied voltage to recover hydrogen at the cathode. The first part of this study demonstrates hydrogen purification using low-temperature PEM-based ECHS from various gas mixtures including methane/hydrogen, carbon dioxide/hydrogen, water gas shift effluent, and hythane. ECHS performance is first investigated for pure hydrogen as a function of membrane thickness, cell temperature, and relative humidity of the anode stream. In the second set of experiments, various ratios of methane/hydrogen and carbon dioxide/hydrogen are introduced to examine the effect of hydrogen concentration in the feed gas mixture on ECHS performance. Finally, experiments are performed for hydrogen purification from a water gas shift (WGS) effluent mixture as well as a practical hythane gas feed. ECHS performance for all gas mixtures was benchmarked against the pure hydrogen case. The purity of the separated hydrogen gas was measured to confirm the effectiveness of the method. The results show that ECHS represents a good solution to separate hydrogen from the hythane mixture at the downstream end of the pipeline. Pertinent to the second electrochemical separation process examined here, after the TWA flight 800 disaster due to a fuel tank explosion in 1996, inerting of aircraft fuel tanks became a priority. During fuel tank inerting, an inert gas like nitrogen is supplied to the tank to reduce its flammability. An electrochemical gas separation and inerting system (EGSIS) is a device that generates nitrogen enriched air (NEA) from ambient air by the application of electrical power. EGSIS combines a PEM electrolyzer anode wherein water is dissociated to release oxygen, and a PEM fuel cell cathode where atmospheric air is converted to NEA. Aircraft tank inerting requires varying NEA flowrates (low during takeoff and ascent, and high during descent). In conventional hollow fiber membrane air separation modules typically used in current aircraft, the total membrane surface area is determined by the maximum required NEA flow rate which results in large and expensive modules. On the other hand, the NEA flow rate can be easily controlled in EGSIS by simply adjusting the applied voltage. This portion of the study focuses on results for a single EGSIS cell and its optimization. Various EGSIS stack configurations are also described in order to develop a practical system. Finally, a techno-economic analysis of EGSIS is presented to show that EGSIS can compete favorably with incumbent technologies in terms of fuel usage and cost.
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Elhenawy, Salma, Majeda Khraisheh, Fares AlMomani, and Mohamed Hassan. "Key Applications and Potential Limitations of Ionic Liquid Membranes in the Gas Separation Process of CO2, CH4, N2, H2 or Mixtures of These Gases from Various Gas Streams." Molecules 25, no. 18 (September 18, 2020): 4274. http://dx.doi.org/10.3390/molecules25184274.
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Heightened levels of carbon dioxide (CO2) and other greenhouse gases (GHGs) have prompted research into techniques for their capture and separation, including membrane separation, chemical looping, and cryogenic distillation. Ionic liquids, due to their negligible vapour pressure, thermal stability, and broad electrochemical stability have expanded their application in gas separations. This work provides an overview of the recent developments and applications of ionic liquid membranes (ILMs) for gas separation by focusing on the separation of carbon dioxide (CO2), methane (CH4), nitrogen (N2), hydrogen (H2), or mixtures of these gases from various gas streams. The three general types of ILMs, such as supported ionic liquid membranes (SILMs), ionic liquid polymeric membranes (ILPMs), and ionic liquid mixed-matrix membranes (ILMMMs) for the separation of various mixed gas systems, are discussed in detail. Furthermore, issues, challenges, computational studies and future perspectives for ILMs are also considered. The results of the analysis show that SILMs, ILPMs, and the ILMMs are very promising membranes that have great potential in gas separation processes. They offer a wide range of permeabilities and selectivities for CO2, CH4, N2, H2 or mixtures of these gases. In addition, a comparison was made based on the selectivity and permeability of SILMs, ILPMs, and ILMMMs for CO2/CH4 separation based on a Robeson’s upper bound curves.
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Andrade, R. M., N. G. Jaques, J. Sousa, R. P. S. Dutra, D. A. Macedo, and L. F. A. Campos. "Preparation of low-cost ceramic membranes for microfiltration using sugarcane bagasse ash as a pore-forming agent." Cerâmica 65, no. 376 (December 2019): 620–25. http://dx.doi.org/10.1590/0366-69132019653762696.
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Abstract Ceramic membranes are of great industrial interest in separation processes. They are characterized by high chemical and thermal stabilities and filtration capacity at high temperatures (>500 °C) in a wide range of pH values. However, the major disadvantage of ceramic membranes is the high-cost of production involving synthetic raw materials, usually alumina and zirconia. In this work, low-cost ceramic membranes were prepared by solid-state reactive firing using a mixture of kaolinite clay and sugarcane bagasse ash. Particle size distribution, thermal, mineralogical, and chemical composition analyses were carried out to study the raw materials. Technological properties and water permeability were investigated in samples fired between 800 and 1000 °C. The filtration efficiency was measured by comparative analyses between the raw water and the filtrate. The mean pore size ranging from 2.5 to 6.0 μm makes the sugarcane bagasse ash derived ceramic membranes suitable for microfiltration processes.
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Flechsler, Jennifer, Thomas Heimerl, Harald Huber, Reinhard Rachel, and Ivan A. Berg. "Functional compartmentalization and metabolic separation in a prokaryotic cell." Proceedings of the National Academy of Sciences 118, no. 25 (June 14, 2021): e2022114118. http://dx.doi.org/10.1073/pnas.2022114118.
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The prokaryotic cell is traditionally seen as a “bag of enzymes,” yet its organization is much more complex than in this simplified view. By now, various microcompartments encapsulating metabolic enzymes or pathways are known for Bacteria. These microcompartments are usually small, encapsulating and concentrating only a few enzymes, thus protecting the cell from toxic intermediates or preventing unwanted side reactions. The hyperthermophilic, strictly anaerobic Crenarchaeon Ignicoccus hospitalis is an extraordinary organism possessing two membranes, an inner and an energized outer membrane. The outer membrane (termed here outer cytoplasmic membrane) harbors enzymes involved in proton gradient generation and ATP synthesis. These two membranes are separated by an intermembrane compartment, whose function is unknown. Major information processes like DNA replication, RNA synthesis, and protein biosynthesis are located inside the “cytoplasm” or central cytoplasmic compartment. Here, we show by immunogold labeling of ultrathin sections that enzymes involved in autotrophic CO2 assimilation are located in the intermembrane compartment that we name (now) a peripheric cytoplasmic compartment. This separation may protect DNA and RNA from reactive aldehydes arising in the I. hospitalis carbon metabolism. This compartmentalization of metabolic pathways and information processes is unprecedented in the prokaryotic world, representing a unique example of spatiofunctional compartmentalization in the second domain of life.
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Winter, Lea R., and Menachem Elimelech. "(Invited) Electrified Membranes for Transformation of Nitrate in Wastewaters." ECS Meeting Abstracts MA2022-01, no. 40 (July 7, 2022): 1798. http://dx.doi.org/10.1149/ma2022-01401798mtgabs.
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The release of nitrate to the environment from wastewater effluent and agricultural runoff contributes to groundwater contamination, harmful algal blooms, and disruption of biogeochemical nitrogen flows. Typical treatment methods are based on nitrate separation, which produces waste streams that are often discharged to the environment. Alternatively, nitrate conversion via electrochemical reduction eliminates the production of concentrated waste streams while avoiding the addition of reductant or hole scavenger chemicals to accomplish the reaction. However, major challenges for nitrate removal from water via electrochemical conversion involve reducing the use of expensive precious metal electrocatalysts while also improving the reaction activity and selectivity, catalyst stability, and mass transport of nitrate to electrocatalyst active sites. The use of electrochemical membranes as multifunctional porous flow-through electrodes could potentially address these challenges based on improved mass transport and altered kinetics under flow conditions within membrane pores. Conductive membranes were fabricated using polymers combined with carbonaceous materials such as reduced graphene oxide (rGO) and carbon nanotubes. The rGO was functionalized with non-precious transition metal oxynitride electrocatalysts, where these catalysts showed higher nitrate conversion activity compared to the unsupported transition metal nitrides. The influence of catalyst materials, membrane fabrication process, and filtration conditions on nitrate reduction activity and selectivity were evaluated. In addition to the environmental impacts of closing the nitrogen loop by converting nitrate into innocuous N2, selective nitrate reduction to ammonia provides opportunities for recovery as fertilizer or carbon-free renewable energy storage. The prospects for reactive nitrogen recovery based on nitrate electrochemical conversion to ammonia were analyzed for various potential source waters.
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Reisert, Michael, Ashish Aphale, and Prabhakar Singh. "Solid Oxide Electrochemical Systems: Material Degradation Processes and Novel Mitigation Approaches." Materials 11, no. 11 (November 2, 2018): 2169. http://dx.doi.org/10.3390/ma11112169.
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Solid oxide electrochemical systems, such as solid oxide fuel cells (SOFC), solid oxide electrolysis cells (SOEC), and oxygen transport membranes (OTM) enable clean and reliable production of energy or fuel for a range of applications, including, but not limited to, residential, commercial, industrial, and grid-support. These systems utilize solid-state ceramic oxides which offer enhanced stability, fuel flexibility, and high energy conversion efficiency throughout operation. However, the nature of system conditions, such as high temperatures, complex redox atmosphere, and presence of volatile reactive species become taxing on solid oxide materials and limit their viability during long-term operation. Ongoing research efforts to identify the material corrosion and degradation phenomena, as well as discover possible mitigation techniques to extend material efficiency and longevity, is the current focus of the research and industrial community. In this review, degradation processes in select solid oxide electrochemical systems, system components, and comprising materials will be discussed. Overall degradation phenomena are presented and certain degradation mechanisms are discussed. State-of-the-art technologies to mitigate or minimize the above-mentioned degradation processes are presented.
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Di Noto, Vito. "(Energy Technology Division Research Award) Interplay between Synthesis, Mechanisms and Performance of Electrocatalysts and Ionomers for Ion-Exchange Membrane Fuel Cells." ECS Meeting Abstracts MA2022-01, no. 35 (July 7, 2022): 1440. http://dx.doi.org/10.1149/ma2022-01351440mtgabs.
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Ion-exchange membrane fuel cells (IEMFCs) are a family of electrochemical energy conversion and storage devices characterized by several attractive features, including outstanding energy conversion efficiency and a clean operation. IEMFCs are a cornerstone of the “hydrogen economy”, one of the most promising avenues to decarbonize the energy sector, with the ultimate purpose to curtail the emissions of greenhouse gases and mitigate global warming. Therefore, a goal of great practical relevance is to devise highly performing, durable and inexpensive IEMFCs . IEMFCs consist of an electrolyte membrane sandwiched between two electrodes. At the membrane-electrode interfaces are located electrocatalytic layers (EC layers) comprising suitable electrocatalysts (ECs) able to promote the redox processes exploited by the IEMFC operation. The IEMFC sub-families are distinguished by the attributes of the membrane, especially in terms of: (i) chemical features (e.g., polymeric backbone); (ii) mobile ion(s) (e.g., protons for proton-exchange membrane fuel cells, PEMFCs, OH- anions for anion-exchange membrane fuel cells, AEMFCs); and (iii) operation temperature. In the environment modulated by the ionomer, the properties of the ECs , with particular reference to the chemical composition of the active sites and support morphology, are correlated to their performance. Hence, to obtain an IEMFC exhibiting a high performance and durability is imperative to rationally design membranes and ECs that are: (i) highly compatible with one another; and (ii) able to express their best performance and durability in the same set of operating conditions. This contribution overviews our research activities aimed at the development of ECs and membranes for application in PEMFCs, high-temperature PEMFCs and AEMFCs. The topics include: (i) the innovative approaches for the synthesis of the functional components; (ii) the aspects of their physicochemical characterization, together with the unique and comprehensive frameworks contrived for the integration and interpretation of the experimental outcomes; and (iii) the steps to integrate the functional components in high-performing IEMFC prototypes. The ECs considered here are meant to promote the oxygen reduction reaction (ORR), a sluggish electrochemical process that is a major bottleneck in the operation of IEMFCs fueled with hydrogen. State-of-the-art ORR ECs are based on Pt nanoparticles supported on carbon (“Pt/C” ECs). Pt/C ECs warrant a sufficient performance, but suffer from a poor durability and require a high loading of platinum, a strategic element that is prone to trigger supply bottlenecks especially in the event of a large-scale rollout of IEMFCs. The ECs devised in our research laboratory are aimed at addressing all of these issues with materials exhibiting a number of unique features, as follows. (i) Active sites with either an intrinsic ORR kinetics much improved above the Pt baseline or completely “Pt-free”, consisting of an “active metal” (e.g., Pt, Fe) whose performance is boosted by one or more “co-catalyst” (e.g., Co, Ni, Cu, Sn). (ii) Strong, covalent interactions between the active sites and the C-/N- ligands of the “coordination nests” on the surface of the EC support, warranting a high durability. (iii) A support featuring a “core-shell” morphology, wherein a “core” consisting of suitable carbon system(s) is covered by a carbon nitride (CN) “shell”, bestowing facile charge and mass transport features (Figure 1(a)). The resulting ECs bestow the IEMFC a high performance with a minimized loading of Pt. Specifically, the PEMFC prototypes mounting the ECs here described yielded more than 20 kW∙gPt -1. The second main topic of this overview is the development and the study of the conductivity mechanism of separator membranes for IEMFCs. The latter consist mainly of ionomer matrices (e.g., perfluorinated systems such as Nafion™, SPEEK and developmental anion-exchange block copolymers), both pristine and doped with suitable nanofillers (e.g., conventional ceramic oxoclusters, “core-shell” oxocluters, among many others). The matrix-nanofiller interactions modulate the physicochemical features of the resulting hybrid inorganic-organic membrane, allowing to improve crucial features for applications in IEMFCs such as: (i) mechanical stability; and (ii) conductivity in dry conditions and high temperature. Other separator membranes are overviewed, including: (i) anion-exchange ionomers based on polyketone matrices (Figure 1(b)); (ii) hybrid inorganic-organic membranes for HT-PEMFCs based on oxocluster nanofillers and polybenzimidazole-like matrices; and (iii) membranes swollen with proton-conducting ionic liquids. These membranes underwent a thorough characterization elucidating their morphology, structure, thermal properties, thermomechanical relaxations and electric response (Figure 1(c)). The integration of all the above knowledges yielded a unique, comprehensive and general framework which proved crucial to elucidate the interplay between the physicochemical properties of the different phases within each membrane and their overall conductivity mechanism. This allowed to trigger the development of new high-performing separator membranes for application in IEMFCs. Figure 1
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Selyanchyn, Olena, Thomas Bayer, Dino Klotz, Roman Selyanchyn, Kazunari Sasaki, and Stephen Matthew Lyth. "Cellulose Nanocrystals Crosslinked with Sulfosuccinic Acid as Sustainable Proton Exchange Membranes for Electrochemical Energy Applications." Membranes 12, no. 7 (June 26, 2022): 658. http://dx.doi.org/10.3390/membranes12070658.
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Nanocellulose is a sustainable material which holds promise for many energy-related applications. Here, nanocrystalline cellulose is used to prepare proton exchange membranes (PEMs). Normally, this nanomaterial is highly dispersible in water, preventing its use as an ionomer in many electrochemical applications. To solve this, we utilized a sulfonic acid crosslinker to simultaneously improve the mechanical robustness, water-stability, and proton conductivity (by introducing -SO3−H+ functional groups). The optimization of the proportion of crosslinker used and the crosslinking reaction time resulted in enhanced proton conductivity up to 15 mS/cm (in the fully hydrated state, at 120 °C). Considering the many advantages, we believe that nanocellulose can act as a sustainable and low-cost alternative to conventional, ecologically problematic, perfluorosulfonic acid ionomers for applications in, e. fuel cells and electrolyzers.
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Ayadi, Saloua, Ilyes Jedidi, Matthieu Rivallin, Frédéric Gillot, Stella Lacour, Sophie Cerneaux, Marc Cretin, and Raja Ben Amar. "Elaboration and characterization of new conductive porous graphite membranes for electrochemical advanced oxidation processes." Journal of Membrane Science 446 (November 2013): 42–49. http://dx.doi.org/10.1016/j.memsci.2013.06.005.
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Marcos-Madrazo, Aitor, Clara Casado-Coterillo, Jesús Iniesta, and Angel Irabien. "Use of Chitosan as Copper Binder in the Continuous Electrochemical Reduction of CO2 to Ethylene in Alkaline Medium." Membranes 12, no. 8 (August 15, 2022): 783. http://dx.doi.org/10.3390/membranes12080783.
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This work explores the potential of novel renewable materials in electrode fabrication for the electrochemical conversion of carbon dioxide (CO2) to ethylene in alkaline media. In this regard, the use of the renewable chitosan (CS) biopolymer as ion-exchange binder of the copper (Cu) electrocatalyst nanoparticles (NPs) is compared with commercial anion-exchange binders Sustainion and Fumion on the fabrication of gas diffusion electrodes (GDEs) for the electrochemical reduction of carbon dioxide (CO2R) in an alkaline medium. They were tested in membrane electrode assemblies (MEAs), where selectivity to ethylene (C2H4) increased when using the Cu:CS GDE compared to the Cu:Sustainion and Cu:Fumion GDEs, respectively, with a Faradaic efficiency (FE) of 93.7% at 10 mA cm−2 and a cell potential of −1.9 V, with a C2H4 production rate of 420 µmol m−2 s−1 for the Cu:CS GDE. Upon increasing current density to 90 mA cm−2, however, the production rate of the Cu:CS GDE rose to 509 µmol/m2s but the FE dropped to 69% due to increasing hydrogen evolution reaction (HER) competition. The control of mass transport limitations by tuning up the membrane overlayer properties in membrane coated electrodes (MCE) prepared by coating a CS-based membrane over the Cu:CS GDE enhanced its selectivity to C2H4 to a FE of 98% at 10 mA cm−2 with negligible competing HER. The concentration of carbon monoxide was below the experimental detection limit irrespective of the current density, with no CO2 crossover to the anodic compartment. This study suggests there may be potential in sustainable alernatives to fossil-based or perfluorinated materials in ion-exchange membrane and electrode fabrication, which constitute a step forward towards decarbonization in the circular economy perspective.
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Zhang, Wenjuan, Wei Cheng, Ramato Ashu Tufa, Caihong Liu, David Aili, Debabrata Chanda, Jing Chang, Shaopo Wang, Yufeng Zhang, and Jun Ma. "Studies on Anion Exchange Membrane and Interface Properties by Electrochemical Impedance Spectroscopy: The Role of pH." Membranes 11, no. 10 (October 10, 2021): 771. http://dx.doi.org/10.3390/membranes11100771.
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Ion-exchange membranes (IEMs) represent a key component in various electrochemical energy conversion and storage systems. In this study, electrochemical impedance spectroscopy (EIS) was used to investigate the effects of structural changes of anion exchange membranes (AEMs) on the bulk membrane and interface properties as a function of solution pH. The variations in the physico/electrochemical properties, including ion exchange capacity, swelling degree, fixed charge density, zeta potentials as well as membrane and interface resistances of two commercial AEMs and cation exchange membranes (CEMs, as a control) were systematically investigated in different pH environments. Structural changes of the membrane surface were analyzed by Fourier transform infrared and X-ray photoelectron spectroscopy. Most notably, at high pH (pH > 10), the membrane (Rm) and the diffusion boundary layer resistances (Rdbl) increased for the two AEMs, whereas the electrical double layer resistance decreased simultaneously. This increase in Rm and Rdbl was mainly attributed to the deprotonation of the tertiary amino groups (-NR2H+) as a membrane functionality. Our results show that the local pH at the membrane-solution interface plays a crucial role on membrane electrochemical properties in IEM transport processes, particularly for AEMs.
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Nativ, Paz, Noga Fridman-Bishop, and Youri Gendel. "Ion transport and selectivity in thin film composite membranes in pressure-driven and electrochemical processes." Journal of Membrane Science 584 (August 2019): 46–55. http://dx.doi.org/10.1016/j.memsci.2019.04.041.
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Ahmad Rizal Lim, Fatin Nasreen, Fauziah Marpani, Victoria Eliz Anak Dilol, Syazana Mohamad Pauzi, Nur Hidayati Othman, Nur Hashimah Alias, Nik Raikhan Nik Him, Jianquan Luo, and Norazah Abd Rahman. "A Review on the Design and Performance of Enzyme-Aided Catalysis of Carbon Dioxide in Membrane, Electrochemical Cell and Photocatalytic Reactors." Membranes 12, no. 1 (December 27, 2021): 28. http://dx.doi.org/10.3390/membranes12010028.
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Multi-enzyme cascade catalysis involved three types of dehydrogenase enzymes, namely, formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH), alcohol dehydrogenase (ADH), and an equimolar electron donor, nicotinamide adenine dinucleotide (NADH), assisting the reaction is an interesting pathway to reduce thermodynamically stable molecules of CO2 from the atmosphere. The biocatalytic sequence is interesting because it operates under mild reaction conditions (low temperature and pressure) and all the enzymes are highly selective, which allows the reaction to produce three basic chemicals (formic acid, formaldehyde, and methanol) in just one pot. There are various challenges, however, in applying the enzymatic conversion of CO2, namely, to obtain high productivity, increase reusability of the enzymes and cofactors, and to design a simple, facile, and efficient reactor setup that will sustain the multi-enzymatic cascade catalysis. This review reports on enzyme-aided reactor systems that support the reduction of CO2 to methanol. Such systems include enzyme membrane reactors, electrochemical cells, and photocatalytic reactor systems. Existing reactor setups are described, product yields and biocatalytic productivities are evaluated, and effective enzyme immobilization methods are discussed.
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Chabalala, Mandla B., Nozipho N. Gumbi, Bhekie B. Mamba, Mohammed Z. Al-Abri, and Edward N. Nxumalo. "Photocatalytic Nanofiber Membranes for the Degradation of Micropollutants and Their Antimicrobial Activity: Recent Advances and Future Prospects." Membranes 11, no. 9 (August 31, 2021): 678. http://dx.doi.org/10.3390/membranes11090678.
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This review paper systematically evaluates current progress on the development and performance of photocatalytic nanofiber membranes often used in the removal of micropollutants from water systems. It is demonstrated that nanofiber membranes serve as excellent support materials for photocatalytic nanoparticles, leading to nanofiber membranes with enhanced optical properties, as well as improved recovery, recyclability, and reusability. The tremendous performance of photocatalytic membranes is attributed to the photogenerated reactive oxygen species such as hydroxyl radicals, singlet oxygen, and superoxide anion radicals introduced by catalytic nanoparticles such as TiO2 and ZnO upon light irradiation. Hydroxyl radicals are the most reactive species responsible for most of the photodegradation processes of these unwanted pollutants. The review also demonstrates that self-cleaning and antimicrobial nanofiber membranes are useful in the removal of microbial species in water. These unique materials are also applicable in other fields such as wound dressing since the membrane allows for oxygen flow in wounds to heal while antimicrobial agents protect wounds against infections. It is demonstrated that antimicrobial activities against bacteria and photocatalytic degradation of micropollutants significantly reduce membrane fouling. Therefore, the review demonstrates that electrospun photocatalytic nanofiber membranes with antimicrobial activity form efficient cost-effective multifunctional composite materials for the removal of unwanted species in water and for use in various other applications such as filtration, adsorption and electrocatalysis.
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Kumar, Mahendra, Moonis Ali Khan, Zeid A. Al-Othman, and Thomas S. Y. Choong. "Recent Developments in Ion-Exchange Membranes and Their Applications in Electrochemical Processes forin situIon Substitutions, Separation and Water Splitting." Separation & Purification Reviews 42, no. 3 (January 2013): 187–261. http://dx.doi.org/10.1080/15422119.2012.690360.
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Zhang, Xuemin, Jian Zhou, Xin Zou, Zhongyu Wang, Yunchen Chu, and Sanfan Wang. "Preparation of Nano-SiO2/Al2O3/ZnO-Blended PVDF Cation-Exchange Membranes with Improved Membrane Permselectivity and Oxidation Stability." Materials 11, no. 12 (December 4, 2018): 2465. http://dx.doi.org/10.3390/ma11122465.
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Ion exchange membranes are used in practically every industry; however, most of them have defects such as low permeability and poor oxidation resistance. In this paper, cation-exchange membranes were prepared with poly (vinylidene fluoride) (PVDF) blended with nano-SiO2, nano-Al2O3 and nano-ZnO. Sulfonic acid groups were injected into the membrane prepared by styrene grafting and sulfonation. The methods used for characterizing the prepared membranes were Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and electrochemical measurements. Membrane performance, such as the ion exchange capacity (IEC), water uptake (WU), transport number, membrane permselectivity, membrane resistance, functional groups, and morphology were also evaluated. The hydrophilia, IEC, and permselectivity of cation-exchange membranes depended on the nanoparticle content of the membrane matrix. High transport property values were obtained, which increased with increasing nano-SiO2/Al2O3/ZnO weight fractions. Finally, the cation-exchange membranes prepared with 1.5% nano-SiO2, 2.0% nano-Al2O3 or 2.0% nano-ZnO all exhibited excellent membrane properties, including membrane permselectivity (PVDF/2% ZnO-g-PSSA membranes, 94.9%), IEC (PVDF/2% Al2O3-g-PSSA membranes, 2.735 mmol·g−1), and oxidation resistance (PVDF/1.5% SiO2-g-PSSA membranes, 2.33%). They can be used to separate applications in a variety of different areas, such as water treatment, electro-driven separation, heavy metal smelting, or other electrochemical processes.
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Karpenko, Tatyana, Nikita Kovalev, Vladislava Shramenko, and Nikolay Sheldeshov. "Investigation of Transport Processes through Ion-Exchange Membranes Used in the Production of Amines from Their Salts Using Bipolar Electrodialysis." Membranes 12, no. 11 (November 10, 2022): 1126. http://dx.doi.org/10.3390/membranes12111126.
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The influence of the nature of amine solutions on the frequency spectrum of the electrochemical impedance of the bipolar membrane aMB-2m is investigated. Moreover, the effect of the circulation rate of solutions in the electrodialyzer chambers on the volt-ampere characteristics of the Ralex AMH and MA-40L anion-exchange membranes and the aMB-2m bipolar membrane has been investigated. The diffusion characteristics of various types of anion-exchange membranes in a system containing dimethylammonium sulfate ((DEA)2H2SO4), as well as the diffusion characteristics of the Ralex AMH membrane in systems with methylammonium sulfate, dimethylammonium sulfate, diethylammonium sulfate, and ethylenediammonium sulfate ((MA)2H2SO4, (DMA)2H2SO4, (DEA)2H2SO4, EDAH2SO4) have been studied. It is shown that diffusion permeability depends on the structure and composition of anion-exchange membranes, as well as on the nature of amines. The technical and economic characteristics of the electromembrane processes for the production of amines and sulfuric acid from amine salts are determined. It is shown that when using Ralex AMH anion-exchange membranes in an electrodialyzer together with bipolar aMB-2m membranes, higher concentrations of diethylamine and sulfuric acid are achieved, compared with the use of MA-40L anion-exchange membranes.
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Pismenskaya, Natalia, Myriam Bdiri, Veronika Sarapulova, Anton Kozmai, Julie Fouilloux, Lassaad Baklouti, Christian Larchet, Estelle Renard, and Lasâad Dammak. "A Review on Ion-Exchange Membranes Fouling during Electrodialysis Process in Food Industry, Part 2: Influence on Transport Properties and Electrochemical Characteristics, Cleaning and Its Consequences." Membranes 11, no. 11 (October 25, 2021): 811. http://dx.doi.org/10.3390/membranes11110811.
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Ion-exchange membranes (IEMs) are increasingly used in dialysis and electrodialysis processes for the extraction, fractionation and concentration of valuable components, as well as reagent-free control of liquid media pH in the food industry. Fouling of IEMs is specific compared to that observed in the case of reverse or direct osmosis, ultrafiltration, microfiltration, and other membrane processes. This specificity is determined by the high concentration of fixed groups in IEMs, as well as by the phenomena inherent only in electromembrane processes, i.e., induced by an electric field. This review analyzes modern scientific publications on the effect of foulants (mainly typical for the dairy, wine and fruit juice industries) on the structural, transport, mass transfer, and electrochemical characteristics of cation-exchange and anion-exchange membranes. The relationship between the nature of the foulant and the structure, physicochemical, transport properties and behavior of ion-exchange membranes in an electric field is analyzed using experimental data (ion exchange capacity, water content, conductivity, diffusion permeability, limiting current density, water splitting, electroconvection, etc.) and modern mathematical models. The implications of traditional chemical cleaning are taken into account in this analysis and modern non-destructive membrane cleaning methods are discussed. Finally, challenges for the near future were identified.
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Vobecká, Lucie, Tomáš Belloň, and Zdeněk Slouka. "Behavior of Embedded Cation-Exchange Particles in a DC Electric Field." International Journal of Molecular Sciences 20, no. 14 (July 22, 2019): 3579. http://dx.doi.org/10.3390/ijms20143579.
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Electrodialysis and electrodeionization are separation processes whose performance depends on the quality and properties of ion-exchange membranes. One of the features that largely affects these properties is heterogeneity of the membranes both on the macroscopic and microscopic level. Macroscopic heterogeneity is an intrinsic property of heterogeneous ion-exchange membranes. In these membranes, the functional ion-exchange component is dispersed in a non-conductive binder. The functional component is finely ground ion-exchange resin particles. The understanding of the effect of structure on the heterogeneous membrane properties and behavior is thus of utmost importance since it does not only affect the actual performance but also the cost and therefore competitiveness of the aforementioned separation processes. Here we study the electrokinetic behavior of cation-exchange resin particle systems with well-defined geometrical structure. This approach can be understood as a bottom up approach regarding the membrane preparation. We prepare a structured cation-exchange membrane by using its fundamental component, which is the ion exchange resin. We then perform an experimental study with four different experimental systems in which the number of used cation-exchange particles changes from 1 to 4. These systems are studied by means of basic electrochemical characterization measurements, such as measurement of current–voltage curves and direct optical observation of phenomena that occur at the interface between the ion-exchange system and the adjacent electrolyte. Our work aims at better understanding of the relation between the structure and the membrane properties and of how structure affects electrokinetic behavior of these systems.
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Ryzhkov, Nikolay V., Natalya A. Mamchik, and Ekaterina V. Skorb. "Electrochemical triggering of lipid bilayer lift-off oscillation at the electrode interface." Journal of The Royal Society Interface 16, no. 150 (January 2019): 20180626. http://dx.doi.org/10.1098/rsif.2018.0626.
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In situ studies of transmembrane channels often require a model bioinspired artificial lipid bilayer (LB) decoupled from its underlaying support. Obtaining free-standing lipid membranes is still a challenge. In this study, we suggest an electrochemical approach for LB separation from its solid support via hydroquinone oxidation. Layer-by-layer deposition of polyethylenimine (PEI) and polystyrene sulfonate (PSS) on the gold electrode was performed to obtain a polymeric nanocushion of [PEI/PSS] 3 /PEI. The LB was deposited on top of an underlaying polymer support from the dispersion of small unilamellar vesicles due to their electrostatic attraction to the polymer support. Since lipid zwitterions demonstrate pH-dependent charge shifting, the separation distance between the polyelectrolyte support and LB can be adjusted by changing the environmental pH, leading to lipid molecules recharge. The proton generation associated with hydroquinone oxidation was studied using scanning vibrating electrode and scanning ion-selective electrode techniques. Electrochemical impedance spectroscopy is suggested to be a powerful instrument for the in situ observation of processes associated with the LB–solid support interface. Electrochemical spectroscopy highlighted the reversible disappearance of the LB impact on impedance in acidic conditions set by dilute acid addition as well as by electrochemical proton release on the gold electrode due to hydroquinone oxidation.
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Lim, Siew Yee, Cheryl Suwen Law, Lina Liu, Marijana Markovic, Carina Hedrich, Robert H. Blick, Andrew D. Abell, Robert Zierold, and Abel Santos. "Electrochemical Engineering of Nanoporous Materials for Photocatalysis: Fundamentals, Advances, and Perspectives." Catalysts 9, no. 12 (November 25, 2019): 988. http://dx.doi.org/10.3390/catal9120988.
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Photocatalysis comprises a variety of light-driven processes in which solar energy is converted into green chemical energy to drive reactions such as water splitting for hydrogen energy generation, degradation of environmental pollutants, CO2 reduction and NH3 production. Electrochemically engineered nanoporous materials are attractive photocatalyst platforms for a plethora of applications due to their large effective surface area, highly controllable and tuneable light-harvesting capabilities, efficient charge carrier separation and enhanced diffusion of reactive species. Such tailor-made nanoporous substrates with rational chemical and structural designs provide new exciting opportunities to develop advanced optical semiconductor structures capable of performing precise and versatile control over light–matter interactions to harness electromagnetic waves with unprecedented high efficiency and selectivity for photocatalysis. This review introduces fundamental developments and recent advances of electrochemically engineered nanoporous materials and their application as platforms for photocatalysis, with a final prospective outlook about this dynamic field.
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Filonova, Elena, Artem Gilev, Tatyana Maksimchuk, Nadezhda Pikalova, Kiryl Zakharchuk, Sergey Pikalov, Aleksey Yaremchenko, and Elena Pikalova. "Development of La1.7Ca0.3Ni1−yCuyO4+δ Materials for Oxygen Permeation Membranes and Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells." Membranes 12, no. 12 (December 2, 2022): 1222. http://dx.doi.org/10.3390/membranes12121222.
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The La1.7Ca0.3Ni1−yCuyO4+δ (y = 0.0–0.4) nickelates, synthesized via a solid-state reaction method, are investigated as prospective materials for oxygen permeation membranes and IT-SOFC cathodes. The obtained oxides are single-phase and possess a tetragonal structure (I4/mmm sp. gr.). The unit cell parameter c and the cell volume increase with Cu-substitution. The interstitial oxygen content and total conductivity decrease with Cu-substitution. The low concentration of mobile interstitial oxygen ions results in a limited oxygen permeability of Cu-substituted La1.7Ca0.3NiO4+δ ceramic membranes. However, increasing the Cu content over y = 0.2 induces two beneficial effects: enhancement of the electrochemical activity of the La1.7Ca0.3Ni1−yCuyO4+δ (y = 0.0; 0.2; 0.4) electrodes and decreasing the sintering temperature from 1200 °C to 900 °C. Enhanced electrode activity is due to better sintering properties of the developed materials ensuring excellent adhesion and facilitating the charge transfer at the electrode/electrolyte interface and, probably, faster oxygen exchange in Cu-rich materials. The polarization resistance of the La1.7Ca0.3Ni1.6Cu0.4O4+δ electrode on the Ce0.8Sm0.2O1.9 electrolyte is as low as 0.15 Ω cm2 and 1.95 Ω cm2 at 850 °C and 700 °C in air, respectively. The results of the present work demonstrate that the developed La1.7Ca0.3Ni0.6Cu0.4O4+δ-based electrode can be considered as a potential cathode for intermediate-temperature solid oxide fuel cells.
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Prabhakaran, Venkateshkumar, Grant E. Johnson, Bingbing Wang, and Julia Laskin. "In situ solid-state electrochemistry of mass-selected ions at well-defined electrode–electrolyte interfaces." Proceedings of the National Academy of Sciences 113, no. 47 (November 7, 2016): 13324–29. http://dx.doi.org/10.1073/pnas.1608730113.
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Molecular-level understanding of electrochemical processes occurring at electrode–electrolyte interfaces (EEIs) is key to the rational development of high-performance and sustainable electrochemical technologies. This article reports the development and application of solid-state in situ thin-film electrochemical cells to explore redox and catalytic processes occurring at well-defined EEIs generated using soft-landing (SL) of mass- and charge-selected cluster ions. In situ cells with excellent mass-transfer properties are fabricated using carefully designed nanoporous ionic liquid membranes. SL enables deposition of pure active species that are not obtainable with other techniques onto electrode surfaces with precise control over charge state, composition, and kinetic energy. SL is, therefore, demonstrated to be a unique tool for studying fundamental processes occurring at EEIs. Using an aprotic cell, the effect of charge state (PMo12O403-/2-) and the contribution of building blocks of Keggin polyoxometalate (POM) clusters to redox processes are characterized by populating EEIs with POM anions generated by electrospray ionization and gas-phase dissociation. Additionally, a proton-conducting cell has been developed to characterize the oxygen reduction activity of bare Pt clusters (Pt30 ∼1 nm diameter), thus demonstrating the capability of the cell for probing catalytic reactions in controlled gaseous environments. By combining the developed in situ electrochemical cell with ion SL we established a versatile method to characterize the EEI in solid-state redox systems and reactive electrochemistry at precisely defined conditions. This capability will advance the molecular-level understanding of processes occurring at EEIs that are critical to many energy-related technologies.
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Liu, Yayuan, Chun-Man Chow, Katherine R. Phillips, Miao Wang, Sahag Voskian, and T. Alan Hatton. "Electrochemically mediated gating membrane with dynamically controllable gas transport." Science Advances 6, no. 42 (October 2020): eabc1741. http://dx.doi.org/10.1126/sciadv.abc1741.
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The regulation of mass transfer across membranes is central to a wide spectrum of applications. Despite numerous examples of stimuli-responsive membranes for liquid-phase species, this goal remains elusive for gaseous molecules. We describe a previously unexplored gas gating mechanism driven by reversible electrochemical metal deposition/dissolution on a conductive membrane, which can continuously modulate the interfacial gas permeability over two orders of magnitude with high efficiency and short response time. The gating mechanism involves neither moving parts nor dead volume and can therefore enable various engineering processes. An electrochemically mediated carbon dioxide concentrator demonstrates proof of concept by integrating the gating membranes with redox-active sorbents, where gating effectively prevented the cross-talk between feed and product gas streams for high-efficiency, directional carbon dioxide pumping. We anticipate our concept of dynamically regulating transport at gas-liquid interfaces to broadly inspire systems in fields of gas separation, miniaturized devices, multiphase reactors, and beyond.
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Escolástico, Sonia, Falk Schulze-Küppers, Stefan Baumann, Katja Haas-Santo, and Roland Dittmeyer. "Development and Proof of Concept of a Compact Metallic Reactor for MIEC Ceramic Membranes." Membranes 11, no. 7 (July 16, 2021): 541. http://dx.doi.org/10.3390/membranes11070541.
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The integration of mixed ionic–electronic conducting separation membranes in catalytic membrane reactors can yield more environmentally safe and economically efficient processes. Concentration polarization effects are observed in these types of membranes when O2 permeating fluxes are significantly high. These undesired effects can be overcome by the development of new membrane reactors where mass transport and heat transfer are enhanced by adopting state-of-the-art microfabrication. In addition, careful control over the fluid dynamics regime by employing compact metallic reactors equipped with microchannels could allow the rapid extraction of the products, minimizing undesired secondary reactions. Moreover, a high membrane surface area to catalyst volume ratio can be achieved. In this work, a compact metallic reactor was developed for the integration of mixed ionic–electronic conducting ceramic membranes. An asymmetric all-La0.6Sr0.4Co0.2Fe0.8O3–δ membrane was sealed to the metallic reactor by the reactive air brazing technique. O2 permeation was evaluated as a proof of concept, and the influence of different parameters, such as temperature, sweep gas flow rates and oxygen partial pressure in the feed gas, were evaluated.
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Kaczur, Jerry J., Liam J. McGlaughlin, and Prasad S. Lakkaraju. "Investigating Pervaporation as a Process Method for Concentrating Formic Acid Produced from Carbon Dioxide." C — Journal of Carbon Research 6, no. 2 (June 20, 2020): 42. http://dx.doi.org/10.3390/c6020042.
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New methods in lowering energy consumption costs for evaporation and concentration are needed in many commercial chemical processes. Pervaporation is an underutilized, low-energy processing method that has a potential capability in achieving lower energy processing costs. A recently developed new electrochemical process that can generate a 5–25 wt% pure formic acid (FA) from the electrochemical reduction of CO2 requires a low-energy process for producing a more concentrated FA product for use in both on-site and commercial plant applications. In order to accomplish this, a 25 cm2 membrane area pervaporation test cell was constructed to evaluate the FA-H2O system separation performance of three distinct types of membrane candidates at various FA feed concentrations and temperatures. The selection included one cation ion exchange, two anion ion exchange, and two microporous hydrophobic membranes. The permeation flux rates of FA and H2O were measured for FA feed concentrations of 10, 20, 40, and 60 wt% at corresponding temperatures of 22, 40, and 60 °C. The separation performance results for these particular membranes appeared to follow the vapor liquid equilibrium (VLE) characteristics of the vapor phase in the FA-H2O system as a function of temperature. A Targray microporous hydrophobic high-density polyethylene (HDPE) membrane and a Chemours Nafion® N324 membrane showed the best permeation selectivities and mass flux rates FA feed concentrations, ranging from 10 to 40 wt%. The cation and anion ion exchange membranes evaluated were found not to show any significant enhancements in blocking or promoting the transport of the formate ion or FA through the membranes. An extended permeation cell run concentrated a 10.12% FA solution to 25.38% FA at 40 °C. Azeotropic distillation simulations for the FA-H2O system using ChemCad 6.0 were used to determine the energy requirement using steam costs in processing FA feed concentrations ranging from 5 to 30 wt%. These experimental results indicate that pervaporation is a potentially useful unit process step with the new electrochemical process in producing higher concentration FA product solutions economically and at lower capital costs. One major application identified is in on-site production of FA for bioreactors employing new types of microbes that can assimilate FA in producing various chemicals and bio-products.
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Čížek, Jan, Petr Cvejn, Jaromír Marek, and David Tvrzník. "Desalination Performance Assessment of Scalable, Multi-Stack Ready Shock Electrodialysis Unit Utilizing Anion-Exchange Membranes." Membranes 10, no. 11 (November 17, 2020): 347. http://dx.doi.org/10.3390/membranes10110347.
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Incumbent electromembrane separation processes, including electrodialysis (ED) and electrodeionization (EDI), provide competitive techniques for desalination, selective separation, and unique solutions for ultra-pure water production. However, most of these common electrochemical systems are limited by concentration polarization and the necessity for multistep raw water pre-treatment. Shock electrodialysis (SED) utilizes overlimiting current to produce fresh, deionized water in a single step process by extending ion depleted zones that propagate through a porous medium as a sharp concentration gradient or a shock wave. So far, SED has been demonstrated on small scale laboratory units using cation-exchange membranes. In this work, we present a scalable and multi-stack ready unit with a large, 5000 mm2 membrane active area designed and constructed at the Technical University of Liberec in cooperation with MemBrain s.r.o. and Mega a.s. companies (Czechia). We report more than 99% salt rejection using anion-exchange membranes, depending on a dimensionless parameter that scales the constant applied current by the limiting current. It is shown that these parameters are most probably associated with pore size and porous media chemistry. Further design changes need to be done to the separator, the porous medium, and other functional elements to improve the functionality and energy efficiency.
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Reyes-Aguilera, José A., Liliana Villafaña-López, Elva C. Rentería-Martínez, Sean M. Anderson, and Jesús S. Jaime-Ferrer. "Electrospinning of Polyepychlorhydrin and Polyacrylonitrile Anionic Exchange Membranes for Reverse Electrodialysis." Membranes 11, no. 9 (September 18, 2021): 717. http://dx.doi.org/10.3390/membranes11090717.
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The saline gradient present in river mouths can be exploited using ion-exchange membranes in reverse electrodialysis (RED) for energy generation. However, significant improvements in the fabrication processes of these IEMs are necessary to increase the overall performance of the RED technology. This work proposes an innovative technique for synthesizing anion exchange membranes (AEMs) via electrospinning. The AEM synthesis was carried out by applying a high voltage while ejecting a mixture of polyepichlorohydrin (PECH), 1,4-diazabicyclo [2.2.2] octane (DABCO® 33-LV) and polyacrylonitrile (PAN) at room temperature. Different ejection parameters were used, and the effects of various thermal treatments were tested on the resulting membranes. The AEMs presented crosslinking between the polymers and significant fiber homogeneity with diameters between 1400 and 1510 nm, with and without thermal treatment. Good chemical resistance was measured, and all synthesized membranes were of hydrophobic character. The thickness, roughness, swelling degree, specific fixed-charge density and ion-exchange capacity were improved over equivalent membranes produced by casting, and also when compared with commercial membranes. Finally, the results of the study of the electrospinning parameters indicate that a better performance in electrochemical properties was produced from fibers generated at ambient humidity conditions, with low flow velocity and voltage, and high collector rotation velocity.