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Kozmai AE, Mareev SA, Butylskii DY, Ruleva VD, Pismenskaya ND, Nikonenko VV. Low-frequency impedance of ion-exchange membrane with electrically heterogeneous surface. Electrochim Acta 2023. [DOI: 10.1016/j.electacta.2023.142285] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/31/2023]
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2
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Zhang J, Guo C, Fang S, Zhao X, Li L, Jiang H, Liu Z, Fan Z, Xu W, Xiao J, Zhong M. Accelerating electrochemical CO 2 reduction to multi-carbon products via asymmetric intermediate binding at confined nanointerfaces. Nat Commun 2023; 14:1298. [PMID: 36894571 PMCID: PMC9998885 DOI: 10.1038/s41467-023-36926-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Accepted: 02/22/2023] [Indexed: 03/11/2023] Open
Abstract
Electrochemical CO2 reduction (CO2R) to ethylene and ethanol enables the long-term storage of renewable electricity in valuable multi-carbon (C2+) chemicals. However, carbon-carbon (C-C) coupling, the rate-determining step in CO2R to C2+ conversion, has low efficiency and poor stability, especially in acid conditions. Here we find that, through alloying strategies, neighbouring binary sites enable asymmetric CO binding energies to promote CO2-to-C2+ electroreduction beyond the scaling-relation-determined activity limits on single-metal surfaces. We fabricate experimentally a series of Zn incorporated Cu catalysts that show increased asymmetric CO* binding and surface CO* coverage for fast C-C coupling and the consequent hydrogenation under electrochemical reduction conditions. Further optimization of the reaction environment at nanointerfaces suppresses hydrogen evolution and improves CO2 utilization under acidic conditions. We achieve, as a result, a high 31 ± 2% single-pass CO2-to-C2+ yield in a mild-acid pH 4 electrolyte with >80% single-pass CO2 utilization efficiency. In a single CO2R flow cell electrolyzer, we realize a combined performance of 91 ± 2% C2+ Faradaic efficiency with notable 73 ± 2% ethylene Faradaic efficiency, 31 ± 2% full-cell C2+ energy efficiency, and 24 ± 1% single-pass CO2 conversion at a commercially relevant current density of 150 mA cm-2 over 150 h.
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Affiliation(s)
- Jin Zhang
- College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210023, China
| | - Chenxi Guo
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian, 116023, China
| | - Susu Fang
- Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Xiaotong Zhao
- College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210023, China
| | - Le Li
- College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210023, China
| | - Haoyang Jiang
- College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210023, China
| | - Zhaoyang Liu
- College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210023, China
| | - Ziqi Fan
- College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210023, China
| | - Weigao Xu
- Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing, 210023, China
| | - Jianping Xiao
- State Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Zhongshan Road 457, Dalian, 116023, China. .,University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Miao Zhong
- College of Engineering and Applied Sciences, Jiangsu Key Laboratory of Artificial Functional Materials, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing, 210023, China.
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Li L, Liu Z, Yu X, Zhong M. Achieving High Single-Pass Carbon Conversion Efficiencies in Durable CO 2 Electroreduction in Strong Acids via Electrode Structure Engineering. Angew Chem Int Ed Engl 2023; 62:e202300226. [PMID: 36810852 DOI: 10.1002/anie.202300226] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 02/13/2023] [Accepted: 02/21/2023] [Indexed: 02/24/2023]
Abstract
Acidic CO2 reduction (CO2 R) holds promise for the synthesis of low-carbon-footprint chemicals using renewable electricity. However, the corrosion of catalysts in strong acids causes severe hydrogen evolution and rapid deterioration of CO2 R performance. Here, by coating catalysts with an electrically nonconductive nanoporous SiC-NafionTM layer, a near-neutral pH was stabilized on catalyst surfaces, thereby protecting the catalysts against corrosion for durable CO2 R in strong acids. Electrode microstructures played a critical role in regulating ion diffusion and stabilizing electrohydrodynamic flows near catalyst surfaces. This surface-coating strategy was applied to three catalysts, SnBi, Ag, and Cu, and they exhibited high activity over extended CO2 R operation in strong acids. Using a stratified SiC-NafionTM /SnBi/polytetrafluoroethylene (PTFE) electrode, constant production of formic acid was achieved with a single-pass carbon efficiency of >75 % and Faradaic efficiency of >90 % at 100 mA cm-2 over 125 h at pH 1.
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Affiliation(s)
- Le Li
- College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, 163 Xianlin Avenue, Qixia District, Nanjing, 210023, China
| | - Zhaoyang Liu
- College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, 163 Xianlin Avenue, Qixia District, Nanjing, 210023, China
| | - Xiaohan Yu
- College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, 163 Xianlin Avenue, Qixia District, Nanjing, 210023, China
| | - Miao Zhong
- College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, Jiangsu Key Laboratory of Artificial Functional Materials, Nanjing University, 163 Xianlin Avenue, Qixia District, Nanjing, 210023, China
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4
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Al-Amshawee SKA, Yunus MYBM. Electrodialysis desalination: The impact of solution flowrate (or Reynolds number) on fluid dynamics throughout membrane spacers. ENVIRONMENTAL RESEARCH 2023; 219:115115. [PMID: 36574794 DOI: 10.1016/j.envres.2022.115115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Revised: 11/13/2022] [Accepted: 12/17/2022] [Indexed: 06/17/2023]
Abstract
The incorporation of a spacer among membranes has a major influence on fluid dynamics and performance metrics. Spacers create feed channels and operate as turbulence promoters to increase mixing and reduce concentration/temperature polarization effects. However, spacer geometry remains unoptimized, and studies continue to investigate a wide range of commercial and custom-made spacer designs. The in-depth discussion of the present systematic review seeks to discover the influence of Reynolds number or solution flowrate on flow hydrodynamics throughout a spacer-filled channel. A fast-flowing solution sweeping one membrane's surface first, then the neighboring membrane's surface produces good mixing action, which does not happen commonly at laminar solution flowrates. A sufficient flowrate can suppress the polarization layer, which may normally require the utilization of a simple feed channel rather than complex spacer configurations. When a recirculation eddy occurs, it disrupts the continuous flow and effectively curves the linear fluid courses. The higher the flowrate, the better the membrane performance, the higher the critical flux (or recovery rate), and the lower the inherent limitations of spacer design, spacer shadow effect, poor channel hydrodynamics, and high concentration polarization. In fact, critical flow achieves an acceptable balance between improving flow dynamics and reducing the related trade-offs, such as pressure losses and the occurrence of concentration polarization throughout the cell. If the necessary technical flowrate is not used, the real concentration potential for transport is relatively limited at low velocities than would be predicted based on bulk concentrations. Electrodialysis stack therefore may suffer from the dissociation of water molecules. Next studies should consider that applying a higher flowrate results in greater process efficiency, increased mass transfer potential at the membrane interface, and reduced stack thermal and electrical resistance, where pressure drop should always be indicated as a consequence of the spacer and circumstances used, rather than a problem.
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Affiliation(s)
| | - Mohd Yusri Bin Mohd Yunus
- Centre for Sustainability of Ecosystem & Earth Resources (Earth Centre), Universiti Malaysia Pahang, 26300, Pahang, Malaysia; Faculty of Chemical and Process Engineering Technology, Universiti Malaysia Pahang, 26300, Pahang, Malaysia
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5
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Yang F, Zhao W, Kuang C, Wang G. Rapid AC Electrokinetic Micromixer with Electrically Conductive Sidewalls. MICROMACHINES 2021; 13:mi13010034. [PMID: 35056199 PMCID: PMC8777699 DOI: 10.3390/mi13010034] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/11/2021] [Revised: 12/20/2021] [Accepted: 12/23/2021] [Indexed: 12/03/2022]
Abstract
We report a quasi T-channel electrokinetics-based micromixer with electrically conductive sidewalls, where the electric field is in the transverse direction of the flow and parallel to the conductivity gradient at the interface between two fluids to be mixed. Mixing results are first compared with another widely studied micromixer configuration, where electrodes are located at the inlet and outlet of the channel with electric field parallel to bulk flow direction but orthogonal to the conductivity gradient at the interface between the two fluids to be mixed. Faster mixing is achieved in the micromixer with conductive sidewalls. Effects of Re numbers, applied AC voltage and frequency, and conductivity ratio of the two fluids to be mixed on mixing results were investigated. The results reveal that the mixing length becomes shorter with low Re number and mixing with increased voltage and decreased frequency. Higher conductivity ratio leads to stronger mixing result. It was also found that, under low conductivity ratio, compared with the case where electrodes are located at the end of the channel, the conductive sidewalls can generate fast mixing at much lower voltage, higher frequency, and lower conductivity ratio. The study of this micromixer could broaden our understanding of electrokinetic phenomena and provide new tools for sample preparation in applications such as organ-on-a-chip where fast mixing is required.
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Affiliation(s)
- Fang Yang
- Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education, School of Life Sciences, Jilin University, Changchun 130012, China
- Correspondence: (F.Y.); (G.W.)
| | - Wei Zhao
- State Key Laboratory of Photon-Technology in Western China Energy, International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application, Institute of Photonics and Photon-Technology, Northwest University, Xi’an 710127, China;
| | - Cuifang Kuang
- State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China;
| | - Guiren Wang
- State Key Laboratory of Photon-Technology in Western China Energy, International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application, Institute of Photonics and Photon-Technology, Northwest University, Xi’an 710127, China;
- Department of Mechanical Engineering and Biomedical Engineering Program, University of South Carolina, Columbia, SC 29208, USA
- Correspondence: (F.Y.); (G.W.)
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Zhang D, Zhang X, Xing L, Li Z. Numerical Simulation of Continuous Extraction of Li + from High Mg 2+/Li + Ratio Brines Based on Free Flow Ion Concentration Polarization Microfluidic System. MEMBRANES 2021; 11:membranes11090697. [PMID: 34564514 PMCID: PMC8472120 DOI: 10.3390/membranes11090697] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/08/2021] [Accepted: 09/08/2021] [Indexed: 11/30/2022]
Abstract
Ion concentration polarization (ICP) is a promising mechanism for concentrating and/or separating charged molecules. This work simulates the extraction of Li+ ions in a diluted high Mg2+/Li+ ratio salt lake brines based on free flow ICP focusing (FF-ICPF). The model solution of diluted brine continuously flows through the system with Li+ slightly concentrated and Mg2+ significantly removed by ICP driven by external pressure and perpendicular electric field. In a typical case, our results showed that this system could focus Li+ concentration by ~1.28 times while decreasing the Mg2+/Li+ ratio by about 85% (from 40 to 5.85). Although Li+ and Mg2+ ions are not separated as an end product, which is preferably required by the lithium industry, this method is capable of decreasing the Mg2+/Li+ ratio significantly and has great potential as a preprocessing technology for lithium extraction from salt lake brines.
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Affiliation(s)
- Dongxiang Zhang
- College of Mechanical and Electrical Engineering, Wenzhou University, Wenzhou 325000, China;
- School of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, China;
- National Engineering Research Center for Technological Innovation Method and Tool, Tianjin 300401, China
| | - Xianglei Zhang
- College of Mechanical and Electrical Engineering, Wenzhou University, Wenzhou 325000, China;
- Correspondence: (X.Z.); (Z.L.)
| | - Leilei Xing
- School of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, China;
- National Engineering Research Center for Technological Innovation Method and Tool, Tianjin 300401, China
| | - Zirui Li
- School of Mechanical Engineering, Hebei University of Technology, Tianjin 300401, China;
- National Engineering Research Center for Technological Innovation Method and Tool, Tianjin 300401, China
- Correspondence: (X.Z.); (Z.L.)
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Kwon S, Lee H, Kim SJ. Pulsed electric field-assisted overlimiting current enhancement through a perm-selective membrane. LAB ON A CHIP 2021; 21:2153-2162. [PMID: 33908534 DOI: 10.1039/d1lc00064k] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Overlimiting current through a perm-selective membrane has been actively researched not only for the fundamental advancement of electrokinetics but also for energy/environmental applications such as electrodialysis, fuel cells, etc. In particular, various strategies were reported for the enhancement of overlimiting current because these applications demand efficient mass transport through the membrane. In this work, we presented in operando visualization and rigorous numerical study for the overlimiting current density enhancement using a pulsed electric field which is one of the most cost-effective parameters to be externally controlled. We clearly demonstrated that the current density had a peak value as a function of the pulse frequency and would suggest its correlation to a concentration profile and diffusion relaxation time ([small tau, Greek, tilde]diff). As the pulse frequency was chosen which is similar to ([small tau, Greek, tilde]diff)-1, the concentration profiles (i.e. established current paths) were maintained even in off-state due to remnant current paths helping the fast ion transportation. The fundamental evidence presented in this work would provide a strategical design of a perm-selective membrane system for a higher mass transportation efficiency.
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Affiliation(s)
- Soonhyun Kwon
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, 08826, Republic of Korea.
| | - Hyomin Lee
- Department of Chemical and Biological engineering, Jeju National University, 63243, Republic of Korea.
| | - Sung Jae Kim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul, 08826, Republic of Korea. and Inter-university Semiconductor Research Center, Seoul National University, Seoul, 08826, South Korea and Nano Systems Institute, Seoul National University, Seoul, 08826, South Korea
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8
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Hu Z, Zhao T, Zhao W, Yang F, Wang H, Wang K, Bai J, Wang G. Transition from periodic to chaotic
AC
electroosmotic flows near electric double layer. AIChE J 2021. [DOI: 10.1002/aic.17148] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Zhongyan Hu
- State Key Laboratory of Photon‐Technology in Western China Energy, International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application, Institute of Photonics and Photon‐Technology Northwest University Xi'an 710127 China
| | - Tianyun Zhao
- School of Automation Northwestern Polytechnical University Xi'an China
| | - Wei Zhao
- State Key Laboratory of Photon‐Technology in Western China Energy, International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application, Institute of Photonics and Photon‐Technology Northwest University Xi'an 710127 China
- Department of Mechanical Engineering & Biomedical Engineering Program University of South Carolina Columbia South Carolina USA
| | - Fang Yang
- Key Laboratory for Molecular Enzymology and Engineering of Ministry of Education Jilin University Changchun P.R. China
| | - Hongxun Wang
- Aeronautics Engineering College Air Force Engineering University Xi'an China
| | - Kaige Wang
- State Key Laboratory of Photon‐Technology in Western China Energy, International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application, Institute of Photonics and Photon‐Technology Northwest University Xi'an 710127 China
| | - Jintao Bai
- State Key Laboratory of Photon‐Technology in Western China Energy, International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application, Institute of Photonics and Photon‐Technology Northwest University Xi'an 710127 China
| | - Guiren Wang
- State Key Laboratory of Photon‐Technology in Western China Energy, International Scientific and Technological Cooperation Base of Photoelectric Technology and Functional Materials and Application, Institute of Photonics and Photon‐Technology Northwest University Xi'an 710127 China
- Department of Mechanical Engineering & Biomedical Engineering Program University of South Carolina Columbia South Carolina USA
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Gurreri L, Tamburini A, Cipollina A, Micale G. Electrodialysis Applications in Wastewater Treatment for Environmental Protection and Resources Recovery: A Systematic Review on Progress and Perspectives. MEMBRANES 2020; 10:E146. [PMID: 32660014 PMCID: PMC7408617 DOI: 10.3390/membranes10070146] [Citation(s) in RCA: 97] [Impact Index Per Article: 24.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2020] [Revised: 07/02/2020] [Accepted: 07/04/2020] [Indexed: 12/19/2022]
Abstract
This paper presents a comprehensive review of studies on electrodialysis (ED) applications in wastewater treatment, outlining the current status and the future prospect. ED is a membrane process of separation under the action of an electric field, where ions are selectively transported across ion-exchange membranes. ED of both conventional or unconventional fashion has been tested to treat several waste or spent aqueous solutions, including effluents from various industrial processes, municipal wastewater or salt water treatment plants, and animal farms. Properties such as selectivity, high separation efficiency, and chemical-free treatment make ED methods adequate for desalination and other treatments with significant environmental benefits. ED technologies can be used in operations of concentration, dilution, desalination, regeneration, and valorisation to reclaim wastewater and recover water and/or other products, e.g., heavy metal ions, salts, acids/bases, nutrients, and organics, or electrical energy. Intense research activity has been directed towards developing enhanced or novel systems, showing that zero or minimal liquid discharge approaches can be techno-economically affordable and competitive. Despite few real plants having been installed, recent developments are opening new routes for the large-scale use of ED techniques in a plethora of treatment processes for wastewater.
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Affiliation(s)
| | - Alessandro Tamburini
- Dipartimento di Ingegneria, Università degli Studi di Palermo, viale delle Scienze Ed. 6, 90128 Palermo, Italy; (L.G.); (A.C.); (G.M.)
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Investigation on the Stability of Random Vortices in an Ion Concentration Polarization Layer with Imposed Normal Fluid Flow. MICROMACHINES 2020; 11:mi11050529. [PMID: 32456039 PMCID: PMC7281587 DOI: 10.3390/mi11050529] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 05/20/2020] [Accepted: 05/20/2020] [Indexed: 01/17/2023]
Abstract
While nanoscale electrokinetic studies based on ion concentration polarization has been actively researched recently, random vortices naturally occur, leading to significantly destabilize in laboratory experiments or practical applications. These random vortices agitate the fluid inside microchannels and let the sample molecules seriously leak out preventing them from being controlled. Therefore, several trials have been reported to regulate those uninvited fluctuations by fluid flow tangential to a nanoporous membrane. Indeed, the influence of normal flow should be studied since the mass transport happens in the normal direction to the membrane. Thus, in this work, the nonlinear influence of normal flow to the instability near ion-selective surface was investigated by fully-coupled direct numerical simulation using COMSOL Multiphysics. The investigation on the effect of normal flow revealed that a space charge layer plays a significant role in the onset and growth of instability. The normal flow from the reservoir into the ion-selective surface pushed the space charge layer and decreased the size of vortices. However, there existed a maximum point for the growth of instability. The squeeze of the space charge layer increased the gradient of ion concentration in the layer, which resulted in escalating the velocity of vortices. On the other hand, the normal flow from the ion-selective surface into the reservoir suppressed the instability by spreading ions in the expanding space charge layer, leading to the reduction of ion concentration delayed the onset of instability. These two different mechanisms rendered asymmetric transition of stability as a function of the Peclet number and applied voltage. Therefore, this investigation would help understand the growth of instability and control the inevitable random vortices for the inhibition of fluid-agitation and leakage.
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Liu W, Zhou Y, Shi P. Shear electroconvective instability in electrodialysis channel under extreme depletion and its scaling laws. Phys Rev E 2020; 101:043105. [PMID: 32422815 DOI: 10.1103/physreve.101.043105] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2019] [Accepted: 03/23/2020] [Indexed: 11/07/2022]
Abstract
The electroconvective instability (ECI) in an electrodialysis channel under a strong electric field is studied here. The phenomenon of ECI with extreme depletion (ECI-HD) is reported; that is, the overlapping vortices cause the extreme depletion zone to propagate in the horizontal direction. Using scaling theory and direct numerical simulation, we indicate a series of features under the ECI-HD. The decrease in ion transport rate with voltage in ECI-HD is different from the enhancement in the ECI with moderate depletion (ECI-MD), which results in a unique peak in the voltage-current curve. More importantly, we reveal that the ECI is regulated by a scaling factor consisting of the electric field, hydrodynamic coupling coefficient, and Péclet number. For the ECI-HD, the scaling factor has an opposite effect on the vortex size and overlimiting current as that on the ECI-MD. The extreme depletion zone of the ECI-HD also has an uncommon diffusion self-similar dynamics. These unique scaling laws allow one to establish the quantitative bridge between the ion concentration, electric field, and vortex size by the overlimiting current.
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Affiliation(s)
- Wei Liu
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, People's Republic of China
| | - Yueting Zhou
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, People's Republic of China
| | - Pengpeng Shi
- School of Civil Engineering & Institute of Mechanics and Technology, Xi'an University of Architecture and Technology, Xi'an 710055, Shaanxi, People's Republic of China and State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center of NDT and Structural Integrity Evaluation, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, Shaanxi, People's Republic of China
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12
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Potentiodynamic and Galvanodynamic Regimes of Mass Transfer in Flow-Through Electrodialysis Membrane Systems: Numerical Simulation of Electroconvection and Current-Voltage Curve. MEMBRANES 2020; 10:membranes10030049. [PMID: 32245124 PMCID: PMC7143499 DOI: 10.3390/membranes10030049] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/09/2020] [Accepted: 03/19/2020] [Indexed: 11/17/2022]
Abstract
Electromembrane devices are usually operated in two electrical regimes: potentiodynamic (PD), when a potential drop in the system is set, and galvanodynamic (GD), when the current density is set. This article theoretically investigates the current-voltage curves (CVCs) of flow-through electrodialysis membrane systems calculated in the PD and GD regimes and compares the parameters of the electroconvective vortex layer for these regimes. The study is based on numerical modelling using a basic model of overlimiting transfer enhanced by electroconvection with a modification of the boundary conditions. The Dankwerts’ boundary condition is used for the ion concentration at the inlet boundary of the membrane channel. The Dankwerts’ condition allows one to increase the accuracy of the numerical implementation of the boundary condition at the channel inlet. On the CVCs calculated for PD and DG regimes, four main current modes can be distinguished: underlimiting, limiting, overlimiting, and chaotic overlimiting. The effect of the electric field regime is manifested in overlimiting current modes, when a significant electroconvection vortex layer develops in the channel.
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13
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Guan Y, Riley J, Novosselov I. Three-dimensional electroconvective vortices in cross flow. Phys Rev E 2020; 101:033103. [PMID: 32289920 DOI: 10.1103/physreve.101.033103] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 02/05/2020] [Indexed: 06/11/2023]
Abstract
This study focuses on the three-dimensional (3D) electrohydrodynamic flow instability between two parallel electrodes driven by unipolar charge injection with and without cross flow. Lattice Boltzmann method with a two-relaxation time model is used to compute flow patterns. In the absence of cross flow, the base-state solution is hydrostatic, and the electric field is one-dimensional. With strong charge injection and high electrical Rayleigh number, the system exhibits electroconvective vortices. Disturbed by perturbation patterns, such as rolling pattern, square pattern, and hexagon pattern, the flow develops corresponding to the most unstable mode. The growth rate and pattern transitions are studied using dynamic mode decomposition of the transient numerical solutions. The interactions between cross flow and electroconvective vortices lead to suppression and disappearance of structures with velocity components in the direction of cross flow, while the other components are not affected. Surprisingly, the transition from a 3D to a 2D flow pattern enhances the convective charge transport, marked by an increase in the electric Nusselt number. Hysteresis in the 3D to 2D transition is characterized by the nondimensional parameter Y, a ratio of the electrical force term to the viscous term in the momentum equation.
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Affiliation(s)
- Yifei Guan
- Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195, USA
| | - James Riley
- Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195, USA
| | - Igor Novosselov
- Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195, USA
- Institute for Nano-Engineered Systems, University of Washington, Seattle, Washington 98195, USA
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14
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Mathematical Modeling of the Effect of Water Splitting on Ion Transfer in the Depleted Diffusion Layer Near an Ion-Exchange Membrane. MEMBRANES 2020; 10:membranes10020022. [PMID: 32023962 PMCID: PMC7073578 DOI: 10.3390/membranes10020022] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/04/2020] [Revised: 01/30/2020] [Accepted: 01/30/2020] [Indexed: 11/22/2022]
Abstract
Water splitting (WS) and electroconvection (EC) are the main phenomena affecting ion transfer through ion-exchange membranes in intensive current regimes of electrodialysis. While EC enhances ion transport, WS, in most cases, is an undesirable effect reducing current efficiency and causing precipitation of sparingly soluble compounds. A mathematical description of the transfer of salt ions and H+ (OH−) ions generated in WS is presented. The model is based on the Nernst–Planck and Poisson equations; it takes into account deviation from local electroneutrality in the depleted diffusion boundary layer (DBL). The current transported by water ions is given as a parameter. Numerical and semi-analytical solutions are developed. The analytical solution is found by dividing the depleted DBL into three zones: the electroneutral region, the extended space charge region (SCR), and the quasi-equilibrium zone near the membrane surface. There is an excellent agreement between two solutions when calculating the concentration of all four ions, electric field, and potential drop across the depleted DBL. The treatment of experimental partial current–voltage curves shows that under the same current density, the surface space charge density at the anion-exchange membrane is lower than that at the cation-exchange membrane. This explains the negative effect of WS, which partially suppresses EC and reduces salt ion transfer. The restrictions of the analytical solution, namely, the local chemical equilibrium assumption, are discussed.
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15
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Electrokinetic ion transport at micro–nanochannel interfaces: applications for desalination and micromixing. APPLIED NANOSCIENCE 2019. [DOI: 10.1007/s13204-019-01207-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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16
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Li J, Chen D, Ye J, Zhang L, Zhou T, Zhou Y. Direct Numerical Simulation of Seawater Desalination Based on Ion Concentration Polarization. MICROMACHINES 2019; 10:mi10090562. [PMID: 31450684 PMCID: PMC6780573 DOI: 10.3390/mi10090562] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2019] [Revised: 08/22/2019] [Accepted: 08/23/2019] [Indexed: 11/23/2022]
Abstract
The problem of water shortage needs to be solved urgently. The membrane-embedded microchannel structure based on the ion concentration polarization (ICP) desalination effect is a potential portable desalination device with low energy consumption and high efficiency. The electroosmotic flow in the microchannel of the cation exchange membrane and the desalination effect of the system are numerically analyzed. The results show that when the horizontal electric field intensity is 2 kV/m and the transmembrane voltage is 400 mV, the desalting efficiency reaches 97.3%. When the electric field strength increases to 20 kV/m, the desalination efficiency is reduced by 2%. In terms of fluid motion, under the action of the transmembrane voltage, two reverse eddy currents are formed on the surface of the membrane due to the opposite electric field and pressure difference on both sides of the membrane, forming a pumping effect. The electromotive force in the channel exhibits significant pressure-flow characteristics with a slip boundary at a speed approximately six times that of a non-membrane microchannel.
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Affiliation(s)
- Jie Li
- School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430070, China.
| | - Dilin Chen
- School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430070, China
| | - Jian Ye
- School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430070, China
| | - Lai Zhang
- School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430070, China
| | - Teng Zhou
- Mechanical and Electrical Engineering College, Hainan University, Haikou 570228, China.
| | - Yi Zhou
- School of Energy and Power Engineering, Wuhan University of Technology, Wuhan 430070, China.
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17
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Park S, Abu-Rjal R, Rosentsvit L, Yossifon G. Novel Electrochemical Flow Sensor Based on Sensing the Convective-Diffusive Ionic Concentration Layer. ACS Sens 2019; 4:1806-1815. [PMID: 31204472 DOI: 10.1021/acssensors.9b00431] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Presented is a novel flow sensor based on electrochemical sensing of the ionic concentration-polarization (CP) layer developed within a microchannel-ion permselective membrane device. To demonstrate the working principle of the electrochemical flow sensor, the effect of advection on the transient and steady-state ionic concentration-polarization (CP) phenomenon in microchannel-Nafion membrane systems is studied. In particular, we focused on the local impedance, measured using an array of electrode pairs embedded at the bottom of the microchannel, as well as the total current across the permselective medium, as two approaches for estimating the flow. We examined both a stepwise application of CP under steady-state flow and a stepwise application of flow under steady-state CP.
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Affiliation(s)
- Sinwook Park
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion − Israel Institute of Technology, Technion City 3200000, Israel
| | - Ramadan Abu-Rjal
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion − Israel Institute of Technology, Technion City 3200000, Israel
| | - Leon Rosentsvit
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion − Israel Institute of Technology, Technion City 3200000, Israel
| | - Gilad Yossifon
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion − Israel Institute of Technology, Technion City 3200000, Israel
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18
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Li G, Archer LA, Koch DL. Electroconvection in a Viscoelastic Electrolyte. PHYSICAL REVIEW LETTERS 2019; 122:124501. [PMID: 30978047 DOI: 10.1103/physrevlett.122.124501] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 12/31/2018] [Indexed: 06/09/2023]
Abstract
Direct numerical simulations of a liquid electrolyte with polymer additives demonstrate that viscoelasticity promotes an earlier transition from steady to unsteady electroconvective flow. Viscoelasticity also decreases the overlimiting current resulting from convection by up to 40%. Both of these effects would reduce the time-averaged spatial variability of ion flux suggesting that polymeric fluids may inhibit dendrite growth. Polymer relaxation near a surface destabilizes the flow structures and decreases the time duration of high current fluxes. This mechanism of polymer-induced flux reduction is general to wall bounded flows with transfer of mass, heat or momentum.
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Affiliation(s)
- Gaojin Li
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Lynden A Archer
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Donald L Koch
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
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19
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2D Mathematical Modelling of Overlimiting Transfer Enhanced by Electroconvection in Flow-Through Electrodialysis Membrane Cells in Galvanodynamic Mode. MEMBRANES 2019; 9:membranes9030039. [PMID: 30862024 PMCID: PMC6468424 DOI: 10.3390/membranes9030039] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/20/2019] [Revised: 03/05/2019] [Accepted: 03/06/2019] [Indexed: 11/17/2022]
Abstract
Flow-through electrodialysis membrane cells are widely used in water purification and the processing of agricultural products (milk, wine, etc.). In the research and operating practice of such systems, a significant place is occupied by a galvanodynamic (or galvanostatic) mode. 2D mathematical modelling of ion transfer in the galvanodynamic mode requires solving the problem of setting the average current density equal to a certain value, while the current density distribution in the system is uneven. This article develops a 2D mathematical model of the overlimiting transfer enhanced by electroconvection in a flow-through electrodialysis cell in the galvanodynamic mode. The model is based on the system of Navier–Stokes, Nernst–Planck, Poisson equations and equations for the electric current stream function. To set the electric mode we use a boundary condition, relating the electric field strength and current density. This approach allows us to describe the formation of the extended space charge region and development of electroconvection at overlimiting currents. For the first time, chronopotentiograms and current–voltage characteristics of the membrane systems are calculated for the galvanodynamic mode taking into account the forced flow and development of electroconvection. The behaviors of the calculated chronopotentiograms and current–voltage characteristic coincide qualitatively with experimental data. The effects of the electrolyte concentration, forced flow velocity and channel size on the mass transfer at overlimiting currents are estimated.
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20
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Kim J, Davidson S, Mani A. Characterization of Chaotic Electroconvection near Flat Inert Electrodes under Oscillatory Voltages. MICROMACHINES 2019; 10:mi10030161. [PMID: 30813604 PMCID: PMC6470596 DOI: 10.3390/mi10030161] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 02/20/2019] [Accepted: 02/20/2019] [Indexed: 11/16/2022]
Abstract
The onset of electroconvective instability in an aqueous binary electrolyte under external oscillatory electric fields at a single constant frequency is investigated in a 2D parallel flat electrode setup. Direct numerical simulations (DNS) of the Poisson–Nernst–Planck equations coupled with the Navier–Stokes equations at a low Reynolds number are carried out. Previous studies show that direct current (DC) electric field can create electroconvection near ion-selecting membranes in microfluidic devices. In this study, we show that electroconvection can be generated near flat inert electrodes when the applied electric field is oscillatory in time. A range of applied voltage, the oscillation frequency and the ratio of ionic diffusivities is examined to characterize the regime in which electroconvection takes place. Similar to electroconvection under DC voltages, AC electroconvection occurs at sufficiently high applied voltages in units of thermal volts and is characterized by transverse instabilities, physically manifested by an array of counter-rotating vortices near the electrode surfaces. The oscillating external electric field periodically generate and destroy such unsteady vortical structures. As the oscillation frequency is reduced to O(10−1) of the intrinsic resistor–capacitor (RC) frequency of electrolyte, electroconvective instability is considerably amplified. This is accompanied by severe depletion of ionic species outside the thin electric double layer and by vigorous convective transport involving a wide range of scales including those comparable to the distance L between the parallel electrodes. The underlying mechanisms are distinctly nonlinear and multi-dimensional. However, at higher frequencies of order of the RC frequency, the electrolyte response becomes linear, and the present DNS prediction closely resembles those explained by 1D asymptotic studies. Electroconvective instability supports increased electric current across the system. Increasing anion diffusivity results in stronger amplification of electroconvection over all oscillation frequencies examined in this study. Such asymmetry in ionic diffusivity, however, does not yield consistent changes in statistics and energy spectrum at all wall-normal locations and frequencies, implying more complex dynamics and different scaling for electrolytes with unequal diffusivities. Electric current is substantially amplified beyond the ohmic current at high oscillation frequencies. Also, it is found that anion diffusivity higher than cation has stronger impact on smaller-scale motions (≲0.1L).
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Affiliation(s)
- Jeonglae Kim
- School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, AZ 85287, USA.
- Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA.
| | - Scott Davidson
- Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA.
| | - Ali Mani
- Center for Turbulence Research, Stanford University, Stanford, CA 94305, USA.
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21
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1D Mathematical Modelling of Non-Stationary Ion Transfer in the Diffusion Layer Adjacent to an Ion-Exchange Membrane in Galvanostatic Mode. MEMBRANES 2018; 8:membranes8030084. [PMID: 30235846 PMCID: PMC6161193 DOI: 10.3390/membranes8030084] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/09/2018] [Revised: 09/04/2018] [Accepted: 09/16/2018] [Indexed: 11/29/2022]
Abstract
The use of the Nernst–Planck and Poisson (NPP) equations allows computation of the space charge density near solution/electrode or solution/ion-exchange membrane interface. This is important in modelling ion transfer, especially when taking into account electroconvective transport. The most solutions in literature use the condition setting a potential difference in the system (potentiostatic or potentiodynamic mode). However, very often in practice and experiment (such as chronopotentiometry and voltammetry), the galvanostatic/galvanodynamic mode is applied. In this study, a depleted stagnant diffusion layer adjacent to an ion-exchange membrane is considered. In this article, a new boundary condition is proposed, which sets a total current density, i, via an equation expressing the potential gradient as an explicit function of i. The numerical solution of the problem is compared with an approximate solution, which is obtained by a combination of numerical solution in one part of the diffusion layer (including the electroneutral region and the extended space charge region, zone (I) with an analytical solution in the other part (the quasi-equilibrium electric double layer (EDL), zone (II). It is shown that this approach (called the “zonal” model) allows reducing the computational complexity of the problem tens of times without significant loss of accuracy. An additional simplification is introduced by neglecting the thickness of the quasi-equilibrium EDL in comparison to the diffusion layer thickness (the “simplified” model). For the first time, the distributions of concentrations, space charge density and current density along the distance to an ion-exchange membrane surface are computed as functions of time in galvanostatic mode. The calculation of the transition time, τ, for an ion-exchange membrane agree with an experiment from literature. It is suggested that rapid changes of space charge density, and current density with time and distance, could lead to lateral electroosmotic flows delaying depletion of near-surface solution and increasing τ.
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22
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Uzdenova AM, Kovalenko AV, Urtenov MK, Nikonenko VV. Theoretical Analysis of the Effect of Ion Concentration in Solution Bulk and at Membrane Surface on the Mass Transfer at Overlimiting Currents. RUSS J ELECTROCHEM+ 2018. [DOI: 10.1134/s1023193517110179] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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23
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de Valença J, Jõgi M, Wagterveld RM, Karatay E, Wood JA, Lammertink RGH. Confined Electroconvective Vortices at Structured Ion Exchange Membranes. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:2455-2463. [PMID: 29345950 PMCID: PMC5822219 DOI: 10.1021/acs.langmuir.7b04135] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Revised: 01/17/2018] [Indexed: 05/26/2023]
Abstract
In this paper, we investigate electroconvective ion transport at cation exchange membranes with different geometry square-wave structures (line undulations) experimentally and numerically. Electroconvective microvortices are induced by strong concentration polarization once a threshold potential difference is applied. The applied potential required to start and sustain electroconvection is strongly affected by the geometry of the membrane. A reduction in the resistance of approximately 50% can be obtained when the structure size is similar to the mixing layer (ML) thickness, resulting in confined vortices with less lateral motion compared to the case of flat membranes. From electrical, flow, and concentration measurements, ion migration, advection, and diffusion are quantified, respectively. Advection and migration are dominant in the vortex ML, whereas diffusion and migration are dominant in the stagnant diffusion layer. Numerical simulations, based on Poisson-Nernst-Planck and Navier-Stokes equations, show similar ion transport and flow characteristics, highlighting the importance of membrane topology on the resulting electrokinetic and electrohydrodynamic behavior.
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Affiliation(s)
- Joeri de Valença
- Soft
Matter, Fluidics and Interfaces Group, MESA Institute
of Nanotechnology, University of Twente, 7500AE Enschede, The Netherlands
- Wetsus, European
Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA Leeuwarden, The Netherlands
| | - Morten Jõgi
- Wetsus, European
Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA Leeuwarden, The Netherlands
| | - R. Martijn Wagterveld
- Wetsus, European
Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911MA Leeuwarden, The Netherlands
| | - Elif Karatay
- Department
of Mechanical Engineering, Stanford University, Stanford, California 94305, United States
| | - Jeffery A. Wood
- Soft
Matter, Fluidics and Interfaces Group, MESA Institute
of Nanotechnology, University of Twente, 7500AE Enschede, The Netherlands
| | - Rob G. H. Lammertink
- Soft
Matter, Fluidics and Interfaces Group, MESA Institute
of Nanotechnology, University of Twente, 7500AE Enschede, The Netherlands
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24
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Wang C, Bao J, Pan W, Sun X. Modeling electrokinetics in ionic liquids. Electrophoresis 2017; 38:1693-1705. [PMID: 28314048 DOI: 10.1002/elps.201600455] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 02/13/2017] [Accepted: 03/05/2017] [Indexed: 11/06/2022]
Abstract
Using direct numerical simulations, we provide a thorough study regarding the electrokinetics of ionic liquids. In particular, modified Poisson-Nernst-Planck equations are solved to capture the crowding and overscreening effects characteristic of an ionic liquid. For modeling electrokinetic flows in an ionic liquid, the modified Poisson-Nernst-Planck equations are coupled with Navier-Stokes equations to study the coupling of ion transport, hydrodynamics, and electrostatic forces. Specifically, we consider the ion transport between two parallel charged surfaces, charging dynamics in a nanopore, capacitance of electric double-layer capacitors, electroosmotic flow in a nanochannel, electroconvective instability on a plane ion-selective surface, and electroconvective flow on a curved ion-selective surface. We also discuss how crowding and overscreening and their interplay affect the electrokinetic behaviors of ionic liquids in these application problems.
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Affiliation(s)
- Chao Wang
- Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Jie Bao
- Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
| | - Wenxiao Pan
- Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA
| | - Xin Sun
- Physical and Computational Science Directorate, Pacific Northwest National Laboratory, Richland, WA, USA
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25
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TRIPATHI DHARMENDRA, BHUSHAN SHASHI, BÉG OANWAR. ANALYTICAL STUDY OF ELECTRO-OSMOSIS MODULATED CAPILLARY PERISTALTIC HEMODYNAMICS. J MECH MED BIOL 2017. [DOI: 10.1142/s021951941750052x] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A mathematical model is developed to analyze electro-kinetic effects on unsteady peristaltic transport of blood in cylindrical vessels of finite length. The Newtonian viscous model is adopted. The analysis is restricted under Debye–Hückel linearization (i.e., wall zeta potential [Formula: see text] 25[Formula: see text]mV) is sufficiently small). The transformed, nondimensional conservation equations are derived via lubrication theory and long wavelength and the resulting linearized boundary value problem is solved exactly. The case of a thin electric double layer (i.e., where only slip electro-osmotic velocity considered) is retrieved as a particular case of the present model. The response in pumping characteristics (axial velocity, pressure gradient or difference, volumetric flow rate, local wall shear stress) to the influence of electro-osmotic effect (inverse Debye length) and Helmholtz–Smoluchowski velocity is elaborated in detail. Visualization of trapping phenomenon is also included and the bolus dynamics evolution with electro-kinetic effects examined. A comparative study of train wave propagation and single wave propagation is presented under the effects of thickness of EDL and external electric field. The study is relevant to electrophoresis in haemotology, electrohydrodynamic therapy and biomimetic electro-osmotic pumps.
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Affiliation(s)
- DHARMENDRA TRIPATHI
- Department of Mechanical Engineering, Manipal University, Jaipur 303007, India
| | - SHASHI BHUSHAN
- Department of Mechanical Engineering, Manipal University, Jaipur 303007, India
| | - O. ANWAR BÉG
- Fluid Mechanics, Bio-Propulsion and Nano-Systems, Department of Mechanical and Aeronautical Engineering, Salford University, Newton Building, The Crescent, Salford M54WT, England, UK
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26
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Yang KD, Ko WR, Lee JH, Kim SJ, Lee H, Lee MH, Nam KT. Morphology‐Directed Selective Production of Ethylene or Ethane from CO
2
on a Cu Mesopore Electrode. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201610432] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Affiliation(s)
- Ki Dong Yang
- Department of Materials Science and Engineering Seoul National University 1 Gwanak-ro, Gwanak-gu Seoul 08826 Korea
| | - Woo Ri Ko
- Department of Applied Chemistry Kyung Hee University Yongin, Gyeonggi 17104 Korea
| | - Jun Ho Lee
- Department of Materials Science and Engineering Seoul National University 1 Gwanak-ro, Gwanak-gu Seoul 08826 Korea
| | - Sung Jae Kim
- Department of Electrical and Computer Engineering Big Data Institute Inter-University Semiconductor Research Center Seoul National University 1 Gwanak-ro, Gwanak-gu Seoul 08826 Korea
| | - Hyomin Lee
- Department of Electrical and Computer Engineering Institute of Advanced Machines and Design Seoul National University 1 Gwanak-ro, Gwanak-gu Seoul 08826 Korea
| | - Min Hyung Lee
- Department of Applied Chemistry Kyung Hee University Yongin, Gyeonggi 17104 Korea
| | - Ki Tae Nam
- Department of Materials Science and Engineering Seoul National University 1 Gwanak-ro, Gwanak-gu Seoul 08826 Korea
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27
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Yang KD, Ko WR, Lee JH, Kim SJ, Lee H, Lee MH, Nam KT. Morphology-Directed Selective Production of Ethylene or Ethane from CO 2 on a Cu Mesopore Electrode. Angew Chem Int Ed Engl 2016; 56:796-800. [PMID: 28000371 DOI: 10.1002/anie.201610432] [Citation(s) in RCA: 147] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 11/15/2016] [Indexed: 11/07/2022]
Abstract
The electrocatalytic conversion of CO2 to value-added hydrocarbons is receiving significant attention as a promising way to close the broken carbon-cycle. While most metal catalysts produce C1 species, such as carbon monoxide and formate, the production of various hydrocarbons and alcohols comprising more than two carbons has been achieved using copper (Cu)-based catalysts only. Methods for producing specific C2 reduction outcomes with high selectivity, however, are not available thus far. Herein, the morphological effect of a Cu mesopore electrode on the selective production of C2 products, ethylene or ethane, is presented. Cu mesopore electrodes with precisely controlled pore widths and depths were prepared by using a thermal deposition process on anodized aluminum oxide. With this simple synthesis method, we demonstrated that C2 chemical selectivity can be tuned by systematically altering the morphology. Supported by computational simulations, we proved that nanomorphology can change the local pH and, additionally, retention time of key intermediates by confining the chemicals inside the pores.
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Affiliation(s)
- Ki Dong Yang
- Department of Materials Science and Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Korea
| | - Woo Ri Ko
- Department of Applied Chemistry, Kyung Hee University, Yongin, Gyeonggi, 17104, Korea
| | - Jun Ho Lee
- Department of Materials Science and Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Korea
| | - Sung Jae Kim
- Department of Electrical and Computer Engineering, Big Data Institute, Inter-University Semiconductor Research Center, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Korea
| | - Hyomin Lee
- Department of Electrical and Computer Engineering, Institute of Advanced Machines and Design, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Korea
| | - Min Hyung Lee
- Department of Applied Chemistry, Kyung Hee University, Yongin, Gyeonggi, 17104, Korea
| | - Ki Tae Nam
- Department of Materials Science and Engineering, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, Korea
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28
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Andersen MB, Wang KM, Schiffbauer J, Mani A. Confinement effects on electroconvective instability. Electrophoresis 2016; 38:702-711. [DOI: 10.1002/elps.201600391] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2016] [Revised: 10/20/2016] [Accepted: 10/25/2016] [Indexed: 11/10/2022]
Affiliation(s)
| | - Karen M. Wang
- Department of Mechanical Engineering Stanford University Stanford CA USA
| | - Jarrod Schiffbauer
- Faculty of Mechanical Engineering Technion‐Israel Institute of Technology Technion City Israel
| | - Ali Mani
- Department of Mechanical Engineering Stanford University Stanford CA USA
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29
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Nikonenko VV, Vasil'eva VI, Akberova EM, Uzdenova AM, Urtenov MK, Kovalenko AV, Pismenskaya NP, Mareev SA, Pourcelly G. Competition between diffusion and electroconvection at an ion-selective surface in intensive current regimes. Adv Colloid Interface Sci 2016; 235:233-246. [PMID: 27457287 DOI: 10.1016/j.cis.2016.06.014] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Revised: 06/09/2016] [Accepted: 06/29/2016] [Indexed: 11/19/2022]
Abstract
Considering diffusion near a solid surface and simplifying the shape of concentration profile in diffusion-dominated layer allowed Nernst and Brunner to propose their famous equation for calculating the solute diffusion flux. Intensive (overlimiting) currents generate electroconvection (EC), which is a recently discovered interfacial phenomenon produced by the action of an external electric field on the electric space charge formed near an ion-selective interface. EC microscale vortices effectively mix the depleted solution layer that allows the reduction of diffusion transport limitations. Enhancement of ion transport by EC is important in membrane separation, nano-microfluidics, analytical chemistry, electrode kinetics and some other fields. This paper presents a review of the actual understanding of the transport mechanisms in intensive current regimes, where the role of diffusion declines in the profit of EC. We analyse recent publications devoted to explore the properties of different zones of the diffusion layer. Visualization of concentration profile and fluid current lines are considered as well as mathematical modelling of the overlimiting transfer.
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Affiliation(s)
- V V Nikonenko
- Department of Physical Chemistry, Kuban State University, 149 Stavropolskaya St., 350040 Krasnodar, Russia.
| | - V I Vasil'eva
- Department of Analytical Chemistry, Voronezh State University, 394018, Universitetskaya pl. 1, Voronezh, Russia
| | - E M Akberova
- Department of Analytical Chemistry, Voronezh State University, 394018, Universitetskaya pl. 1, Voronezh, Russia
| | - A M Uzdenova
- Department of Computer Technology and Applied Mathematics, Kuban State University, 149 Stavropolskaya St., 350040 Krasnodar, Russia
| | - M K Urtenov
- Department of Computer Technology and Applied Mathematics, Kuban State University, 149 Stavropolskaya St., 350040 Krasnodar, Russia
| | - A V Kovalenko
- Department of Computer Technology and Applied Mathematics, Kuban State University, 149 Stavropolskaya St., 350040 Krasnodar, Russia
| | - N P Pismenskaya
- Department of Physical Chemistry, Kuban State University, 149 Stavropolskaya St., 350040 Krasnodar, Russia
| | - S A Mareev
- Department of Physical Chemistry, Kuban State University, 149 Stavropolskaya St., 350040 Krasnodar, Russia
| | - G Pourcelly
- Institut Européen des Membranes, UMR 5635, Université Montpellier, ENSCM, CNRS, CC047, 34095 Montpellier Cedex 5, France
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30
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Karatay E, Andersen MB, Wessling M, Mani A. Coupling between Buoyancy Forces and Electroconvective Instability near Ion-Selective Surfaces. PHYSICAL REVIEW LETTERS 2016; 116:194501. [PMID: 27232024 DOI: 10.1103/physrevlett.116.194501] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Indexed: 06/05/2023]
Abstract
Recent investigations have revealed that ion transport from aqueous electrolytes to ion-selective surfaces is subject to electroconvective instability that stems from coupling of hydrodynamics with electrostatic forces. These systems inherently involve fluid density variation set by salinity gradients. However, the coupling between the buoyancy effects and electroconvective instability has not yet been investigated although a wide range of electrochemical systems are naturally prone to these interplaying effects. In this study we thoroughly examine the interplay of gravitational convection and chaotic electroconvection. Our results reveal that buoyant forces can significantly influence the transport rates, otherwise set by electroconvection, when the Rayleigh number Ra of the system exceeds a value Ra∼1000. We show that buoyancy forces can significantly alter the flow patterns in these systems. When the buoyancy acts in the stabilizing direction, it limits the extent of penetration of electroconvection, but without eliminating it. When the buoyancy destabilizes the flow, it alters the electroconvective patterns by introducing upward and downward fingers of respectively light and heavy fluids.
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Affiliation(s)
- Elif Karatay
- Department of Mechanical Engineering, Stanford University and Center for Turbulence Research, Stanford University, Stanford, California 94305, USA
| | - Mathias Bækbo Andersen
- Department of Mechanical Engineering, Stanford University and Center for Turbulence Research, Stanford University, Stanford, California 94305, USA
| | - Matthias Wessling
- RWTH Aachen University, Aachener Verfahrenstechnik, 52056 Aachen, Germany
| | - Ali Mani
- Department of Mechanical Engineering, Stanford University and Center for Turbulence Research, Stanford University, Stanford, California 94305, USA
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On the Dynamical Regimes of Pattern-Accelerated Electroconvection. Sci Rep 2016; 6:22505. [PMID: 26935925 PMCID: PMC4776150 DOI: 10.1038/srep22505] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/15/2016] [Indexed: 11/21/2022] Open
Abstract
Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes, and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states.
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Green Y, Edri Y, Yossifon G. Asymmetry-induced electric current rectification in permselective systems. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:033018. [PMID: 26465567 DOI: 10.1103/physreve.92.033018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Indexed: 06/05/2023]
Abstract
For a symmetric ion permselective system, in terms of geometry and bulk concentrations, the system response is also symmetric under opposite electric field polarity. In this work we derive an analytical solution for the concentration distribution, electric potential, and current-voltage response for a four-layered system comprised of two microchambers connected by two permselective regions of varying properties. It is shown that any additional asymmetry in the system, in terms of the geometry, bulk concentration, or surface charge property of the permselective regions, results in current rectification. Our work is divided into two parts: when both permselective regions have the same surface charge sign and the case of opposite signs. For the same sign case we are able to show that the system behaves as a dialytic battery while accounting for field-focusing effects. For the case of opposite signs (i.e., bipolar membrane), our system exhibits the behavior of a bipolar diode where the magnitude of the rectification can be of order 10^{2}-10^{3}.
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Affiliation(s)
- Yoav Green
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion - Israel Institute of Technology, Technion City 32000, Israel
| | - Yaron Edri
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion - Israel Institute of Technology, Technion City 32000, Israel
| | - Gilad Yossifon
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion - Israel Institute of Technology, Technion City 32000, Israel
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Femmer R, Mani A, Wessling M. Ion transport through electrolyte/polyelectrolyte multi-layers. Sci Rep 2015; 5:11583. [PMID: 26111456 PMCID: PMC4481379 DOI: 10.1038/srep11583] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 05/29/2015] [Indexed: 12/01/2022] Open
Abstract
Ion transport of multi-ionic solutions through layered electrolyte and polyelectrolyte structures are relevant in a large variety of technical systems such as micro and nanofluidic devices, sensors, batteries and large desalination process systems. We report a new direct numerical simulation model coined EnPEn: it allows to solve a set of first principle equations to predict for multiple ions their concentration and electrical potential profiles in electro-chemically complex architectures of n layered electrolytes E and n polyelectrolytes PE. EnPEn can robustly capture ion transport in sub-millimeter architectures with submicron polyelectrolyte layers. We proof the strength of EnPEn for three yet unsolved architectures: (a) selective Na over Ca transport in surface modified ion selective membranes, (b) ion transport and water splitting in bipolar membranes and (c) transport of weak electrolytes.
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Affiliation(s)
- Robert Femmer
- AVT Chemical Process Engineering, RWTH Aachen University, Turmstr. 46, 52064 Aachen, Germany
| | - Ali Mani
- Department of Mechanical Engineering, Stanford University, Stanford, CA 94305, USA
| | - Matthias Wessling
- 1] AVT Chemical Process Engineering, RWTH Aachen University, Turmstr. 46, 52064 Aachen, Germany [2] DWI, Forckenbeckstr. 50, 52074 Aachen, Germany
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