1
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Efficient desalination system for brackish water incorporating biomass-derived porous material. J Taiwan Inst Chem Eng 2022. [DOI: 10.1016/j.jtice.2022.104316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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2
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Uwayid R, Guyes EN, Shocron AN, Gilron J, Elimelech M, Suss ME. Perfect divalent cation selectivity with capacitive deionization. WATER RESEARCH 2022; 210:117959. [PMID: 34942526 DOI: 10.1016/j.watres.2021.117959] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/07/2021] [Accepted: 12/09/2021] [Indexed: 06/14/2023]
Abstract
Capacitive deionization (CDI) is an emerging membraneless water desalination technology based on storing ions in charged electrodes by electrosorption. Due to unique selectivity mechanisms, CDI has been investigated towards ion-selective separations such as water softening, nutrient recovery, and production of irrigation water. Especially promising is the use of activated microporous carbon electrodes due to their low cost and wide availability at commercial scales. We show here, both theoretically and experimentally, that sulfonated activated carbon electrodes enable the first demonstration of perfect divalent cation selectivity in CDI, where we define "perfect" as significant removal of the divalent cation with zero removal of the competing monovalent cation. For example, for a feedwater of 15 mM NaCl and 3 mM CaCl2, and charging from 0.4 V to 1.2 V, we show our cell can remove 127 μmol per gram carbon of divalent Ca2+, while slightly expelling competing monovalent Na+ (-13.2 μmol/g). This separation can be achieved with excellent efficiency, as we show both theoretically and experimentally a calcium charge efficiency above unity, and an experimental energy consumption of less than 0.1 kWh/m3. We further demonstrate a low-infrastructure technique to measure cation selectivity, using ion-selective electrodes and the extended Onsager-Fuoss model.
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Affiliation(s)
- Rana Uwayid
- Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Eric N Guyes
- Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Amit N Shocron
- Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa, Israel
| | - Jack Gilron
- The Jacob Blaustein Institutes for Desert Research, Zuckerberg Institute for Water Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
| | - Menachem Elimelech
- Department of Chemical and Environmental Engineering, Yale University, New Haven, United States
| | - Matthew E Suss
- Faculty of Mechanical Engineering, Technion - Israel Institute of Technology, Haifa, Israel; Wolfson Department of Chemical Engineering, Technion - Israel Institute of Technology, Haifa, Israel; Grand Technion Energy Program, Technion - Israel Institute of Technology, Haifa, Israel.
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3
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Correlation between physicochemical and electrochemical properties of an activated carbon doped with lanthanum for fluoride electrosorption. Sep Purif Technol 2021. [DOI: 10.1016/j.seppur.2021.118702] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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4
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Liu R, Yao S, Shen Y. Pore-scale investigation on ion transport and transfer resistance in charged porous media with micro-macro structure. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.114481] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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5
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Pan SY, Haddad AZ, Kumar A, Wang SW. Brackish water desalination using reverse osmosis and capacitive deionization at the water-energy nexus. WATER RESEARCH 2020; 183:116064. [PMID: 32745671 DOI: 10.1016/j.watres.2020.116064] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 05/30/2020] [Accepted: 06/14/2020] [Indexed: 06/11/2023]
Abstract
In this article, we present a critical review of the reported performance of reverse osmosis (RO) and capacitive deionization (CDI) for brackish water (salinity < 5.0 g/L) desalination from the aspects of engineering, energy, economy and environment. We first illustrate the criteria and the key performance indicators to evaluate the performance of brackish water desalination. We then systematically summarize technological information of RO and CDI, focusing on the effect of key parameters on desalination performance, as well as energy-water efficiency, economic costs and environmental impacts (including carbon footprint). We provide in-depth discussion on the interconnectivity between desalination and energy, and the trade-off between kinetics and energetics for RO and CDI as critical factors for comparison. We also critique the results of technical-economic assessment for RO and CDI plants in the context of large-scale deployment, with focus on lifetime-oriented consideration to total costs, balance between energy efficiency and clean water production, and pretreatment/post-treatment requirements. Finally, we illustrate the challenges and opportunities for future brackish water desalination, including hybridization for energy-efficient brackish water desalination, co-removal of specific components in brackish water, and sustainable brine management with innovative utilization. Our study reveals that both RO and CDI should play important roles in water reclamation and resource recovery from brackish water, especially for inland cities or rural regions.
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Affiliation(s)
- Shu-Yuan Pan
- Department of Bioenvironmental Systems Engineering, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei City, 10617, Taiwan, ROC.
| | - Andrew Z Haddad
- Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Arkadeep Kumar
- Energy Technologies Area, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Sheng-Wei Wang
- Department of Water Resources and Environmental Engineering, Tamkang University, New Taipei City, 251301, Taiwan, ROC
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6
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Wang L, Liang Y, Zhang L. Enhancing Performance of Capacitive Deionization with Polyelectrolyte-Infiltrated Electrodes: Theory and Experimental Validation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:5874-5883. [PMID: 32216292 DOI: 10.1021/acs.est.9b07692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
The energy efficiency of capacitive deionization (CDI) with porous carbon electrodes is limited by the high ionic resistance of the macropores in the electrodes. In this study, we demonstrate a facile approach to improve the energy efficiency by filling the macropores with ion-conductive polyelectrolytes, which is termed polyelectrolyte-infiltrated CDI (pie-CDI or πCDI). In πCDI, the filled polyelectrolyte effectively turns the macropores into a charged ion-selective layer and thus increases the conductivity of macropores. We show experimentally that πCDI can save up to half of the energy consumption compared to membrane CDI, achieving identical desalination during the charging step. The energy consumption can be even lower if the process is operated at a smaller average salt adsorption rate. Further energy breakdown analysis based on a theoretical model confirms that the improved energy efficiency is largely attributed to the increased conductivity in the macropores.
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Affiliation(s)
- Li Wang
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, Tennessee 37235-1831, United States
| | - Yuanzhe Liang
- Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, Tennessee 37235-1831, United States
| | - Li Zhang
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, The Netherlands
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7
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Legrand L, Shu Q, Tedesco M, Dykstra J, Hamelers H. Role of ion exchange membranes and capacitive electrodes in membrane capacitive deionization (MCDI) for CO2 capture. J Colloid Interface Sci 2020; 564:478-490. [DOI: 10.1016/j.jcis.2019.12.039] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Revised: 12/10/2019] [Accepted: 12/11/2019] [Indexed: 11/28/2022]
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8
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Salamat Y, Hidrovo CH. Significance of the micropores electro-sorption resistance in capacitive deionization systems. WATER RESEARCH 2020; 169:115286. [PMID: 31734390 DOI: 10.1016/j.watres.2019.115286] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/12/2019] [Accepted: 11/05/2019] [Indexed: 06/10/2023]
Abstract
Capacitive Deionization (CDI) is an emerging technology representing a potential alternative to the common, energy-intensive desalination methods for low salinity water streams. In CDI an electrical field is applied to separate ionic species from aqueous solutions and electro-adsorb them into a highly porous material. CDI is a complex multi-scale system which requires robust mathematical models to closely describe its performance. Here, a dynamic two-dimensional model is developed coupling the diffusion and advection of the species in the bulk solution with their diffusion and electro-sorption in the porous electrodes. In this model, the adsorption/desorption resistance between the micropores and macropores along with variable non-electrostatic attractive forces in the micropores are also incorporated. The proposed theory is validated against experiments using a circular CDI cell operating under various conditions, where different transport mechanisms are limiting the total ion removal process. Performance of the CDI systems is also evaluated using inclusive figures of merit. The obtained results accentuate the significant effect of the rate-limited transfer of the ionic species from the macropores into the micropores, especially in systems subject to severe ion starvation, where neglecting this electro-sorption resistance leads to up to 50% and 210% overestimation of the energy efficiency and overall desalination performance, respectively. Furthermore, although the commonly used transport theory describing CDI fails to capture the dynamics of the systems at low initial concentration and high adsorption capacity by assuming fast electro-sorption without any resistance, the presented theory closely models the transport mechanisms in such systems. Moreover, we experimentally and numerically demonstrate a trade-off between the energetic and desalination performance in systems with low and high mass Péclet number.
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Affiliation(s)
- Yasamin Salamat
- Mechanical and Industrial Engineering Department, Northeastern University, 334 Snell Engineering Center, 360 Huntington Ave, Boston, MA, 02115, USA
| | - Carlos H Hidrovo
- Mechanical and Industrial Engineering Department, Northeastern University, 334 Snell Engineering Center, 360 Huntington Ave, Boston, MA, 02115, USA.
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9
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Delgado A, Jiménez M, Iglesias G, Ahualli S. Electrical double layers as ion reservoirs: applications to the deionization of solutions. Curr Opin Colloid Interface Sci 2019. [DOI: 10.1016/j.cocis.2019.09.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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10
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Enhanced cycling stability of capacitive deionization via effectively inhibiting H2O2 formation: The role of nitrogen dopants. J Electroanal Chem (Lausanne) 2019. [DOI: 10.1016/j.jelechem.2019.113488] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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11
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Mubita TM, Dykstra JE, Biesheuvel PM, van der Wal A, Porada S. Selective adsorption of nitrate over chloride in microporous carbons. WATER RESEARCH 2019; 164:114885. [PMID: 31426005 DOI: 10.1016/j.watres.2019.114885] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 07/04/2019] [Accepted: 07/18/2019] [Indexed: 05/05/2023]
Abstract
Activated carbon is the most common electrode material used in electrosorption processes such as water desalination with capacitive deionization (CDI). CDI is a cyclic process to remove ions from aqueous solutions by transferring charge from one electrode to another. When multiple salts are present in a solution, the removal of each ionic species can be different, resulting in selective ion separations. This ion selectivity is the result of combined effects, such as differences in the hydrated size and valence of the ions. In the present work, we study ion selectivity from salt mixtures with two different monovalent ions, chloride and nitrate. We run adsorption experiment in microporous carbons (i.e., without applying a voltage), as well as electrosorption experiments (i.e., based on applying a voltage between two carbon electrodes). Our results show that i) during adsorption and electrosorption, activated carbon removes much more nitrate than chloride; ii) at equilibrium, ion selectivity does not depend strongly on the composition of the water, but does depend on charging voltage in CDI; and iii) during electrosorption, ion selectivity is time-dependent. We modify the amphoteric Donnan model by including an additional affinity of nitrate to carbon. We find good agreement between our experimental results and the theory. Both show very high selectivity towards nitrate over chloride, [Formula: see text] ∼10, when no voltage is applied, or when the voltage is low. The selectivity gradually decreases with increasing charging voltage to [Formula: see text] ∼6 at Vch = 1.2 V. Despite this decrease, the affinity-effect for nitrate continues to play an important role also at a high voltage. In general, we can conclude that our work provides new insights in the importance of carbon-ion interactions for electrochemical water desalination.
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Affiliation(s)
- T M Mubita
- Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, the Netherlands; Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, the Netherlands
| | - J E Dykstra
- Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, the Netherlands.
| | - P M Biesheuvel
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, the Netherlands
| | - A van der Wal
- Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708 WG Wageningen, the Netherlands; Evides Water Company, Schaardijk 150, 3063 NH Rotterdam, the Netherlands
| | - S Porada
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA Leeuwarden, the Netherlands; Soft Matter, Fluidics and Interfaces Group, Faculty of Science and Technology, University of Twente, Meander ME 314, 7500 AE Enschede, the Netherlands
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12
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Guyes EN, Malka T, Suss ME. Enhancing the Ion-Size-Based Selectivity of Capacitive Deionization Electrodes. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2019; 53:8447-8454. [PMID: 31187620 DOI: 10.1021/acs.est.8b06954] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Capacitive deionization (CDI) is an emerging water treatment technology often applied to brackish water desalination and water softening. Typical CDI cells consist of two microporous carbon electrodes sandwiching a dielectric separator, and desalt feedwater flowing through the cell by storing ions in electric double layers (EDLs) within charged micropores. CDI cells have demonstrated size-based ion selectivity wherein smaller hydrated ions are preferentially electrosorbed over larger hydrated ions. We demonstrate that such size-based selectivity can be substantially enhanced through the addition of chemical charge to micropores via surface functionalization. We develop a micropore EDL theory that includes both finite ion size effects and micropore chemical charge, which predicts such enhancements and elucidates that they result from denser counterion packing in micropores. With our experimental CDI cell, we desalted an electrolyte consisting of equimolar potassium (K+) and lithium (Li+) ions. We show that use of a surface-functionalized (oxidized) cathode significantly increased the electrosorption ratio of smaller K+ to larger Li+ compared to a cell with a pristine cathode, for example, from ∼1 to 1.84 for a charging voltage of 0.4 V. Our model predicts yet-higher electrosorption ratios are attainable, but our experimental cell suffered from significant cathode chemical charge degradation at applied voltages of ∼1 V.
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13
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Hawks SA, Ramachandran A, Porada S, Campbell PG, Suss ME, Biesheuvel PM, Santiago JG, Stadermann M. Performance metrics for the objective assessment of capacitive deionization systems. WATER RESEARCH 2019; 152:126-137. [PMID: 30665159 DOI: 10.1016/j.watres.2018.10.074] [Citation(s) in RCA: 84] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 10/25/2018] [Accepted: 10/28/2018] [Indexed: 06/09/2023]
Abstract
In the growing field of capacitive deionization (CDI), a number of performance metrics have emerged to describe the desalination process. Unfortunately, the separation conditions under which these metrics are measured are often not specified, resulting in optimal performance at minimal removal. Here we outline a system of performance metrics and reporting conditions that resolves this issue. Our proposed system is based on volumetric energy consumption (Wh/m3) and throughput productivity (L/h/m2) reported for a specific average concentration reduction, water recovery, and feed salinity. To facilitate and rationalize comparisons between devices, materials, and operation modes, we propose a nominal standard separation of removing 5 mM from a 20 mM NaCl feed solution at 50% water recovery. We propose this particular separation as a standard, but emphasize that the rationale presented here applies irrespective of separation details. Using our proposed separation, we compare the desalination performance of a flow-through electrode (fte-CDI) cell and a flow between membrane (fb-MCDI) device, showing how significantly different systems can be compared in terms of generally desirable desalination characteristics. In general, we find that performance analysis must be considered carefully so to not allow for ambiguous separation conditions or the maximization of one metric at the expense of another. Additionally, for context and clarity, we discuss a number of important underlying performance indicators and cell characteristics that are not performance measures in and of themselves but can be examined to better understand differences in performance.
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Affiliation(s)
- Steven A Hawks
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, United States
| | - Ashwin Ramachandran
- Department of Aeronautics & Astronautics, Stanford University, Stanford, CA, 94305, United States
| | - Slawomir Porada
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA, Leeuwarden, The Netherlands; Soft Matter, Fluidics and Interfaces Group, Faculty of Science and Technology, University of Twente, Meander ME 314, 7500 AE, Enschede, the Netherlands
| | - Patrick G Campbell
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, United States
| | - Matthew E Suss
- Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Haifa, Israel
| | - P M Biesheuvel
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911 MA, Leeuwarden, The Netherlands
| | - Juan G Santiago
- Department of Mechanical Engineering, Stanford University, Stanford, CA, 94305, United States
| | - Michael Stadermann
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA, United States.
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14
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Arulrajan AC, Ramasamy DL, Sillanpää M, van der Wal A, Biesheuvel PM, Porada S, Dykstra JE. Exceptional Water Desalination Performance with Anion-Selective Electrodes. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2019; 31:e1806937. [PMID: 30624840 DOI: 10.1002/adma.201806937] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 11/30/2018] [Indexed: 05/12/2023]
Abstract
Capacitive deionization (CDI) typically uses one porous carbon electrode that is cation adsorbing and one that is anion adsorbing. In 2016, Smith and Dmello proposed an innovative CDI cell design based on two cation-selective electrodes and a single anion-selective membrane, and thereafter this design was experimentally validated by various authors. In this design, anions pass through the membrane once, and desalinated water is continuously produced. In the present work, this idea is extended, and it is experimentally shown that also a choice for anion-selective electrodes, in combination with a cation-selective membrane, leads to a functional cell design that continuously desalinates water. Anion-selective electrodes are obtained by chemical modification of the carbon electrode with (3-aminopropyl)triethoxysilane. After chemical modification, the activated carbon electrode shows a substantial reduction of the total pore volume and Brunauer-Emmett-Teller (BET) surface area, but nevertheless maintains excellent CDI performance, which is for the first time that a low-porosity carbon electrode is demonstrated as a promising material for CDI.
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Affiliation(s)
- Antony C Arulrajan
- Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708, WG, Wageningen, The Netherlands
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911, MA, Leeuwarden, The Netherlands
| | - Deepika L Ramasamy
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911, MA, Leeuwarden, The Netherlands
- Department of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130, Mikkeli, Finland
| | - Mika Sillanpää
- Department of Green Chemistry, Lappeenranta University of Technology, Sammonkatu 12, 50130, Mikkeli, Finland
| | - Albert van der Wal
- Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708, WG, Wageningen, The Netherlands
| | - P Maarten Biesheuvel
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911, MA, Leeuwarden, The Netherlands
| | - Slawomir Porada
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Oostergoweg 9, 8911, MA, Leeuwarden, The Netherlands
- Soft Matter, Fluidics and Interfaces Group, Faculty of Science and Technology, University of Twente, Meander ME 314, 7500, AE, Enschede, The Netherlands
| | - Jouke E Dykstra
- Department of Environmental Technology, Wageningen University, Bornse Weilanden 9, 6708, WG, Wageningen, The Netherlands
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15
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Zhang Y, Xue Q, Li F, Dai J. Removal of heavy metal ions from wastewater by capacitive deionization using polypyrrole/chitosan composite electrode. ADSORPT SCI TECHNOL 2019. [DOI: 10.1177/0263617418822225] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
A polypyrrole/chitosan composite material was obtained by chemical polymerization. The adsorption performance of a hot-molded polypyrrole/chitosan composite electrode was tested by adsorption/desorption experiments. Scanning electron microscopy and Fourier-transform infrared spectroscopy both showed the deposition of polypyrrole on the chitosan surface. The specific capacitance of the polypyrrole/chitosan composite was determined by cyclic voltammetry in 1.0 M KCl at 0.01 V/s as 102.96 F/g. The adsorption/desorption experiments indicated that the specific adsorption capacity of the composite for Cu2+ was 99.67 mg/g, while the removal performance for other metal ions, such as Ag+, Pb2+, and Cd2+, was good. The results of multicycle adsorption/desorption tests showed that the adsorption rate of the polypyrrole/chitosan composite electrode for Cu2+ was decreased from 56.4 to 51.4% over 10 cycles, demonstrating the stable metal-ion adsorption/desorption behavior of the composite electrode. The obtained performances show that the prepared polypyrrole/chitosan composite material is an ideal electrode material for the removal of heavy metal ions.
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Affiliation(s)
- Yujie Zhang
- School of Chemistry and Chemical Engineering,Xi’an University of Architecture and Technology, Xi’an, China
| | - Quanqin Xue
- School of Chemistry and Chemical Engineering,Xi’an University of Architecture and Technology, Xi’an, China
| | - Fei Li
- School of Chemistry and Chemical Engineering,Xi’an University of Architecture and Technology, Xi’an, China
| | - Jizhe Dai
- School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi’an, China
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16
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Oyarzun DI, Hemmatifar A, Palko JW, Stadermann M, Santiago JG. Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation. WATER RESEARCH X 2018; 1:100008. [PMID: 31194024 PMCID: PMC6549908 DOI: 10.1016/j.wroa.2018.100008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2018] [Revised: 10/30/2018] [Accepted: 10/31/2018] [Indexed: 05/12/2023]
Abstract
Capacitive deionization (CDI) is a promising technique for salt removal and may have potential for highly selective removal of ion species. In this work, we take advantage of functional groups usually used with ionic exchange resins and apply these to CDI. To this end, we functionalize activated carbon with a quaternary amines surfactant and use this surface to selectively and passively (no applied field) trap nitrate ions. We then set the cell voltage to a constant value to regenerate these electrodes, resulting in an inverted capacitive deionization (i-CDI) operation. Unlike resins, we avoid use of concentrated chemicals for regeneration. We measure the selectivity of nitrate versus chloride ions as a function of regeneration voltage and initial chloride concentration. We experimentally demonstrate up to about 6.5-fold (observable) selectivity in a cycle with a regeneration voltage of 0.4 V. We also demonstrate a novel multi-pass, air-flush i-CDI operation to selectively enrich nitrate with high water recovery. We further present a dynamic, multi-species electrosorption and equilibrium solution-to-surface chemical reaction model and validate the model with detailed measurements. Our i-CDI system exhibits higher nitrate selectivity at lower voltages; making it possible to reduce NaNO3 concentrations from ∼170 ppm to below the limit of maximum allowed values for nitrate in drinking water of about 50 ppm NaNO3.
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Affiliation(s)
- Diego I. Oyarzun
- Department of Mechanical Engineering, Stanford University Stanford, CA 94305, USA
| | - Ali Hemmatifar
- Department of Mechanical Engineering, Stanford University Stanford, CA 94305, USA
| | - James W. Palko
- Department of Mechanical Engineering, University of California, Merced, CA 95343, USA
| | - Michael Stadermann
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA
| | - Juan G. Santiago
- Department of Mechanical Engineering, Stanford University Stanford, CA 94305, USA
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17
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Dykstra JE, Porada S, van der Wal A, Biesheuvel PM. Energy consumption in capacitive deionization - Constant current versus constant voltage operation. WATER RESEARCH 2018; 143:367-375. [PMID: 29986246 DOI: 10.1016/j.watres.2018.06.034] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2017] [Revised: 05/24/2018] [Accepted: 06/15/2018] [Indexed: 06/08/2023]
Abstract
In the field of Capacitive Deionization (CDI), it has become a common notion that constant current (CC) operation consumes significantly less energy than constant voltage operation (CV). Arguments in support of this claim are that in CC operation the endpoint voltage is reached only at the end of the charging step, and thus the average cell voltage during charging is lower than the endpoint voltage, and that in CC operation we can recover part of the invested energy during discharge. Though these arguments are correct, in the present work based on experiments and theory, we conclude that in operation of a well-defined CDI cycle, this does not lead, for the case we analyze, to the general conclusion that CC operation is more energy efficient. Instead, we find that without energy recovery there is no difference in energy consumption between CC and CV operation. Including 50% energy recovery, we find that indeed CC is more energy efficient, but also in CV much energy can be recovered. Important in the analysis is to precisely define the desalination objective function, such as that per unit total operational time -including both the charge and discharge steps- a certain desalination quantity and water recovery must be achieved. Another point is that also in CV operation energy recovery is possible by discharge at a non-zero cell voltage. To aid the analysis we present a new method of data representation where energy consumption is plotted against desalination. In addition, we propose that one must analyze the full range of combinations of cycle times, voltages and currents, and only compare the best cycles, to be able to conclude which operational mode is optimal for a given desalination objective. We discuss three methods to make this analysis in a rigorous way, two experimental and one combining experiments and theory. We use the last method and present results of this analysis.
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Affiliation(s)
- J E Dykstra
- Department of Environmental Technology, Wageningen University, the Netherlands; Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, the Netherlands.
| | - S Porada
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, the Netherlands; Soft matter, Fluidics and Interfaces Group, Faculty of Science and Technology, University of Twente, Enschede, the Netherlands
| | - A van der Wal
- Department of Environmental Technology, Wageningen University, the Netherlands; Evides, Rotterdam, the Netherlands
| | - P M Biesheuvel
- Wetsus, European Centre of Excellence for Sustainable Water Technology, Leeuwarden, the Netherlands
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