Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation
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 car...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Elsevier
2018-12-01
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| Series: | Water Research X |
| Online Access: | http://www.sciencedirect.com/science/article/pii/S2589914718300082 |
| _version_ | 1818039580872409088 |
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| author | Diego I. Oyarzun Ali Hemmatifar James W. Palko Michael Stadermann Juan G. Santiago |
| author_facet | Diego I. Oyarzun Ali Hemmatifar James W. Palko Michael Stadermann Juan G. Santiago |
| author_sort | Diego I. Oyarzun |
| collection | DOAJ |
| description | 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. Keywords: Ion selectivity, Capacitive deionization, Nitrate, Surface charge, Surfactant treatment |
| first_indexed | 2024-12-10T08:00:54Z |
| format | Article |
| id | doaj.art-6bac112966cf4c159255088a001413cd |
| institution | Directory Open Access Journal |
| issn | 2589-9147 |
| language | English |
| last_indexed | 2024-12-10T08:00:54Z |
| publishDate | 2018-12-01 |
| publisher | Elsevier |
| record_format | Article |
| series | Water Research X |
| spelling | doaj.art-6bac112966cf4c159255088a001413cd2022-12-22T01:56:48ZengElsevierWater Research X2589-91472018-12-011Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validationDiego I. Oyarzun0Ali Hemmatifar1James W. Palko2Michael Stadermann3Juan G. Santiago4Department of Mechanical Engineering, Stanford University Stanford, CA 94305, USADepartment of Mechanical Engineering, Stanford University Stanford, CA 94305, USADepartment of Mechanical Engineering, University of California, Merced, CA 95343, USALawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USADepartment of Mechanical Engineering, Stanford University Stanford, CA 94305, USA; Corresponding author.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. Keywords: Ion selectivity, Capacitive deionization, Nitrate, Surface charge, Surfactant treatmenthttp://www.sciencedirect.com/science/article/pii/S2589914718300082 |
| spellingShingle | Diego I. Oyarzun Ali Hemmatifar James W. Palko Michael Stadermann Juan G. Santiago Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation Water Research X |
| title | Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation |
| title_full | Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation |
| title_fullStr | Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation |
| title_full_unstemmed | Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation |
| title_short | Ion selectivity in capacitive deionization with functionalized electrode: Theory and experimental validation |
| title_sort | ion selectivity in capacitive deionization with functionalized electrode theory and experimental validation |
| url | http://www.sciencedirect.com/science/article/pii/S2589914718300082 |
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