WORCESTER BOSCH SET OF ELECTRODES 87186643010

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We introduce the volumetric partitioning function Φ exc, i = exp( μ exc, i,∞ − μ exc, i), and a similar term for affinity-based effects, Φ aff, i = exp( μ aff, i,∞ − μ aff, i), which lumps together all effects acting on the ion that are not ideal (entropy), volumetric, or charge-related. These factors Φ exc, i and Φ aff, i will be between 0 and 1 when such effects act to repel the ion from the micropore environment but will be >1 when they act to adsorb the ion into the micropore. We use Φ i = Φ exc, i· Φ aff, i. We obtain from eqn (3) a modified Boltzmann relation R. K. Kalluri, M. M. Biener, M. E. Suss, M. D. Merrill, M. Stadermann, J. G. Santiago, T. F. Baumann, J. Biener and A. Striolo, Phys. Chem. Chem. Phys., 2013, 15, 2320 RSC. Ren et al. employed a flow MCDI (FCDI) cell to remove phosphate and ammonium from an aqueous solution. 133 Although it was found to be possible to remove large amounts of phosphate, the selectivity using this cell design was not explored. Further insight about selectivity using FCDI was reported by Bian et al. who studied the best operational conditions for the removal of phosphate and nitrate. 134 They observed a strong increase in the phosphate removal by increasing the carbon loading of the anode. This increase was steeper than that for nitrate (and ammonia), and was ascribed to the physical adsorption of phosphate in addition to electrosorption ( Fig. 6E), similar to the results obtained by Ge et al. On the other hand, for low carbon loadings, FCDI was found to be much more selective towards nitrate (1.1 at 15 wt% carbon loading to 1.7 at 5 wt%).

At the spacer-electrode edge, the flux by diffusion and electro-migration of the two cations is continuous, i.e., the same on each side of this edge, and ion concentrations are also continuous. Finally, the charge balance is given by

Worcester 8716121817 Set Of Electrodes Replaces 87186643010

Moving forward, research into new electrode materials and chemistries, modification and optimization of existing materials, investigation of parameters in selectivity operation, modeling of selectivity at the system and molecular level, and finally, techno-economic analysis into the viability of selective ion separation via CDI will be crucial for fully realizing the potential of ion-selectivity via CDI. S. Porada, L. Borchardt, M. Oschatz, M. Bryjak, J. S. Atchison, K. J. Keesman, S. Kaskel, P. M. Biesheuvel and V. Presser, Energy Environ. Sci., 2013, 6, 3700–3712 RSC. d Department of Chemical and Environmental Engineering, Yale University, New Haven, CT 06520-8286, USA Introduction Fresh water scarcity and rapidly increasing global demand for clean water have stimulated scientists to seek out innovative methods of securing potable water supplies. Even though water desalination is deeply rooted within the human history, spanning across centuries, 1 it was not until the latter half of 20th century that desalination techniques became commercialized. 2 Conventional desalination methods, such as reverse osmosis (RO), electrodialysis (ED), multi-stage-flash (MSF), and multi-effect desalination (MED), are commonly used, but in some cases require significant energy input to produce fresh water. Furthermore, the majority of these systems often desalinate ‘to completion’, or do not preferentially remove the ions that are desired to be removed or even harvested. Ion selectivity is of key importance because it is often not necessary, and perhaps even detrimental, to remove the vast majority or entirety of ions from water. There are ample examples where one specific ion is to be removed because of its toxicity (arsenic, boron, heavy metals, ions leading to fouling, and sodium in irrigation water) or value (lithium, gold). In this review we focus on the ion selectivity ( i.e. preferential removal of a particular ion of interest within a mixture of ions) aspect of water desalination via capacitive deionization (CDI).

Adsorption and ion transport dynamics in intercalation materials. Theory for ion transport in CDI electrodes with ion mixtures has until now focused on electrodes based on porous carbons. Here, we extend the state-of-the-art and present the first model calculations for CDI with porous electrodes made from an intercalation material (such as NiHCF, a Prussian blue analogue). Our calculation results illustrate the general observation of ion selectivity studies that the ideal, or maximum attainable, or “thermodynamic”, separation factor (selectivity), is not easily reached in a practical process. This is because mass transfer limitations and mixing of ions lead to a lower selectivity value in the actual desalination process than the ideal value. This is also the case in the example calculation of CDI with intercalation materials presented below. Therefore, this example calculation serves to underscore the point that careful design of an electrochemical desalination cell and the operational conditions, thereby reducing transfer resistances and avoiding mixing, is crucial in increasing the actual selectivity to values as close as possible to the ideal, thermodynamic selectivity. where c i is the concentration of ion i in the micropores. The chemical potential of ion i is given by 49,77 I. Cohen, B. Shapira, E. Avraham, A. Soffer and D. Aurbach, Environ. Sci. Technol., 2018, 52, 6275–6281 CrossRef CAS.

J. W. Blair and G. W. Murphy, Saline Water Conversion, Washington, DC, 1960, pp. 206–223 Search PubMed. P. Srimuk, J. Lee, S. Fleischmann, M. Aslan, C. Kim and V. Presser, ChemSusChem, 2018, 11, 2091–2100 CrossRef CAS. P. M. Biesheuvel, H. V. M. Hamelers and M. E. Suss, Colloid Interface Sci. Commun., 2015, 9, 1–5 CrossRef CAS. S. Buczek, M. L. Barsoum, S. Uzun, N. Kurra, R. Andris, E. Pomerantseva, K. A. Mahmoud and Y. Gogotsi, Energy Environ. Mater., 2020, 3, 398–404 CrossRef CAS. Another recent approach that has provided viable results for selectivity between mono/divalent ions is the use of monovalent ion-selective membranes. Pan et al. investigated the use of such membranes to separate fluoride and nitrite from sulfate. 137 Using an equimolar solution, the authors observed a selectivity ( ρ) of ≈1.4 for fluoride ions over sulfate ions. Furthermore, it was found that the pH of the feed solution was an important parameter to control and improve the ion selectivity. Higher pH values increased the selectivity towards fluoride, while for acidic solutions the selectivity was lost due to an interaction between protons and the surface of the membrane. The effect of the feed concentration was also explored, keeping the concentration ratio between the two anions constant. An increasing fluoride selectivity was observed upon increasing the concentration of both F − and SO 4 2−. When the cell voltage was increased, the selectivity was reduced towards F − demonstrating that high cell voltages cannot attain high selectivity. This result is in line with other works that show lower selectivity at higher cell voltages. 41,77