Influence of the type of anion membrane on solvent flux and back diffusion in electrodialysis of concentrated NaCl solutions

Rottiers, Thomas; Ghyselbrecht, Karel; Meesschaert, Boudewijn; Bruggen, Bart Van der; Pinoy, Luc

doi:10.1016/j.ces.2014.04.008

Cited by 79 publications

(46 citation statements)

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“…Thus, one can imagine that with stronger membrane-ion interaction, stronger dehydration of the ions may happen. As a result, lower hydration numbers can be expected [10,17,19,29]. Indeed, lower salt hydration number of NaCl (4.5 [10] and 3.5 [19]) have been sometimes reported, compared with that (equal to 14) obtained in this study.…”

Section: Discussionmentioning

confidence: 42%

“…In fact, knowing both the salt and the water flux in the system, it is possible to determine the salt hydration number. But a proper dissociation of the salt hydration is further necessary to get the individual contributions of the ions and this is still problematic [10,13,18,19]. Some simplifications can be made to split the total water transfer like for instance to assume that the ions have the same hydration numbers [10].…”

Section: Introductionmentioning

confidence: 99%

“…But a proper dissociation of the salt hydration is further necessary to get the individual contributions of the ions and this is still problematic [10,13,18,19]. Some simplifications can be made to split the total water transfer like for instance to assume that the ions have the same hydration numbers [10]. Finally, the few studies reported mainly focus on single electrolyte (NaCl) while in practice the solutions treated in ED can be much more complex, probably with multi-components and sometimes not only mixed inorganic salts but also organic matter.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the water transfer may limit the application of ED as a concentration process in different application fields [9,10]. For example, in case of coarse salt production from brine, it is crucial to limit the water transfer through the membrane to avoid the dilution of the final brine solution [11].…”

Section: Introductionmentioning

confidence: 99%

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Ion hydration number and electro-osmosis during electrodialysis of mixed salt solution

2015

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Hydration numbers of ions can be calculated from water and ion fluxes.• Ion hydration number is independent from solution composition and current.• The influence of the membrane on the ion hydration is discussed. a b s t r a c tWater transfer is an important aspect to be considered in electrodialysis since it fixes the performances of the process. It is due to electro-osmosis, i.e. the water carried by the migrating species and is thus related to their hydration. Few results were reported about the hydration number of solutes transferring through ion-exchange membranes. In this work, a methodology is proposed to calculate the hydration numbers of ions transferring through ion exchange membranes during electrodialysis. It is based on the experimental measurements of ion and water transfer under different conditions, like salt compositions and current. Salt hydration is first obtained, and then the hydration numbers of 4 transferring ions (Na + , Mg 2+ , Cl − , SO 4 2− ) are calculated simultaneously. It is shown that these hydration numbers are constant, independent from the salt composition and current. The hydration number for monovalent ions is found to be lower than that of divalent ones, which is in agreement with the values of the hydration free energy. Further comparison with the reported values concerning the hydration of the same ions in solution shows that for monovalent ions the hydration numbers are close to those reported for the 1st hydration shell while much higher values are obtained for divalent ions.

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Section: Discussionmentioning

confidence: 42%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Ion hydration number and electro-osmosis during electrodialysis of mixed salt solution

2015

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“…For electro-concentration processes it is recommended to use membranes which minimise water flux (Lu et al 2011;Rottiers et al 2014). Also, a less studied membrane attributes are membrane resistance to back diffusion and resistance to uncharged species (e.g.…”

Section: Membrane Developmentmentioning

confidence: 99%

Nutrient recovery from wastewater using electrodialysis

Brewster¹

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The production of synthetic fertilisers from traditional sources has several issues regarding sustainability, particularly the energy intensity required for production, limited mineral resources and loss of terrestrial environment. Nutrient recovery from wastewaters is an opportunity for alternative fertiliser manufacture, largely due to the high quantities of nutrients present. Electrodialysis (ED) is an optimal technology to recover, particularly, NH 4 + -N and K + -K. In this thesis, a mechanistic modelling approach is used to study ED for nutrient recovery. Existing ED models lack the capacity to mechanistically evaluate complex, multi-ion solutions (like real wastewater), the integration of electrochemistry and physicochemical phenomena across the whole reactor domain, and model validation using system dynamics. These limitations are addressed by development of a mechanistic modelling approach, with key mechanisms determined through targeted laboratory scale experiments using synthetic and real wastewaters. The first major study in this thesis includes development of a mechanistic model validated using dynamic experiments fed with synthetic wastewater. It was found that membrane resistance was the major contributor to potential drop and that apparent boundary layers were relatively thick (3 ± 1 mm) due to reactor design and operational conditions. This study also established that non-ideal solution effects such as ion pairing and ionic activity had a major impact, enhancing the capability of ED to recover monovalent nutrient ions such as K + and NH 4 + . The second major study used real centrifuged anaerobic digester rejection water (centrate) to study membrane scaling. Dynamic laboratory experiments demonstrated electro-concentration of nutrients in centrate to several times the feed concentration. An 87±7% by weight reduction in scale occurred when the centrate was pre-treated by upstream struvite recovery and the product pH was controlled at pH 5, compared to untreated centrate and no pH control. A mechanistic model for the inorganic processes was developed by extending the previously developed model to include the composition of a real wastewater feed solution and precipitation. This extended model revealed a reduction in struvite scale to the removal of phosphate during the struvite pretreatment, and reduction in calcium carbonate scale to pH control resulting in the stripping of carbonate as carbon dioxide gas; indicating that multiple strategies may be required to control precipitation. A third major study evaluated the mechanisms limiting high product concentrations during electro-concentration of synthetic urine. Modelling this system using similar methods to the first study identified that high concentrations in the product are prevented by back diffusion of ions across the membrane, current leakage (when buffering ii capacity is exhausted), and water fluxes across the membranes. Mechanistic discoveries in this thesis provide practical guidelines for pilot and full-scale operation of nutri...

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Mitigating Water Crossover by Crosslinked Coating of Cation‐Exchange Membranes for Brine Concentration

Rommerskirchen

Roth

Linnartz

et al. 2021

Adv Materials Technologies

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desalination and brine concentration tasks. [4,5] However, undesired water crossover is a major limitation in such processes applying ion-exchange membranes. The effect is twofold: 1) the water stream, which is to be desalinated, is desalinated less efficiently due to the unwanted removal of water; and 2) the brine stream, which is to be concentrated, is concentrated less efficiently, due to the unwanted crossover of water molecules into the brine stream. [6,7] Hence, the desalination and concentration efficiency of the processes are limited, while the energy demand to achieve a certain level of desalination or concentration is increased. This effect is especially pronounced when treating high salinity solutions, which goes hand in hand with high concentration differences across the membranes and the crossover of a large number of ions including their hydration shells through the ion-exchange membranes. [8,9] The issue of water crossover through proton exchange membranes is intensively studied and addressed in numerous publications. [10] Whereas, the mitigation of water crossover in cationexchange membranes (CEM) is an overlooked domain in ion transport and high salinity conditions are rarely studied. ED and FCDI FundamentalsElectrodialysis (ED) and FCDI are electrical potential driven desalination techniques. The ions move in an electric field toward the oppositely charged electrode, respectively. Thus, ions are selectively separated from the water. Electrodialysis uses a stack of ion-exchange membranes creating separate diluate and concentrate channels. Faradaic reactions convert the applied electric current in the electrode chambers filled with a rinse solution. [11,12] The principles of ED have already been described in 1940, and the first commercial application of ED for brackish water treatment is known since the early 1950s. A further field of application for ED is the food industry, where ED can be used to produce table salt or for the deacidification of apple juice. [13] Within the family of electrically driven desalination processes, FCDI is a novel technology, bearing promising potentials for the future of efficient water treatment. In 2013, Jeon et al., introduced FCDI, where static porous carbon electrodes from membrane capacitive deionization are replaced by carbon slurries, which allow for continuous desalination operation. [4,14,15] Undesired water crossover through ion-exchange membranes is a significant limitation in electrically driven desalination processes. The effect of mitigating water crossover is twofold: 1) The desalination degree is less reduced due to the unwanted removal of water, and 2) the brine concentration is increased due to decreased dilution by an unwanted crossover of water molecules. Hence, water crossover limits the desalination and concentration efficiency of the processes, while the energy demand to achieve a certain level of desalination or concentration increases. This effect is especially pronounced when treating high salinity solutions, which goes hand in hand with th...

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Influence of the type of anion membrane on solvent flux and back diffusion in electrodialysis of concentrated NaCl solutions

Cited by 79 publications

References 20 publications

Ion hydration number and electro-osmosis during electrodialysis of mixed salt solution

Ion hydration number and electro-osmosis during electrodialysis of mixed salt solution

Nutrient recovery from wastewater using electrodialysis

Mitigating Water Crossover by Crosslinked Coating of Cation‐Exchange Membranes for Brine Concentration

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