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Reuse of Treated Wastewater through Emerging Technologies
Published in Maulin P. Shah, Wastewater Treatment, 2022
Rifat Ara Masud, Farzana Yeasmin, M. Mehedi Hasan, Md. Kamruzzaman
NF is a pressure-driven separation process for the elimination of dissolved micropollutants and multivalent ions from wastewater, in which transport through the membrane occurs by a combination of solvent diffusion, transport, and electrostatic repulsive interactions at the membrane surface and within the nanopores. NF can be as loose RO as the separation occurs following the same principle as RO with a somewhat larger pore size or a higher MWCO compared with RO membranes. Polymeric NF membranes can have ionizable groups, such as sulfonic or carboxylic acid groups, which bring out the surface charge duo to the feed solution. Donnan potential is used to measure the equilibrium potential between the charged membrane and the bulk solution, where Donnan exclusion permits the removal of under sized ions more than the pore size of the membrane.
Sensing of Toxic Metals Using Innovative Sorption-Based Technique
Published in Arup K. Sengupta, Ion Exchange and Solvent Extraction, 2017
Chatterjee Prasun K., SenGupta Arup K.
The Gibbs–Donnan equation that describes the “Donnan membrane equilibrium” arises from the unequal distribution of the mobile ions70 or, in other words, the inability of ions to diffuse from one phase to the other through interface. The polymeric phase of an ion exchanger can be viewed as a polyelectrolyte where functional groups (e.g., quaternary ammonium or R4N+ groups for anion exchangers and sulfonic acid or SO3− groups for cation exchangers) are covalently attached and, hence, non-diffusible. Both counterions and co-ions in the bulk solution phase are mobile and can move freely under chemical or electrical potential gradient. The presence of fixed functional groups in the exchanger phase makes the ion exchanger a semi-permeable membrane that essentially gives rise to the development of the Donnan potential.70,71
Electro-membrane processes for the removal of trace toxic metal ions from water
Published in Alberto Figoli, Jan Hoinkis, Jochen Bundschuh, Membrane Technologies for Water Treatment: Removal of Toxic Trace Elements with Emphasis on Arsenic, Fluoride and Uranium, 2016
Svetlozar Velizarov, Adrian Oehmen, Maria Reis, João Crespo
Although the driving force in Donnan dialysis is not an external electric potential difference but a concentration difference, the latter leads to the establishment of an internal electric (Donnan) potential difference, which can be utilized for transport and separation of target ionic species. Moreover, as will be discussed in more detail later, this process is especially appropriate for removing trace target ions from low salinity waters. The Donnan dialysis type of operation requires the presence in the stripping solution of a so-called “driving” counter-ion, which is transported across the membrane in a direction opposite to that of the target counter-ion(s) in order to maintain overall electroneutrality in the system. From the operational, economic and environmental points of view, chloride has been generally considered as a suitable driving counter-ion when anionic pollutants have to be removed from contaminated drinking water supplies (Velizarov et al., 2004). In the case of cationic pollutants, sodium, potassium or hydrogen ions appear to be the best possible choices.
A numerical evaluation of felt electrodes in a vanadium redox flow battery
Published in International Journal of Green Energy, 2023
Mert Taş, Phil-Jacques Alphonse, Gülşah Elden
The Donnan potential occurred as the result of the differences in proton concentration across the membrane (K. W. Knehr and Kumbur 2011). A transient model of VRFB with anion exchange membrane (AEM) was proposed by Lei et al (Lei et al. 2022). They found that the donnan potential occurred in the membrane reduced the cell voltage during the discharge process. Similarly, the equilibrium thermodynamic was used to properly determine the VRFB open circuit voltage (Pavelka, Wandschneider, and Mazur 2015; Wandschneider et al. 2014). This study revealed that batteries with cation-exchange membrane (CEM) have a different Nernst relation than batteries with anion exchange membrane. This discrepancy is due to the varying conditions for equilibrium of the species carried across the membranes. A time-dependent model of VRFB including Donnan effect was created by Lei et al (Lei et al. 2015). They observed that the vanadium crossover in Nafion membranes reduced due to the Donnan effect. Moreover, in another study, they proposed a transient one-dimensional model of VRFB based on bipolar cation exchange layer and anion exchange layer (Lei et al. 2021). They discovered that Donnan effect between cation exchange layer and anion exchange layer made more complicated the ion distributions in bipolar membranes.