The need for ion-exchange membranes with high charge densities

Kitto, David; Kamcev, Jovan

doi:10.1016/j.memsci.2023.121608

Cited by 34 publications

(25 citation statements)

References 69 publications

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“…Figure b presents the fixed charge concentration ( C A m,w ) vs the water volume fraction (ϕ w ) of the membranes. As with most reported IEMs, high C A m,w values are typically achieved by driving down the membrane water content, so there is an inverse correlation between C A m,w and ϕ w . The selected membranes exhibit a wide range of C A m,w and ϕ w values, allowing us to explore a significant portion of the relevant materials space.…”

Section: Resultsmentioning

confidence: 92%

“…Regulating solvent transport across the membrane, which occurs via osmosis or electro-osmosis, is also important and can impact the performance of the system at high salinities . Previous studies on membranes contacted with relatively dilute salt solutions have demonstrated a trade-off relationship between the counter-ion conductivity and selectivity, which emphasizes the difficulty in synthesizing membranes capable of both fast and selective ion transport. − Understanding this trade-off relationship at higher salt concentrations is crucial for defining the scope of possibilities for IEMs in contact with brine solutions, where the ionic strength of the external solutions approaches that of many commercial membranes. − Moreover, an improved fundamental understanding of ion transport in IEMs at high salinities would facilitate the rational design of membranes that overcome the limitations of existing materials.…”

Section: Introductionmentioning

confidence: 99%

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Counter-ion Conductivity and Selectivity Trade-Off for Commercial Ion-Exchange Membranes at High Salinities

Espinoza,

Kitto,

Kamcev

2023

ACS Appl. Polym. Mater.

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Counter-ion Conductivity and Selectivity Trade-Off for Commercial Ion-Exchange Membranes at High Salinities

Espinoza,

Kitto,

Kamcev

2023

ACS Appl. Polym. Mater.

Self Cite

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“…Cross-pollination of ideas across disparate applications is a significant driver of technology improvements , that could dramatically accelerate innovation rates in membrane separation technologies. Although there have been a few recent efforts to translate developments across membrane processes, notably using reverse osmosis (RO) membranes in water electrolysis, redox flow batteries, and electrodialysis, , and comparing properties of ion exchange properties across diverse applications, such cross-pollination in membrane science remains the exception rather than the rule.…”

Section: Introductionmentioning

confidence: 99%

Unifying the Conversation: Membrane Separation Performance in Energy, Water, and Industrial Applications

Dischinger,

Miller,

Vermaas

et al. 2024

ACS EST Eng.

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Dense polymer membranes enable a diverse range of separations and clean energy technologies, including gas separation, water treatment, and renewable fuel production or conversion. The transport of small molecular and ionic solutes in the majority of these membranes is described by the same solution-diffusion mechanism, yet a comparison of membrane separation performance across applications is rare. A better understanding of how structure−property relationships and driving forces compare among applications would drive innovation in membrane development by identifying opportunities for crossdisciplinary knowledge transfer. Here, we aim to inspire such crosspollination by evaluating the selectivity and electrochemical driving forces for 29 separations across nine different applications using a common framework grounded in the physicochemical characteristics of the permeating and rejected solutes. Our analysis shows that highly selective membranes usually exhibit high solute rejection, rather than fast solute permeation, and often exploit contrasts in the size and charge of solutes rather than a nonelectrostatic chemical property, polarizability. We also highlight the power of selective driving forces (e.g., the fact that applied electric potential acts on charged solutes but not on neutral ones) to enable effective separation processes, even when the membrane itself has poor selectivity. We conclude by proposing several research opportunities that are likely to impact multiple areas of membrane science. The highlevel perspective of membrane separation across fields presented herein aims to promote cross-pollination and innovation by enabling comparisons of solute transport and driving forces among membrane separation applications.

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“…Perfluorinated sulfonated membranes (PFSMs) such as Nafion are typically used for the selective cation transport in electrochemical flow systems. − As current commercial PFSMs are extremely expensive and their production process involves unsustainable chemistry that generates toxic perfluorinated species, researchers have been exploring alternative approaches for improving the economic and sustainable viability of cation exchange membranes (CEMs). − In particular, new cost-effective membrane alternatives are imperative to enable emerging clean technologies, such as alkaline CO 2 sorbent regeneration for direct air CO 2 capture (DAC), redox flow batteries, and electrodialysis.…”

Section: Introductionmentioning

confidence: 99%

Polyamide-Based Ion Exchange Membranes: Cation-Selective Transport through Water Purification Membranes

Wang,

Lim,

Wang

et al. 2024

ACS Appl. Polym. Mater.

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Ion-selective membranes are necessary components of many electrochemical systems including fuel cells, electrolyzers, redox flow batteries, and electrodialyzers. Perfluorinated sulfonated membranes (PFSMs) dominate these applications due to their excellent combination of fast ion transport, stability, and processability. However, perfluorinated cation exchange membranes (CEMs) are expensive, and their production process involves chemistry that generates toxic perfluorinated chemicals. The development of affordable, nonfluorinated membranes with a competitive combination of high ion selectivity, transport, and stability could help enable the widespread use of the technologies listed above while hastening the development of emerging electrochemical systems, including aqueous alkaline CO 2 sorbent regeneration. To this end, we pursue the use of thin-film composite polyamide (PA-TFCs) membranes�those that typically find application in reverse osmosis and nanofiltration desalination�as cation-selective exchange membranes. Given their negative surface charge under neutral-to-alkaline conditions, PA-TFCs can serve as effective CEMs in these pH regimes. We prepared a series of PA-TFCs from traditional monomers (trimesoyl chloride and piperazine) and compared their thicknesses, charge densities, water transport properties, ion transport properties, and long-term stability in a high pH environment to traditional CEMs (Nafion and FKE) and commercial nanofiltration and reverse osmosis membranes. We find that some of the best-performing PA-TFC membranes have similar resistances and Na + transference numbers compared to Nafion 117 in Na 2 SO 4 and NaHCO 3 -containing solutions. This proof-ofprinciple study suggests that further optimization of PA-TFCs could enable cost-effective ion exchange membrane alternatives to PFSMs.

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The need for ion-exchange membranes with high charge densities

Cited by 34 publications

References 69 publications

Counter-ion Conductivity and Selectivity Trade-Off for Commercial Ion-Exchange Membranes at High Salinities

Counter-ion Conductivity and Selectivity Trade-Off for Commercial Ion-Exchange Membranes at High Salinities

Unifying the Conversation: Membrane Separation Performance in Energy, Water, and Industrial Applications

Polyamide-Based Ion Exchange Membranes: Cation-Selective Transport through Water Purification Membranes

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