Impact of Cation–Ligand Interactions on the Permselectivity of Ligand-Functionalized Polymer Membranes in Single and Mixed Salt Systems

Sachar, Harnoor Singh; Zofchak, Everett S.; Marioni, Nico; Zhang, Zidan; Kadulkar, Sanket; Duncan, Tyler J.; Freeman, Benny D.; Ganesan, Venkat

doi:10.1021/acs.macromol.2c00543

Cited by 14 publications

(27 citation statements)

References 45 publications

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“…The net effect on S i/j , hence, depends on the modifications to , , , and , and the eventual outcome on separation selectivity can swing either way. While the previous studies reported selective transport of the complexed ion (Chaudhury et al, 2014;Sheng et al, 2014;Tas et al, 2016;DuChanois et al, 2022;Sachar et al, 2022), a recent atomistic molecular dynamics simulation found that coordination chemistry will actually favor the transport of noncomplexing species (Zofchak et al, 2022). The reversal in trend is caused by exceedingly strong ligand-ion interactions drastically retarding mobility of the coordinated ion, overwhelming the benefits of higher partitioning.…”

Section: Specific Ion Selectivitymentioning

confidence: 94%

Advancing ion-exchange membranes to ion-selective membranes: principles, status, and opportunities

Fan

Huang

Yip

2022

Front. Environ. Sci. Eng.

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Ion-exchange membranes (IEMs) are utilized in numerous established, emergent, and emerging applications for water, energy, and the environment. This article reviews the five different types of IEM selectivity, namely charge, valence, specific ion, ion/solvent, and ion/uncharged solute selectivities. Technological pathways to advance the selectivities through the sorption and migration mechanisms of transport in IEM are critically analyzed. Because of the underlying principles governing transport, efforts to enhance selectivity by tuning the membrane structural and chemical properties are almost always accompanied by a concomitant decline in permeability of the desired ion. Suppressing the undesired crossover of solvent and neutral species is crucial to realize the practical implementation of several technologies, including bioelectrochemical systems, hypersaline electrodialysis desalination, fuel cells, and redox flow batteries, but the ion/solvent and ion/uncharged solute selectivities are relatively understudied, compared to the ion/ion selectivities. Deepening fundamental understanding of the transport phenomena, specifically the factors underpinning structure-property-performance relationships, will be vital to guide the informed development of more selective IEMs. Innovations in material and membrane design offer opportunities to utilize ion discrimination mechanisms that are radically different from conventional IEMs and potentially depart from the putative permeability-selectivity tradeoff. Advancements in IEM selectivity can contribute to meeting the aqueous separation needs of water, energy, and environmental challenges.

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Section: Specific Ion Selectivitymentioning

confidence: 94%

Advancing ion-exchange membranes to ion-selective membranes: principles, status, and opportunities

Fan

Huang

Yip

2022

Front. Environ. Sci. Eng.

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“…Such trends arise as a result of a reduction in the self-diffusivity of the LS cations as discussed in our previous work. 23 Similarly, the true salt diffusivity ratio also decreases with an increase in ϵ LS Cation-Ligand . However, in comparing the two results (ideal and true salt diffusivity ratios), ionic correlations are seen to increase the salt diffusivity ratio at high LS cation−ligand interaction strengths (ϵ LS Cation-Ligand / k B T > 3.0) but have negligible impact on the salt diffusivity ratio at low LS cation−ligand interaction strengths (up to ϵ LS Cation-Ligand /k B T = 3.0).…”

Section: Impact Of Ionic Correlations In Mixed Saltmentioning

confidence: 94%

“…The ideal salt diffusivity ratio [i.e., D LS Salt ideal /D LA Salt ideal ] decreases with increasing ϵ LS Cation-Ligand primarily because of the reduction in the LS cation self-diffusivity as discussed in our previous manuscript. 23 From Figure 2b, the true salt diffusivity ratio [i.e., D LS Salt GK / D LA Salt GK ] is seen to be lower than the ideal salt diffusivity ratio (albeit only marginally) at low values of ϵ LS Cation-Ligand (ϵ LS Cation−Ligand /k B T = 1, 2, 3), whereas the converse is true at relatively high values of ϵ LS Cation-Ligand (ϵ LS Cation−Ligand /k B T = 4, 5, 6). In other words, ionic correlations are seen to reduce (marginally enhance) the selective transport of LA salt relative to LS salt at high (low) LS cation−ligand interaction strengths.…”

Section: Impact Of Ionic Correlations In Single Saltmentioning

confidence: 99%

“…The initial increase in ideal salt diffusivity ratio (with ϵ LS Cation-Ligand ) of single salt systems relative to that of mixed salt systems stems from the fact that the anions enhance ideal salt diff usivity ratio in single salt systems but do not explicitly affect the ideal salt dif f usivity ratio in mixed salt systems, as explained in our prior manuscript. 23 As a result, the reduction of ideal LS salt diffusivity relative to the ideal LA salt diffusivity upon an initial increase in ϵ LS Cation-Ligand is less pronounced in single salt systems (compared to their mixed salt counterparts).…”

Section: Comparison Of Single and Mixed Salt Systemsmentioning

confidence: 99%

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Impact of Ionic Correlations on Selective Salt Transport in Ligand-Functionalized Polymer Membranes

et al. 2023

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We present a theoretical formalism quantifying the interplay between cation–ligand interaction strength and dynamical ionic correlations on salt diffusivities in the transport of single salt and binary (mixed) salts through ligand-functionalized polymer membranes. The Onsager framework is utilized to capture the effect of correlated ionic motions on salt diffusivities. Such a framework is implemented in the context of a coarse-grained model of systems involving ligand-selective (LS) and/or ligand-agnostic (LA) salts in ligand-functionalized polymer membranes. Our results indicate that ionic correlations speed up the diffusivities of both LS and LA salts relative to the ideal, uncorrelated case. At small values of cation–ligand interaction strength, such a speedup arises from a general trend of positively correlated motion among the mobile ions. On the other hand, ionic correlation-mediated speedup in salt diffusivities at large values of cation–ligand interaction strength can be attributed to the correlated hopping of the cations bound to the ligands in both single and mixed salt systems. At low cation–ligand interaction strengths, ionic correlations reduce the ratio of salt diffusivities of LS to LA salts (relative to the uncorrelated case) in single salt systems. Disparately, ionic correlations enhance the ratio of salt diffusivities of LS to LA salts (relative to the uncorrelated case) at large values of the cation–ligand interaction strengths in both single and mixed salt systems. We observe that single salt systems exhibit higher LS to LA salt diffusivity ratios than their mixed salt analogs up to a certain value of the cation–ligand interaction strength, beyond which the salt diffusivity ratios for the two systems converge.

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“…For example, Wieland et al observed that the measured conductivities in such systems are only a fraction of the conductivity expected based on the ideal (Nernst–Einstein) ion diffusivities . Simulation results demonstrated such observations to be a consequence of dynamical correlations, that is, the influence of dynamics of one or more of the ions on the motion of a different ion. , In the case of polyILs, such correlations were shown to arise from both between the mobile ion and the immobilized ions on the polymer backbone. Studies in the context of solvated polyelectrolytes have also demonstrated similar results and underlying mechanisms. , …”

mentioning

confidence: 99%

Ion Correlations and Partial Ionicities in the Lamellar Phases of Block Copolymeric Ionic Liquids

Zhang

Sass

Krajniak³

et al. 2022

ACS Macro Lett.

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Recently, significant interest has arisen on the impact of dynamical ion correlations on the conductivity and transport properties of polymeric electrolyte materials. It has been hypothesized that confining ion motion to narrow channels may reduce such ion correlations and enhance the resulting ionic conductivity. Motivated by such considerations, in this study we used a multiscale simulation framework to study the dynamical ion correlations in the microphase-separated lamella phase of block copolymeric ionic liquids and compare with the corresponding results for homopolymeric systems. We probed the influence of ion correlations through the partial ionicity, Δ, which quantifies the ratio of true conductivity to the ideal, Nernst–Einstein conductivity for the anion-related contributions. Consistent with our original hypothesis, our results demonstrate that the partial ionicity relating to the mobile anions is much larger in the lamella phases of block copolymers compared to that in homopolymers. Analysis of the distinct conductivity contributions demonstrates that such results arise as a result of an intricate compensation among the nonideal dynamical correlations relating to anions in lamella phases. Together, our results suggest that self-assembled phases of block copolymers may provide an avenue to tune the dynamical ion correlations in polymer electrolyte systems.

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Impact of Cation–Ligand Interactions on the Permselectivity of Ligand-Functionalized Polymer Membranes in Single and Mixed Salt Systems

Cited by 14 publications

References 45 publications

Advancing ion-exchange membranes to ion-selective membranes: principles, status, and opportunities

Advancing ion-exchange membranes to ion-selective membranes: principles, status, and opportunities

Impact of Ionic Correlations on Selective Salt Transport in Ligand-Functionalized Polymer Membranes

Ion Correlations and Partial Ionicities in the Lamellar Phases of Block Copolymeric Ionic Liquids

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