Molecular methods for assessing the morphology, topology, and performance of polyamide membranes

Vickers, Riley; Weigand, T. M.; Miller, Cass T.; Coronell, Orlando

doi:10.1016/j.memsci.2021.120110

Cited by 19 publications

(9 citation statements)

References 64 publications

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“…Specifically, many of the current collaborations to explore transport in membranes are based on extensive experimental work supported by some simulated data. Notably, such simulated data are most often generated using model pores or channels that are structurally far different and simpler than polymeric RO and NF membranes, rendering the support for the experimental work highly qualitative and nonspecific. ,, Despite the highly cross-linked and void-like nature of polyamide’s porous structure, which makes the simulation of the polyamide layer quite challenging, there are a few successful reports on the simulation of the polyamide layer of RO or NF membranes that support specific experimental data. ,− Beside the increased structural similarity required between real membranes and simulated pore systems, enthalpic and entropic barriers generated by molecular simulations for specific transport phenomena can help break down effective experimental barriers into local and more specific barriers.…”

Section: Future Research Needs and Outlookmentioning

confidence: 99%

Applying Transition-State Theory to Explore Transport and Selectivity in Salt-Rejecting Membranes: A Critical Review

Shefer

Lopez

Straub

et al. 2022

Environ. Sci. Technol.

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Membrane technologies using reverse osmosis (RO) and nanofiltration (NF) have been widely implemented in water purification and desalination processes. Separation between species at the molecular level is achievable in RO and NF membranes due to a complex and poorly understood combination of transport mechanisms that have attracted the attention of researchers within and beyond the membrane community for many years. Minimizing existing knowledge gaps in transport through these membranes can improve the sustainability of current water-treatment processes and expand the use of RO and NF membranes to other applications that require high selectivity between species. Since its establishment in 1949, and with growing popularity in recent years, Eyring’s transition-state theory (TST) for transmembrane permeation has been applied in numerous studies to mechanistically explore molecular transport in membranes including RO and NF. In this review, we critically assess TST applied to transmembrane permeation in salt-rejecting membranes, focusing on mechanistic insights into transport under confinement that can be gained from this framework and the key limitations associated with the method. We first demonstrate and discuss the limited ability of the commonly used solution-diffusion model to mechanistically explain transport and selectivity trends observed in RO and NF membranes. Next, we review important milestones in the development of TST, introduce its underlying principles and equations, and establish the connection to transmembrane permeation with a focus on molecular-level enthalpic and entropic barriers that govern water and solute transport under confinement. We then critically review the application of TST to explore transport in RO and NF membranes, analyzing trends in measured enthalpic and entropic barriers and synthesizing new data to highlight important phenomena associated with the temperature-dependent measurement of the activation parameters. We also discuss major limitations of the experimental application of TST and propose specific solutions to minimize the uncertainties surrounding the current approach. We conclude with identifying future research needs to enhance the implementation and maximize the benefit of TST application to transmembrane permeation.

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Section: Future Research Needs and Outlookmentioning

confidence: 99%

Applying Transition-State Theory to Explore Transport and Selectivity in Salt-Rejecting Membranes: A Critical Review

Shefer

Lopez

Straub

et al. 2022

Environ. Sci. Technol.

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“…Concerning the non-equilibrium simulation of pure and brine water, 0.1 MPa (standard atmosphere) and an initial simulation time 2 ns are first exerted to the graphene sheets to allow the solutions and PA membrane to equilibrate under the NVT ensemble at 300 K fully. And then, a higher pressure (ΔP = 30, 60, 90, 120, or 150 MPa) is applied to the left graphene piston on the feed side while keeping the right graphene piston at 0.1 MPa under the NVT ensemble at 300 K. Compared with the typical PA RO membrane processes, these higher pressures can facilitate the well-converged statistics within a reasonable time scale [69][70][71]. Besides, Gaussian velocity distribution is used for initializing the initial temperature-consistent of molecules, and a Nosé-Hoover thermostat [72,73] is employed to maintain the system at 300 K under the NVT ensemble.…”

Section: Nemd Simulations For Ro Desalination Through Pa Membranementioning

confidence: 99%

Molecular insights into the structure-property relationships of 3D printed polyamide reverse-osmosis membrane for desalination

Yang

McCutcheon

et al. 2022

Journal of Membrane Science

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“…Existing molecular models, while decent representations of actual membranes, are not perfect (Figure a). The distance-based criterion, noted above, neglects the realistic chemistry of polymerization by physically defining bond formation, rather than chemically. ,, The inability to model the realistic chemistry of polymerization also obscures the formation of functional groups across the membrane. Existing models require rough estimation of functional group density that is arbitrarily dispersed across the polymer networkan inaccurate reflection of chemical inhomogeneities common to polymer membranes .…”

Section: Models Structurally Representative Of Membranesmentioning

confidence: 99%

“…The simulated polymerization relies on a simple heuristic criterion, where a new bond is introduced when the intermolecule distance between polymer chains is within a predefined distance. These distance-based methods lack detailed information about polymerization reaction chemistry. ,, Fidelity in simulations for predicting ion and water transport at the molecular level depends on the level of structural and chemical accuracy of membrane models.…”

Section: Introductionmentioning

confidence: 99%

Molecular Simulations to Elucidate Transport Phenomena in Polymeric Membranes

Heiranian

DuChanois

Ritt

et al. 2022

Environ. Sci. Technol.

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Despite decades of dominance in separation technology, progress in the design and development of high-performance polymer-based membranes has been incremental. Recent advances in materials science and chemical synthesis provide opportunities for molecular-level design of next-generation membrane materials. Such designs necessitate a fundamental understanding of transport and separation mechanisms at the molecular scale. Molecular simulations are important tools that could lead to the development of fundamental structure–property–performance relationships for advancing membrane design. In this Perspective, we assess the application and capability of molecular simulations to understand the mechanisms of ion and water transport across polymeric membranes. Additionally, we discuss the reliability of molecular models in mimicking the structure and chemistry of nanochannels and transport pathways in polymeric membranes. We conclude by providing research directions for resolving key knowledge gaps related to transport phenomena in polymeric membranes and for the construction of structure–property–performance relationships for the design of next-generation membranes.

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Molecular methods for assessing the morphology, topology, and performance of polyamide membranes

Cited by 19 publications

References 64 publications

Applying Transition-State Theory to Explore Transport and Selectivity in Salt-Rejecting Membranes: A Critical Review

Applying Transition-State Theory to Explore Transport and Selectivity in Salt-Rejecting Membranes: A Critical Review

Molecular insights into the structure-property relationships of 3D printed polyamide reverse-osmosis membrane for desalination

Molecular Simulations to Elucidate Transport Phenomena in Polymeric Membranes

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