Nanoscale Chemical Heterogeneity in Aromatic Polyamide Membranes for Reverse Osmosis Applications

McGilvery, Catriona M.; Abellán, Patricia; Kłosowski, Michał M.; Livingston, Andrew G.; Cabral, João T.; Ramasse, Quentin M.; Porter, Alexandra E.

doi:10.1021/acsami.0c01473

Cited by 14 publications

(9 citation statements)

References 35 publications

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“…The presence of functional groups in the active layer determines the physicochemical properties of the membrane. McGilvery et al [ 59 ] have stated that the type and concentration of functional groups present in the membrane active layer affect membrane–solute and membrane–solvent interactions. In turn, membrane performance such as permeability and rejection is influenced.…”

Section: Resultsmentioning

confidence: 99%

Characterization of Selected Polymeric Membranes Used in the Separation and Recovery of Palladium-Based Catalyst Systems

et al. 2020

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Membrane separation processes tender a capable option for energy-demanding separation processes. Nanofiltration (NF) and reverse osmosis (RO) membranes are among the most explored, with a latent use in the chemical industry. In this study, four commercial membranes (NF90, NF270, BW30, and XLE) were investigated for their applicability based on the key structural performance characteristics in the recycling of Pd-based catalysts from Heck coupling post-reaction mixture. Pure water and organic solvent permeabilities, uncharged solute permeability, swelling, and catalyst rejection studies of the membranes were conducted as well as the morphological characterization using Fourier transform infrared, field emission gun scanning electron microscopy, and atomic force microscopy. Characterization results showed trends consistent with the manufactures’ specifications. Pure water and organic solvent fluxes generally followed the trend NF270 > NF90 > BW30 > XLE, with the solvent choice playing a major role in the separation process. Pd(PPh3)2Cl2 was well rejected by almost all membranes in 2-propanol; however, XLE rejects Pd(OAc)2 better at high pressure in acetonitrile. Our study, therefore, revealed that the separation and reuse of the two catalysts by NF90 at 10 bar resulted in 97% and 49% product yields with 52% and 10% catalyst retention for Pd(OAc)2 while Pd(PPh3)2Cl2. gave 87% and 6% yields with 58% and 36% catalyst retention in the first and second cycles, respectively. Considering, the influence of membrane–solute interactions in Pd-catalyst rejection, a careful selection of the polymeric membrane and solvent, a satisfactory separation, and recovery can be achieved.

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Section: Resultsmentioning

confidence: 99%

Characterization of Selected Polymeric Membranes Used in the Separation and Recovery of Palladium-Based Catalyst Systems

et al. 2020

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“…We finally consider how our diffusion data can be predictively related to the macroscopic performance observed in PA RO membranes, and specifically on the water permeance (L m −2 h −1 bar −1 , defined by the flux normalized by the applied hydraulic pressure. Estimating transport across a PA membrane, with active and inactive, connected and disjoined, permeation pathways, is evidently challenging, and work is still needed to resolve membrane structure at the nanoscale 17,18,52 at in or near operando conditions. A number of engineering models 9 take into account membrane observables, including water uptake, an "effective" thickness, and mass or density changes (from which a "void fraction" and water partition coefficient are computed) to infer molecular diffusion parameters from permeance data, subject to a series of assumptions 49 .…”

Section: Resolving Controversy With Previous Qens Measurementsmentioning

confidence: 99%

“…PA membrane formation via IP proceeds dynamically via a mechanism of cluster formation, diffusion-limited aggregation, and percolation, resulting in a well-known inhomogeneous film structure with a distribution of pore sizes, functional group asymmetry and surface polarization [10][11][12][13][14][15][16][17][18] . TMC/MPD oligomeric "clusters" are thought to form and coalesce to yield a "coherent film" of dense clusters within lower-density structures, which have been analytically and numerically modeled 14,15,19,20 .…”

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confidence: 99%

Multimodal confined water dynamics in reverse osmosis polyamide membranes

et al. 2022

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While polyamide (PA) membranes are widespread in water purification and desalination by reverse osmosis, a molecular-level understanding of the dynamics of both confined water and polymer matrix remains elusive. Despite the dense hierarchical structure of PA membranes formed by interfacial polymerization, previous studies suggest that water diffusion remains largely unchanged with respect to bulk water. Here, we employ neutron spectroscopy to investigate PA membranes under precise hydration conditions, and a series of isotopic contrasts, to elucidate water transport and polymer relaxation, spanning ps-ns timescales, and Å-nm lengthscales. We experimentally resolve, for the first time, the multimodal diffusive nature of water in PA membranes: in addition to (slowed down) translational jump-diffusion, we observe a long-range and a localized mode, whose geometry and timescales we quantify. The PA matrix is also found to exhibit rotational relaxations commensurate with the nanoscale confinement observed in water diffusion. This comprehensive ‘diffusion map’ can anchor molecular and nanoscale simulations, and enable the predictive design of PA membranes with tuneable performance.

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“…RO processes use hydraulic pressure from pumps to generate a flow of clean water through a membrane. The energy requirement for seawater RO (SWRO) in the 1970's was over 15 kwh/m 3 , but has been reduced to 2.5-3.5 kwh/m 3 due to technological innovations such as high efficiency pumps and energy recovery systems. 8 However, this requirement is still higher than the theoretical absolute minimum of 1.06 kwh/m 3 at a typical recovery of 50%.…”

Section: Introductionmentioning

confidence: 99%

“…Water scarcity is listed as one of the largest global risks, requiring the development of inexpensive, effective and industrially scalable desalination technology. Desalination has become a promising approach for producing fresh water in the face of global population growth and rapid industrialization; however, it is still considered a cost- and energy-intensive technology. − Desalination using reverse osmosis (RO) has continuously grown its installed capacity worldwide, largely replacing the traditional distillation process, as distillation consumes much larger quantities of energy. RO processes use hydraulic pressure from pumps to generate a flow of clean water through a membrane.…”

Section: Introductionmentioning

confidence: 99%

Composite Membranes with Nanofibrous Cross-Hatched Supports for Reverse Osmosis Desalination

Kim

Heath

Kentish

2020

ACS Appl. Mater. Interfaces

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A novel membrane structure comprised of cross-hatched electrospun nanofibers is developed. We illustrate that this novel structure allows for much higher water permeability when used as a support for reverse osmosis thin-film composite membranes. Reinforcement and lamination of the aligned nanofibres generates mechanically robust structures that retain very high porosity and low tortuosity when applied to high pressure seawater desalination operations. The cross-hatched nanofibre layers support the polyamide active layer firmly and reduce resistance to water flow due to the high porosity, low tortuosity, high mechanical strength and minimal thickness of the structures. The nanofibre composite membrane gives a water flux significantly greater than when a traditional support layer is used, at 99 ± 5 m -2 h -1 with NaCl rejection of 98.7 % at 15.5 bar.

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Nanoscale Chemical Heterogeneity in Aromatic Polyamide Membranes for Reverse Osmosis Applications

Abstract: This is a repository copy of Nanoscale chemical heterogeneity in aromatic polyamide membranes for reverse osmosis applications.

Cited by 14 publications

References 35 publications

Characterization of Selected Polymeric Membranes Used in the Separation and Recovery of Palladium-Based Catalyst Systems

Characterization of Selected Polymeric Membranes Used in the Separation and Recovery of Palladium-Based Catalyst Systems

Multimodal confined water dynamics in reverse osmosis polyamide membranes

Composite Membranes with Nanofibrous Cross-Hatched Supports for Reverse Osmosis Desalination

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