What makes aromatic polyamide membranes superior: New insights into ion transport and membrane structure

Fridman-Bishop, Noga; Freger, Viatcheslav

doi:10.1016/j.memsci.2017.06.035

Cited by 49 publications

(23 citation statements)

References 66 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In this case, R 2 -NH 2 + densities would be representative of the total R 2 -NH content (i.e., surface and interior). The roughly constant value for Br − uptake below pH 7 also suggests that the counterion probe is associating with ionized amine groups rather than being cosorbed alongside protons, as has been recently proposed for fully aromatic polyamides (33)(34)(35). If proton uptake was the predominant means by which Br − was associated into the membrane, one would instead expect an exponential increase in Br − uptake as pH decreases.…”

Section: Areal R 2 -Nhmentioning

confidence: 61%

Ionization behavior of nanoporous polyamide membranes

Ritt

Werber

Wang

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

103

105

View full text Add to dashboard Cite

Escalating global water scarcity necessitates high-performance desalination membranes, for which fundamental understanding of structure–property–performance relationships is required. In this study, we comprehensively assess the ionization behavior of nanoporous polyamide selective layers in state-of-the-art nanofiltration (NF) membranes. In these films, residual carboxylic acids and amines influence permeability and selectivity by imparting hydrophilicity and ionizable moieties that can exclude coions. We utilize layered interfacial polymerization to prepare physically and chemically similar selective layers of controlled thickness. We then demonstrate location-dependent ionization of carboxyl groups in NF polyamide films. Specifically, only surface carboxyl groups ionize under neutral pH, whereas interior carboxyl ionization requires pH >9. Conversely, amine ionization behaves invariably across the film. First-principles simulations reveal that the low permittivity of nanoconfined water drives the anomalous carboxyl ionization behavior. Furthermore, we report that interior carboxyl ionization could improve the water–salt permselectivity of NF membranes over fourfold, suggesting that interior charge density could be an important tool to enhance the selectivity of polyamide membranes. Our findings highlight the influence of nanoconfinement on membrane transport properties and provide enhanced fundamental understanding of ionization that could enable novel membrane design.

show abstract

Section: Areal R 2 -Nhmentioning

confidence: 61%

Ionization behavior of nanoporous polyamide membranes

Ritt

Werber

Wang

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

103

105

View full text Add to dashboard Cite

show abstract

“…This implies that the highly rejecting commercial RO membranes may have a higher crosslinking ratio compared to lower rejecting membranes. Furthermore, recent research [57] showed that the pH dependent performance of seawater polyamide RO membranes cannot be correlated with the pH dependence of the membrane charge. Similarly, in this study the brackish water type Koch XR membrane showed only a small increase in negative surface charge, from -11 to -12 mV, as pH was increased from 6 to 10 while its rejection increased significantly from 55 to 77%.…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Defect-free highly selective polyamide thin-film composite membranes for desalination and boron removal

Ali

Sunbul

Pacheco

et al. 2019

Journal of Membrane Science

107

View full text Add to dashboard Cite

Removal of boron from saline water sources has presented a major challenge for commercially available reverse osmosis desalination membranes. In this work, we report the boron and sodium chloride separation properties of truly defect-free, highly selective, interfacially polymerized aromatic polyamide thin-film composite membranes. The fabricated membranes show potential for separating sodium chloride with a maximum rejection of 99.6% obtained for the optimized film-forming protocol under lab-scale brackish water desalination conditions. This translated into promising boron rejection performance with rejections of up to 99% at pH 10, higher than a number of commercially available reverse osmosis membranes tested in-house. Comprehensive characterization including X-ray photoelectron spectroscopy, atomic force microscopy, scanning electron microscopy, ellipsometry, and surface charge measurements revealed intimate insights on interfacially polymerized polyamide membrane structure-property relationships. Increased membrane crosslinking was shown to be the primary determining factor for membrane permselectivity performance. Furthermore, relationships were established between microstructural properties such as crosslinking and morphological characteristics like surface roughness, highlighting an intricate and complex structure formation mechanism.

show abstract

“…The low molecular mass and chemical properties of VFAs enable NF and RO to be plausible choices. RO membranes offer the tightest pores for pressure-driven processes and accordingly have the highest rejection for ionic species, along with a reasonable water flux and energy consumption thanks to the intensive R&D and optimization works of the past decades by the scientific and industrial community [ 8 , 9 , 10 ]. In RO, solution pH levels where VFAs are mainly in ionized forms seem to increase the retention properties up to 99.7% [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Separation of Volatile Fatty Acids from Model Anaerobic Effluents Using Various Membrane Technologies

et al. 2020

View full text Add to dashboard Cite

Effluents of anaerobic processes still contain valuable components, among which volatile fatty acids (VFAs) can be regarded and should be recovered and/or used further in applications such as microbial electrochemical technology to generate energy/energy carriers. To accomplish the separation of VFAs from waste liquors, various membrane-based solutions applying different transport mechanisms and traits are available, including pressure-driven nanofiltration (NF) and reverse osmosis (RO) which are capable to clarify, fractionate and concentrate salts and organics. Besides, emerging techniques using a membrane such as forward osmosis (FO) and supported liquid membrane (SILM) technology can be taken into consideration for VFA separation. In this work, we evaluate these four various downstream methods (NF, RO, FO and SILM) to determine the best one, comparatively, for enriching VFAs from pH-varied model solutions composed of acetic, butyric and propionic acids in different concentrations. The assessment of the separation experiments was supported by statistical examination to draw more solid conclusions. Accordingly, it turned out that all methods can separate VFAs from the model solution. The highest average retention was achieved by RO (84% at the applied transmembrane pressure of 6 bar), while NF provided the highest permeance (6.5 L/m2hbar) and a high selectivity between different VFAs.

show abstract

What makes aromatic polyamide membranes superior: New insights into ion transport and membrane structure

Cited by 49 publications

References 66 publications

Ionization behavior of nanoporous polyamide membranes

Ionization behavior of nanoporous polyamide membranes

Defect-free highly selective polyamide thin-film composite membranes for desalination and boron removal

Separation of Volatile Fatty Acids from Model Anaerobic Effluents Using Various Membrane Technologies

Contact Info

Product

Resources

About