Asymmetric polyelectrolyte multilayer membranes with ultrathin separation layers for highly efficient micropollutant removal

Brinke, Esra te; Reurink, Dennis M.; Achterhuis, Iske; Grooth, Joris de; Vos, Wiebe M. de

doi:10.1016/j.apmt.2019.100471

Cited by 40 publications

(86 citation statements)

References 26 publications

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“…According to the structural model of PEMs, one would expect that membranes prepared from [PAH/PAA] will consist of small yet hydrophilic pores, whereas [PSS/PAH] would lead to membranes with larger, more hydrophobic pores. Indeed, this behavior is perfectly reflected in the results of te Brinke et al ( 21 ) shown in Table 3 , where the asymmetric [PSS/PAH] 8.5 [PAH/PAA] 2 and [PSS/PAH] 7.5 [PAH/PAA] 3 membranes have higher micropollutant retentions (and lower MWCO values) and thus lower effective pore sizes than the symmetric [PSS/PAH] 10.5 membranes. In addition, the NR results reveal that [PAH/PAA] layers are more hydrated than the [PSS/PAH] layers (compare 55–63% water content with ∼47%) supporting the hypothesis that the higher charge density [PAH/PAA] layers are more hydrophilic than the [PSS/PAH] layers.…”

Section: Results and Discussionsupporting

confidence: 67%

“…For comparable asymmetric multilayers, te Brinke et al roughly estimated the thicknesses of the top [PAH/PAA] layers to be ∼160 Å for the three-layer system and ∼40 Å for the two-layer system. 21 The discrepancy between the ellipsometry measurements of te Brinke et al and the thicknesses measured here by NR could be due to penetration of [PAH/PAA] into the support multilayer of [PSS/PAH]. While these estimates based on ellipsometry measurements are reasonable, NR reveals that the [PAH/d-PAA] 3 separation layer is thinner than first reported.…”

Section: Results and Discussioncontrasting

confidence: 67%

“…Recently, te Brinke and co-workers 21 showed that it is possible to resolve this problem by coating so-called asymmetric PEMs, a concept first invoked by the Bruening group. 35 , 36 In this approach, 21 a relatively thick [PSS/PAH] multilayer was coated first (support layer, closing the pores) followed by a much thinner [PAA/PAH] multilayer coated on top (separation layer). The improvement in membrane performance was striking, with on average 98% micropollutant retention and 5–10 times higher water permeance compared to commercial membranes with similar micropollutant retentions.…”

Section: Introductionmentioning

confidence: 99%

“…The new findings are then related to the performance of analogous asymmetric PEM membranes recently reported by Reurink et al ( 22 ) and te Brinke et al . 21 …”

Section: Introductionmentioning

confidence: 99%

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Structure and Hydration of Asymmetric Polyelectrolyte Multilayers as Studied by Neutron Reflectometry: Connecting Multilayer Structure to Superior Membrane Performance

et al. 2020

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Porous membranes coated with so-called asymmetric polyelectrolyte multilayers (PEMs) have recently been shown to outperform commercial membranes for micropollutant removal. They consist of open support layers of poly(styrene sulfonate) (PSS)/poly(allylamine) (PAH) capped by denser and more selective layers of either PAH/poly(acrylic acid) (PAA) or PAH/Nafion. Unfortunately, the structure of these asymmetric PEMs, and thus their superior membrane performance, is poorly understood. In this work, neutron reflectometry (NR) is employed to elucidate the multilayered structure and hydration of these asymmetric PEMs. NR reveals that the multilayers are indeed asymmetric in structure, with distinct bottom and top multilayers when air-dried and when solvated. The low hydration of the top [PAH/Nafion] multilayer, together with the low water permeance of comparable [PAH/Nafion]-capped PEM membranes, demonstrate that it is a reduction in hydration that makes these separation layers denser and more selective. In contrast, the [PAH/PAA] capping multilayers are more hydrated than the support [PSS/PAH] layers, signifying that, here, densification of the separation layer occurs through a decrease in the mesh size (or effective pore size) of the top layer due to the higher charge density of the PAH/PAA couple compared to the PSS/PAH couple. The [PAH/PAA] and [PAH/Nafion] separation layers are extremely thin (∼4.5 and ∼7 nm, respectively), confirming that these asymmetric PEM membranes have some of the thinnest separation layers ever achieved.

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Section: Results and Discussionsupporting

confidence: 67%

Section: Results and Discussioncontrasting

confidence: 67%

Section: Introductionmentioning

confidence: 99%

“…The new findings are then related to the performance of analogous asymmetric PEM membranes recently reported by Reurink et al ( 22 ) and te Brinke et al . 21 …”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Structure and Hydration of Asymmetric Polyelectrolyte Multilayers as Studied by Neutron Reflectometry: Connecting Multilayer Structure to Superior Membrane Performance

et al. 2020

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“…The rejection of VFAs is on the lower side in the case of NF compared to RO, especially considering the unusually low pressure applied for RO (with higher pressure, higher rejection can be expected). If the goal is also NaCl (or other monovalent salt) passage besides VFA retention, then further consideration of such LbL NF membranes might be worthwhile, especially if tighter LbL membranes become available commercially, such as the asymmetric membrane developed by te Brinke et al [ 62 ].…”

Section: Discussionmentioning

confidence: 99%

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

et al. 2020

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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.

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Ultrathin Membranes for Separations: A New Era Driven by Advanced Nanotechnology

et al. 2022

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Asymmetric polyelectrolyte multilayer membranes with ultrathin separation layers for highly efficient micropollutant removal

Cited by 40 publications

References 26 publications

Structure and Hydration of Asymmetric Polyelectrolyte Multilayers as Studied by Neutron Reflectometry: Connecting Multilayer Structure to Superior Membrane Performance

Structure and Hydration of Asymmetric Polyelectrolyte Multilayers as Studied by Neutron Reflectometry: Connecting Multilayer Structure to Superior Membrane Performance

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

Ultrathin Membranes for Separations: A New Era Driven by Advanced Nanotechnology

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