Dielectric analysis of nanofiltration membrane in electrolyte solutions: Influences of permittivity of wet membrane and volume charge density on ion permeability

Zhao, Kongshuang; Ni, Guizhi

doi:10.1016/j.jelechem.2011.08.005

Cited by 10 publications

(9 citation statements)

References 30 publications

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“…The dielectric exclusion coefficient decreased at higher concentrations because the water was more confined within the pores, and the Donnan exclusion coefficient increased because the charge density effect was more screened. These findings are in agreement with previous works, reporting that the Donnan effect is more relevant at low feed concentrations and the dielectric effect at high feed concentrations [73,74].…”

Section: Model Results and Discussionsupporting

confidence: 94%

Experimental and theoretical characterization of commercial nanofiltration membranes for the treatment of ion exchange spent regenerant

Micari

Diamantidou

Heijman

et al. 2020

Journal of Membrane Science

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This work presents a joint experimental and simulation campaign aimed at characterizing two nanofiltration membranes (TS80 and NF270) in the presence of a multi-ionic water solution simulating the spent regenerant of cationic ion exchange resins employed for water softening. We identified the membrane parameters, which allowed for predicting the performances through the Donnan Steric Pore Model with Dielectric Exclusion. A good agreement between model and experimental trends of rejection as a function of the applied pressure was observed (error < 15%). The analysis of trans-membrane fluxes and exclusion coefficients showed that dielectric exclusion was the crucial mechanism for the ionic partition. In fact, the lower pore dielectric constant found for TS80 justified the higher rejections to divalent cations with respect to NF270. Moreover, negative charge densities were found for both membranes, because of the high concentration of chloride ions in the feed, which likely adsorbed onto the membrane. However, it was observed that the experimental rejections did not change significantly with the feed pH. This result, in line with the minor role of the Donnan exclusion resulting from the model, suggested that the membrane performances were not much affected by the charge density at high feed ionic strengths (~1 M).

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Section: Model Results and Discussionsupporting

confidence: 94%

Experimental and theoretical characterization of commercial nanofiltration membranes for the treatment of ion exchange spent regenerant

Micari

Diamantidou

Heijman

et al. 2020

Journal of Membrane Science

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“…The EDL only covered ∼18% of the nanochannel, and the electrostatic effect was not very obvious. In addition, the Mg 2+ solvation energy barrier was higher than that of Na + according to the dielectric exclusion effect, making it more difficult across the membrane (calculated by Zhao et al Δ W Na + = 1.88 × 10 –20 J , Δ W Mg 2+ = 6.34 × 10 –20 J ). Therefore, because of the two effects, the α Na + / Mg 2+ was slightly enhanced to the twice of the bulk diffusion coefficient ratio.…”

Section: Results and Discussionmentioning

confidence: 99%

“…In ceramic nanochannels, electrostatic-based ionic selectivity is highly dependent on the surface charge and solution properties. The main influencing factors of ion permeation through the channel are steric, Donnan, and dielectric exclusion effects, among which the Donnan effect plays an important role in low electrolyte concentrations, whereas the dielectric exclusion effect is the dominant influencing factor in high electrolyte concentrations. − Herein, a TiO 2 -based, three-dimensional (3D) nanofluidic transport membrane with a pore size of 2.3 nm was prepared. An external electric field was employed to gate or control the ion transport in the confined channel with nonoverlapped EDL.…”

Section: Introductionmentioning

confidence: 99%

Electric Field-Controlled Ion Transport In TiO₂ Nanochannel

Jing

et al. 2015

ACS Appl. Mater. Interfaces

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On the basis of biological ion channels, we constructed TiO2 membranes with rigid channels of 2.3 nm to mimic biomembranes with flexible channels; an external electric field was employed to regulate ion transport in the confined channels at a high ionic strength in the absence of electrical double layer overlap. Results show that transport rates for both Na+ and Mg2+ were decreased irrespective of the direction of the electric field. Furthermore, a voltage-gated selective ion channel was formed, the Mg2+ channel closed at -2 V, and a reversed relative electric field gradient was at the same order of the concentration gradient, whereas the Na+ with smaller Stokes radius and lower valence was less sensitive to the electric field and thus preferentially occupied and passed the channel. Thus, when an external electric field is applied, membranes with larger nanochannels have promising applications in selective separation of mixture salts at a high concentration.

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“…While the characteristics under working conditions are more closely related to membrane performance and the separation mechanism, such as being soaked in solutions. Dielectric relaxation spectrum (DRS) or electrochemical impedance spectroscopy was widely used to acquire the information of polarized behavior of heterogeneous systems, especially those composed of polymer membranes and electrolytes (membranes in working conditions) [30][31][32]. Many studies on special phenomena in different membrane/solution systems have been reported, such as concentration polarization [33], pore dielectric properties [34], fouling [35] and ion selectivity [36].…”

Section: Introductionmentioning

confidence: 99%

Desalination behavior analysis of interior-modified carbon nanotubes doped membrane by dielectric spectrum and molecular simulation

Zhao

Liu

et al. 2020

Nanotechnology

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Carbon nanotube (CNT)-doped polyamide (PA) membranes have attracted much attention in reverse osmosis (RO) membranes due to their significant advantages of water flux and desalination. In this study, we synthesized multi-walled carbon nanotube (MWNT)/PA RO membrane by 12-oxodidodecanoic acid methyl ester group interior-modified MWNTs (MWNT-C14H25O4). Then, their mechanism of desalination behavior was successfully analyzed by combining dielectric relaxation spectrum (DRS) and molecular dynamics (MD) simulation. DRS analysis mainly focuses on two aspects: (1) the water volume fraction, average pore size and dielectric parameters of MWNT-C14H25O4/PA and PA membranes were obtained by model analysis of DRS data. These data of MWNT-C14H25O4/PA membrane are higher than PA membrane, which indicates that the water flux of the MWNT-C14H25O4/PA membrane was higher than that of the PA membrane. (2) Further analysis shows that the MWNT-C14H25O4/PA membranes have high average charge density, ion solvation barrier and reflection coefficient, which indicates that the added interior-modified MWNT can improve the salt rejection of PA membranes. In the microscopic aspect, the desalination behavior of the MWNT-C14H25O4/PA and PA membrane was analyzed from the aspects of free volume distribution, the dynamic diffusion process of water and ions. The results show that the microscopic data of dynamic simulation well support the conclusion of the DRS method. This study provides a convenient methodology to characterize the properties of the membrane from the aspect of membrane structure.

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Dielectric analysis of nanofiltration membrane in electrolyte solutions: Influences of permittivity of wet membrane and volume charge density on ion permeability

Cited by 10 publications

References 30 publications

Experimental and theoretical characterization of commercial nanofiltration membranes for the treatment of ion exchange spent regenerant

Experimental and theoretical characterization of commercial nanofiltration membranes for the treatment of ion exchange spent regenerant

Electric Field-Controlled Ion Transport In TiO₂ Nanochannel

Desalination behavior analysis of interior-modified carbon nanotubes doped membrane by dielectric spectrum and molecular simulation

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Dielectric analysis of nanofiltration membrane in electrolyte solutions: Influences of permittivity of wet membrane and volume charge density on ion permeability

Cited by 10 publications

References 30 publications

Experimental and theoretical characterization of commercial nanofiltration membranes for the treatment of ion exchange spent regenerant

Experimental and theoretical characterization of commercial nanofiltration membranes for the treatment of ion exchange spent regenerant

Electric Field-Controlled Ion Transport In TiO2 Nanochannel

Desalination behavior analysis of interior-modified carbon nanotubes doped membrane by dielectric spectrum and molecular simulation

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Electric Field-Controlled Ion Transport In TiO₂ Nanochannel