The electrostatic and steric-hindrance model for the transport of charged solutes through nanofiltration membranes

Wang, Xiaolin; Tsuru, Toshinori; Nakao, Shin-ichi; Shoji, K.

doi:10.1016/s0376-7388(97)00125-7

Cited by 322 publications

(155 citation statements)

References 36 publications

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“…Because the ion transport is dominated by flow through large uncovered pores (B100 nm in diameter), steric hindrance effects are not significant 27,28 and ions can go through the pores without much retardation 5 , so that we can describe our system using the Donnan theory for membrane equilibria 29 . In the Donnan model, the rejection, R, of an ionic species is controlled by the charge density of the membrane via 30…”

Section: Resultsmentioning

confidence: 99%

“…In addition, the presence of pores that are partially covered and thus have a smaller effective size could inflate the charge density extracted from the measurements. Lastly, some deviations from a 1/r scaling could come from the assumption of a purely Donnanbased rejection mechanism, which would explain deviations at smaller pore sizes [27][28][29]34 . At large pore sizes, especially for the bare PC substrates, we believe sample-to-sample and measurement uncertainties are responsible.…”

Section: Resultsmentioning

confidence: 99%

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Ion transport controlled by nanoparticle-functionalized membranes

et al. 2014

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From proton exchange membranes in fuel cells to ion channels in biological membranes, the well-specified control of ionic interactions in confined geometries profoundly influences the transport and selectivity of porous materials. Here we outline a versatile new approach to control a membrane's electrostatic interactions with ions by depositing ligand-coated nanoparticles around the pore entrances. Leveraging the flexibility and control by which ligated nanoparticles can be synthesized, we demonstrate how ligand terminal groups such as methyl, carboxyl and amine can be used to tune the membrane charge density and control ion transport. Further functionality, exploiting the ligands as binding sites, is demonstrated for sulfonate groups resulting in an enhancement of the membrane charge density. We then extend these results to smaller dimensions by systematically varying the underlying pore diameter. As a whole, these results outline a previously unexplored method for the nanoparticle functionalization of membranes using ligated nanoparticles to control ion transport.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Ion transport controlled by nanoparticle-functionalized membranes

et al. 2014

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“…Glucose, saccharose, raffinose, and α-cyclodextrin were purchased from Sigma-Aldrich (USA). Molecular weights, diffusivity properties, and Stokes radii of the neutral solutes are listed in Table 1 [32]. High-purity Milli-Q water with an electrical resistivity of 18.2 MΩ cm was used in all experiments.…”

Section: Methodsmentioning

confidence: 99%

Fabrication of novel poly(m-phenylene isophthalamide) hollow fiber nanofiltration membrane for effective removal of trace amount perfluorooctane sulfonate from water

Wang

Zhao

et al. 2015

Journal of Membrane Science

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a b s t r a c tThis study investigated the separation performance of a hollow fiber nanofiltration membrane, which was fabricated from poly(m-phenylene isophthalamide) (PMIA) using a dry-jet wet spinning technology, for sustainable water recovery from water containing trace amount of perfluorooctane sulfonate (PFOS) that was a persistent organic pollutant commonly existed in water. SEM spectra indicated that the cross section of the hollow fiber membrane had an asymmetrical structure that consisted of a dense outer surface acting as a selectively layer, a spongy-like transition layer, and finger-like microvoids close to the inner surface. The average pore size and molecular weight cut-off, which were estimated using the solute rejection method, were 0.404 nm and 904 Da, respectively. The PFOS rejection experiments were carried out at the trans-membrane pressures ranging from 4 Â 10 5 Pa to 1.0 Â 10 6 Pa and PFOS concentrations from 50 μg/L to 500 μg/L. In all cases, the PFOS rejections were found to be increased as the PFOS concentration increased. The impact of the pH value and Ca 2 þ concentration of the feed solution on the PFOS rejections was studied in detail. The PFOS rejections improved from 91.17% to 97.49% with an increase in pH from 3.2 to 9.5 at 4 Â 10 5 Pa. An increase of Ca 2 þ concentration from 0.1 mM to 2 mM enhanced PFOS rejection from 97.10% to 99.40% at a trans-membrane pressure of 4 Â 10 5 Pa. The sorption/desorption experiments indicated that the amount of PFOS adsorbed on the membrane surface was five times higher in the presence of Ca 2 þ (2 mM). AFM experiments also demonstrated that the membrane surface was rough with the addition of Ca 2 þ . Hence, the presence of Ca 2 þ enhanced the PFOS adsorption in the membrane surface and caused more pore blockage of the membrane. As such, the declination in the water flux and augmentation in the PFOS rejection were observed.

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“…Three kinds of P(AN-co-AA) copolymers prepared with a AA fraction of 10 mol%, 15 mol% and 26 mol%, [23] were used as base membranes for ESA treatment. Then, the surfaces were modified with ESA layers of CTAC and PAA to study the effect of AA fractions contained in the base membrane on the removal properties of modified membranes.…”

Section: Ir Measurement Of Membranes With Esa Multilayermentioning

confidence: 99%