Characterization of pore size distribution (PSD) in cellulose triacetate (CTA) and polyamide (PA) thin active layers by positron annihilation lifetime spectroscopy (PALS) and fractional rejection (FR) method

Kim, Sung Jo; Kook, Seungho; O’Rourke, Brian; Lee, Jun Young; Hwang, Moon-Hyun; Kobayashi, Yoshinori; Suzuki, Ryoichi; Kim, In Soo

doi:10.1016/j.memsci.2016.12.064

Cited by 49 publications

(27 citation statements)

References 50 publications

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“…PA1, however, had somewhat larger voids that were assumed to have come from the space around the center region of the cell, as shown in Figure 5a. On the other hand, the PA2 model had a void of approximately 0.6 nm, which is very close to the dominant void size of the polyamide material, as measured by PALS [38,39]. Therefore, PA2 exhibited a more reasonable typical polyamide structure.…”

Section: Resultssupporting

confidence: 62%

Molecular Dynamics Simulation Study of Polyamide Membrane Structures and RO/FO Water Permeation Properties

et al. 2018

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Polyamide (PA) membranes possess properties that allow for selective water permeation and salt rejection, and these are widely used for reverse osmotic (RO) desalination of sea water to produce drinking water. In order to design high-performance RO membranes with high levels of water permeability and salt rejection, an understanding of microscopic PA membrane structures is indispensable, and this includes water transport and ion rejection mechanisms on a molecular scale. In this study, two types of virtual PA membranes with different structures and densities were constructed on a computer, and water molecular transport properties through PA membranes were examined on a molecular level via direct reverse/forward osmosis (RO/FO) filtration molecular dynamics (MD) simulations. A quasi-non-equilibrium MD simulation technique that uses applied (RO mode) or osmotic (FO mode) pressure differences of several MPa was conducted to estimate water permeability through PA membranes. A simple NVT (Number, Volume, and Temperature constant ensemble)-RO MD simulation method was presented and verified. The simulations of RO and FO water permeability for a dense PA membrane model without a support layer agreed with the experimental value in the RO mode. This PA membrane completely rejected Na+ and Cl− ions during a simulation time of several nano-seconds. The naturally dense PA structure showed excellent ion rejection. The effect that the void size of PA structure exerted on water permeability was also examined.

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Section: Resultssupporting

confidence: 62%

Molecular Dynamics Simulation Study of Polyamide Membrane Structures and RO/FO Water Permeation Properties

et al. 2018

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“…In a pioneer work Chen et al 44 combined DBES and PAS to measure free volume of TFC membranes as a function of depth. The method has been explored by only a few groups [45][46][47][48][49][50] and has been chosen as the most convenient in this work. observed for the membranes with 100 wt% PAMAM G0, followed by those with 50 wt% PAMAM G0.…”

Section: Resultsmentioning

confidence: 99%

Dendrimeric Thin-Film Composite Membranes: Free Volume, Roughness, and Fouling Resistance

Duong

Zuo

Nunes

2017

Ind. Eng. Chem. Res.

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Copolyamide films with a thickness from 50 to 780 nm were fabricated by interfacial polymerization between mixtures of m-phenylene diamine and primary amine-terminated polyamidoamine dendrimers (PAMAM) in the aqueous phase and trimesoyl chloride (TMC) in the organic phase. Different PAMAM generations (G0, d = 15 Å, Z = 4; G3, d = 36 Å, Z = 32; and G5, d = 54, Z = 128, where d is the measured diameter and Z is the number of terminal groups) and concentrations were used to obtain copolyamide films with different crosslinked structures. The influences of the concentration and degree of branching (PAMAM generation) on free volume were analysed via positon annihilation spectroscopy (PAS) and correlated with the separation properties of copolyamide films. Besides, surface and intrinsic properties of copolyamide films prepared under different conditions were compared. The high hydrophilicity of PAMAM in the copolyamide network leads to the formation of a hydration layer on the copolyamide surface, which minimizes fouling. The separation performance of copolyamide membranes with various PAMAM networks was investigated in forward osmosis (FO) experiments. Understanding the correlation between the PAMAM structure/concentration, free volume, thickness, and surface intrinsic properties leads to the design of suitable fouling resistant thin-film composite membranes in a single interfacial polymerization process.

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“…PALS provides information of pore size and associated free volume, by correlation with the positronium (electron-positron transitory bound state) lifetime. Ortho-positroniums ( o -Ps), which are generated when electrons-positrons with parallel spin states combine, exhibit an intrinsic self-annihilation lifetime of 142 ns in vacuum, which can be shortened by their interaction with free electrons in pores within the structure they penetrate, usually polymeric thin films 20 . The pore size and pore quantity are related to the o -Ps lifetime (labeled τ 3 ) by the Tao-Eldrup model, as described in the materials and methods section and elsewhere 21 , 22 .…”

Section: Resultsmentioning

confidence: 99%

Robust water desalination membranes against degradation using high loads of carbon nanotubes

Ortiz‐Medina

Inukai

Araki

et al. 2018

Sci Rep

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Chlorine resistant reverse osmosis (RO) membranes were fabricated using a multi-walled carbon nanotube-polyamide (MWCNT-PA) nanocomposite. The separation performance of these membranes after chlorine exposure (4800 ppm·h) remained unchanged (99.9%) but was drastically reduced to 82% in the absence of MWCNT. It was observed that the surface roughness of the membranes changed significantly by adding MWCNT. Moreover, membranes containing MWCNT fractions above 12.5 wt.% clearly improved degradation resistance against chlorine exposure, with an increase in water flux while maintaining salt rejection performance. Molecular dynamics and quantum chemical calculations were performed in order to understand the high chemical stability of the MWCNT-PA nanocomposite membranes, and revealed that high activation energies are required for the chlorination of PA. The results presented here confirm the unique potential of carbon nanomaterials embedded in polymeric composite membranes for efficient RO water desalination technologies.

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Characterization of pore size distribution (PSD) in cellulose triacetate (CTA) and polyamide (PA) thin active layers by positron annihilation lifetime spectroscopy (PALS) and fractional rejection (FR) method

Cited by 49 publications

References 50 publications

Molecular Dynamics Simulation Study of Polyamide Membrane Structures and RO/FO Water Permeation Properties

Molecular Dynamics Simulation Study of Polyamide Membrane Structures and RO/FO Water Permeation Properties

Dendrimeric Thin-Film Composite Membranes: Free Volume, Roughness, and Fouling Resistance

Robust water desalination membranes against degradation using high loads of carbon nanotubes

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