Double-tagged self-diffusion and structural properties of water in membranes and ionic solutions

Thau-Alexandrowicz, G.

doi:10.1016/s0376-7388(00)83293-7

Cited by 8 publications

(3 citation statements)

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“…The validity of these assumptions was based on the fact that the values of the self-diffusion coefficients of water traced by three isotopes D, T, and 18 O were found to be very close to each other. 36 Therefore, the HTO-exchange rate profiles were analyzed using eq 3 to deduce self-diffusion coefficients of water in the PIMs. The comparison of experimental data and fitted data is shown in Figure 7.…”

Section: ' Results and Discussionmentioning

confidence: 99%

“…This means that tritium transfer from a water molecule to another in pure water is negligible, and the isotopic effect on diffusion mobility is also within the uncertainty limit of the experimental measurements. The validity of these assumptions was based on the fact that the values of the self-diffusion coefficients of water traced by three isotopes D, T, and 18 O were found to be very close to each other . Therefore, the HTO-exchange rate profiles were analyzed using eq to deduce self-diffusion coefficients of water in the PIMs.…”

Section: Resultsmentioning

confidence: 99%

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Diffusional Transport of Ions in Plasticized Anion-Exchange Membranes

Kumar¹,

Pandey²,

Sharma³

et al. 2011

J. Phys. Chem. B

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Diffusional transport properties of hydrophobic anion-exchange membranes were studied using the polymer inclusion membrane (PIM). This class of membranes is extensively used in the chemical sensor and membrane based separation processes. The samples of PIM were prepared by physical containment of the trioctylmethylammonium chloride (Aliquat-336) in the plasticized matrix of cellulose triacetate (CTA). The plasticizers 2-nitrophenyl octyl ether, dioctyl phthalate, and tris(2-ethylhexyl)phosphate having different dielectric constant and viscosity were used to vary local environment of the membrane matrix. The morphological structure of the PIM was obtained by atomic force microscopy and transmission electron microscopy (TEM). For TEM, platinum nanoparticles (Pt nps) were formed in the PIM sample. The formation of Pt nps involved in situ reduction of PtCl(6)(2-) ions with BH(4)(-) ions in the membrane matrix. Since both the species are anions, Pt nps thus formed can provide information on spatial distribution of anion-exchanging molecules (Aliquat-336) in the membrane. The glass transitions in the membrane samples were measured to study the effects of plasticizer on physical structure of the membrane. The self-diffusion coefficients (D) of the I(-) ions and water in these membranes were obtained by analyzing the experimentally measured exchange rate profiles of (131)I(-) with (nat)I(-) and tritiated water with H(2)O, respectively, between the membrane and equilibrating solution using an analytical solution of Fick's second law. The values of D(I(-)) in membrane samples with a fixed proportion of CTA, plasticizer, and Aliquat-336 were found to vary significantly depending upon the nature of the plasticizer used. The comparison of values of D with properties of the plasticizers indicated that both dielectric constant and viscosity of the plasticizer affect the self-diffusion mobility of I(-) ions in the membrane. The value of D(I(-)) in the PIM samples did not vary significantly with concentration of Aliquat-336 up to 0.5 mequiv g(-1), and thereafter D(I(-)) increased linearly with Aliquat-336 concentration in the membrane. The self-diffusion coefficients of water D(H(2)O) in PIM samples were found to be 1 order of magnitude higher than the value of D(I(-)) and varied slightly depending upon the plasticizer present in the membrane. It was observed in electrochemical impedance spectroscopic studies of the PIM samples that diffusion mobility of NO(3)(-) ions was 1.66 times higher than that of I(-) ions, and diffusion mobility of SO(4)(2-) ions was half of that for I(-) ions. The theoretical interpretation of experimental counterions exchange rate profiles in terms of the Nernst-Planck equation for interdiffusion also showed higher diffusion mobility of NO(3)(-) ions in the PIM than Cl(-), I(-), and ClO(4)(-) ions, which have comparable diffusion mobility.

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Section: ' Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Diffusional Transport of Ions in Plasticized Anion-Exchange Membranes

Kumar¹,

Pandey²,

Sharma³

et al. 2011

J. Phys. Chem. B

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“…(2) that D m H 2 O would be equal to D aq H 2 O at V p = 0. Yasuda and co-workers considered value of D aq H 2 O as self-diffusion coefficient of pure water [24,25], which was reported to be 2.5 × 10 −5 cm 2 /s [29,30]. This was based on the fact that water molecules may move in the water-swollen membrane through preexisting water channels, and the translation oscillation frequency, free energy, entropy, and energy of activation for diffusion of water in the membrane may be same as that of bulk water at given temperature.…”

Section: Resultsmentioning

confidence: 99%