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Chronopotentiometric characterization of electrodialysis module

Koter S., Guler C., Koter I.

Architecture Civil Engineering Environment

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2016

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Vol. 9, no. 3

129--133

EN

Classical and chronopotentiometric characterization of the electrodialysis module at the same concentrations of diluate and concentrate was performed. Limiting current was determined from the Cowan-Brown plot, the current efficiency and the mean transport number of counterions – from the concentration changes on the exit of the ED module. The electric resistance was determined from the chronopotentiometric curve. For electric currents higher than the limiting one, the transition time (inflection point) was observed. Thus, having such curves for different values of electric current, the limiting current can be roughly estimated. To estimate a mean counterion transport number from the transition time, an equation, analogous to the Sand equation, should be developed which include both types of membrane.

PL

Przedstawiono krzywe chronopotencjometryczne elektrodialitycznego modułu membranowego, Stwierdzono, że na ich podstawie można określić, czy zastosowane natężenie prądu nie przekracza prądu granicznego, a tym samym w przybliżeniu określić wartość tego ostatniego. Oszacowana na podstawie kilku krzywych chronopotencjo-metrycznych wartość prądu granicznego jest zgodna z wyznaczoną wartością na podstawie wykresu Cowana-Browna. Obserwowane na krzywych punkty przegięcia można wykorzystać do wyznaczenia średniej liczby przenoszenia przeciwjonów. W tym celu należy wyprowadzić równanie analogiczne do wzoru Sanda, które by brało pod uwagę oba chronopotencjometryczne pozwoliły na proste i szybkie wyznaczenie oporu elektrycznego modułu.

2

Leakage of mono- and divalent cations through the weak-base anion exchange membrane in the process of electrodialysis of H2SO4 and its metal salt mixture

Kultys M., Koter S., Gilewicz-Łukasik B., Koter I.

Ars Separatoria Acta

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2011

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No. 8

101-108

EN

Experimental results on the separation of sulfuric acid from its mixture with sodium- and magnesium sulfate, respectively, by the electrodialytic method have been presented. The Selemion AVV membrane as anion-exchange membrane was used. It was found that the leakage of Na+ from the cathode to the anode side of the AAV was higher than that of Mg2+. The leakage of Na+ decreased with the acid concentration whereas that of Mg2+ increased. Surprisingly enough, the permeability of Na+ increased with the electric current density, indicating a substantial contribution of electroosmotic convection to the Na+ flow. The current efficiency of the anions transport (HSO4 -, SO4 2-) through the AAV hardly exceeded 50%. It was independent of the kind of salt present on the cathode side of the AAV.

3

Autooxidation of leuco-Methylene Blue – the Role of the Methylene Blue Radicals and Reactive Oxygen Species

Katafias A., Koter S.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 6

1139-1146

EN

Autooxidation of leuco-Methylene Blue to the dye, Methylene Blue, was studied in the 1.9–7.8 pH range under a large molar excess of dioxygen dissolved in the reaction solution using electronic spectroscopy. The synproportionation of the substrate and the reaction product, yielding Methylene Blue radical, plays a key role in the over all redox process. Numerical simulation of the complicated kinetic curves shows that presence of this radical opens an effective reaction path for the autooxidation process and results in coupling of the reaction steps. Reactive oxygen species (HO2 ź /O2 ź - / and H2O2) formed in the examined system are not effective oxidants and do not affect the autooxidation kinetics under applied conditions.

4

Application of Molecular Descriptors to the Prediction of Retention in Organic Solvent Nanofiltration

Koter S., Gilewicz-Łukasik B., Nowaczyk A., Nowaczyk J.

Polish Journal of Chemistry

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2009

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Vol. 83, nr 12

2137-2152

EN

An attempt to apply the molecular descriptors for the characterization of retention of solutes in organic solvent nanofiltration has been performed. The descriptors were calculated using the program Dragon. The geometry of each solute molecule has been optimized using GaussianŽ. Two linear equations relating the retention coefficient, R, with one or two descriptors have been tested using two sets of solutes. The first one (“soft” set) consisted of saturated and aromatic hydrocarbons (data of White, J. Membr.Sci., 205, 191 (2002)), the second one (“hard” set) contained the substituted aromatic hydro carbons with heteroatoms (data of Geens et al., J. Membr. Sci., 281, 139 (2006)). It has been found that the “soft” set of compounds is described reasonably well by both equations. The best descriptors belong to GET AWAY descriptors and Burdeneigen values. Regarding the “hard” set of compounds only the 2-descriptors equation yields a satisfactory fitting of R. Here the 3D-MoRSE descriptors are the best for 7 of 14 membrane-solvent systems.

5

Transport przez membrany jonowymienne w ujęciu modelu kapilarnego

Koter S.

Zeszyty Naukowe. Inżynieria Środowiska / Politechnika Śląska

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2002

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z. 46

303-312

PL

Do opisu transportu przez membrany jonowymienne zaproponowano model kapilarny oparty na termodynamice nierównowagowej. Stwierdzono, że z pewnymi ograniczeniami model ten można stosować do przewidywań właściwości transportowych układów membranowych.

EN

The capillary model of transport through ion-exchange membranes, based on the nonequilibrium thermodynamics, has been presented and compared with the experiment data. It has been found that the agreement of model with the experiment data is reasonably good and with some limitations it can be used for the prediction of transport properties of membrane systems.

6

Porównanie odwróconej osmozy i perwaporacji w rozdziale mieszaniny woda-metanol

Koter S., Kujawski W.

Zeszyty Naukowe. Inżynieria Środowiska / Politechnika Śląska

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2002

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z. 46

331-338

PL

Przedstawiono uogólnione równania wg modelu rozpuszczania-dyfuzji, pozwalające porównać selektywność membran w procesie odwróconej osmozy (RO) i perwaporacji (PV). W rozwiązaniu przyjęto, że każdy ze składników może być traktowany jako rozpuszczalnik, a skład transportowanej mieszaniny wyrażono za pomocą ułamków molowych. Eksperymentalnie wyznaczono wartości współczynników selektywności membrany Nafion 117 w formie Na+, w rozdziale mieszaniny woda-metanol techniką RO i PV. Wyniki eksperymentalne porównano z przewidywaniami modelu rozpuszczania-dyfuzji. Stwierdzono, że w przypadku roztworów o dużej zawartości metanolu wyniki obliczeń różnią się znacznie od wyników eksperymentalnych, co spowodowane może być nieuwzględnieniem w modelu struktury nadmolekularnej membrany Nafion oraz innym rozkładem ciśnień w membranie niż zakłada model.

EN

The set of general equations based on solution-diffusion model was presented for reverse osmosis (RO) and pervaporation (PV). It was assumed that each mixture component can be treated as a solvent. The mixture composition was expressed in terms of molar fractions. Selectivity coefficients of Nafion 117 membrane in sodium form were determined for the separation of water-methanol mixtures by RO and pervaporation PV processes. Experimental results were compared with model calculations. It was found that for feed mixture with high methanol content (xwater=0.1) model calculations were substantially different from experimental results. Such results suggested that in the model a supermolecular structure of Nafion membrane should be taken into account. An assumption about the equality of pressures in feed and membrane should be also verified.

7

Analysis of Membrane Selectivity in the Pressure Driven Transport in terms of the solution-diffusion Models and Irreversible Thermodynamics

Koter S., Kujawski W.

Polish Journal of Chemistry

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2002

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Vol. 76 / nr 11

1637-1647

EN

A comparison of different models has been presented for the pressure driven stationary transport of the mixture of two liquids (1,2) through a membrane. The following models have been discussed: the solution-diffusion model (SD), modified solution-diffusions models (SDI and SDIY) and the "black-box" approach (BB) based on linear irreversible thermodynamics. The set of general equations describing separation factor (SF1/2) has been derived for each model. It has been found that if SF1/2(SD) > 1, then SF1/2(SD) > SF1/2(SDI) > SF1/2(SDIY). For the moderate pressure differences (_p = 10 bar) the SD model and its modifications (SDI, SDIY) yield SF1/2 very close to unity and cannot describe the experimental results. Contrary to them the BB approach is able to predict the experimental SF1/2. SF1/2(BB) increases with the increase of coupling between fluxes, however, its upper limit is determined by the conditions of the positive entropy production and of the positive fluxes.

8

Electrokinetic Properties of Nafion 117 in NaCL+KCl Solutions

Koter S.

Polish Journal of Chemistry

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2001

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Vol. 75, nr 7

1001-1017

EN

The applicability of the extended Nernst-Planck equation with the homogeneous distribution of ions and the capillary model (the Boltzmann distribution of ions) to the description of electrokinetic phenomena in the system Nafion 117|0.1 M mixture of NaCl and KCl has been discussed. It has been found that only the capillary model can reasonably describe those phenomena, simultaneously preserving the Onsager reciprocity relation. The extended Nernst-Planck equation gives unsatisfactory results by either strongly breaking the reciprocity relation or, assuming the reciprocity relation (_i must be 1), leading to large discrepancies between the hydrodynamic permeability and the electrical conductivity. The interpretation of _i in terms of the capillary model has been given. _i < 1 for counterions and _i > 1 for coions result from the radial concentration profiles of those ions and of the convective velocity. The dependence of _i on the kind of acting force has been proved.