ISSN 10231935, Russian Journal of Electrochemistry, 2014, Vol. 50, No. 1, pp. 38–45. © Pleiades Publishing, Ltd., 2014. Original Russian Text © V.I. Zabolotskii, R.Kh. Chermit, M.V. Sharafan, 2014, published in Elektrokhimiya, 2014, Vol. 50, No. 1, pp. 45–52.

Mass Transfer Mechanism and Chemical Stability of Strongly Basic AnionExchange Membranes under Overlimiting Current Conditions V. I. Zabolotskii, R. Kh. Chermitz, and M. V. Sharafan Kuban State University, ul. Stavropol’skaya 149, Krasnodar, 350040 Russia Received February 26, 2013

Abstract—The dynamics of changes in overall and partial voltammetric characteristics with respect to chlo ride and hydroxide ions is studied by the method of rotating membrane disk (RMD) under the conditions of stabilized diffusion layer thickness for the original strongly basic MA41P and homogeneous AMX mem branes and also for the modified heterogeneous MA41PM membrane at high current densities. For unmodified anionexchange membranes at currents exceeding the limiting value, the hydrolysis of fixed ammonium bases produces secondary and ternary amino groups which are catalytically active in the reaction of water molecule dissociation. The hydrolysis of amino groups in the membrane surface layer is the mecha nism of degradation of electrochemical characteristics of strongly basic membranes. This results in the increase of transport numbers with respect to hydroxide ions and weakening of mass transfer with respect to salt ions. For the surfacemodified heterogeneous anionexchange membranes, no degradation of electro chemical characteristics is observed. The characteristics of the surfacemodified MA41PM membrane remain stable: after longterm operation of the energized membrane, the partial currents with respect to hydroxide ions are close to zero and the mass transfer with respect to salt ions is considerably intensified. The dependences of the thickness of the hydrolyzed layer of a strongly basic anionexchange membrane on the time of its exposure to solutions of high pH are determined. An original method is developed for determination of the hydrolyzed layer thickness for stronglybasic anionexchange membranes, which is based on the copper ability to form sta ble complex compounds with weakly basic amino groups of anionexchange membranes. Keywords: anionexchange membrane, water dissociation, modification, rotating membrane disk, ion trans fer, limiting current DOI: 10.1134/S102319351401011X

INTRODUCTION

undesired phenomena that complicate the elec tromembrane process. Alkalization of solutions induces conversion of hydrocarbonates to carbonates and precipitation of hardness salts; acidification leads to precipitation of polysilicic acids and transition of certain ampholytes into their molecular form. More over, the pH shifts due to dissociation of water mole cules that occurs in the electromembrane system (EMS) at current densities exceeding the limiting cur rent can have a substantial effect on the structure and chemical composition of the surface of ionexchange membranes and, particularly, induce the hydrolysis of quaternary amine groups in the membrane surface layer by the Hofmann reaction [1, 2] to afford ternary amino groups which accelerate the water dissociation [3].

The transition to highly intense electromembrane processes is among the foreground problems of mem brane electrochemistry and electromembrane tech nology. The use of intense current modes many times exceeding the limiting diffusion current is often the necessary condition of operation modern electrodial ysis cells for the production of deionized and super pure water. In its turn, this dictates new requirements to ionexchange membranes used in these apparatus. Carrying out desalination processes in electromem brane systems under highintensity current conditions is complicated by one of the most wellknown phe nomena that accompany the concentration polariza tion, namely, the dissociation of water molecules at the membrane/solution interface, which in turn gives rise to changes in the pH in the membrane channel.

The sofar published data on the transfer of salt ions and water dissociation products through ion exchange membranes at high current densities dem onstrated that the water dissociation rate at the inter face anionexchange membrane/solution is higher as compared with the cationexchange membrane/solu tion interface [4–8]. The data presented in cited pub

Water dissociation and shifts of pH in both alkaline and acidic directions bring about not only a decrease in the current efficiency but also quite a number of z

Corresponding author: chermit[email protected] (R.Kh. Chermit).

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lications suggest that the water dissociation rate may be determined by several factors. These are, first of all, the nature of ionexchange groups [9] and polymer matrix, the chemical and electrical heterogeneity of the membrane surface [10] and its geometric relief (profiled, rough membranes) [11], the electrolyte concentration, and the hydrodynamic conditions at the membrane surface or in membrane channels [12]. To date it was found that ionexchange groups of cationexchange membranes exhibit the higher chem ical and thermal stability as compared with fixed groups of anionexchange membranes and are virtu ally never subjected to thermochemical destruction [13–15]. Hence, today the most burning problem is the development of anionexchange membranes capable of suppressing the water dissociation and operating at overlimiting current densities and in alka line electrolyte solutions. A method has been developed [16] for modifying heterogeneous mediumbasic membranes with sec ondary and ternary functional groups. Studying ion transport and water dissociation in these modified membranes has shown that as the voltage on the membrane drops up to 3–4 V, no water dissociation occurs on membranes because quaternary ammo nium bases bidentally bound with the matrix are highly stable as regards the alkaline thermohydrolysis and only weakly catalytically active in water dissoci ation reaction [3, 13]. The mentioned modification method can be used only for low and mediumbasic membranes contain ing secondary and ternary amines. Such modified membranes demonstrate the high electric resistance in solutions containing anions of organic acids and also two or threecharged anions of inorganic acids due to their coordination and chemical interaction with sec ondary and ternary amino groups of the original mem branesupport. The present study is devoted to elucidation of the mechanism of transfer of salt ions in systems involving homogeneous highly basic AMX membrane (Tokuyama Soda, Japan), heterogeneous highly basic MA41P membrane (Shchekinoazot, Russia), and sur facemodified anionexchange membrane MA41PM and also to studying the chemical stability of these membranes under the conditions of highintensity electrodialysis. STUDY OBJECTS AND EXPERIMENTAL METHODS The study objects were the original commercial anionexchange membranes MA41P (Shchekinoa zot, Russia) synthesized based on crosslinked anion ite AV172P (with 2% of divinylbenzene) containing quaternary ammonium bases (TU (Technological Ser tificate) 2255001957463922012), homogeneous strongly basic membranes AMX (Tokuyama Soda, Japan) and also MA41PM anionexchange mem RUSSIAN JOURNAL OF ELECTROCHEMISTRY

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Physicochemical properties of studied membranes Membrane MA41P AMX MA41PM

Q, mol/cm3 0.0012 0.0016 [18] 0.0013

d, cm 0.045 0.02 0.045

Q is the exchange capacity of the swelled membrane; d is the membrane thickness.

branes, which were developed in our studies by surface modification with a strong polyelectrolyte complex. The surface layer of the latter membranes contained quaternary ammonium bases bidentally bound with the membrane polymer matrix. The procedure of measurements with a rotating membrane disk (RMD) [17] was described in detail elsewhere [19–22]. The studies were carried out in sodium chloride solutions with the concentration of 0.01 M at 25°С. Membrane samples were preliminar ily subjected to chemical treatment by a standard method. Voltammograms (VA) of the membrane sys tem were recorded in the galvanostatic mode at the stepwise increase in the current density by means of a galvanostat. The membrane disk rotation rate was var ied from 100 to 500 rpm; in this rate range, the laminar liquid flow was observed [32]. The distribution of ionogenic groups in original membranes and those subjected to alkaline hydrolysis and thermohydrolysis were determined as follows. The membranes washed from alkali were exposed for 48 h to 1 M copper sulfate solution with pH 4. The fixed weakly basic amino groups, in contrast to strongly basic groups, can form chemically stable complexes with Cu2+ ions which are similar to ammonium com plexes where a copper ion is coordinated with four donor nitrogen atoms containing an unshared electron pair [24]. After the mentioned procedure, the mem brane samples were washed with deionized water and dried. Then, cross sections of anionexchange mem branes under study were prepared in the liquid nitro gen medium. The cross sections were scanned to the depth of 5 μm along the membrane transverse coordi nate (along the transport axis); in parallel, the elemen tal analysis was carried out by means of an attachment (FESEM JSM7500F, Jeol). Microimages of sections were contrasted by means of Photoshop programs. As an example, here we show a contrasted microimage with elemental analysis for the MA41P membrane (Fig. 1). Each white dot corresponds to the detection signal from copper ions with the concentration higher than the limiting concentration in the membrane local region of ca. 1 μm. Along the transverse coordinate, the total thickness of the scanned region of the mem brane cross section was divided into strips 20μm wide and in each strip the surface occupied by copper ion No. 1

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ZABOLOTSKII et al. i, mA/cm2 20 15 1 2 3 4

10 5 100 μm 0 0 Fig. 1. Contrasted microimage and results of elemental analysis of the hydrolyzed anionexchange membrane MA41P subjected to alkaline hydrolysis in 0.2 M NaOH at 50°C for 15 min. A half of membrane section thickness is shown.

2.5

3.5 Δϕ, V

Fig. 2. Overall VA of the electromembrane system with MA41P membrane in 0.01 M NaCl solution at different rotation rates of the membrane disk, rpm: (1) 100, (2) 200, (3) 300, (4) 500.

localization regions was determined. According to this microimage, in some regions, white dots merge together to form continuous fields; this is why, to sim plify the procedure and increase the accuracy of calcu lating these regions, we used the Photoshop software. The surface occupied by dots (S) was normalized by the surface of the 20μm strip scanned (Sо), α = S/Sо × 100% (ratio of surfaces in percents). The ratio of the scanned membrane surface in which copper ions were detected indicated of the presence of fixed weakly basic amino groups in this region. Based on the found ratios α, for each scanned strip, the distribution of α along the transverse coordinate of the membrane was plotted, which provided information on the distri bution of fixed weakly basic amino groups throughout the membrane thickness and allowed judging on the thickness of hydrolyzed layers in membranes. iОН–, mA/cm2

1.5

0.5

ION TRANSFER AND WATER DISSOCIATION Figure 2 shows VA of the electromembrane system containing the membrane under study for different rotation rates of the membrane disk. It is seen that for the MA41P membrane, the VA shape differs from the classical shape due to the appearance of accompany ing effects of concentration polarization. Figure 3 compares partial VA with respect to hydroxide and chloride ions for the original strongly basic anionexchange membrane MA41P and a membrane that has worked for 10 h under the condi tions of intense electric current flow i/ilim = 2.5 at the membrane disk rotation rate of 100 rpm. According to this figure, virtually no water dissoci ation occurs on the original membrane MA41P at the potential difference Δϕ < 1 V, which corresponds to iCl–, mA/cm2 12

(a)

(b)

7 8

5

1 2

3

1 2 4

1 0

1.0

2.0

3.0

0 Δϕ, V

1.0

2.0

3.0

Δϕ, V

Fig. 3. Partial VA with respect to (a) hydroxide and (b) chloride ions for the electromembrane systems involving a MA41P mem brane in 0.01 M NaCl solution at the membrane disk rotation rate of 100 rpm: (1) original membrane, (2) after 10h work. The current density on the membrane 2.5ilim, ilim = 6.2 mA/cm2. RUSSIAN JOURNAL OF ELECTROCHEMISTRY

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4 3

2

20

1

10

0 3

1

5 Δϕ, V

Fig. 4. Overall VA of the electromembrane systems involv ing AMX membrane in 0.01 M NaCl solution at various rotation rates of the membrane disk, rpm: (1) 100, (2) 200, (3) 300, (4) 500.

the region of underlimiting currents (i < ilim). For the potential drop Δϕ = 2.7 V, the water dissociation amounts to ca. 20% of the overall mass transfer (Fig. 3a, points 1). On the membrane that has oper ated for 10 h (Fig. 3, points 2), the water dissociation starts even upon the attainment of the limiting current (Δϕ ≈ 1 V), whereas at Δϕ = 2.7 V, the current fraction transferred by hydroxide ions through the membrane is already 40%. This is accompanied by a decrease in the mass transfer with respect to salt ions (Fig. 3b), which is associated with a decrease in electroconvection. To study the effect of surface morphology of ion exchange membranes and peculiarities of the mecha nism of formation of the overlimiting state and also to assess the effect of electroconvection, we considered the VA and transfer numbers of salt ions and water dis sociation products not only for heterogeneous anion exchange membranes but also for the homogenous iОН–, mA/cm2

anionexchange membrane AMX (Tokuyama Soda, Japan). It can be seen that the VA of heterogeneous anionexchange membranes AMX also differs from the classical curve (Fig. 4). As seen from the partial VA (Fig. 5) with respect to chloride and hydroxide ions, the partial current of ОН– ions on the original AMX membrane is virtually absent when the potential drop Δϕ = 2.7 V is attained and the increase in transfer numbers of hydroxide ions can be observed only at the high potential drops. The transfer numbers reach TОН− = 0.15 at the potential difference Δϕ = 4.5 V. At the same time, on the AMX membrane that has worked for 10 h at the high current density i/ilim = 2.5, the water dissociation can be dis cerned even at the potential drop Δϕ = 1 V, while at Δϕ = 2.7 V the transfer numbers reach the value TОН− = 0.22; simultaneously, we observed considerable weakening of mass transfer with respect to salt ions (Fig. 5b), similarly to the heterogeneous strongly alka line anionexchange membrane MA41P. It deserves mention that the potential range in which water disso ciation is absent on the original anionexchange mem branes is wider for homogeneous AMX membranes as compared with heterogeneous MA41P. Figure 6 shows the dependence of the hydrolyzed layer thickness on the polarization time for membrane MA41P in 0.01 M sodium chloride solution in the electrodialysis cell containing MK40 cation exchange and MA41P anionexchange membranes. The current density at the electrodialysis was i = 3ilim. Figure 6 shows that in the original membrane, α = 4% and does not vary throughout the membrane thickness. Earlier [25], it was shown that in the strongly basic anionexchange membrane MA41 (8% divinylbenzene) which has the same fixed ionogenic groups as in the weakly crosslinked membrane MA41P, the ratio of secondary and ternary amino groups is α = 6%. After intense 3h electrodialysis, iCl–, mA/cm2

(a)

7

41

(b)

25

5 15 1 2

1 2

3

5

1 1

3

5 Δϕ, V

1

3

5 Δϕ, V

Fig. 5. Partial VA with respect to (a) ОН– and (b) Cl– ions of EMS involving an AMX membrane in 0.01 NaCl solution at the rotation rate of membrane disk of 100 rpm: (1) original membrane, (2) after 10h work. The current density on the membrane 2.5ilim, ilim = 10.3 mA/cm2. RUSSIAN JOURNAL OF ELECTROCHEMISTRY

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α, % 16

α, % 4

5

60

3 40

10

2 4 20

4 1 0 50 50

0

100

150

150

250

350

200 L, μm

Fig. 6. Dependence of localization regions of weakly basic amino groups (coordinated with copper ions) on the trans verse coordinate (L) of sections of MA41P membranes which have operated for different time at i/ilim = 3: (1) original membrane, (2) 3 h, (2) 10 h, (4) 30 h. Values of α are averaged over 20µmwide areas in the membrane cross section.

d1

3 2 1 450 L, μm

Fig. 8. Dependence of the thickness of hydrolyzed layers of the MA41P heterogeneous membrane on the time of hydrolysis in 0.2 M NaOH solution at 50°C. Hydrolysis time, min: (1) original membrane; (2) 1, (3) 5, (4) 15, (5) 30. Values of α are averaged over 20µmwide areas in the membrane cross section.

The presence of alkaline hydrolysis of fixed strongly basic ammonium bases at the membrane polarization was confirmed by the method of IR spec troscopy for the anionexchange membrane AMX [26], heterogeneous membranes MA41 and Ralex AMH [3], and for the anionexchange layer of the bipolar membrane Neosepta BP1 [2].

Fig. 7. Microimages of sections of a MA41P anionexchange membrane which was subjected to hydrolysis, min: (a) 1, (2) 5, where d1 and d2 are the regions of localization of Cu2+ complexes with ternary amino groups.

To confirm the assumption on the chemical destruction of strongly basic ionogenic groups, the samples of studied membranes were independently (in independent experiments) treated by alkali at 50°C. To determine the number of hydrolyzed quaternary ammonium groups, membrane samples were exposed to copper sulfate solutions according to the procedure described above. Figures 7 and 8 show the contrasted microimages of crosssections of studied membranes obtained by the SEM method combined with elemen tal analysis and also the distribution of the copper localization regions over the membrane thickness at different times of alkaline hydrolysis. As for the mem brane polarization by high current densities, the increase in the membrane exposure in an alkali increased the hydrolyzed layer thickness up to 160 μm at the hydrolysis time of 15 min (in 0.2 M alkali solu tion at 50°С). When a membrane was exposed to alkali for a long time (more than 10 h), the alkaline hydroly sis proceeded throughout the whole thickness of the membrane and was accompanied by the transition of all quaternary ammonium bases to weakly basic amino groups.

α = 9%. In this case, the hydrolyzed layer thickness reached 50 μm. With the further increase in time of membrane operation in the electrodialysis cell, the hydrolyzed layer thickness increased to reach 100 μm after 30h work (i = 3ilim), which amounted to approx imately one fifth of the total membrane thickness.

Thus, the membrane polarization at high current densities in alkali solutions makes it possible to syn thesize a bilayer anionexchange membrane with ion ogenic groups of the mixed chemical composition in which weakly basic (secondary and ternary) amino groups are on the surface and strongly basic original ammonium bases remain in the bulk. The thickness of

(a)

200 μm

d2

d1

(b)

200 μm

d2

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20

1 2 3 4

10

0

5 Δϕ, V

3

1

Fig. 9. Overall VA of the EMS involving a MA41PM membrane in 0.01 M NaCl solution at different RMD rotation rates, rpm: (1) 50, (2) 100, (3) 300, (4) 500.

the hydrolyzed layer depends on the time of electro chemical and chemical treatment of the membrane. Figure 9 shows the overall VA of the electromem brane system involving the anionexchange mem brane MA41PM. It is evident that these VA, like those of the original membrane, differ from the classi cal curves. Figures 10a and 10b illustrate the analysis of partial VA with respect to chloride and hydroxide ions for original MA41P and modified MA41PM. According to Figs. 10a and 5a, the dissociation of water molecules on the modified membrane MA41PM is weaker as compared with original heterogeneous MA41P and homogeneous AMX anionexchange membranes and the more so on membranes polarized for 10 h at i/ilim = 2.5 where dissociation starts only at the potential difference Δϕ = 4 V (at which the current iОН–, mA/cm2

density 2–3 times exceeds ilim). In contrast to the orig inal unmodified homogeneous AMX and heteroge neous MA41P membranes, the modified MA41PM membrane does not change its electrochemical (Fig. 10a) and massexchange (Fig. 10b) characteris tics during its longterm polarization by a high current density (i/ilim = 2.5). It is evident that the mass transfer with respect to salt ions is substantially more intense on the modified membrane MA41PM (Fig. 10b). Figure 11 compares the limiting diffusion currents of membranes under study at various rotation rates of RDM. To exclude the effect of water dissociation, the ilim values are shown for original MA41P and AMX membranes, because as a result of their destruction, the water dissociation proceeds on them even at i = ilim. Figure 11 shows the dependence of the limiting current found by the tangent method on the square root of the RDM angular rate. The solid line shows the calculated dependence of the limiting current on ω according to the Levich theory ilim =

16

FDc0 , (1 − t1)δ 0

(1)

(2) δ 0 = 1.61(D)1 3 ν1 6ω−1 2, where δ is the diffusion layer thickness, cm; F is the Faraday number, C/mol; t1 is the transfer numbers of counter ions in solution; D is the electrolyte diffusion coefficient, cm2/s; c0 is the solution concentration, mol/cm3; ω is the angular rate of the membrane disk (ω = πn/30, where n is the rpm number), rad/s; ν is the kinematic viscosity of solution, cm2/s. The analysis of dependences of limiting currents shows that for the original ionexchange membrane MA41P, the dependences deviate from the straight line. Moreover, it should be noted that the limiting iCl–, mA/cm2

(a)

43

(b)

16

12 1 2 3 4

8

1 2 3 4

8

4

1

3

5 Δϕ, V

1

3

5 Δϕ, V

Fig. 10. Partial VA with respect to (a) hydroxide and (b) chloride ions for EMS containing MA41P and MA41PM membranes in 0.01 M NaCl at the RMD rotation rate of 100 rpm: (1) original MA41P membrane, (2) MA41P membrane after 10h work, (3) original MA41PM membrane; (4) MA41PM membrane after 10h work. Polarization current density 2.5ilim; ilim = 9.8 mA/cm2. RUSSIAN JOURNAL OF ELECTROCHEMISTRY

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ZABOLOTSKII et al. ilim, mA/cm2 18

1

AMX

2

MA412P

3

MA412PМ

12

6

0

2

4

6

8

ω1/2, (rad/s)1/2 Fig. 11. The limiting current density as a function of the square root of the RMD angular rate: the solid line corre sponds to calculations in terms of the Levich theory; the dashed line is the limiting current for the MA41P mem brane theoretically calculated by taking into account sur face roughness [27]; points are experimental limiting cur rents for membranes under study.

current ilim is much lower than its values calculated in terms of the Levich classical electrodiffusion theory and reaches a plateau (Fig. 11, points 2). The reason for the deviation of the ilim vs. ω1/2 dependence from the Levich theory were already discussed for the com mercial anionexchange membrane MA41 [27]. They were associated with the presence of inert regions on the surface of the heterogeneous membrane which were uninvolved in the mass transfer being formed by an inert binder (polyethylene). Figure 11 shows the theoretical dependence (dashed line) of ilim on ω1/2 calculated for the original heterogeneous membrane MA41P by the equation

1 = δ 0(t − t ) + ΘR ln(1 + 0.27 1 − Θ), (3) 2(1 − Θ) ilim zFDc zFDc where Θ is the inert surface fraction, R is the radius of conducting regions, and the other designations are as in Eq. (1). The theory and the procedure of calculating ilim for heterogeneous membranes can be found in [27]. A comparison of limiting diffusion currents on modified MA41PM and original MA41P anion exchange membranes shows that on the former mem brane, the limiting diffusion current much exceeds its value on MA41P and virtually coincides with ilim on the homogeneous membrane AMX. CONCLUSIONS Thus, at intense current modes in alkaline solu tions, the strongly basic homogeneous and heteroge neous membranes containing fixed quaternary ammo nium bases undergo hydrolysis as a result of which the

fixed secondary and ternary ammonium groups cata lytically active in the water dissociation reaction are formed in the membrane surface layer. The membrane surface hydrolysis is one of the reasons for degradation of electrochemical characteristics of strongly basic membranes. The surfacemodification of heterogeneous strongly basic membranes MA41PM makes it possi ble to suppress virtually completely the reaction of water dissociation at the membrane/solution interface and thus substantially enhance the mass transfer in the system (the experimentally found ilim values exceed those calculated in terms of the Levich theory) and make the properties of the original membrane MA41P closer to those of homogeneous membranes AMX. Insofar as the cost of heterogeneous anion exchange membranes including their modified ver sions is several times lower than that of homogeneous anionexchange membranes AMX, the use of these membranes in commercial electrodialysis can be very efficient especially when highly intense electromem brane processes which occur at currents many times exceeding the limiting current are organized. ACKNOWLEDGEMENTS This study was financially supported by the Russian Foundation for Basic Research (grants 120893105 NTsNIL_a and 120831277 mol_a). REFERENCES 1. Sata, T., Tsujimoto, M., Yamaguchi, T., and Matsusaki, K., J. Membr. Sci., 1996, vol. 112, p. 161. 2. Hwang, U. and Choi, J.H., Sep. Purif. Technol., 2006, vol. 48, p. 16. 3. Zabolotskii, V.I., Bugakov, V.V., Sharafan, M.V., and Chermit, R.Kh., Russ. J. Electrochem., 2012, vol. 48, p. 650. 4. Kononov, Yu.A. and Vrevskii, B.M., Zh. Prikl. Khim., 1971, vol. 44, p. 929. 5. Varentsov, V.K. and Pevnitskaya, M.V., Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk, 1973, no. 4, p. 134. 6. Gavish, B. and Lifson, S., J. Chem. Soc., Faraday Trans. 1, 1979, vol. 75, p. 463. 7. Tanaka, Y. and Seno, M., Denki Kagaku, 1983, vol. 51, p. 267. 8. Shaposhnik, V.A., Kastyuchik, A.S., and Koza derova, O.A., Russ. J. Electrochem., 2008, vol. 44, p. 1073. 9. Zabolotskii, V.I., Shel’deshov, N.V., and Gnusin, N.P., Usp. Khim., 1988, vol. 57, p. 1403. 10. Zabolotskii, V.I., Nikonenko, V.V., Urtenov, M.Kh., Lebedev, K.A., and Bugakov, V.V., Russ. J. Electro chem., 2012, vol. 48, p. 692. 11. Zabolotskii, V.I., Loza, S.A., and Sharafan, M.V., Russ. J. Electrochem., 2005, vol. 41, p. 1053.

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MASS TRANSFER MECHANISM AND CHEMICAL STABILITY 12. Zabolotskii, V.I. and Nikonenko, V.V., Perenos ionov v membranakh (Ion Transfer in Membranes), Moscow: Nauka, 1996. 13. Ghalloussi, R., GarciaVasquez, W., Bellakhal, N., Larchet, C., Dammak, L., Huguet, P., and Grande, D., Sep. Purif. Technol., 2011, vol. 80, p. 270. 14. Iwai, Y. and Yamanishi, T., Polym. Degrad. Stab., 2009, vol. V. 94. P. 679. 15. Cheng, Ch. and Fuller, T.F., Polym. Degrad. Stab., 2009, vol. 94, p. 1436. 16. Zabolotskii, V.I., Fedotov, Yu.A., Nikonenko, V.V., Pis’menskaya, N.D., Belova, E.I., and Lopatkova, G.Yu., RF Patent No. 2008141949 (2008). 17. Sharafan, M.V. and Zabolotskii, V.I., RF Patent No. 78577 (2008). 18. Lopatkova, G.Yu., Cand. Sci. (Chem.) Dissertation, Krasnodar, 2006. 19. Zabolotskii, V.I., Shel’deshov, N.V., and Sharafan, M.V., Russ. J. Electrochem., 2006, vol. 42, p. 1345. 20. Zabolotskii, V.I., Sharafan, M.V., Shel’deshov, N.V., and Lovtsov, E.G., Russ. J. Electrochem., 2008, vol. 44, p. 141.

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21. Zabolotskii, V.I., Sharafan, M.V., and Shel’deshov, N.V., Russ. J. Electrochem., 2008, vol. 44, p. 1127. 22. Sharafan, M.V., Zabolotskii, V.I., and Bugakov, V.V., Russ. J. Electrochem., 2009, vol. 45, p. 1162. 23. Levich, V.G., Fizikokhimicheskaya gidrodinamika (Physicochemical Hydrodynamics), Moscow: Fizmatgiz, 1959. 24. Zabolotskii, V.I., Ganych, V.V., and Shel’deshov, N.V., Elektrokhimiya, 1991, vol. 27, p. 1245. 25. Chermit, R.H., Zabolotskii, V.I., Sharafan, M.V., and Bugakov, V.V., Ion Transport in Organic and Inorganic Membranes: Materials. Proceed. Intern. Conf., 2011. 26. Choi, J.H., Moon, S.H., J. Colloid Interface Sci., 2003, p. 93. 27. Bugakov, V.V., Zabolotskii, V.I., and Sharafan, M.V., Sorbtsionnye Khromatogr. Protsessy, 2010, vol. 10, p. 870.

Translated by T. Safonova

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