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ion transfer between two phases

Posted Aug 29, 2011, 4:14 p.m. EDT Version 4.2 5 Replies

Xu Zou
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New user to Comsol and hope someone can help out.

I'm trying to model a process in which a cation transfers from organic phase to aqueous phase when applied a current across the two phases. Then the concentration and potential profiles at the two phases are obtained.

How to model the ion transfer between two phases when applied current or potential?

I don‘t know where to start. Can someone suggest any good example?

Thank you!
5 Replies Last Post Jan 22, 2012, 4:16 a.m. EST
Lasse Murtomäki
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Posted: 1 decade ago Sep 12, 2011, 7:44 a.m. EDT
Let say that you have concentration co in the oil phase and cw in the aqueous phase. Then at the boundary, use flux condition. Ion is transferring from water to oil:

In water: Inward flux = -Kp*(P*cw-co)
In oil. Inward flux = Kp*(P*cw-co)

where Kp is the permeability coefficient, for reversible transfer make it vary large, like 1000 cm/s.
P is the partition coefficient which depends on the potential

P = exp(zF/RT*(E(t)-E0))

and you have to define E(t) as a function. I use flc2hs function for in cyclic voltammetry. If you use an interpolated function (eg. triangle wave) Jacobian matrix fails in the corner point.

For example

E = Ei +v*t-2*flc2hs(t-ts,.0.001)*v*(t-ts)

Wish this replies your question
Let say that you have concentration co in the oil phase and cw in the aqueous phase. Then at the boundary, use flux condition. Ion is transferring from water to oil: In water: Inward flux = -Kp*(P*cw-co) In oil. Inward flux = Kp*(P*cw-co) where Kp is the permeability coefficient, for reversible transfer make it vary large, like 1000 cm/s. P is the partition coefficient which depends on the potential P = exp(zF/RT*(E(t)-E0)) and you have to define E(t) as a function. I use flc2hs function for in cyclic voltammetry. If you use an interpolated function (eg. triangle wave) Jacobian matrix fails in the corner point. For example E = Ei +v*t-2*flc2hs(t-ts,.0.001)*v*(t-ts) Wish this replies your question
Xu Zou
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Posted: 1 decade ago Sep 22, 2011, 5:22 p.m. EDT
Lasse. Thank you very much!
Lasse. Thank you very much!
Umar Ansari
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Posted: 1 decade ago Jan 19, 2012, 9:28 p.m. EST
Hi Lasse

I am new to COMSOL I just wanted to to know which application mode I have to use to evaluate cyclic voltammetry. Secondly how and where to measure the current foe this model.

Umar
Hi Lasse I am new to COMSOL I just wanted to to know which application mode I have to use to evaluate cyclic voltammetry. Secondly how and where to measure the current foe this model. Umar
Lasse Murtomäki
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Posted: 1 decade ago Jan 20, 2012, 3:17 a.m. EST
Application mode is Chemical species transport, and there Transport of diluted species (if they are diluted). Current is obtained in post-processing phase as a surface integral of the flux*n*F.
Application mode is Chemical species transport, and there Transport of diluted species (if they are diluted). Current is obtained in post-processing phase as a surface integral of the flux*n*F.
Umar Ansari
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Posted: 1 decade ago Jan 22, 2012, 4:16 a.m. EST
Thanks Lasse it worked.
Thanks Lasse it worked.

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