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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: Homerinosi on April 21, 2022, 05:26:10 AM

Title: How to create spatial separation/concentration of ions in electrolyte?
Post by: Homerinosi on April 21, 2022, 05:26:10 AM

Dear Experts,
Question first:
How can I create spatial separation/concentration of ions in an electrolyte solution (KCl) without direct electrode-liquid contact?

The (unsuccessful) experiment so far:
Superimposing an electric field on the electrolyte chamber with the setup: conductor 1 (up to 1000V) - insulator (0.5mm) - electrolyte (1mm, 1mM KCl) - insulator (1mm) - conductor 2 (0V).
The measurement method: measurement of impedance with two flat electrodes at the bottom of the electrolyte chamber.
Expectation: there will be a higher ion concentration in the area of the impedance measurement and the impedance will decrease.
Result: Absolutely nothing happens.
Why?

A consideration that may explain the problem: Why do electrodialysis stacks use electrodes with direct electrolyte contact and accept electrode gas production instead of superimposing an electric field on the stack without conductive contact to the electrolyte?

Title: Re: How to create spatial separation/concentration of ions in electrolyte?
Post by: Borek on April 21, 2022, 09:50:59 AM

Try to estimate charge separation that will produce electric field countering the one you applied, use it to estimate number of moles of ions, compare it with the concentration. Is there any chance of detecting the difference?