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Author: Subject: Biofilm formation after electrolysis?
m3gadeth
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[*] posted on 17-5-2021 at 02:52
Biofilm formation after electrolysis?


Hello,

after electrolysis and subsequent water evaporation I have observed white growth on the deposits of iron oxide (rust), would like to know what it is.

Here's the setup:
- tap water in a jar (initially in the form of ice at -24 °C, electrolysis performed at room temperature)
- graphite electrodes approx. 1 cm apart
- input: pulsed DC (230V AC through a diode rectifier)
- a bundle of human hair was present between the electrodes
- some rust (iron oxide) was present in the solution (possibly also some graphite particles)

The white stuff was not visible during electrolysis, I only noticed it after evaporation. I later poured water over it and white stuff was gone (dissolved?).

Here's a photo:


Are these iron oxide reducers (microorganisms) and what was the role of electrolysis? My guess is these organisms came from hair. Perhaps they were activated by ion flow, or this is something else?

[Edited on 17-5-2021 by m3gadeth]

[Edited on 17-5-2021 by m3gadeth]

[Edited on 17-5-2021 by m3gadeth]




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[*] posted on 17-5-2021 at 08:22


Those look like salt crystals to me. It would explain why they appeared after drying and why water washed them away.



As below, so above.
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m3gadeth
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[*] posted on 18-5-2021 at 05:57


Yeah, that was my second thought, but what salt exactly would it be, where would it come from (hair?) and why would it concentrate on iron oxide?



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CharlieA
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[*] posted on 18-5-2021 at 16:07


I would think that the salts came from the tap water.
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m3gadeth
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[*] posted on 18-5-2021 at 20:57


Yes, that seems plausible.
I am not an expert in chemistry, assuming this is salt, can someone explain why its distribution is not random here rather in a form of dendritic crystallization?




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[*] posted on 21-5-2021 at 04:48


Quote: Originally posted by m3gadeth  
Yes, that seems plausible.
I am not an expert in chemistry, assuming this is salt, can someone explain why its distribution is not random here rather in a form of dendritic crystallization?


It is a cool pattern, but I'm not sure there's much more of an explanation than "that's just how it happened to crystallize". Possibly related to the pattern on the surface of the ceramic? But otherwise I'm not aware of a single good explanation.

But hey, enjoy the patterns :)
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[*] posted on 21-5-2021 at 07:54


Yeah, patterns are cool :-)
But I'm not sure that it's related to the pattern on the surface of glass.
The crystals have formed on the layer of rust. After adding water again salt has dissolved and no such patterns were visible in the rust.
Note that rust particles are glued to the glass (somehow) and they stick in the same place when you add water.

I'm aware that salt particles clump together due to ionic bonding, perhaps such growth has something to do with the orientation of molecules - permitting only specific angles in bonding.
And this was further limited to a 2-dimensional plane with water evaporation.




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