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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.



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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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[*] 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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[*] posted on 18-6-2022 at 22:07


Not so related to the thread itself,but it has all to do with the name tough, I had an electrolysis setup with table salt and water, separated by a piece of ceramic, stuff happened and the experiment was abandoned for over a year with the electrolyte in there and stuff - note, the electrodes were graphite and the electrolysis chambers were all glass - back to the story, the cathode chamber had some biofilm growth on it, it did not covered, it was floating and stuff... like a mold wtih withes and greys... and there wasn't just one, one of those was white in the middle.... no way those were crystals, the anode chamber had no growth, I should had taken a picture if I knew that was a thing, whatever it was, I can bet it was some sort of mold, bacteria looks different. If I had a microscope probability would had taken some samples, I mean, very unusual, on a cathode chamber, highly saline enviromement and no doubt the pH was sky high since I used the cell to take chlorihe gas, the anode chamber still smelled like bleach... perhaps the NaOH became Na2CO3 making a less harsh of an environment. .. I don't know, any thoughts ?



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m3gadeth
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[*] posted on 19-6-2022 at 07:50


That's interesting. I wonder if graphite has anything to do with this.
It is known to affect bacterial and fungal composition in soil.
It is used in microbial fuel cells to stimulate bacterial growth and mediate transfer of electrons between bacteria and the electrode.




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