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Author: Subject: Electrolysis of potassium bisulfate
Rainwater
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[*] posted on 9-1-2022 at 16:26
Electrolysis of potassium bisulfate


I have not been able to find much information about KHSO4 but have acquired a few kilos of it and have been searching for a way to convert it into sulfuric acid.
The only real substantial information i have seen is its thermal decomposition, use in refining rhodium and as a fertilizer.(tired of cutting my grass and the roses cant get any better)

My desired overall reaction would look something like
KHSO4 + H2O = KOH + H2SO4


Basicly i want to throw a saturated solution into an electrolysis cell and reclaim my sulfuric acid.
After weeks of researching and distractions i prepared for a worst case experiment.

I setup a sealed apparatus with gas collection. A clay pot as a diaphragm. Sealed in pvc fittings with silicone caulk.
Distilled water in the cathode, saturated khso4 in the anode
Applied 6v and waited for toxic gasses/explosion or anything else Murphy could throw @ me.
Current was a constant .007 amps for 60 hours with minor(.001+/-) deviations that could have been caused by temperature changes.
Current did not increase or decrease through the experiment.
I belive the gasses produced where h2 @ the cathode and o2 @ the anode.
Cathode made a pop and anode made my splint relight.
60 hours was how long it took to fill 2 test tubes with gas from the cathode

After testing the ph of the solution in the cathode it was ~7
Ph at the anode was ~ 2.
there was no change in ph throughout the experiment
Because there was no increase in ph @ the cathode compartment i belive the experiment failed to produce the desired product

I have not tried this experiment again yet because i simply dont know enough chemistry yet to develop a cause for failure, but i do have a list.

1)Gas collection. I used 4 test tubes in the same water bath to capture gases.
The water may have absorbed something and side reactions taken place
2)The clay pot may have been different than what i have successfully used in other reactions. Even tho they look identical.
3) electronegativity of water may be greater than that of the desired product
4) contamination of the reactor from the cheapest sealent i could find could be reacting with the products
5) potassium may simply be to big to pass through the pores in the membrane
6) i just suck until i ask for help( most likely cause)

I have switch my nitric acid production to hcl+ an excess of nitrate salt which does have very good yields but requires fractions distillation that takes forever. And has some hcl contamination which is not good for refining gold inquarted in silver

Which leads to my distraction of automating the distillation.(topic for another thread)




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mysteriusbhoice
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[*] posted on 10-1-2022 at 05:09


ive already made a video on this and there be several issues with your setup but just watch these vids.

Sulfuric acid from gypsum using ion exchange membrane homemade.
https://www.youtube.com/watch?v=ukQOf79q8zs

making cation exchange membranes for various electrochemical applications.
https://www.youtube.com/watch?v=tiMt4tIced8

as for your power supply your amps are too low and you should have used more volts like 8v and 10amps which is what my ion exchange membrane cells run at.
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karolus28
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[*] posted on 10-1-2022 at 06:57


i know it's not electrolysis but what about this https://www.sciencemadness.org/whisper/viewthread.php?tid=79...




Hi, please read about exif data.
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Rainwater
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[*] posted on 10-1-2022 at 08:49


Your thinking it is my diaphragm. K. Im waiting on a good sample of Polyquaternium to be delivered. Been 2 weeks now should be here soon.

As to reacting the bisulfite with ethanol seams like a good way to go. But my primary purpose is nitric acid production and drying. Im not wanting to generate something else i have to get rid of.

Ive gotten my refining down to the only thing i consume and not recover is hcl and nacl. All other reagents and waste products involved are reacted then returned to their original forms with about 90-95% yields including no2 gas.
Its some extra work but my entire refining setup fits inside one shelf in my shop and i only have to worry small quantities of acids.
I can process 12 ounces of material with less that $1 worth of reagents




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[*] posted on 10-1-2022 at 09:13


Are you aware of this?
https://en.wikipedia.org/wiki/Potassium_persulfate
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[*] posted on 10-1-2022 at 10:21


I am now.
$<"(.
Ok so a simple direct method is off the table.
Let me keep digging. Thx




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[*] posted on 10-1-2022 at 18:01



Reference "Handbook of Preparative Inorganic Chemistry" page 392.
They used a simple electrolysis cell with a high current density and pt anode and strict temperature control. The K2S2O8 precipitates from solution very quickly because of its low solubility. And when exposed to moisture and heat decomposes back into the bisulfite.
With a split cell and that low of a current density, i dont think that would have been produced in any measurable quantity.

Im going to try mysteriusbhoice's suggestion and swap out my diaphragm then try again. As well as more research




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mysteriusbhoice
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[*] posted on 11-1-2022 at 01:04


Quote: Originally posted by Rainwater  
Your thinking it is my diaphragm. K. Im waiting on a good sample of Polyquaternium to be delivered. Been 2 weeks now should be here soon.

As to reacting the bisulfite with ethanol seams like a good way to go. But my primary purpose is nitric acid production and drying. Im not wanting to generate something else i have to get rid of.

Ive gotten my refining down to the only thing i consume and not recover is hcl and nacl. All other reagents and waste products involved are reacted then returned to their original forms with about 90-95% yields including no2 gas.
Its some extra work but my entire refining setup fits inside one shelf in my shop and i only have to worry small quantities of acids.
I can process 12 ounces of material with less that $1 worth of reagents


if your goal is nitric acid then why not just oxidize ammonia solution with AEM that being instead of using citric acid you use EDTA or aspartic acid as the crosslinker for anion exchange membranes.
then put ammonia or urea in the anode chamber and any alkali metal hydroxide in the cathode chamber.
soon anode chamber will be filled with HNO3 and NH4+ will be repelled by the membrane thus staying in the anode chamber.
Electrode must be Ir-Ta or PbO2 for this or maybe Pb.

Im just saying since you are doing this electrochemically you may aswell make the nitric acid electrochemically as it would be better.
Since having a good enough membrane to make sulfuric means you can just make one for a direct nitric acid production cell.
PbO2 would be the best since this electrode evolves O3 instead of O2 and that too oxidizes the ammonia or urea.

[Edited on 11-1-2022 by mysteriusbhoice]
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[*] posted on 11-1-2022 at 03:15


I didnt know about that process. Most of what i have studied about nitric acid production involves reacting an acid with a nitrate salt or reacting ammonia with a platinum fiber catalyst in high heat. Then bubbling through h2o
I picked with the easiest method with materials and equipment avaliable.

The sequence i use to recycle my nitric yields 95-99%( reacting copper nitrate with h2so4 then distille) its creating/resuppling the starting material which im having trouble with.

Do you have any links describing this method? Ammonia is available here but sulfuric acid is much harder to get ($30 500mL)
I dont get much metal off my property to make it worth buying reagents in bulk to same money. So i squeeze every penny and love working in my lab. Mainly its the challenge of figuring this process out and streamlining it




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[*] posted on 11-1-2022 at 07:17


Quote: Originally posted by Rainwater  
I didnt know about that process. Most of what i have studied about nitric acid production involves reacting an acid with a nitrate salt or reacting ammonia with a platinum fiber catalyst in high heat. Then bubbling through h2o
I picked with the easiest method with materials and equipment avaliable.

The sequence i use to recycle my nitric yields 95-99%( reacting copper nitrate with h2so4 then distille) its creating/resuppling the starting material which im having trouble with.

Do you have any links describing this method? Ammonia is available here but sulfuric acid is much harder to get ($30 500mL)
I dont get much metal off my property to make it worth buying reagents in bulk to same money. So i squeeze every penny and love working in my lab. Mainly its the challenge of figuring this process out and streamlining it


https://www.youtube.com/watch?v=AbrmHN5wOY8

He doesnt use a proper anion membrane so he ended up with ammonium nitrate instead.

Also he used steel electrodes which wont work for making nitric as that needs PbO2 or Ir-Ta MMO

[Edited on 11-1-2022 by mysteriusbhoice]
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