Alzador
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Separation of Potassium ions from solution.
Hello everyone!
Yesterday I did an experiment: I had some KMnO4 solution on hand that was acidified with a bit of H2SO4 before. The
exact concentrations are not known. This solution's volume was about 200 mL. I managed to boil this solution down to roughly 10-20 mL, this was the
point when SOx fumes started to come out. Throughout the boiling process the permangante ions were destroyed according to this equation I
believe:
2 MnO4{-} = MnO4{2-} + MnO2 + O2
The manganate ions produced are not too stable at these conditions and decompose like this:
3 MnO4{2-} + 2 H2O → 2 MnO4{-} + MnO2 + 4 OH{-}
When I saw the dense fumes come out I immediately submerged the contents of the beaker under water - about 200 ml - ,then I left this chocolate brown
suspension to settle. What I have now is MnO2 powder suspended in a H2SO4 / KHSO4 solution.
My question would be: Is there a way to exchange the potassium ions to protons using some kind of ion-exchange resin?
I am going to measure the pH of the solution tomorrow at my workplace, then I will know something about the sulfuric acid concentration.
Any ideas? 
Alzador
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deltaH
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Passing your solution through a column packed with strong acid type resin will exchange the potassium. You will need quite a lot of resin. What you
will be left with is K-resin afterwards and an acidic solution eluting. Normally to regenerate this resin back to H-resin form, you would need to pass
through a strong acid solution to leach out a K salt again. I don't see this being very practical for you unless you are doing it industrially.
If you want to precipitate the potassium simply to treat the effluent water, then the correct thing to do is to employ the jarosite precipitation.
Jarosite is KFe[3+]3(OH)6(SO4)2 and it's insoluble in water. The nice thing is it gets rid of sulfate too 
As an idea:
You need the right ratio of potassium to sulfate (1:2) first, so you would need to add in acid if you have too little, then you need to electrolyse
with iron anodes so as to release Fe3+ ions and raise the pH, ultimately bring about the precipitation of bright yellow jarosite powder. You can use
it together with iron cathodes as well for simplicity.
[Edited on 6-12-2015 by deltaH]
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Alzador
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Thank you for your answer I will try this. Never heard of this before  . Basically I just wanted to get rid of the potassium to get sulfuric acid out,but
not for practical uses. The whole thing is about doing some chemistry . How is
this precipitation done exactly?
[Edited on 6-12-2015 by Alzador]
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deltaH
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It won't recover the sulfuric acid, that's precipitated too as sulfate in the jarosite structure. The easiest and 'cleanest' way to do this is the
electrolysis with an iron anode IMHO.
Post some pictures if it works, jarosite is supposed to a be a nice orange/yellow powder.
[Edited on 6-12-2015 by deltaH]
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