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 SO_x 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

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]

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]