4
$\begingroup$

My synthesis requires potassium permanganate $\ce{KMnO4}$ to oxidize a side alkyl group on benzene ring. The issue is that the brown manganese dioxide $\ce{MnO2}$ is very fine so it is passing through my filter (a triple up 10 micron polypropylene filter bag).

Reading some stuff online, they say that very fine, almost nanoparticle size manganese dioxide is produced. I do not have a nanofilter, so how do I filter this solution?

I have tried making a bed of sodium chloride (grainy crystalline for kitchen use kind) to no avail. I had some satisfactory results with a very fine calcium carbonate slurry, but it interfered with the filter product, so that's no good.

$\endgroup$
5
  • 3
    $\begingroup$ Take the suspension of your product + MnO2 in an organic solvent (EtOAc is good), add water and sodium metabisulfite until all the MnO2 reduces to Mn2+ (which is water soluble) then do a liquid/liquid extraction. $\endgroup$
    – Waylander
    Jun 23, 2022 at 15:27
  • 2
    $\begingroup$ One solution for filtering $\ce{MnO2}$ is to use a sintered glass funnel under vacuum. Fill the funnel ~halfway with a slurry (water or organic solvent) of Celite, then filter your reaction mixture slowly without disrupting the Celite bed. You may have to score the $\ce{MnO2}$ layer to allow liquid penetration. $\endgroup$
    – user55119
    Jun 23, 2022 at 16:12
  • 2
    $\begingroup$ Is intense centrifuging applicable ? $\endgroup$
    – Poutnik
    Jun 23, 2022 at 16:23
  • $\begingroup$ @user55119 Can you put your comment as the answer because it worked and I have filtered the solution. But instead of a sintered glass funnel (I don't have one), I made a wet bed of celite on the PP filter bags I have and then filtered it with buchner funnel. I even improved it so what I did was is that I put another PP filter bag over the celite layer so most of the manganese dioxide stayed on the bag itself because it couldn't pass down. Made separation from celite easy. Thanks a lot for the suggestion $\endgroup$ Jun 24, 2022 at 2:09
  • 2
    $\begingroup$ Do yourself a favour and buy a ceramic (or sintered glass if that's sufficient) filter crucible. They cost ten bucks at most, with shipping. There is not point in working with unsuitable equipment. $\endgroup$
    – Karl
    Jun 24, 2022 at 12:36

1 Answer 1

3
$\begingroup$

Pulkit Sharma: Per your request. One solution for filtering $\ce{MnO2}$ is to use a sintered glass funnel under vacuum. Fill the funnel ~halfway with a slurry (water or organic solvent) of Celite, then filter your reaction mixture slowly without disrupting the Celite bed. You may have to score the $\ce{MnO2}$ layer to allow liquid penetration. I've used the technique many times for this purpose. BTW, I have found the technique useful on many occasions for breaking emulsions. Celite is diatomaceous earth, which is used in swimming pool filtration systems. PS: The Comment of @Karl is a good one. A ceramic filter crucible (Büchner) is fine with filter paper and Celite. The only downside of sintered glass funnels is that they eventually need serious cleaning. The ceramic ones are easier to maintain.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.