Lionel Spanner
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Removing graphite from glass frit filter
Hello all,
In the course of my experiments I recently vacuum-filtered a water-based mixture with large amount of suspended graphite particles in it through a
glass frit filter (rookie error, I know.)
Not only did this not stop graphite particles passing through - I filtered the grey filtrate again under gravity, which successfully clarified it -
but now the frit has graphite particles embedded in it, and I have yet to find a way to shift or remove them.
Some solvents I have tried using to remove them, without success:
* Cold water
* Hot water
* Acetone
* White spirit
* Liquid paraffin BP
* A few drops of cold red fuming nitric acid
The last of these caused some gentle bubbling, but otherwise did nothing other than staining the underside of the frit a reddish-brown. I didn't dare
use hot nitric acid.
Is there some other way of getting rid of the graphite, or is that filter stained for life?
Many thanks!
[Edited on 11-11-2022 by Lionel Spanner]
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Sulaiman
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Piranha solution
https://en.wikipedia.org/wiki/Piranha_solution
CAUTION : Hobby Chemist, not Professional or even Amateur
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violet sin
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I've never tried to clean such a filter, let alone something like graphite stuck in there. My best guess right off, maybe reverse flow. I have a
small ultrasonic mister for an aquarium. If you fill above a certain height, it just shakes the water without kicking up mist. Set up a reverse flow
water with aquarium pump, in a tub of water overfilled for the mister and let it run for a day pointed at one another? It would either be noticable or
useless with minimal effort. But that's just with what I have on hand and my level of free time. Best of luck
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j_sum1
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I have used pirhana on frit glass before. Came out looking brand new.
Not that I think it really matters too much in most situations. If something is discolouring the frit but not going through, but filtering still
works, then it's mostly ocd and aesthetics that is causing stress.
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Boffis
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Have you tried reversing the flow of water through the frit. If this and Piranha solution don't move it I think you are stuck with it! On the other
hand if these processes won't remove it then I don't think its going to be a long term problem. Graphite is very inert.
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Texium
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Piranha is the way to go. And in the future, if you have to filter such a mixture, a pad of celite pressed into the bottom of the funnel works wonders
and keeps the frit clean.
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Lionel Spanner
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Thank you all, your advice is much appreciated!
I have some 25% and 50% hydrogen peroxide and I'm planning to make some conc. sulphuric acid before long. When I do, I'll be sure to give piranha
solution a go.
Going forward, I'll be using a Buchner funnel for this particular procedure. The filter papers I have (Whatman grade 1 equivalent, medium speed) do an
excellent job of filtering out even the tiniest particles.
[Edited on 11-11-2022 by Lionel Spanner]
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Sulaiman
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Just thought I'd mention that the common acid:peroxide ratio (varies from 3:1 to 7:1 according to wikipedia)
is not required if no tar/organics are present.
A 1:1 molar ratio is suitable for carbon,
in which case you would be making "Caro's acid".
https://en.wikipedia.org/wiki/Peroxymonosulfuric_acid
I think that it would be better (less hazardous) to use your 25% peroxide rather than the 50%
CAUTION : Hobby Chemist, not Professional or even Amateur
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Lionel Spanner
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Quote: Originally posted by Sulaiman  | Just thought I'd mention that the common acid:peroxide ratio (varies from 3:1 to 7:1 according to wikipedia)
is not required if no tar/organics are present.
A 1:1 molar ratio is suitable for carbon,
in which case you would be making "Caro's acid".
https://en.wikipedia.org/wiki/Peroxymonosulfuric_acid
I think that it would be better (less hazardous) to use your 25% peroxide rather than the 50% |
Thank you!
This was actually my plan - because of the way I obtained it (azeotropic distillation) I have a lot more of the 25% peroxide to hand than the 50%.
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Lionel Spanner
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Update: The filter wound up being caked in burnt-on sugars following its use, insufficient washing, and subsequent oven-drying during the preparation
of mucic acid.
Piranha solution, followed by hot alkaline peroxide, worked a treat and restored it to pristine condition - thank you again to all who suggested it!
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