Sciencemadness Discussion Board

Removing cobalt ferricyanide from Büchner funnel plate

Lion850 - 20-8-2020 at 00:01

Looking for advice on how to clean cobalt ferricyanide from the porous plate of my Büchner funnel. Usually I clean the funnel with concentrated hydrochloric acid but as far as I know using strong acids with ferricyanide may lead to formation of cyanide gas. Thanks in advance.

58333598-0580-4541-A9D2-9A7BAE98E7F5.jpeg - 2MB

symboom - 20-8-2020 at 01:18

Only thing I can think of is to oxidize it with Hydrogen peroxide or bleach to form cyanate from ferricyanide in alkaline environment

[Edited on 21-8-2020 by symboom]

Bedlasky - 25-8-2020 at 05:33

Try concentrated ammonia - cobalt forms soluble hexaammine complex.

macckone - 25-8-2020 at 12:16

Approved methods in industry in attached pdf.
Hydrogen peroxide requires a copper catalyst but the cobalt present may do the job.
Bleach will also work.

Now the bad news, iron cyanide compounds are really hard to get rid of.
Most of these methods reduce the cyanide to less soluble forms.
Like prussian blue.
And cobalt ferricyanate is already pretty insoluble.

What you really want to do is make the cyanide soluble so you can clean the filter.

Sodium Oxalate will produce cobalt oxalate and sodium ferricyanide. The sodium ferricyanide is soluble.
https://www.sciencedirect.com/science/article/abs/pii/S00032...

Then cobalt oxylate is soluble in aqueous ammonia.

Finally the cobalt oxylate can be decomposed to cobalt carbonate and the sodium ferricyanide can be reacted to an insoluble form with bleach and ferric sulfate. This yields some nice prussian blue if the molar ratios are right.

Attachment: SGS MIN WA017 Cyanide Destruction EN 11.pdf (241kB)
This file has been downloaded 371 times

Lion850 - 2-9-2020 at 16:54

Thanks for the replies and info gents. I soaked the funnel in each of hydrochloric, sulphuric, and nitric acids and sucking water through inbetween. And make sure the shed doors were open and I was not there while it soaked in the acids.

After this there was still some pale dark stains but the general use since then (the last week or so seems to have removed the rest and it is now perfectly white :)