Recntly I made activated carbon by powdered DIY charcoal with a CaCl2 solution and dried it in a white porcelain evaporating dish on a hotplate to
just over 100 C.
After drying however I cannot remove all black C stains from the dish, even with thorough cleaning agents.
Use piranha water (H2SO4 + 30% H2O2) will help ?
Heating with a small quantity of powdered KClO3 to 350 C should help to oxidize it or is that too hot for the dish ?
Or other ideas ?Dr.Bob - 7-1-2020 at 13:53
A little KOH in EtOH will generally clean most things off of glass or just etch off enough glass to make it look clean. You could just put a little
in the pan and tilt it to wet each area. You shsould not be able to hurt a small porcelain dish with heat, but if there is too much organic, an
oxidant could just blow up, so be careful with oxidizers, do it behind a hood or shield if in doubt. markx - 8-1-2020 at 01:58
Use piranha water (H2SO4 + 30% H2O2) will help ?
Heating with a small quantity of powdered KClO3 to 350 C should help to oxidize it or is that too hot for the dish ?
Or other ideas ?
Piranha solution works wonders cleaning all kinds of organic/carbonaceous residues off porous surfaces. I use it to clean sintered glass CO2 diffusers
that develop a layer of algae and other nasties after working in a planted tank for a while. Within a few minutes after immersing into piranha
solution the diffuser looks brand new and the sintered frits become pure white. I think it is your best bet at getting the carbon residue out.
Would not reccommend heating KClO3 for the purpose....risk of explosion and splatter of the molten salt might do more harm than good.DraconicAcid - 8-1-2020 at 06:50
I find that boiling nitric acid easily cleans out char left over from screaming gummi bear reactions. It may suffice for your dish.metalresearcher - 10-1-2020 at 04:29
Problem solved after three trials.
(-) The KOH in eithanol did not work, even after igniting the C2H5OH to heat the solution.
(-) The piranha water did not work either, I added aboit 1 part H2O2 30% to 3 parts H2SO4 conc. but to no avail. Maybe the H2O2 was degraded, I bought
it in 2014 as 50%.
(+) Finally I heated the dish on a hotplate to 360 C at which the molten KClO3 (a few grams only) wetted the dish and that resulted in cleaning the
dish.
Probably the first two methods do work on glassware, but not on a porcelain dish.
