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Author: Subject: dioxane gunk removal
dactyl
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[*] posted on 23-10-2016 at 10:01
dioxane gunk removal


Hi I made dioxane from ethylene glycol and sulfuric acid in June and distilled it once and kept the distillate.

Last week I distilled it a second time and when the distillation was over much gunk remained in the flask; I added sulfuric acid to dissolve this gunk. The gunk did not dissolve so I heated it in a far away outside fireplace ; it did not dissolve but the contents overflowed.

Now the gunk is stuck to the flask; is it possible to dissolve it in concentrated NaOH or would another method be better.


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BromicAcid
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[*] posted on 23-10-2016 at 10:12


Ehhh, what a mess. I would go mechanical removal before trying with 'solvents' again, likely you just have carbonized junk which will not dissolve in much of anything. I would be reluctant to use Piranha on it since you likely have plenty of more readily oxidizeable garbage in there which can lead to problems. What size is the flask, it's hard to tell. A wooden doll rod is a good place to start because if you slip you likely will not punch a hole in your flask.



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dactyl
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[*] posted on 23-10-2016 at 10:14


1000 ml
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[*] posted on 23-10-2016 at 11:44


This sort of thing helps.
http://www.lakeland.co.uk/8949/Magic-Copper-Balls-For-Cleani...

If you dig most of the char out with a spatula or something then swirl the copper beads round they scour out quite a lot more.
You will probably end up using something like boiling H2SO4 to get the last of the junk out.
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dactyl
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[*] posted on 23-10-2016 at 11:56


Would boiling the junk with H2SO4 turn it into carbon dioxide? What about piranha?
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[*] posted on 23-10-2016 at 12:49


At a high enough temperature
C + 2 H2SO4 --> CO2 +2SO2+ 2 H2O

(at that temperature you are pretty near the point where C + O2 --> CO2 and also near the pint where the glass melts)
Piranha works too
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dactyl
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[*] posted on 23-10-2016 at 12:52


sulfuric acid would be a gas most likely at atmospheric pressure
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[*] posted on 23-10-2016 at 16:11


Instead of copper balls I have used rock salt and methanol to shake around in flasks to abrade the gunk off the walls.



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AJKOER
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[*] posted on 24-10-2016 at 05:07


Apply physical methods.

Then, run a much less physical and more advanced photochemical or Fenton reaction to produce hydroxyl radicals in the presence of hydrogen gas (best under pressure) to attack the carbon. Place in sunlight and let it sit for some time.

Reference:
April 1975, Vol.13(2):115–124, doi:10.1016/0008-6223(75)90268-7, link http://www.sciencedirect.com/science/article/pii/00086223759... to "The reaction of hydroxyl radicals with carbon at 298 K", by M.F.R. Mulcahy and B.C. Young.

Logic: Both the hydroxyl radical and the hydrogen atom radical (from the action of the hydroxyl radical on H2) attack carbon.

Sample embodiment: Place a very small amount of Zinc metal in a large excess of cheap HCl or H2SO4 together with sheets or bars of Iron and Copper. Seal after venting out air to form a pressurized hydrogen atmosphere. Place in sunlight.
-------------------------------

Another idea, not as gaseous but full of juice. Make an electrode with say a stainless steel ball soldered on to an insulated copper wire. The other electrode is copper that is positioned in the middle of the flask. Rest the ball/electrode on the carbon surface and move it around as needed during an electrolysis (using a battery source) of an electrolyte of, say, aqueous MgSO4. My experience with graphite is that is it just falls apart in the process of making CuSO4 and a white precipitate of Mg(OH)2.

[Edited on 24-10-2016 by AJKOER]
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[*] posted on 24-10-2016 at 09:56


K2Cr2O7 (or CrO3) with concentrated H2SO4 and then heating this in the flask. This dissolves many difficult to remove organic/carbonized compounds. It is more toxic than piranha solution, but much safer to use, because there is no risk of explosion.

Piranha solution is much better from an environmental point of view. You can mitigate the waste issue somewhat by dissolving the orange acid/hexavalent chromium mix in water and adding sodium metabisulfite until the color is purely green with a bluish hue. If that point is reached you have trivalent chromium. You can flush that down the drain with a lot of water.




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dactyl
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[*] posted on 2-12-2016 at 21:16


Thanks for the replies.

I would have responded much sooner but I got stuck with work and later sick.

The dissolution in piranha acid seem slow to a degree when I added it. A majority of the product I suspect is carbon since I dont believe piranha oxidized elemental carbon well.
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[*] posted on 3-12-2016 at 00:51


If I have carbonized gunk in a flask, I usually put a bit of nitric acid in it, and hit it with a bunsen burner.



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[*] posted on 3-12-2016 at 05:25


Quote: Originally posted by dactyl  
The dissolution in piranha acid seem slow to a degree when I added it.

did you use 30% H2O2 ? Did you use the right ratio ?
https://www.youtube.com/watch?v=cLpSapjKcxM
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[*] posted on 3-12-2016 at 10:54


I bet some copper coated metal BB's would work just as well, and you could probably pick them up at the closest big store.
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[*] posted on 6-12-2016 at 08:43


I think Praixchys used acetone in one of his videos to clean it.
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[*] posted on 6-12-2016 at 09:36


I'll second Woelen's idea. Chromic acid is very effective at getting rid of nasty organic residues, not just by reacting but by physically detaching them from the flask. And while you're at it you may as well reduce the leftover hexavalent chromium with some ethanol and add sodium carbonate to precipitate chromium(III) hydroxide which is fun to have around.



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[*] posted on 6-12-2016 at 09:50


I personally use store bought copper coated steel BB's. Swirl them around the flask with 10=15 mls of water then use a strong magnet to get them out of the carbon water solution.
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Herr Haber
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[*] posted on 7-12-2016 at 04:58


I'm not terribly good at maths but...

H2SO4 + H2O2 (or K2Cr2O7) + danger involved and time spent in cleaning = more than than what I'd pay for a new RBF
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[*] posted on 12-2-2017 at 18:42


@CuReUS

The concentration was 15%; this likely was one of my issues.

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[*] posted on 12-2-2017 at 18:45


ignore the attachment
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[*] posted on 13-2-2017 at 06:29


Anything strongly oxidizing in combination with sulfuric acid and strong heating should work. You can try dichromates, permanganates, H2O2, nitrates, and persulfates. Always use these mixtures with extreme caution. Certain organic materials form explosive mixtures with these strong oxidizers.



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[*] posted on 13-2-2017 at 07:26


Hot NaOH solution seems to be very good, not at dissolving this kind of gunk, but physically detaching it from the glass surface. I often do this and then use a sharp tool to kind of break up the stuff so that it can fit through the glass joints out of the flask.
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