Freeze drying Phosphoric acid

  • #1
Hello all.
I have carbonaceous material soaking in Phosphoric acid. I'd like to anneal it under an inert environment to activate the carbon. One method used in literature involved freeze drying the mixture and annealing it as is, as opposed to filtering or centrifuging the mixture. However, I am limited to a regular household freezer and a vacuum chamber. Does anyone have recommendations on how to achieve this with specialty tools?
Cheers
 
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Answers and Replies

  • #2
An update.
I built a small size vacuum chamber and placed the Phosphoric acid soaked material in a petri dish inside the chamber. After pumping the air out, I place the chamber in the freezer. After 24 hours there was build up of sublimated vapor in the chamber, so I pumped that out one more time and replaced the chamber in the freezer.
This is likely to fail. Here my opinion on why drying this into a powder would not work using this method: Freeze drying requires a continuous suction to extract the phosphoric acid vapors out of the chamber. This is would likely not happen using my contraption as my suction is not continuous and hence what I am doing is freezing a substance under vacuum. I'll keep at it for a few more days and update on the progress.
 
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  • #3
Nidum
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What are you actually trying to do ?
 
  • #4
Well, the idea is to dry this carbon which is soaking in Phosphoric acid to obtain carbon-phosphoric acid powder to be later activated at high temperature under inert environment. This creates surface groups on the carbon as well as increases porosity.
 
  • #5
Well, the idea is to dry this carbon which is soaking in Phosphoric acid to obtain carbon-phosphoric acid powder to be later activated at high temperature under inert environment. This creates surface groups on the carbon as well as increases porosity.
AN Update:
Contrary to my expectations, it worked! the gooey phosphoric acid soaked material turned into powder 4 days later. If anyone is interested in the vacuum chamber schematics, let me know.
 
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