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VeritasC&E
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Removing trace impurities from H2O2
Hello,
I have some H2O2 at 9% concentration and I'd like to use it in small quantities for applications with puriss. reagents I would not like to
contaminate.
How would you go about purifying it (in the sense of removing impurities other than water and H2O2 down to maybe <1ppm for any single impurity)?
I'm predominantly concerned about traces of metal ions and maybe stabilizer additives from the pre-dilution H2O2 solution it was probably made from.
I looked it up in a lab chemicals purification book but the process there was for concentrating H2O2, not riding it from impurities.
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morganbw
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I do not want to come off as being rude but sometimes if you need the good stuff you need to buy. Of course you may figure it out, I am just pointing
out my thought process.
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Metacelsus
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What are the impurities? An ion-exchange resin might work.
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VeritasC&E
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Is there is no reasonable way to purify it and is it just better to produce it pure from scratch? Or do you mean in terms of time saving?
I like to purify stuff myself when possible. A point here is that the price per liter literally varies from ~$2 to ~$20 going between probably fairly
clean H2O2 solution and puriss. H2O2. I can afford to do chemistry only at fairly priced consumables.
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VeritasC&E
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I'm not sure what they are. I know sometimes stabilizers are added to the more concentrated H2O2 it might have been made from, and other likely
impurities would be ions from the water (say it's made from RO water for economical reasons), and maybe from the apparatus that was used to produce it
(Fe, Ni, Cr for instance if stainless steel was used).
Do you know which stabilizers are commonly used in commercial H2O2 solutions?
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DraconicAcid
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I suspect hydrogen peroxide would be too prone to decomposition during purification to bother trying.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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VeritasC&E
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So we just have to rely on the pricing of big companies if we absolutely want it pure?
[Edited on 2-9-2020 by VeritasC&E]
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unionised
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I can't see any theoretical objections to sub distillation at home. as long as you have the kit.
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VeritasC&E
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Should I vacuum distill the solution below boiling point with the goal in mind to get a much purer (albeit initially less concentrated) H2O2 solution
in the receiver? And in a second step boil away enough H2O to reconcentrate the purified solution to the initial 9%?
Thank you for your contribution!
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teodor
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As far as I remember from this video - https://www.youtube.com/watch?v=nVAe__ToAOY
you can distil without vacuum H2O2 as 25-30% mixture with water. I didn't try it by myself and if I would do I would take a lot of precautions, there
are some safety issues especially if you have little experience in this.
[Edited on 2-9-2020 by teodor]
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unionised
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I think you need to start by looking up "sub distillation" i.e. "sub boiling distillation".
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zed
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H2O2 is easy to concentrate. Problem is, it usually contains stabilizers that are easily concentrated too.
Easily concentrated, and hard to eliminate, when present in your final product. In years past, acetanilide was a common stabilizer. Might still be.
I don't know. But, in some applications it presents a real problem.
The solution to this problem, is to start with H2O2 that doesn't contain stabilizing agents, that are gonna mess things up.
Oh yeah, and apparently H2O2 may be able to "etch" ordinary glasses. Thereby contaminating itself. Grrrr.
Gotta find a way to obtain "better" peroxide, if your work is critical.
An ancient paper on the subject, yet still so contemporary!
There may be numerous contaminants in commercial peroxide, and they may have to be contended with under some circumstances. Perhaps the author's
difficulties, will provide illumination.
https://archive.org/details/interactionofpla00shaf/page/n1/m...
[Edited on 2-9-2020 by zed]
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VeritasC&E
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Isn't this just slow distillation under BP? Woudn't it be enhanced by vacuum? (which also also would allow a significantly reduced rate of
decomposition)
Your suggestion is good but I just want to be sure I correctly understand the process to follow and how efficient that would be. How much H2O2 can I
expect to carry away with the water vapour into the receiver flask (i.e. what concentration can I expect in my receiver starting with my 9% material)?
[Edited on 2-9-2020 by VeritasC&E]
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VeritasC&E
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In theory, separation by freezing could be a route (assuming H2O2 is a bad solvent)
In practice however the process looks it could be very tedious (very close MPs), and hard to perform without contaminating the solution that is
supposedly being purified.
In theory:
Freeze a portion of the solution > Pass through pre-cleaned Frit > Dilute again with Distilled Water > Mix Well > Repeat
The main problems I could see:
1) How to minimize H2O2 loss in the ice?
2) Contamination during filtration
3) Energy & Time Cost
[Edited on 2-9-2020 by VeritasC&E]
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unionised
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Quote: Originally posted by VeritasC&E  |
Isn't this just slow distillation under BP? Woudn't it be enhanced by vacuum? (which also also would allow a significantly reduced rate of
decomposition)
Your suggestion is good but I just want to be sure I correctly understand the process to follow and how efficient that would be. How much H2O2 can I
expect to carry away with the water vapour into the receiver flask (i.e. what concentration can I expect in my receiver starting with my 9% material)?
[Edited on 2-9-2020 by VeritasC&E] |
The important aspect is that you don't boil the material.
That way, you don't generate "spray" which carries over involatiles like stabilisers.
In principle, starting with 9% you end up with 9%.
But without any involatile materials.
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VeritasC&E
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| Quote: Originally posted by unionised | | Quote: Originally posted by VeritasC&E |
Isn't this just slow distillation under BP? Woudn't it be enhanced by vacuum? (which also also would allow a significantly reduced rate of
decomposition)
Your suggestion is good but I just want to be sure I correctly understand the process to follow and how efficient that would be. How much H2O2 can I
expect to carry away with the water vapour into the receiver flask (i.e. what concentration can I expect in my receiver starting with my 9% material)?
[Edited on 2-9-2020 by VeritasC&E] |
The important aspect is that you don't boil the material.
That way, you don't generate "spray" which carries over involatiles like stabilisers.
In principle, starting with 9% you end up with 9%.
But without any involatile materials. |
But isn't there a significant BP difference between H2O and H2O2? Do they form an azeotrope? In which case, would you know within which proportions
and parameters?
[Edited on 2-9-2020 by VeritasC&E]
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unionised
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They might form an azeotrope, I think so, but I'd need to look it up.
However, an azeotrope is only relevant if you are boiling something and...
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VeritasC&E
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| Quote: Originally posted by unionised | They might form an azeotrope, I think so, but I'd need to look it up.
However, an azeotrope is only relevant if you are boiling something and...
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Yes, we are not boiling.
What I mean is that unless they behave like such, I don't understand quite why I would get in the receiver flask the same concentration as in the
original concentration when the BP of the two miscibles are so far appart. Per my limited understanding, I wouldn't expect that to happen. I'm not
sure how to use their relative vapour pressures but I'd expect that they could be used to indicate what the concentration in the receiver might look
like (I would expect it to be lower, or even somewhat higher, but not the same as in the initial solution).
[Edited on 3-9-2020 by VeritasC&E]
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unionised
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Because, in principle, you evaporate all of the contents of the distillation flask and condense all of it in the receiver.
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VeritasC&E
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| Quote: Originally posted by unionised | Because, in principle, you evaporate all of the contents of the distillation flask and condense all of it in the receiver.
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Is there no risk of overconcentrating the H2O2 in either the initial portion of the receiver or (more likely) in the very late portion of the source
flask?
When only half of the solution has been carried over, do you know if the receiver will have an increased or rather a decreased H2O2 concentration?
I know 9% H2O2 is very safe, but I also know H2O2 vapours or more concentrated solutions can be dangerous, so it's important that I can visualize the
dynamics of the process to know where H2O2 can get concentrated in case I need to do something to avoid it.
Thanks a lot for your contributions by the way!
[Edited on 3-9-2020 by VeritasC&E]
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teodor
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Could the method of purification by crystallisation with pure urea or sodium carbonate be as good as distillation?
Also, you will unable to remove some usual tap water organic or gases like NH3 with a distillation. By the way, the presence of organic matter and
small quantities of resulting organic peroxides probably is something which should be considered when performing distillation, what do you think?
[Edited on 3-9-2020 by teodor]
[Edited on 3-9-2020 by teodor]
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unionised
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| Quote: Originally posted by VeritasC&E | | Quote: Originally posted by unionised | Because, in principle, you evaporate all of the contents of the distillation flask and condense all of it in the receiver.
|
Is there no risk of overconcentrating the H2O2 in either the initial portion of the receiver or (more likely) in the very late portion of the source
flask?
When only half of the solution has been carried over, do you know if the receiver will have an increased or rather a decreased H2O2 concentration?
I know 9% H2O2 is very safe, but I also know H2O2 vapours or more concentrated solutions can be dangerous, so it's important that I can visualize the
dynamics of the process to know where H2O2 can get concentrated in case I need to do something to avoid it.
Thanks a lot for your contributions by the way!
[Edited on 3-9-2020 by VeritasC&E] |
When you are half way through, one container or the other will hold more than 9% H2O2
My guess is that water will evaporate preferentially at first leaving more concentrated H2O2 in the distillation flask and a more dilute solution in
the receiver.
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VeritasC&E
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| Quote: Originally posted by unionised | | Quote: Originally posted by VeritasC&E | | Quote: Originally posted by unionised | Because, in principle, you evaporate all of the contents of the distillation flask and condense all of it in the receiver.
|
Is there no risk of overconcentrating the H2O2 in either the initial portion of the receiver or (more likely) in the very late portion of the source
flask?
When only half of the solution has been carried over, do you know if the receiver will have an increased or rather a decreased H2O2 concentration?
I know 9% H2O2 is very safe, but I also know H2O2 vapours or more concentrated solutions can be dangerous, so it's important that I can visualize the
dynamics of the process to know where H2O2 can get concentrated in case I need to do something to avoid it.
Thanks a lot for your contributions by the way!
[Edited on 3-9-2020 by VeritasC&E] |
When you are half way through, one container or the other will hold more than 9% H2O2
My guess is that water will evaporate preferentially at first leaving more concentrated H2O2 in the distillation flask and a more dilute solution in
the receiver. |
Is there no danger towards the end of the process?
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VeritasC&E
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| Quote: Originally posted by teodor | Could the method of purification by crystallisation with pure urea or sodium carbonate be as good as distillation?
Also, you will unable to remove some usual tap water organic or gases like NH3 with a distillation. By the way, the presence of organic matter and
small quantities of resulting organic peroxides probably is something which should be considered when performing distillation, what do you think?
[Edited on 3-9-2020 by teodor] |
Hello! Could you describe that method?
[Edited on 3-9-2020 by VeritasC&E]
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Fyndium
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I'm under impression H2O2 can be safely vacuum distilled to a high concentration.
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