Sciencemadness Discussion Board

disposal of likely contaminated waste

averageaussie - 16-9-2024 at 16:08

Hello all,
I am planning on doing a small synthesis of Nitromethane using sodium chloroacetate and sodium nitrite, and am currently writing up a procedure for review.
One issue I have run into is the disposal of any nitromethane contaminated waste. the procedure produces a large amount of water which will likely have nitromethane contained in it, and I have been unable to find a way of disposing of it in a safe way. is there a reaction I can use that will render the nitromethane safe to dispose of?
for example, sodium hydroxide attacks nitromethane turning it into methanol, but this reaction is reportedly rather energetic, as noted on the wiki page.
also, the procedures that I am referencing refer to the ph needing to be "faintly alkaline to phenolphthalein" (https://www.orgsyn.org/demo.aspx?prep=CV1P0401), what ph does this refer to? I have assumed a ph of 8-9, but someone with more expertise in terminology would probably know better.
any aid with this question, or just general tips, would be appreciated.
Thanks, Average

[Edited on 17-9-2024 by averageaussie]

Sulaiman - 16-9-2024 at 19:48

Phenolphthalein goes pink at about pH = 10
https://en.m.wikipedia.org/wiki/Phenolphthalein
you could use a pH meter but it is easier to use phenolphthalein ;)

For me, disposal methods often depend upon the volume to be neutralised.
What scale are you considering operating at ?

bnull - 17-9-2024 at 04:51

Quote:
also, the procedures that I am referencing refer to the ph needing to be "faintly alkaline to phenolphthalein" (https://www.orgsyn.org/demo.aspx?prep=CV1P0401), what ph does this refer to? I have assumed a ph of 8-9, but someone with more expertise in terminology would probably know better.

About 8 should do; that's when you begin to have the impression that the solution is almost turning pink. Sounds ridiculous but it's the best way I can describe. Chloroacetate is hydrolised to glycolate at higher pH, thus lowering the yield of nitromethane. Even bicarbonate can lower the yield. See notes 1 and 6 of the preparation.

Rainwater - 17-9-2024 at 07:45




Screenshot_20240917_114057_Samsung Internet.jpg - 33kB

averageaussie - 17-9-2024 at 15:24

Quote: Originally posted by Sulaiman  

For me, disposal methods often depend upon the volume to be neutralised.
What scale are you considering operating at ?

I am working with 1.25 mol of sodium chloroacetate (havent done the maths on it quite yet, in excess as recommended by the paper)
The issue I face is the contaminated water and solid left in the reaction vessel. the paper says the waste water "contains too little nitromethane to pay for recovery" (specifically in reference to the initial distillations, but I imagine this applies to all of the water produced)
The solid can be easily dissolved away, and is reportedly sodium chloride and sodium carbonate, which are safe enough to dump when diluted. again though, it is likely contaminated with who knows what.
the total waste for the procedure in terms of chemicals is likely to be; NaCl, NaCO3, NaOH, water, sodium glycolate (a small amount is likely produced unavoidably, hence the excess of sodium chloroacetate), and boric acid + borax, all of which is likely contaminated with dirty nitromethane.
while all of these can be poured down the drain if diluted sufficiently, since they are likely contaminated with nitromethane, making that a non-viable method of disposal. the question I am trying to ask is this:
how do I convert the nitromethane into a compound that can be safely disposed of in the trash or down the sink that doesn't involve burning it, as it isn't really viable in this scenario?
Quote: Originally posted by bnull  

About 8 should do; that's when you begin to have the impression that the solution is almost turning pink. Sounds ridiculous but it's the best way I can describe. Chloroacetate is hydrolised to glycolate at higher pH, thus lowering the yield of nitromethane. Even bicarbonate can lower the yield. See notes 1 and 6 of the preparation.

Thats what I figured, thanks. do you know what ph it hydrolyses at?

bnull - 18-9-2024 at 06:19

Conversion of --NO2 to --NH2 seems good. Sewers are full of amines anyway. How would you do that, that's another question.

Or perhaps paraffin wax could capture it from water. It works with chloroform, if I'm not mistaken.
Quote: Originally posted by averageaussie  
do you know what ph it hydrolyses at?

All of them, apparently. Chloroacetate hydrolyses to glycolate in the presence of water, but the rate at which it happens increases with pH. It's the reason why you add hydroxide to chloroacetic acid with good stirring, and not the inverse. I'm attaching some papers about it.

Attachment: L. F. Berhenke, E. C. Britton - Effect of pH on Hydrolysis Rate of Chloroacetic Acid.pdf (417kB)
This file has been downloaded 53 times
Attachment: H. M. Dawson, E. R. Pycock - The Kinetics of the Alkaline Hydrolysis of the Halogen-substituted Acetates.pdf (567kB)
This file has been downloaded 44 times
Attachment: L. F. Berhenke, E. C. Britton - Effect of pH on Hydrolysis Rate of Chloroacetic Acid.pdf (417kB)
This file has been downloaded 45 times
Attachment: H. M. Dawson, E. R. Pycock - The Kinetics of the Alkaline Hydrolysis of the Halogen-substituted Acetates.pdf (567kB)
This file has been downloaded 45 times

[Edited on 18-9-2024 by bnull]

averageaussie - 19-9-2024 at 15:38

Quote: Originally posted by bnull  
Conversion of --NO2 to --NH2 seems good. Sewers are full of amines anyway. How would you do that, that's another question.

Or perhaps paraffin wax could capture it from water. It works with chloroform, if I'm not mistaken.

Quote: Originally posted by averageaussie  
do you know what ph it hydrolyses at?

All of them, apparently. Chloroacetate hydrolyses to glycolate in the presence of water, but the rate at which it happens increases with pH. It's the reason why you add hydroxide to chloroacetic acid with good stirring, and not the inverse. I'm attaching some papers about it.

[Edited on 18-9-2024 by bnull]

Thanks a lot! these are really useful resources

bnull - 20-9-2024 at 05:47

Quote: Originally posted by averageaussie  
these are really useful resources

Oh, yes, really useful, especially when I manage to attach, not four different papers, but two papers and two copies (one of each). :mad:

I'll attach the two other papers here since it's too late to edit the post. Sorry for that one.

Attachment: H. M. Dawson, E. R. Pycock, Gilbert F. Smith - The Elimination of Chlorine (yada yada).pdf (393kB)
This file has been downloaded 47 times

Attachment: H. M. Dawson, E. R. Pycock - The Elimination of Chlorine in the Hydrolysis (yada yada).pdf (515kB)
This file has been downloaded 43 times

Note: The file names are too long and causing a bug when I upload the files.

averageaussie - 22-9-2024 at 14:37

no worries, we all make mistakes.