Chemical High-Frequency Ultrasound In Situ Conversion of Ammonia to Hydrazine

[dwtmint]

https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.202212719


I was recently reading about how @Lou and @4metals favorite (or second favorite) way to reduce PM salts to metal was using hydrazine (N2H2).

I initially studied the ammonia/urea and bleach synthesis methods, but after reading up on its toxicity (think blood, brain, liver toxic and cancerous explosive lye), and the associated annoying safety protocols, I began to investigate the possibility of the in situ (in place) generation of hydrazine.

Interestingly, hydrazine is much less toxic while in solution or as a salt (losing most of its routes of exposure and explosiveness), and its decomposition products are relatively safe (depending on conditions: nitrogen gas, ammonia gas, hydrogen gas and water).

I had a few ideas I was chasing down when I ran across this ammonia solution sonochemistry method that I found most interesting, the first paper was in 2021 and then another in 2022.

The 2021 paper was proof of concept and the 2022 paper was actually using the hydrazine as an in situ reducing agent.

The ultrasonic sonicator they used is the Sinaptec NexTgen LAB1000 with a transducer frequency of 525 kHz. I was able to find a 400 kHz one on ebay for a couple hundred bucks. I'm wondering if 400kHz would be enough. I intend to do more research and possibly experimentation.

Would be neat to put a glove on this thing and lower it into a solution of PM and ammonia, turn it on and have the metal rain out with nothing but nitrogen gas bubbles as a by product.

Hydrazine safety summary:
nervous system antidote (seizures, coma, cognitive): Vitamin B6 gram for gram of exposure up to 5g at 0.5g/min and then rest over period of 6 hours.
blood antidote: intravenous Methylene Blue 1mg/kg, or 300mg orally, to prevent destruction of red blood cells (hydrazine detectable in blood 30 seconds after skin contact)
ingestion antidote: activated charcoal, must be administered immediately, no good by the time you get to hospital (will block oral Methylene Blue)
skin: immediately treat same as caustic (sodium hydroxide) burns (wash, dilute, neutralize contact area, delayed burns possible)
NOTE: all antidotes safe to use before noticeable symptoms
NOTE: as of 2023, "There have only been 2 reported cases of death from direct hydrazine toxicity."

 

[Yggdrasil]

View attachment 67077
https://onlinelibrary.wiley.com/doi/epdf/10.1002/anie.202212719
View attachment 67076

I was recently reading about how @Lou and @4metals favorite (or second favorite) way to reduce PM salts to metal was using hydrazine (N2H2).

I initially studied the ammonia/urea and bleach synthesis methods, but after reading up on its toxicity (think blood, brain, liver toxic and cancerous explosive lye), and the associated annoying safety protocols, I began to investigate the possibility of the in situ (in place) generation of hydrazine.

Interestingly, hydrazine is much less toxic while in solution or as a salt (losing most of its routes of exposure and explosiveness), and its decomposition products are relatively safe (depending on conditions: nitrogen gas, ammonia gas, hydrogen gas and water).

I had a few ideas I was chasing down when I ran across this ammonia solution sonochemistry method that I found most interesting, the first paper was in 2021 and then another in 2022.

The 2021 paper was proof of concept and the 2022 paper was actually using the hydrazine as an in situ reducing agent.

The ultrasonic sonicator they used is the Sinaptec NexTgen LAB1000 with a transducer frequency of 525 kHz. I was able to find a 400 kHz one on ebay for a couple hundred bucks. I'm wondering if 400kHz would be enough. I intend to do more research and possibly experimentation.

Would be neat to put a glove on this thing and lower it into a solution of PM and ammonia, turn it on and have the metal rain out with nothing but nitrogen gas bubbles as a by product.

Hydrazine safety summary:
nervous system antidote (seizures, coma, cognitive): Vitamin B6 gram for gram of exposure up to 5g at 0.5g/min and then rest over period of 6 hours.
blood antidote: intravenous Methylene Blue 1mg/kg, or 300mg orally, to prevent destruction of red blood cells (hydrazine detectable in blood 30 seconds after skin contact)
ingestion antidote: activated charcoal, must be administered immediately, no good by the time you get to hospital (will block oral Methylene Blue)
skin: immediately treat same as caustic (sodium hydroxide) burns (wash, dilute, neutralize contact area, delayed burns possible)
NOTE: all antidotes safe to use before noticeable symptoms
NOTE: as of 2023, "There have only been 2 reported cases of death from direct hydrazine toxicity."

The major question is what concentration is needed and if the generation of Hydrazine is sufficient for this purpose.

If I'm not mistaken Hydrazine is cheap and relatively easy to aquire if you have the proper paperwork/licenses in order.
It's toxisity should be manageable as long as proper fume hoods and gear are used.

 

[Yggdrasil]

Cavitation bubble chemistry and physics are quite intriguing and create "impossible" effects.

Or rather previously assumed impossible results.

 

[dwtmint]

The major question is what concentration is needed and if the generation of Hydrazine is sufficient for this purpose.

That's a good question. In my ignorance, I'd assumed that a molecule of hydrazine would reduce a molecule of salt and get used up as fast as it is made, that may not be the case.

 

[Yggdrasil]

That's a good question. In my ignorance, I'd assumed that a molecule of hydrazine would reduce a molecule of salt and get used up as fast as it is made, that may not be the case.

The chemistry do not change, so the molarity equations still rule.
But how much ultrasonic energy is needed in a given Ammonia concentration to create the needed amount of Hydrazine to get the job done?

It is always like this:
If the big boys(companies) don't use it it has some drawbacks we do not see at the moment.
Or it may just be too new and untested, which is not very likely, since they are always on a lookout for newer cheaper ways to do things.

 

[orvi]

The major question is what concentration is needed and if the generation of Hydrazine is sufficient for this purpose.

If I'm not mistaken Hydrazine is cheap and relatively easy to aquire if you have the proper paperwork/licenses in order.
It's toxisity should be manageable as long as proper fume hoods and gear are used.

Hydrazine is effectively 4 electron reducing agent if I see and remember it correctly. Single N-N bond is oxidized in the process into elemental nitrogen gas, thus gaining 4 electrons. Meaning a lot chemistry-wise in comparison to like sulfur dioxide or zinc/copper, which only donate 2 electrons.

Hydrazine is quite cheap. And salt is much more accessible due to lowered explosive/toxicity/exposure hazards and less shipping requirements.

But I will advise to use hydrazine for PM reductions only when your business/shop was licensed and you can legally use it in the process. That means (in many countries), that some folks visited your operation and made complaints/required some improvements/you signed liability papers etc... Because hydrazine is toxic. On the scale used as sole precipitant in small refinery, I would say significantly dangerous substance in the light of overall used substances used every day in the premises.

I never needed hydrazine to do the job with common 5 PM´s. And I tried it even for mid-sized batches few times. It was good - results were impressive, quick and working. No complaints there. But there is that second side. Which I thoroughly passed through as an organic chemist. If the hydrazine was the sole precipitant for gold or other PMs in the universe, I will use it. But it isn´t. So I don´t.

 

[dwtmint]

I discovered a flaw in my design that was due to my lack of ultrasonic knowledge. The power rating of your transducer is important and must match the viscosity of your fluid to achieve cavitation. That is, the little sound induced bubble reactors that are capable of converting ammonia in solution to hydrazine and therefore reduce your precious metals.

"For acoustic cavitation to occur, a power threshold must be reached. This threshold is 0.5 W / cm² at 20 kHz, for water at atmospheric pressure and of a few W / cm² for organic solvents. The amplitude of the vacuum to be supplied in order to reach the cavitation threshold depends on several parameters: the higher the viscosity of the medium (that is to say the internal cohesion of the liquid), the more difficult it is to obtain cavitation because the particles are more difficult to separate."
https://www.silabtec.com/en/general-principle-the-cavitation/

So from an economic side, you need to determine the minimum power required to induce cavitation in PM and ammonia solution viscosity, as the cost of the inducer is proportional the the power it can handle. The power level required appears to be substantially higher than what the gas flow, fuel level, imaging and range finding sonic transducers in this frequency range are normally capable of. Which is a good thing, you don't want to be transmuting your fuel, but bad for the refiner that wants in situ hydrazine.

 

[dwtmint]

https://onlinelibrary.wiley.com/act...e=anie202109516-sup-0001-misc_information.pdf

This is from the supplementary information page for the 2021 paper. Interestingly, it looks like the power requirement for hydrazine creation is lower than specified in the general statement on power requirements for cavitation posted earlier. In addition to power flexibility, it seems that we may have some frequency flexibility too, as below they were able to convert ammonia to hydrazine inside a poly bottle with the transducer outside of the poly bottle (see pic below). I assume the poly bottle would alter the frequency. I've seen cheap (read lower power) 1 MHz and even 2 MHz transducers, I wonder if you raise the frequency, the power requirements go down for a specific reaction. For example, the general statement says 0.5w/ml @ 20 kHz required, but the 2021 paper achieved cavitation induced conversion to hydrazine using half of that power and lower @ 525 kHz. That makes me hopeful enough to do some experimentation anyway.

 

[dwtmint]

Important part of the video, besides describing how to rig up a DIY sonic transducer, is how to increase the gain.