Sciencemadness Discussion Board

Urea to Ammonia using urease

vanBassum - 5-10-2023 at 23:56

Hello,

Let me start off by saying that my knowledge of bio is just about enough to keep myself alive. So please bear with me. :D

Every so often I have the urge to try and make nitric / nitrates. Last time I made platinum on quartz wool and used a pump to bubble air through an ammonia solution. That worked, but doesn't seem very economical or practical. While I was looking around for possible candidates to convert into nitrates, urea seems to be the most economical. Problem is, I need to convert the urea to ammonia. I have looked into thermal decomposition and a process called eU2A that uses electrolysis. When using these methods, I soon found that the output of ammonia isn't steady enough to leave it running for a couple of hours.

While searching the internet, I found that urea could be hydrolyzed to ammonia using an enzyme called urease. Apparently, this enzyme is found in watermelon seeds. My idea is to get a watermelon and just try it out. (I mean, they are delicious, so win-win.) As a first test, I was thinking of just crushing up some seeds and put them in a solution of water and urea. Then I hope to smell ammonia after a bit. If this works, I just pump air through the solution, driving the ammonia / air mixture through the catalyst. I assume you need quite a lot to get a decent production of ammonia. I was thinking of filling a 25L bottle. As a very nice bonus, the urea is converted into ammonia and CO2, so there won't be any products left after the urea is depleted. It might be possible to just keep feeding the reaction more urea.


Now for my questions:
- Has anybody got experience using urease?
- How many seeds would I need per liter?
- Could the urease be isolated from the seeds?
- What concentrations of urea do I need?
- Is this a viable idea?

Sources:
- eU2A: https://iopscience.iop.org/article/10.1149/2.0041510eel
- Urease: https://microbiologyinfo.com/urease-test-principle-media-pro...

Alkoholvergiftung - 6-10-2023 at 04:10

I ve only read that before ww1 an Factory in Yokohama worked with urease and urin. They made ammonia in worth of 140Mark (that was an lot worth) a day. The urease was form soya beans. Maybe you finde more with google.

UC235 - 6-10-2023 at 20:40

Enzymes don't really work like that. They're generally quite slow relative to lab chemistry, they tend to die when their solutions are bubbled (physical denaturation at the air/water interface), and typically require buffer solutions with pH control for activity. Without pH control, formation of ammonia will rapidly raise pH and the enzyme stops working. It may even irreversibly denature it but that is enzyme specific

Tsjerk - 7-10-2023 at 09:08

Not to mention the effect of concentration of the product often effects the enzyme activity. When the concentration of ammonia/ammonia salts becomes too high activity will drop.