A New Year's Reef Chemistry Puzzle (How to totally remove 10ppm ammonia in 10min)

[taricha]

Happy New Year!
Here's something a bit different just for fun. A riddle or puzzle of sorts.
Here is a "product" (not really) that completely removes large amounts of ammonia very quickly (really).
Below is a video of the process.


1L of tank water with ~10ppm total ammonia added
2.3mL reagent A (stir and wait 10 min)
7.0mL reagent B
1.2mL reagent C1
1 red sea scoop of reagent C2 (stir and wait 3 min)

then Done!


(At the end I added the water to a paly just to show there is nothing super toxic in the water that would make the paly react and close up.)


So what's in it? What are Reagent A, B, C?
for entertainment purposes only

I'll confirm correct answers in a day or two.

 

[Randy Holmes-Farley]

Nice. Thanks for posting it.

I'm not sure what chemicals you have in mind, and I suspect this is not even close, but a carboxylic acid chloride or other active ester may well do it. Such as acetyl chloride. Products are acetic acid, acetamide, and HCl.

It's a known way of synthesizing amides: acid chloride plus amine in water at pH above 7 (preferably around 10) gives an amide.

Acid chlorides react with ammonia, 1° amines and 2° amines to form amides

chem.libretexts.org

 

[taricha]

I'm not sure what chemicals you have in mind, and I suspect this is not even close

you're right, that's not very similar to the approach I was thinking of.
I'm learning new things though.

 

[taricha]

A hint in the video is that at 0:30-0:60 you can see that adding Reagent A causes a reaction with ammonia that turns the water quite yellow temporarily.

 

[J1a]

A wild guess from me, reagent A is probably hydroiodic acid, probably looking for an oxidating agent.

I saw precipitation when C is added. So presumably C should have a fairly high pH.

Are the volumes of reactants so chosen based on stoichiometry, or are they just a distractor?

 

[taricha]

No iodine involved.

Are the volumes of reactants so chosen based on stoichiometry, or are they just a distractor?

The volumes don't tell you much of anything, because those chemicals exist in many concentrations. I picked conveniently concentrated ones so I could do small volumes.
I had to overshoot the stoichiometry to make the ammonia consuming reaction fast (10 min).

 

[taricha]

So here's the fairly commonplace chemicals that were used to achieve the result in the video: Bleach, thiosulfate, and NaOH.

"Reagent A" is household 7.5% Bleach (7.1% available Chlorine).
So "reagent B" is the dechlorinator - 2% solution of sodium thiosulfate pentahydrate.
And "Reagent C1 & C2" are pH corrections by C1 = 1M NaOH, and C2 = a scoop of API pH 8.2 (Carbonate / Bicarbonate buffer)

Approximate mM for each:
Ammonia - 0.59
Hypochlorite - 2.12
Thiosulfate - 0.56
NaOH - 1.2
(plus 1 scoop of API carbonate/bicarbonate buffer)

article Hypochlorite oxidation of ammonia. Effective removal of ammonia from wastewater by UV-irradiation [pdf]
(I had to overshoot the bleach:ammonia ratio to make the reaction quick.)


It's just a puzzle and not a product, because you wouldn't want to actually do it for any useful amount of aquarium water. The chlorination of saltwater seems to unavoidably produce some amounts of Trihalomethanes (THM). These are probably harder to get rid of than either the ammonia or the chlorine.