Sciencemadness Discussion Board - Activated charcoal and ammonia

Activated charcoal and ammonia

Endimion17 - 1-11-2011 at 20:43

Seems to me like someone planted a disinformation on Wikipedia.

Quote:

"Contrary to a claim repeated[citation needed] throughout the web, activated carbon does not adsorb ammonia."

It was removed by one user, only to be written again. Of course, most of the editors "solve" problems by adding those pesky brackets instead of looking for an information.

They often engage in pointless rants, too, so in order to create a real evidence to use in their potential flame war, I've conducted an experiment which once and for all disprooves this lie I've seen elsewhere, too.

<iframe sandbox width="420" height="315" src="http://www.youtube.com/embed/bmsev_upccs" frameborder="0" allowfullscreen></iframe>

If this is not a solid piece of evidence, I don't know what is.

Takron - 1-11-2011 at 22:38

I"m glad to see experimentation to prove a point has not been lost on the world.

hkparker - 1-11-2011 at 22:43

Fits BromicAcid's signature I'd say.

Well done, good editing.

TheNaKLaB - 2-11-2011 at 01:51

Brilliant video! I agree with fully Takron. Now, someone needs to rewrite that statement on Wiki

Chemistry Alchemist - 2-11-2011 at 01:53

Where abouts is it? i could change it if you like... type what u want it to say an i can do it

Bot0nist - 2-11-2011 at 03:59

Very nice experiment Endimion17!

Neil - 2-11-2011 at 04:01

Nifty, I use AC to strip the lemon-yellow satan spew out of store ammonia and have always thought that the first 100ml or so that ran through were drastically reduced in ammonia.

Ignoring wiki and looking elsewhere it was hard to find a consensus answer on the absorption of ammonia by charcoal.

ScienceSquirrel - 2-11-2011 at 04:23

Activated charcoal is commonly used to strip ammonia out of water in aquariums, it also removes a lot of other higher molecular weight gunk from the water.
Generally activated charcoal likes big molecules with plenty of reactivity eg tannins, caramels, etc are preferred to small neutral molecules eg carbon monoxide or highly polar ions like sodium or chloride.
Thus it removes the crap that the fish do not like while leaving the things that they need like dissolved salts and oxygen.

Neil - 2-11-2011 at 04:36

Back when I saw a wee young lad that is what I used AC for, stripping ammonia out of my fish tanks. Now the AC online and the pet stores ramble about needing special ammonia absorption and all this other gibberish.

A fast google shows the same, seems like marketing has sown seeds of disinformation.

google seach for "activated charcoal absorb ammonia"

[Edited on 2-11-2011 by Neil]

Endimion17 - 2-11-2011 at 08:18

Thanks.

I've edited the wiki article around the same time this thread came to life and added a note on the talk page. So far no bots appeared.

I think charcoal's affinity towards NH<sub>4</sub><sup>+</sup> is only a fragment of the affinity towards gaseous ammonia. Polar water is in the way. Wet AC is ok for big molecules (dyes), but ammonium cation is very small and has to "fight" its way to the AC surface.
That's why gas masks work great and aquarium scrubbers... not so great. That might be one of the reasons why this myth appeared.

ScienceSquirrel - 2-11-2011 at 08:40

That depends on the pH of the water.
Ammonia is quite a weak base so at fish tank pH I would guess that some is available as the free base so it will stick to the charcoal.
There is a lot of charcoal in the average filter and not a lot of ammonia in the tank so it does not have to be very efficient anyway.

Adas - 2-11-2011 at 09:23

Wow, cool experiment mate, keep up the good work

bahamuth - 2-11-2011 at 10:24

Nice experiment.

Kinda neat to know that it does in fact adsorbes ammonia.

Have you tested it with different types of AC?

Know different types AC adsorbs variously to same molecule in both strength and amount.

From what kind of wood did you make the AC from and what methode? That might have a huge impact on the outcome of the experiment.

AndersHoveland - 2-11-2011 at 12:05

I found it surprising that the activated charcoal had enough affinity for NH3 that it could produce a pressure differential strong enough to raise the column of mercury several cm [mercury is a very dense heavy liquid!], while absorbing several times its volume of the ammonia gas.

One would suspect the affinity of water for ammonia gas is much higher than the absorbtive properties of carbon, however.

Quote:

"Contrary to a claim repeated[citation needed] throughout the web, activated carbon does not adsorb ammonia."

So this quote is generally true for most ordinary purposes, where the ammonia is in water, but certainly not in the strict scientific sense.

[Edited on 2-11-2011 by AndersHoveland]

White Yeti - 2-11-2011 at 12:06

Nice work!

But that tub of mercury scared the wits out of me. Is there not something less hazardous?

AndersHoveland - 2-11-2011 at 12:12

I do not think there were many other options besides mercury. The ammonia could not be soluble in the liquid, while at the same time the liquid could not be absorbed into the activated charcoal. So mercury was probably the best choice, although there does exist an alloy of gallium, indium, and tin, which is a liquid at room temperature, melting at [minus] -20°C.

White Yeti - 2-11-2011 at 12:33

How about using a saturated aqueous solution of ammonia instead of mercury? The ammonia cannot dissolve into the water (since it's saturated) and the charcoal can float on a piece of inert plastic. It would probably give less accurate results and you'd have to do a ton of vapour pressure calculations, but you wouldn't need to go buy some mercury off the interwebs.

This is a nice demo, but it's not something too many people can replicate. Speaking for myself, if I were to replicate this experiment, I would duplicate it with 20x less mercury, the same amount of ammonia and 4x more activated carbon. The thing that struck me in this demo, was the excess of mercury and the small amount of carbon used. This experiment was demonstrated to prove a point, no? To make carbon's affinity for ammonia more obvious, I would have definitely used more carbon, but that's just me.

Endimion17 - 2-11-2011 at 14:47

Quote: Originally posted by bahamuth

Nice experiment.

Kinda neat to know that it does in fact adsorbes ammonia.

Have you tested it with different types of AC?

Know different types AC adsorbs variously to same molecule in both strength and amount.

From what kind of wood did you make the AC from and what methode? That might have a huge impact on the outcome of the experiment.

I didn't have the time to try it out with different samples. I used a piece of wood (I have no idea what kind of wood), wrapped in an aluminium foil and heated over a flame.
It would be interesting to try it out using different materials (tree bark, dry blood, bones, meat, etc.).
I doubt different kinds of wood would make a huge difference. Charred animal tissues, certainly.

Quote: Originally posted by AndersHoveland

I found it surprising that the activated charcoal had enough affinity for NH3 that it could produce a pressure differential strong enough to raise the column of mercury several cm [mercury is a very dense heavy liquid!], while absorbing several times its volume of the ammonia gas.

I knew what should happen but it was interesting nonetheless. If it was water (disregarding the fact ammonia dissolves in it), the column would be almost 34 cm tall.

Quote: Originally posted by White Yeti

Nice work!

But that tub of mercury scared the wits out of me. Is there not something less hazardous?

Thanks.
There was ventilation and I left the room while the camera was filming.
Mercury is really the best choice. If you ventilate the area and follow the rules, there is no danger. It's not like you're going to do this more than 2-3 times in your life... Are you?

Quote: Originally posted by White Yeti

How about using a saturated aqueous solution of ammonia instead of mercury? The ammonia cannot dissolve into the water (since it's saturated) and the charcoal can float on a piece of inert plastic. It would probably give less accurate results and you'd have to do a ton of vapour pressure calculations, but you wouldn't need to go buy some mercury off the interwebs.

That is an option, but it's not just the vapor pressure. It's the water vapor fighting for the charcoal.

Quote:

This is a nice demo, but it's not something too many people can replicate. Speaking for myself, if I were to replicate this experiment, I would duplicate it with 20x less mercury, the same amount of ammonia and 4x more activated carbon. The thing that struck me in this demo, was the excess of mercury and the small amount of carbon used. This experiment was demonstrated to prove a point, no? To make carbon's affinity for ammonia more obvious, I would have definitely used more carbon, but that's just me.

I was in a hurry, having only 30 minutes to complete the experiment. If there was more time, I'd use more charcoal.
Less mercury is possible, but as I don't have a great deal of appropriate handy glassware, and got lots of mercury (not a flask, but certainly much more than you see in the video), I just made the setup nice as possible.
Plus my camera can't use macro while filming. Larger setup means I can record the experiment better.

IIRC, this is how it was done back in the old days, except everyone was sniffing the vapors. It's a shame no one does these things today.

mr.crow - 2-11-2011 at 16:32

Wow!!!

Nice synth music too

Big pools of mercury were how everyone did experiments back in the old days. I love how its back to basics

Was the activated charcoal totally dry? It would be a shame if your results were just ammonia dissolving in the water (like the ammonia fountain).

Endimion17 - 2-11-2011 at 17:25

I'm just waiting for the Youtube nincompoops to send me a copyright notice, even if I did nothing wrong.

It was dry in a sense it was made from a piece of wood some ten minutes before it was used. So yeah, I'd say it was reasonably dry.

Magpie - 2-11-2011 at 18:02

That's a nice experimental proof - simple, clean, and neat.

I wanted to comment on the pool of mercury. I view this as basically non-hazardous as long as it is at room temperature and is not dispersed. It always amazes me how people seem to over-react to metallic mercury. I once saw a professor of chemical engineering go bananas when he found out someone had dropped a Hg thermometer and it broke. And just today a professor (PhD in organic chemistry) was telling me "that he questioned the wisdom of using mercury although he had once used some in an instrument of some kind." It was like he was talking about some substance from another planet.

I feel fortunate that I had experience handling mercury, literally, when I was young, not routinely but once or twice. We boys rubbed it onto some coins to make them shiny, just for fun. I also managed to get it all over my gold ring and had to take it to a jeweler to get the Hg removed. I have no irrational fear of mercury and will use it, with the proper precautions, when it is needed.

According to this site, which has much information about mercury, "...at 20°C...its vapor pressure is 1.2 μmHg...":

http://mysite.du.edu/~jcalvert/phys/mercury.htm

Sedit - 2-11-2011 at 18:15

Has the experiment been performed without and absorbent material to be 100% sure that the Ammonia is not dissolving in the large excess of Hg? I doubt it myself but there will always be those who will attempt to use this as "proof" of a failed experiment.

[Edited on 3-11-2011 by Sedit]

Endimion17 - 3-11-2011 at 08:32

@Magpie: I have experience with the kind of academics you've described. Sometimes it goes to the absurd levels, as if something "radiates with evil". Nerds (not geeks!) that have the power of sucking in everything they read into their brains (like AC with ammonia) but critical thinking, naaaaah. Such dipshits slowly but surely destroy science in a country, and if there's a critical mass, might even consider pseudoscience to be a nice thing (happened here more than once).
When dealing with mercury, exposed surface and temperature are important. The temperature was 15 °C and the surface was ~36 cm<sup>2</sup>. Time of exposure to air was ~12 minutes.

@Sedit: That's a very good point... No, it hasn't.

AFAIK, ammonia solubility in mercury is negligible for this demo experiment. You're welcome to try, as is anyone else. Fill a piece of one side sealed glass tubing with ammonia and dunk it in a test tube with some mercury. Record the results and post here. Why not, that's a great idea.

BTW my video already got one negative vote. Few more and all that will be left then is a memewhore saying: "n people were adsorbed by charcoal."

Sedit - 3-11-2011 at 09:07

I might attempt this I'm not really sure yet. I have some Hg but its sealed in glass vials I would have to break open then deal with storage of it.

I want to think it through before I even consider dealing with the handling of the Hg because I don't wish to carry it in for my children to get even if it is trace amounts on my cloths or what not. I'm not so concerned with my brain but they are still developing nerve sheaths and I don't wish to foul that up any time soon.

Variables I wish to exclude is the temperature of the Ammonia gas and solubility of Ammonia in Hg. Both of these issues I feel could be solved by placing the Test tube in the Hg and leaving it there for a bit with observation... then once stabilized insert a small piece of AC with tweezers under the Hg so that it would float up and into the test tube, that it would prove without any doubt that the AC is absorbing the NH3 if the Hg stayed level until the AC was placed in.

MrHomeScientist - 3-11-2011 at 09:51

Great experiment! It's really satisfying to see a problem and be able to demonstrate the solution so cleanly and clearly.

Quote: Originally posted by Sedit

Variables I wish to exclude is the temperature of the Ammonia gas and solubility of Ammonia in Hg. Both of these issues I feel could be solved by placing the Test tube in the Hg and leaving it there for a bit with observation... then once stabilized insert a small piece of AC with tweezers under the Hg so that it would float up and into the test tube, that it would prove without any doubt that the AC is absorbing the NH3 if the Hg stayed level until the AC was placed in.

I like this plan a lot. That would difinitively prove that it is in fact the AC, and AC alone, that the ammonia is interacting with. Go play with mercury!