[lax123]

Hello,

im desperatly looking for a liquid in which CO2 does not dissolve. At least much less should dissolve then in water.
The liquid would be used at 40°C and should have a high viscosity at that temperature. I spend so many hours searching, but found nothing suitable.
Except for maybe Hg, but thats too dangerous.
The liquid would be sealing a gas of 50% CO2 and 50%Methane from air.
But due to the strong ability of CO2 to solve in water and the diffusion to air with a much smaller partial pressure of CO2 im loosing large amounts of that CO2/Methane Gas

I would be greatful if you could helpme :-)

[orgopete]

Carbonic acid?

[lax123]

Hi,

why would you think that? The problem is not the chemical solved CO2 with reactions to carbonic acids and carbonate, but the physically dissolved CO2, which makes up for 99% of CO2 that can be solved in water, at least thats how i understand the literature, that lowering pH would not really help at all.

[discodermolide]

Hello,

im desperatly looking for a liquid in which CO2 does not dissolve. At least much less should dissolve then in water.
The liquid would be used at 40°C and should have a high viscosity at that temperature. I spend so many hours searching, but found nothing suitable.
Except for maybe Hg, but thats too dangerous.
The liquid would be sealing a gas of 50% CO2 and 50%Methane from air.
But due to the strong ability of CO2 to solve in water and the diffusion to air with a much smaller partial pressure of CO2 im loosing large amounts of that CO2/Methane Gas

I would be greatful if you could helpme :-)

Heptane?

[Honclbrif]

You may be battling Henry's Law on this one.

[lax123]

Heptane?

unfortunately, as strangely as it sounds i found oils such as parrafine oil/ (would be similar to heptane, (i guess)) /mineral oils show even a better solubility for CO2 then water :-(

http://www.ritter.de/Ondina-909.135+M52087573ab0.0.html

can´t imagine thats it is impossible to find a practical liquid that stops sucking out the CO2 out of my gas :-/

[Fluoroantimonicacid]

I think you can use saturated carbonic acid.

[fledarmus]

I think you can use saturated carbonic acid.

That just makes a permeable membrane - carbon dioxide will be absorbed on one side and released on the other until the two sides are in equilibrium

[lax123]

jap, thats quite the problem... sure i can saturate a liquid, but still, the loss of gas by diffusion from high p(CO2) in my gas to low p(CO2) in air is high. so also a liquid with high viscosity but very slow diffusion of the gas could be helpfull.

please explain to me, why u think especially carbonic acid would be so helpfull in this matter?

[discodermolide]

Hello,

im desperatly looking for a liquid in which CO2 does not dissolve. At least much less should dissolve then in water.
The liquid would be used at 40°C and should have a high viscosity at that temperature. I spend so many hours searching, but found nothing suitable.
Except for maybe Hg, but thats too dangerous.
The liquid would be sealing a gas of 50% CO2 and 50%Methane from air.
But due to the strong ability of CO2 to solve in water and the diffusion to air with a much smaller partial pressure of CO2 im loosing large amounts of that CO2/Methane Gas

I would be greatful if you could helpme :-)

Ionic liquids are they of any use?

[lax123]

thought about it, read about it, people using a saturated NaCl/Salt-solution. But i dont know how that would help, like i read that 90% of the times acid solved in water is used for CO2 sealing, but by digging in more into literature i found that that would not actually make a big difference... so i guess with ions it would be the same as with acid... having effect on chemical bound CO2, but not on the 99% thats dissolved physically. Or as in my link the paraffine oil is used as sealing liquid, also quite expensive... but that oil dissolves even more CO2 then water... what the heck? the major problem is finding some evidence or good source on this matter.

[Honclbrif]

Is it critical that you use water/liquid as a sealant. Could you build a physically sealed apparatus?

[lax123]

im afraid not, having gas flowing somewhere in but not out can have quite devestating effects ;-)
to be serious: the gas pushes the liquid away and finally bubbles through the hole, after blubbling, the water level goes back to where it was at start. by that effect i can easily measue how much gas was produced. the black "thingy" measures the liquids level. problem is, to let the water level fall again, an amount of air("Luft") is sucked in, so phyisically "a one way valve" wont work either

to describe the major problem again, as u can see, when there is currently no gas flow, the CO2 can still dissolve in the water and reach the air, even if the water was saturated it would not much help, since the partial pressure of CO2 in air is so low there is diffusion all over the place

[Fluoroantimonicacid]

Why don't you filtrate CO₂ with Ca(OH)₂ first, then measure CH₄?

[lax123]

Yea just measuring methane would be quite easy just using 120g NaOH/per liter giving a 3m solution, fixing >99% CO2, if flowrate is slow enough, been there done that :-) , but the total amount of gas is what i need, knowing the methane amount/ percentage would be something like an interesting bonus feature ;-)
its a biogas, so also the percentages of CO2 and Methane r constantly changing, resulting in different p(CO2) thus resulting in different amounts of soluble CO2 and CO2 diffusion speeds, which also kinda makes it impossible to calculate a compensation or something like that.


currently im thinking about if something like that might work:
http://upload.wikimedia.org/wikipedia/commons/thumb/9/96/G%C3%A4rr%C3%B6hrchen.jpg/284px-G%C3%A4rr%C3%B6hrchen.jpg
sry dont know the word in english
if it also would let air in if sucked on it, or if it would work similar to a one way valve, which would be fail. then only the water in this trap would exchange gas with air and not the big outer cylinder, still there would be dissolved CO2 in the big cylinder, but the amount of diffusion might get reduced