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I would like to use a liquid solvent for some experimentation with a carbon dioxide solubility as low as possible under usual pressure and temperature conditions (say, $\pu{1 atm}$ and $\pu{293 K}$).

Until then, I was unable to find much information on the topic:

  • A study of $\ce{CO2}$ solubility in water and seawater by Weiss [1], indicating that $\ce{CO2}$ is less soluble in saline water than in pure water.

  • Publications concerning several organic solvent (acetone, cyclohexane, ethanol, methanol, etc.), a sum-up in IUPAC SDS Vol 50 [2]. To the naked eye, it seems that all of them can dissolve much more $\ce{CO2}$ than water, being poor candidates to answer my needs.

  • Publications concerning olive, linseed or other origin oils (see Simon and Gutknecht [3] for instance). However such fats seems to also have a higher solubility coefficient than water.

I do not know if such liquid does exist, but it would be great. Up to now, my best candidate is salty water.

References

  1. Weiss, R. F. Carbon Dioxide in Water and Seawater: The Solubility of a Non-Ideal Gas. Marine Chemistry 1974, 2 (3), 203–215. https://doi.org/10/cb6n2j.
  2. Carbon Dioxide in Non-Aqueous Solvents at Pressures Less than 200 kPa; Fogg, P. G., Clever, H. L., Eds.; Solubility data series; Pergamon Press: Oxford, 1992. ISBN 978-0-08-040495-0. PDF
  3. Simon, S. A.; Gutknecht, J. Solubility of Carbon Dioxide in Lipid Bilayer Membranes and Organic Solvents. Biochimica et Biophysica Acta (BBA) - Biomembranes 1980, 596 (3), 352–358. https://doi.org/10/bj647m.

Update

I understand the "like dissolves the like"[1] rule of thumb so that a highly polar solvent would be the worst for a non-polar molecule such as $\ce{CO2}$. Water as a solvent would then be the best choice (possibly salted to further reduce its $\ce{CO2}$ solubility) for my needs.

But as Rolf pointed out, the dissociation of $\ce{CO2}$ into carbonate ions also happens and might increase its solubility. For such reasons an aprotic solvent could be useful.

However, when comparing between water (molar fraction 0.00061) which is a strongly polar (dielectric constant: 80 and dipole moment 1.85$~$D) but protic solvent and dimethyl sulfoxide (molar fraction 0.0091[2]) which is also polar (dielectric constant: 47 and dipole moment 3.96$~$D) but aprotic solvent, dimethyl sulfoxide as a higher solubility for carbon dioxide than water.

What can be the reasons for such unexpected outcome? Are my reasonings and assumptions correct or am I flawed in my thinkings?

References

  1. Polar Protic? Polar Aprotic? Nonpolar? All About Solvents. - Master Organic Chemistry. https://www.masterorganicchemistry.com/2012/04/27/polar-protic-polar-aprotic-nonpolar-all-about-solvents/
  2. Li Hua & Chen Wanren, 2005, Solubility of dilute SO2 and CO2 in dimethyl sulfoxide, Physics and Chemistry of Liquids, 43:3, 289-298, DOI: 10.1080/00319100500083583
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    $\begingroup$ You're going the wrong way; check out highly polar solvents. $\endgroup$
    – Mithoron
    Commented Aug 13, 2019 at 20:13
  • $\begingroup$ Solubility of CO2 in water (total dissolved inorganic carbon, or DIC) also controlled by stepwise formation of carbonic acid (i.e. H2O + CO2(aq) = H2CO3 = H+ + HCO3– = ...) bicarbonate, and carbonate ion. $\endgroup$
    – Rolf
    Commented Aug 14, 2019 at 3:25
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    $\begingroup$ Liquid mercury is a well-established gas seal, it doesn't solve any gases. Though it isn't exactly an organic solvent =). Gallium would work too. $\endgroup$
    – permeakra
    Commented Aug 15, 2019 at 11:26

1 Answer 1

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To find a solvent with low solubility for non polar gases like CO2 you have to compare the polarity of the solvents. A very polar solvent like water is the best choice.
There's a related question here: Dissolving of non polar gases in water (liquid)

At the end of this answer I have added two links. The first one gives you the solubility of CO2 in water. According to this source, at room temperature and around atmospheric pressure of Co2, the molar fraction in water is 0.00061. The second link compares many other solvents. At room temperature and 1atm of CO2 the molar fraction is 0.012 in hexane that is the lowest for straight chain alkenes(Fig.1). Overall, among alkanes and cyclic alkanes, cyclohexane is the only one that at room temperature has a CO2 solubility below 0.01(fig.2). Among aromatic hydrocarbons, you can reach a molar fraction as low as 0.006 if you use 1-Methylnaphthalene(fig.3) and this value is interestingly similar to what you can reach using methanol(you can find a graph comparing alcohols there as well(pag.129). Apparently the CO2 solubility with aromatic compounds is comparable to alcohols(polar).

With all this in mind, water is the best option and if you add salts the solubility of CO2 decreases further as you mentioned.

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enter image description here Solubility of Carbon Dioxide in Water:
https://sites.chem.colostate.edu/diverdi/all_courses/CRC%20reference%20data/solubility%20of%20carbon%20dioxide%20in%20water.pdf

CARBON DIOXIDE IN NON-AQUEOUS SOLVENTS:
https://srdata.nist.gov/solubility/IUPAC/SDS-50/SDS-50.pdf

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