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Home :FAQ :Environmental chemistryPrint | Comment
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Is there a safe chemical way to remove CO2 from air?

I know that alkali metal hydroxides (column I and II metal hydroxides) can be used to absorb carbon dioxide (CO2) in an enclosed atmosphere, like in a space craft or submarine. However, they're corrosive and absorb water vapor. (1) Is there any commonly-available material that is not toxic/dangerous that will absorb CO2? (2) What is used in underwater rebreathers/CO2-scrubbers? Thanks.
Garcia Oliver

Plants absorb CO2, of course, but they take up a lot of room and are slow, inefficient CO2 absorbers.

Most industrial CO2 scrubbers use chemicals that don't meet your criteria. Monoethanolamine (MEA) is used to scrub carbon dioxide from gas streams, but it's corrosive and toxic in very small amounts. Ascarite IIMSDS is a very efficient CO2 absorbent, but it's basically nonfibrous asbestos covered with sodium hydroxide.

Potassium superoxide is an interesting possibility for spacecraft and submarine CO2 scrubbing, since it regenerates oxygen as it reacts with carbon dioxide:

4 KO2(s) + 2 CO2(g) = 2 K2CO3(s) + 3 O2(g)
But it isn't common, and it is quite toxic.

Calcium hydroxide (mixed with a small amount of sodium and potassium hydroxides) is used in most underwater rebreathers. The reaction between the hydroxides and CO2 is exothermic, and divers can tell from the warmth of the scrubber canister that the absorption reaction is working. Failure of the canister lid can give the diver a mouthful of hydroxides- called a "caustic cocktail" in diving circles. It's apparently a memorable experience.

You can learn more about the construction and chemistry of rebreathers here.

Related Links

Carbon dioxide sequestration (U. S. Department of Energy)
Technical information on programs and technologies to reduce carbon dioxide emissions.
http://www.fe.doe.gov/coal_power/sequestration/index.html (10/28/00)

Climate Change Information Kit (United Nations Environmental Programme)
Background information on climate change and its potential impact on human activities and recommended policies and technologies for limiting carbon dioxide emissions.
http://www.unep.ch/iuc/submenu/infokit/factcont.htm (10/28/00)

Physico-Chemical Life Support Systems (The Mars Club)
Information on several different chemical techniques for purifying air and recycling wastes aboard spacecraft.
http://marsacademy.com/lifes2.htm (3/21/99)

Regenerative Life Support: Carbon Dioxide Control (James Atwater)
Details on several CO_2_ recycling technologies for life support systems, including lithium hydroxide absorption, molecular sieves, solid phase amines, and silver oxides.
http://ucs.orst.edu/~atwaterj/co2.htm (3/21/99)

Regenerative Life Support: Water Production (James Atwater)
Outline of water generation from carbon dioxide using the Sabatier and Bosch processes.
http://ucs.orst.edu/~atwaterj/h2o_gen.htm (3/21/99)

Author: Fred Senese senese@antoine.frostburg.edu



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Last Revised 08/17/15.URL: http://antoine.frostburg.edu/chem/senese/101/environmental/faq/co2-recycling