September 08, 2004
Serpentine Dissolved In Sulfuric Acid Could Capture Carbon Dioxide

The naturally occurring mineral serpentine sequesters carbon dioxide very slowly over eons. Some Penn State researchers have found that by dissolving serpentine in sulfuric acid they can produce compounds that will very rapidly bind to carbon dioxide.

The metamorphic mineral serpentine -- or magnesium silicate hydroxide -- is composed of magnesium, silicon and oxygen and is plentiful. He researchers used material from the Cedar Hills quarry on the Pennsylvania/ Maryland border for this study, but the mineral is available in large quantities in many places. The U.S. deposits of the minerals that can be used for this process serpentine and ovivine can sequester all the carbon dioxide emissions produced from fossil fuels.

"Previous researchers investigating serpentine for use in sequestering carbon dioxide have crushed serpentine very finely, to sizes smaller than beach sand, but, even at these small sizes, it takes high temperatures to speed up the reaction, "says Maroto-Valer. "With our method, we do not need to crush it that fine and we do not need high temperatures. In fact, the reaction gives off heat. Our method is much less energy expensive."

They aren't done developing this method to the point of being practically useful. Also, there is no big push in the United States at this point to reduce carbon dioxide emissions. Still, this could turn out to be a useful technique if global warming is eventually proven to be a serious problem.

They crush serpentine, dissolve it in sulfuric acid, treat part of it with sodium hydroxide, and the result will react with carbon dioxide to produce magnesium carbonate or magnasite.

The researchers, who also include John M. Andresen, director of the Consortium for Premium Carbon Products from Coal (CPCPC), the Energy Institute; Yinzhi Zhang, post doctoral fellow, the Energy Institute; Matthew E. Kuchta, graduate student in geo-environmental engineering, all at Penn State; and Dan J. Fauth, U.S. Department of Energy's National Energy Laboratory in Pittsburgh, dissolved the crushed serpentine in sulfuric acid.

When serpentine dissolves in sulfuric acid, the silicon in the mineral becomes silicon dioxide, or sand, and falls to the bottom, while the magnesium becomes magnesium sulfate. Treating some of this magnesium sulfate with sodium hydroxide also creates some magnesium hydroxide. The researchers were able to convert large amounts of the serpentine's magnesium to these chemicals providing large surface areas for reactions to occur in solution at room temperature.

Carbon dioxide passed through the solution of magnesium sulfate and magnesium hydroxide converts both to magnesium carbonate or magnesite, which becomes a solid and falls to the bottom. This solid can be used to manufacture construction blocks and there is also a small market for hydrated magnesium carbonate in the cosmetics industry. The silicon dioxide can be used to remove sulfur dioxide from the flue gases, which can subsequently be converted to sulfuric acid to use in the first part of the process.

"The high surface area of the silicon dioxide makes it a natural sorbent for capturing more carbon dioxide and sulfur dioxide," says Maroto-Valer.

Suppose coal can be made to burn extremely cleanly without even generating carbon dioxide emissions. Add in future advances in battery technology that make batteries light enough and cheap enough to be used in electric cars. Then at some point we might burn coal to supply electricity to charge batteries in electric cars.

Share |      Randall Parker, 2004 September 08 04:00 PM  Engineering Environmental

Conrad said at September 9, 2004 9:26 AM:

This is a good idea, to try to achieve C02 balance. At least until climate trends are better defined.
Randall, as you very well know, C02 is not the only driver of climate, and may not even be in the top 3 in importance.

Eventually, if we seem to be coming hard upon an ice age, it may be necessary to increase C02 levels.
At that point, a different mentality entirely will be required.

Fly said at September 9, 2004 12:05 PM:

Using CO2 to flush oil out of underground reservoirs and storing CO2 in the empty reservoir is also promising. Long before global warning was recognized as a potential threat, pumping CO2 into the ground was used to maximize oil field production.

Mark said at September 9, 2004 12:20 PM:

Can anyone provide the chemical equations for this set of reactions? I'm too lazy to do so at the moment. I'm particularly interested in the gaseous byproducts. For example, if O2 is given off, this would be a very powerful terraforming technique.

Engineer-Poet said at September 17, 2004 10:24 PM:

I think we can convert coal to vehicular power more directly than through a heat engine, and also sequester all the carbon (probably directly, as liquid CO2).  I'll be blogging on this sometime.

Mark:  I don't know the chemical formula for serpentine, but the sequestration reactions are very simple:

Mg(OH)2 + CO2 -> MgCO3 + H2O
MgSO4 + CO2 -> MgCO3 + SO3

Sam said at October 1, 2004 1:20 PM:

The chemical reactions as given by Engineer poet are slightly misleading as being the last reaction:
MgSO4 + CO2 -> MgCO3 + SO3
Will not occur spontaneously because sulfuric acid (H2SO3, represented by SO3 in the above equation) is far stronger than carbonic acid (H2CO3, as represented by CO2 in the above equation). What this translates into is that the above reaction will require an energy input in some form to form the final MgCO3 product.
What the group at Penn State does is actually the following set of reactions:

1- (1/3)Mg3Si2O5(OH)4 + H2SO4 --> MgSO4 + (2/3)SiO2 (sand) + 2H2O (water)

2- MgSO4 + 2NaOH --> Mg(OH)2 + NaSO4

3- Mg(OH)2 + CO2 --> MgCO3 + H2O

This process has been described in a 1960's patent in which the production of magnesium from serpentine was the ultimate goal and analagous processes with acids other than sulfuric acid have been developed at Albany Research Center and Los Alamos National Labs. What this press release doesn't explain, is that with this particular process, the use of such a strong acid and the consequent need to use a strong base results in the salt NaSO4 which takes a tremendous amount of energy to break back into the original H2SO4 and NaOH acid and base form. The process would be far too expensive to perform on an industrial scale if one wasn't recycling the acid and the base, but in this case, the energy needed for the recycling will prove prohibitive as well.

matt said at October 31, 2004 8:27 PM:

I would like to know the references to the equations and patents that you mentioned SAM... my son is trying to do a research project in this area and has had trouble finding references....thanks

sulf said at June 25, 2005 1:20 AM:

Вы можете писать по-русски, а? Ни фига ведь не понятно !!!

O.Piedrahita said at January 27, 2006 4:01 PM:

If your son is interested try in Google with

Paul Dietz said at February 14, 2006 3:03 PM:

Yes, this scheme is silly. If you have sodium hydroxide, just use it to neutralize CO2, for example by adding it to seawater so the oceans themselves soak up more CO2. That will do even better, since two sodium hydroxide ions will sequester two CO2 molecules as bicarbonate.

Gabriel said at October 8, 2007 7:52 AM:

sam i really do need your help on this,you seem very informed on this issue.i have been trying to get a complete breakdown of how serpentine does this locking-in of CO2.Could you help with thhis.thank you

Zach said at December 15, 2009 5:47 PM:

I would say the suggestion to add sodium hydroxide to our oceans is a very bad idea. This could have huge environmental impact. I would also like to point out that magnesium hydroxide or milk of magnesia is commonly used in exhaust flue treatment and sewer treatment. My question is whether or not it is unstable enough to react with the CO2 at a reasonable rate.

Anonymous said at April 3, 2010 6:03 PM:

Where can I sell serpentine with the highest rate of energy resistance

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