A common mineral can remove carbon dioxide from combustion gases, but in its natural state, it is glacially slow. Now, a team of Penn State researchers is changing serpentine so that it sequesters the carbon dioxide from fossil fuel burning in hours, not eons.

The metamorphic mineral serpentine -- or magnesium silicate hydroxide -- is composed of magnesium, silicon and oxygen and is plentiful. 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.

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 researchers have not yet tested the process on a working coal-fired stationary boiler, but they are working on developing a reactor in the laboratory that can continuously treat the flue gas. At the same time they would like to regenerate the sulfuric acid to minimize costs.

Because carbon dioxide will be the last gas in the emission stream treated, there are two options for commercial implementation. Fossil fuel burning plants could simply place a serpentine reactor as the last component of their emissions clean up and sequester carbon on site. Or, if the area is heavy with fossil fuel burning plants, each plant could pipe their carbon dioxide to a central treatment plant.

9/3/2004