Making use of minerals in carbon capture
23 May 2013
Ammonium salts could provide a viable way of removing carbon dioxide from the atmosphere.
Researchers at the National Junior College of Singapore and Åbo Akademi University in Finland, claim to have found a cheaper and more permanent solution to prevent the CO2 escaping back into the atmosphere.
Their work focused on using carbon mineralisation- a process that involves a reaction between CO2 and minerals, such as magnesium silicates, to form solid carbonates.
Natural carbon mineralisation is very slow, so scientists are working to accelerate the process in an energy-efficient and carbon-neutral way.
Using ammonium salts and magnesium-silicate-rich serpentine rocks, the research team induced rapid carbon mineralisation. They also found that milling the solids could convert serpentine directly into stable carbonate.
To accelerate the extraction of magnesium (as soluble sulfate) from serpentine, the researchers used ammonium sulfate. This reaction generates by-products such as iron oxide that may be useful for the steel industry.
They trapped the leftover ammonia in water, and recycled this by-product in an aqueous wash with the magnesium solution to produce a mineral form of magnesium hydroxide called brucite.
Finally, the researchers carbonated the brucite in a pressurised reactor. The heat generated by this exothermic process was recycled to help power the initial magnesium extraction.
A key aim throughout the processing was to recycle as much ammonium sulfate as possible. The final products, magnesites (magnesium carbonates), could also be useful.
