Serpentine and single stage mineral carbonation for the storage of carbon dioxide

Mineral carbonation is the formation of stable calcium, magnesium, and iron carbonates from the reaction between the metals in common minerals and carbon dioxide. The benign and long-term nature of this CO2 sequestration option has led to ongoing research efforts. Magnesium silicates such as olivine and serpentine have been the focus of mineral carbonation research for the sequestration of CO2 for over a decade. The aqueous carbonation route has received more attention over simpler solid-gas reactions due to reaction kinetics and carbonation conversion efficiencies. However, the removal of magnesium from the magnesium silicate matrix remains as a challenge for the aqueous carbonation scheme. Strong acids such as sulfuric and hydrochloric acid have been used to improve upon the rate limiting step of magnesium removal. Although the use of an acid-accelerating medium can improve the reaction kinetics and reduce the reaction pressures and temperatures, it requires an additional step. Reagents are required to raise the pH to support carbonation, therefore imparting costs to the reaction process that, to date, are prohibitive. Our preliminary investigations have demonstrated that serpentine has the intrinsic ability to buffer against the acidic conditions resulting from the dissolution via carbonic acid, while leaching magnesium into solution for subsequent carbon storage.