Developing a Mechanistic Understanding of Lamellar Hydroxide Mineral Carbonation Reaction Processes to Reduce CO2 Mineral Sequestration Process Cost

The potential environmental effects of increasing atmospheric CO2 levels are of major worldwide concern. One alternative for managing CO2 emissions is carbon sequestration: the capture and secure confinement of CO2 before it is emitted to the atmosphere. Successful technologies must be environmentally benign, permanent, economically viable, safe and effective. As a result, their timely development represents a significant challenge. Unlike many other proposed CO2 sequestration technologies, which provide storage, CO2 mineral sequestration provides permanent disposal via geologically stable mineral carbonates (e.g., MgCO3). As such, mineral sequestration guarantees permanent containment and avoids adverse environmental consequences and the cost of continuous site monitoring. The major remaining challenge for CO2 mineral sequestration is economically viable process development. This is the focus of the CO2 Mineral Sequestration Working Group managed by DOE, which also includes members from the Albany Research Center, Los Alamos National Laboratory, National Energy Technology Laboratory, and Science Applications International Corporation. Our goal is to develop the necessary understanding of mineral carbonation reaction mechanisms to engineer new materials and processes to enhance carbonation reaction rates and reduce process cost. Herein, we focus on Mg-rich lamellar hydroxide feedstock materials (e.g., Mg(OH)2 and serpentine minerals), due to their low cost and wide availability. In situ dynamic high-resolution transmission electron microscopy has been used to directly observe dehydroxylation/rehydroxylation-carbonation reaction processes down to the atomic level. These studies are combined with detailed quantum mechanical modeling and a variety of complementary studies to explore the associated reaction mechanisms. Control of dehydroxylation/rehydroxylation processes prior to and/or during carbonation have been found to dramatically enhance carbonation reactivity.