(631f) Effect of Carbonic Anhydrases on Carbonation of Mg-Bearing Minerals for Environmentally-Benign Carbon Sequestration

Carbon dioxide is a greenhouse gas that causes global warming. Historically, the atmospheric concentration of carbon dioxide fluctuated naturally on the timescales of ice ages. Concerns, however, stem from the recent dramatic increase in the CO2 concentration, which coincides with global industrial development. In order to meet the ever-increasing global energy demands while stabilizing the CO2 level in the atmosphere, it is widely believed that current carbon emissions must be reduced by at least a factor of three.

Mineral carbonation is a new and consequently less studied method of sequestering CO2. This method mimics the natural mineral weathering process involving the exothermic reaction of CO2 with non-carbonate minerals to form geologically and thermodynamically stable mineral carbonates. Hence this sequestration process truly presents a safe and permanent method of CO2 containment that is based on chemical fixation of CO2 in a solid mineral matrix.

Earlier studies by the PI on mineral carbonation indicated promise with regard to enhanced dissolution rates of serpentine in a mineral slurry system using a mixture of weak acids and chelating agents. This previous research resulted in the development of the pH swing process that fixes CO2 into a solid matrix while producing value-added solid products such as high surface area silica and iron oxide. The next challenge for carbon mineral sequestration is how to recycle or conserve acid and base required for the pH swing. Thus, this study is performed to search for chemical additives that can promote the carbonation reaction near neutral pH.

The proposed research focuses on the effect of carbonic anhydrases on the carbonation of Mg-bearing minerals. Carbonic anhydrases are found in many organisms, including human, and can catalyze CO2 hydration. Compared to water, a zinc-bound hydroxide ion which is sufficiently nucleophilic is much more reactive to CO2, and thus, the concentration of HCO3- and CO32- in an aqueous solution would increase as carbonic anhydrase is introduced. In this study, the reaction mechanisms and the reaction kinetics are investigated while determining the optimum pH conditions.