Membrane-separated reactor for an integrated CO2 capture-mineralization process using carbonic anhydrase

Abstract

To achieve carbon neutrality through CO2 mineralization, it is important to design the novel reaction process through a distinct understanding of the critical reaction steps, CO2 hydration, and calcium carbonation. A semi-batch system was introduced to conduct a model mineralization reaction to confirm the reaction-determining step (RDS) of CO2 mineralization. The CO2 hydration step was confirmed as RDS according to various model reactions in a semi-batch reactor. CA enzyme was introduced to promote CO2 hydration to increase the overall reaction rate. With the introduction of the CA enzyme, the hydration reaction rate was increased by about 4-fold, but the CA enzyme was lost due to coprecipitation with CaCO3 during the reaction. A membrane-separated reactor was designed to maintain high activity and decrease the loss of CA enzyme during the reaction. Furthermore, in the membrane-separated reactor, the CA enzyme facilitated the CO2 mineralization much more effectively in the K2CO3 aqueous solution than in the D.I. water because the K2CO3 aqueous solution has a higher CO2 absorption capacity and a weekly alkaline condition favorable for CA enzyme operation. Finally, by proposing a continuous reaction system for reusing enzymes and water, we suggested that the membrane-separated reactor could be applied in practical CO2 capture-mineralization.