Mass\nTransfer-Reaction Modeling of CO<sub>2</sub> Capture\nMediated by Immobilized Carbonic Anhydrase Enzyme on Multiscale Supporting\nStructures

Immobilized\ncarbonic anhydrase (CA) enzyme enhances CO<sub>2</sub> absorption\nin potassium carbonate (PC) solutions, offering an attractive\nalternative to amine-based processes for postcombustion carbon capture.\nIn this work, the cross-scale models of mass transfer coupled with\nabsorption reactions were developed to evaluate the structural impacts\nof different enzyme immobilization supporting materials, including\nnonporous nanoparticle carriers (nano scale), porous microparticle\ncarriers (micro scale), and fixed packing structures (macro scale),\non the rate enhancement effect of the immobilized CA. Increasing enzyme\nactivity was demonstrated to be an effective approach to promoting\nthe CO<sub>2</sub> absorption rate; however, there was an upper limit\ndue to the limitation of CO<sub>2</sub> diffusion in the liquid phase,\neither adjacent to the gas–liquid interface or the liquid–solid\ninterface. The size of particle carriers is another critical factor\naffecting the CO<sub>2</sub> absorption rate. Only nanoscale particle\ncarriers could directly enter the region within the liquid film of\nmass transfer, thus providing effective enzymatic enhancement. When\nthe particle size was reduced to below 0.35 μm, the PC promoted\nwith the immobilized CA outperformed the benchmark monoethanolamine\nsolution. The solid-side mass transfer resistance became dominant\nas the particle size decreased. Modeling results also showed that\nusing stagnant packing materials in a fixed bed as a supporting structure\nfor CA immobilization would be impractical for accelerating CO<sub>2</sub> absorption.