Enzyme-immobilized flat-sheet membrane contactor for green carbon capture

Abstract

• Enzyme-mediated CO 2 capture in a flat-sheet gas–liquid membrane contactor. • Biocatalytic membranes with immobilized carbonic anhydrase on amine functionalized PP. • Multiscale modeling considering enzyme attached on membrane surface and inside pores. • Mass transfer in wetted pores mitigated by enzymatic CO 2 hydration inside the pores. Membrane contactors (MC) represent an attracting system for CO 2 capture due to the enhanced mass transfer and gas–liquid interfaces, modularity, and compactness. A novel gas–liquid MC with biocatalytic flat sheet membrane was developed. The biocatalytic membrane was prepared via co-deposition of polydopamine (PDA)/ polyethyleneimine (PEI) and covalent bonding of carbonic anhydrase (CA) on polypropylene (PP) flat sheet membrane, using different deposition and enzyme immobilization conditions. The highest CA activity was achieved for 7 h deposition time, PDA/PEI ratio = 2/2, 1.0 (v/v)% glutaraldehyde, 0.8 mg/ml CA solution, 32 h immobilization time, and pH 6.0 in the immobilization process. The biocatalytic membrane showed good storage stability after 40-day. The MC performance was investigated under various conditions, including buffer type/concentration, liquid flow rate, temperature, and counter-current/co-current operating conditions. A CO 2 absorption flux of 0.29 × 10 -3 mol/m 2 s was obtained when the biocatalytic membrane was integrated into a flat sheet MC and 100 mM Tris in water was used in the absorption process. The absorption rate stability of the biocatalytic MC was also examined for several hours to verify the potential of the new flat sheet bioreactor in industrial applications. A multiscale model (with gas-filled or partially liquid-filled membrane porous structure and enzyme attached on the surface of the membrane and inside the pores) was developed to investigate the behaviour of the MC. Overall, the employment of biocatalytic membrane in flat sheet MC is a novel, green, and environmentally friendly approach allowing CO 2 capture with water (in presence of buffer) as absorbent.