Development of green CO2 capture technologies using immobilized carbonic anhydrase enzyme
|Authors:||Rasouli Kenari, Hannaneh|
|Advisor:||Bougie, Francis; Iliuta, Maria-Cornélia|
|Abstract:||Anthropogenic activities have significantly enhanced the amount of greenhouse gases (GHGs) in the atmosphere and are a major contributor to global warming. Carbon dioxide (CO2) is a primary greenhouse gas that contributes to climate change. Various technologies are being explored across the world to tackle CO2 capture and sequestration. Despite their efficiency, amine-based solutions have negative environmental impact and the process is energy intensive. CO2 absorption using carbonic anhydrase (CA) enzyme as catalyst (free insolution or immobilized) is a promising technology which offers high selectivity and efficiency in CO2 capture processes by using nontoxic and more energy efficient solvents. CA is a well-known biocatalyst endowed with an extraordinary turnover number (TON), which offers to it a very high capacity to boost CO2 hydration. CA immobilization on solid surfaces enhances the enzyme stability, and reusability and provides the ability for easy separation of the reaction products without biocatalyst contamination. In this context, the present thesis focuses on the investigation of CO2 absorption process using immobilized CA in different bioreactors. More specifically, the main objectives are: i) developing an enhanced enzymatic process with immobilized CA enzyme in a packed-bedcolumn bioreactor, ii) studying the CO2 absorption in membrane contactor with immobilized CA enzyme on membrane surface, and iii) proposing a novel hybrid enzymatic process in an intensified flat sheet membrane contactor for improving CO2 absorption via immobilized CA enzyme on both membrane and magnetic nanoparticles (MNPs). An improved CA immobilization technique was developed in this work using two steps: (i) co-deposition of Polydopamine (PDA)/Polyethyleneimine (PEI) with amino functional groups for amine-functionalization of surfaces and (ii) covalent enzyme immobilization on the aminated surfaces using glutaraldehyde. The proposed approach is appealing because ofits simplicity, abundant amine functionalities of PEI, and great adhesion capacity of PDA during surface functionalization process, as well as the stability and reusability of immobilized enzyme via covalent bonding. A hybrid enzymatic process with CA enzyme immobilized on packing surface and MNPs dispersed in the liquid absorbent (water) was developed in a gas-liquid packed-bed column bioreactor. CA was immobilized on amine functionalized surface of MNPs and packings via covalent attachments. Even after 40 days of storage in buffer solution, the immobilized CA on packing and MNPs showed remarkable stability, retaining 80% and 84.7% of its original activity, respectively. Since the enzyme immobilized on MNPs operates as a free solution-phase enzyme, the CO2 hydration process improved significantly, specially when the diffusion limitation in the enzymatic process with immobilized CA enzyme on the packing surface was significant. CA enzyme immobilized on polypropylene (PP) flat sheet membrane surface via co-deposition of PDA/PEI through covalent bonding method showed the highest activity and preserved most of its initial activity after 40 days (82.3%). A CO2 absorption flux of 0.29×10-3 mol/m2s was attained by integrating the biocatalytic membrane into a flat sheet membrane contactor (FSMC) using water as absorbent. Stable CO2 absorption rate was obtained during a longer time operation (6 hours), illustrating its potential for industrial applications. Mass transfer resistance in partially liquid-filled membrane pores was shown to be reduced by the catalyzed CO2 hydration in these pores in the presence of immobilized CA. CO2 absorption in flat sheet membrane contactor with immobilized CA on membrane surface was intensified by the incorporation of immobilized CA on the surface of MNPs dispersed in the liquid phase. CO2 absorption process was improved due to the presence of biocatalytic MNPs, which act as a free solution-phase enzyme. CA was covalently immobilized on amine-functionalized MNPs surface. The proposed innovative hybrid enzymatic process in the intensified membrane contactor improved the CO2 absorption by maximizing the utilization of CA’s large TON, specially at lower CA loadings on the biocatalytic membrane. Immobilized membrane and MNPs demonstrated their reusability and retained their initial activities even after 10 absorption cycles. The intensified membrane contactor also displayed a stable operation for several hours. In conclusion, the results achieved in our work illustrate that CO2 capture using immobilized CA can offer a cost-effective, green, and environmentally friendly strategy, representing an attracting alternative to customary technologies using amine-based absorbents. With the growing environmental crisis, enzymatic CO2 capture technologies are becoming more important, prompting more attempts to implement them on industrial scales.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||6 June 2022|
|Collection:||Thèses et mémoires|
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