Effect of Temperature and CO2 Flowrate on the Formation of CaCO3 in the Hydration Reaction of CO2 Catalyzed by Immobilized Carbonic anhydrase into PVDF Membrane

Abstract

CO2 conversion to mitigate CO2 emissions is of great importance to reduce the negative impact of CO2 on climate change. Different technologies have been developed for CO2 conversion, including chemical, photocatalytic, electrochemical, and biological transformation. Among them, biological conversion by using Carbonic anhydrase (CA) to efficiently convert CO2 to HCO3– is a promising one, owing to its high specificity and selectivity under the mild condition and presenting environmentally friendly nature. The production of CO2 hydrates requires relatively high pressures and low temperatures, to make these applications feasible. However, free CA unable to withstand with too extreme temperature and pressure. Thus, the present work was conducted with the aim to determine the optimum parameter in the CO2 hydration using immobilized CA. In this research, CO2 hydrate were formed using CaCl biomimetic solution with an immobilized CA into PDVF membrane. Temperature variation from 30 to 85 °C and CO2 flowrate from 100 – 800 mL/min were evaluated for the CO2 hydration process. Time taken to reach pH 7 and the amount of CaCO3 precipitate formed during the process were used to elucidate the performance of the CO2 hydration process. The finding indicated that temperature plays an important role in reducing time taken for pH 7 to be reached. At 30 °C, 16 min was required for the CO2 hydration process and reaction time was decreased with the increasing of the temperature. At higher temperature of 85 °C, 3.4 min was recorded as an optimum time for the pH to turn to 7. Similar trend was observed with increasing of CO2 flowrate. Higher CO2 flowrate has shorter the time for the reaction to occur and 3 to 4 min was recorded as an optimum time for CO2 hydration process in the CO2 membrane reactor. This work might help comprehend CO2 hydrate storage technology, in separation of CO2 from methane gas and could give theoretical basis for subsequent applications in the sector.