Carbon dioxide capture by a droplet plays a fundamental role for reducing atmospheric greenhouse effect stemming from anthropogenic activities. To recognize the CO2 capture dynamics by a quiescent water droplet, a theoretical analysis on the mass transfer of CO2 from the gas phase to the liquid phase is performed in this work, with emphasis on the effect of acoustic excitation upon the absorption process. The dimensionless fluctuated amplitude and frequency of the acoustic wave are in the ranges of 0.1-0.99 and 0.1-1000, respectively. The analyses suggest that an acoustic wave with smaller amplitude and higher frequency leads to a more significant energy decay in the droplet due to the role of damping played by the droplet. In contrast, pressure excitation along with larger amplitude and lower frequency has a pronounced effect on the mass transfer process, as a result of higher efficiency of energy penetrating into the liquid phase. From the perspective of achieving carbon capture and storage (CCS), the acoustic excitation with the dimensionless frequency of unity is recommended to capture CO2 by a droplet and the exposure time of the droplet should be controlled at the dimensionless aqueous diffusion time (τl) between 0.31 and 0.36. The present study has provided a useful insight into the design and application of scrubbers for enhancing CO2 capture by sprays.
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