Enhancement of CO2 Adsorption Kinetics onto Carbon by Low-Frequency High Amplitude Resonant Vibrations

Abstract

Due to the excessive consumption of fossil fuels, which leads to significant greenhouse gas emissions and rapid climate change, it is crucial to develop various carbon capture and sequestration strategies. CO2 sequestration in solid, porous adsorbents like low-cost biochar has emerged as a promising approach to achieve this goal. However, slow adsorption kinetics are one of the issues that limit the widespread use of this approach. While the characteristics of the biochar are important and impact CO2 adsorption, the conditions under which adsorption occurs are equally critical. In this work, a novel strategy is proposed to accelerate the CO2 uptake rate on carbon adsorbents by utilizing Low-Frequency High Amplitude resonant vibratory mixing during the adsorption process. With this approach, the rate of adsorption (characterized by the adsorption rate constant) exhibits an increase of 46.6% and 91.3%, as calculated by two different kinetic models: the Weber and Morris model, and the Pseudo-First-Order model. Experimental observations indicate that adsorption kinetics have a mixed control between external/internal diffusion and the physisorption process. Resonant vibrations enhance system energy, promoting collisions between CO2 molecules and carbon surfaces, subsequently improving CO2 transport and surface/gas interactions, facilitating the adsorption process and thus leading to enhanced kinetic rates. Furthermore, an analysis of variance determined the sensitivity of CO2 uptake to several operating parameters associated with the resonant vibrations. This analysis indicated that the adsorption of CO2 is most sensitive to the level of fill of the adsorption vessel and the time exposed to resonant vibrations.