Accelerated CO2 Separation and Adsorption Kinetics on Carbon Using Resonant Vibrations: A Process Intensification Strategy

Carbonaceous adsorbents, such as biochar, have attracted considerable interest for CO sequestration because of their cost-effective production and environmental friendliness. However, their slow adsorption kinetics – attributable to limited surface area and diffusional limitations – have hindered widespread adoption. Most studies employ surface chemical modifications to enhance the adsorption capabilities of biochar. While often effective, these approaches raise concerns regarding the release of greenhouse gases and the environmental hazards associated with their byproducts. In this study, we introduced a green processing strategy that leverages resonant vibrations to improve the rate of CO adsorption on hemp biochar. Using this method, the adsorption rate constant increased by 46.5% and 91.2%, as determined using a binary kinetic model package, which represents external/internal diffusion and physisorption, respectively. The application of resonant vibrations increases system energy, promotes molecular collisions and gas transfer processes within the carbon surfaces and pore structures in the fluidized bed, and helps overcome the activation energy barrier between CO molecules and adsorption sites during physisorption reactions. These collisions also optimize biochar’s surface area along with microporosity, leading to a 41.14% enhancement in the maximum CO uptake. Furthermore, the vibrations caused a 25.00% increase in adsorption selectivity when simulating a post-combustion scenario with 16% volumetric CO and 84% volumetric N, mimicking emissions from coal-fired power plants. Finally, regeneration studies – the final criterion in evaluating post-combustion adsorption systems – confirmed the reusability of the biochar in CO capture over five cycles.