CO2 Adsorption by Core-shell Structured Hydrogel Particles Fabricated via In-air Microfluidics

The escalating atmospheric CO₂ levels, which has been driving global warming, highlights the necessity to develop efficient CO₂ capture technology, such as solid-based sorbents. Understanding the CO₂ adsorption mechanism in these sorbents is important for their optimization, which, however, current semi-empirical models are not able to comprehensively demonstrate. In this paper, a diffusion-reaction model is proposed to elucidate the CO₂ adsorption of a core-shell structured hydrogel sorbent. As the sorbent comprises a polyethylenimine hydrogel particle encapsulated by a silica shell, the model is developed by considering both physical diffusion and CO₂-amine chemical reactions. As a result, the model describes the CO₂ adsorption capacities of experimentally fabricated particles across diverse adsorption temperatures. Moreover, it unveils the CO₂ adsorption process within the particle by displaying the evolution of amine-CO₂ reaction rates, CO₂ distribution, and amine consumption profiles. Notably, the model shows that the hydrogel core contributes to the primary diffusion resistance, a contrast to the less resistant silica shell. Overall, our diffusion-reaction model illuminates a fresh perspective on interpreting the CO₂ adsorption mechanism of amine-based solid sorbents, from which insights can be gained for optimizing sorbent production in pursuit of carbon capture applications.