\(\textrm{CO}_2\) Adsorption by Core-Shell Hydrogel Particles Fabricated via In-Air Microfluidics

The escalating atmospheric \(\textrm{CO}_2\) levels, which has been driving global warming, highlights the necessity to develop efficient \(\textrm{CO}_2\) capture technology, such as solid-based sorbents. Understanding the \(\textrm{CO}_2\) 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 \(\textrm{CO}_2\) 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 \(\textrm{CO}_2\) -amine chemical reactions. As a result, the model describes the \(\textrm{CO}_2\) adsorption capacities of experimentally fabricated particles across diverse adsorption temperatures. Moreover, it unveils the \(\textrm{CO}_2\) adsorption process within the particle by displaying the evolution of amine- \(\textrm{CO}_2\) reaction rates, \(\textrm{CO}_2\) 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 \(\textrm{CO}_2\) adsorption mechanism of amine-based solid sorbents, from which insights can be gained for optimizing sorbent production in pursuit of carbon capture applications.