Fixed bed adsorption as affected by thermodynamics and kinetics: Yellow tuff for CO2 capture

In this work, a yellow tuffhas been proposed for the first time as sorbent for CO2 capture. Dynamic breakthrough experiments have been performed in a fixed bed reactor at different temperatures (25-150 °C) and CO2 partial pressures (0.01-0.20 atm), focusing on the process thermodynamics and kinetics. The thermodynamic and ki- netic studies highlighted that the CO2 adsorption on the tuff in the low pressure region typical of combustion flue gases can be properly described by Freundlich's isotherm model and by the pseudo-first order kinetic model, respectively, thus indicating a physical, multilayer and heterogeneous surface binding mechanism. Based on the results obtained, it has been demonstrated that, in the framework of a real application for post- combustion CO2 capture, the natural tuff, i.e. a low-cost natural sorbent, could be more conveniently employed in vacuum swing or mixed mode in order to minimize the energy penalty of the process.