Dynamic breakthrough analysis of natural tuff for CO2 adsorption: thermodynamic and kinetic assessment

CO2 adsorption on a yellow tuff has been studied, by performing dynamic breakthrough experiments in fixed bed, focusing on the thermodynamics and kinetics of the process. The effect of both temperature (25 - 150 °C) and CO2 partial pressure (0.01 - 0.20 atm) has been assessed. The CO2 adsorption isotherms in the low pressure region typical of combustion flue gases are more accurately described by the Freundlich equation than by the Langmuir one, thus indicating a multilayer and heterogeneous surface binding. The obtained values of the main thermodynamic parameters suggested that the adsorption process is spontaneous, exothermic and physical in nature. The pseudo-first order kinetic model better fitted the experimental data at all the investigated adsorption temperatures than the pseudo-second order does. Based on the thermodynamic properties, some insights into the process strategy for post-combustion capture (i.e. pressure vs vacuum swing) are derived.