Thermodynamics and kinetics of CO2 adsorption on a fine activated carbon in a sound assisted fluidized bed

This work is focused on the investigation of the mechanism (isotherm), nature/strength (thermodynamics) and rate (kinetics) of CO2 adsorption on a commercial activated carbon in a sound assisted fluidized bed. Langmuir and Freundlich equations were used to model the CO2 adsorption isotherm in the low pressure region (i.e. typical of a combustion flue gas). The results revealed that Freundlich equation was more accurate for predicting the adsorbed amount than the Langmuir one, which indicates a heterogeneous surface binding. Then, adsorption behaviour was elucidated by energy function such as standard Gibbs free energy, enthalpy and entropy, suggesting the spontaneity and feasibility of adsorption of CO2 by activated carbon, and its exothermic and physical nature. The isosteric heat of adsorption was also evaluated; its decrease with surface loading further indicated the heterogeneity of adsorption sites and also variation in adsorbate-adsorbent interactions. Finally, this study also presented a kinetic analysis of CO2 adsorption, from which CO2 binding on activated carbon was deduced to follow pseudo-first order kinetic.