Comparative studies on adsorption isotherm and kinetic for CO2 capture using iron oxide impregnated activated carbon

Activated carbon AC was treated with Kmn04 and the treated AC was used to be impregnated with iron oxide. The ratio of 0.1 M KMnO4 treatment on AC to the 0.1 M iron sulfate precursor (0.1KMnO4:0.1Fe) showed the most efficient adsorbent with an adsorption capacity of 108.60 mg/g. The CO2 adsorption isotherm at 25 °C was assessed with the adsorption isotherm model found that the Freundlich model to be the best fit which implies the multilayer adsorption onto heterogeneity surface. The adsorbent was used to perform CO2 adsorption at 30, 40, 50 and 70 °C in which the optimum adsorption temperature was at 30 °C. The decrease in adsorption capacity with increasing temperature indicates that a physisorption process takes place. The kinetic data for CO2 adsorption at different temperatures were well fitted to the pseudo-second-order kinetic. The adsorption was near to the chemisorption process based on the activation energy of 39.8 kJ/mol. It might be due to the weak interaction between CO2 and AC and strong bonding between CO2 and iron oxide. The adsorption capacity insignificantly reduced by 3.5% after four cycles showed practically efficient in CO2 capture.