Activated Carbon as an Adsorbent for CO₂ Capture: Adsorption, Kinetics, and RSM Modeling

The main objective of this research is to investigate the adsorption isotherms and the optimization of the carbon dioxide (CO₂) adsorption process on activated carbon (AC). The AC has been characterized by X-ray diffraction, scanning electron microscopy, and nitrogen (N₂) adsorption-desorption. The CO₂ isotherms measured under three adsorption temperatures (318, 308, and 298 K) were investigated by the Langmuir and linear driving force model. It is found that the Langmuir model could well predict the adsorption behavior of AC with a correlation factor of about 0.99. The kinetic model shows that the amount of CO₂ increases at higher pressures. The response surface methodology (RSM) was applied to investigate the effects of process variables and their interaction on the response to reach the optimal conditions. Based on the analysis of variance, pressure and temperature are the main factors influencing the CO₂ adsorption capacity. The effective parameters obtained through this model are found to have a value of p < 0.05. In addition, a semiempirical correlation was developed under the optimal operating conditions which are 25 °C and 9 bar. The results indicated that RSM models provide an effective method for evaluating CO₂ adsorption. These results point that AC is a potential adsorbent for CO₂ capture.