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.

Experimental and theoretical study of CO2 adsorption by activated clay using statistical physics modeling.

The objective of this paper was to study CO2 adsorption on activated clay in the framework of geological storage. The activation of clay was characterized via scanning electron microscopy, N2 adsorption-desorption isotherms, and X-ray diffraction. The adsorption isotherms were generated at different temperatures, namely, 298 K, 323 K, and 353 K. Based on the experimental result, a new model was simulated and interpreted using a multi-layer model with two interaction energies. The physicochemical parameters that described the CO2 adsorption process were determined by physical statistical formalism. The characteristic parameters of the CO2 adsorption isotherm such as the number of carbon dioxide molecules per site (n), the receptor site densities (NM), and the energetic parameters were investigated. In addition, the thermodynamic functions that governed the adsorption process such as the internal energy, entropy, and Gibbs free energy were determined by a statistical physics model. Thus, the results showed that CO2 adsorption on activated clay was spontaneous and exothermic in nature.