Nanoclay montmorillonite as an adsorbent for CO2 capture: Experimental and modeling

Today, the tendency to use mineral adsorbents has increased due to its low cost for removal of the flue gas of fossil-fuel power plants. In this research, the optimization of the CO2 adsorption process using the sodium-montmorillonite adsorbent was investigated. The response surface methodology (RSM), combined with central composite design, was used to assess the effects of process variables and their interaction on the response (CO2 adsorption capacity) to achieve the optimal conditions. According to the analysis of variance, temperature and pressure parameters are the variables that affect the CO2 adsorption capacity. Moreover, one semi-empirical correlation was established to calculate the optimum operating conditions of the CO2 adsorption process. The optimal variables of the process obtained from numerical optimization are 25 degrees C and 9 bar for temperature and pressure, respectively. Based on the optimal conditions, the adsorption capacity of 100.67 mg/g was achieved. Furthermore, additional experiments were performed to examine the isotherm, kinetic, and thermodynamic models of absorption. Kinetic studies showed that adsorption was in accordance with the second-order reaction. Equilibrium data were analyzed using Langmuir, Freundlich, Hill, and D-R isotherm models at different temperatures. The D-R isotherm provides the best description for the adsorption experimental data.