Exploiting response surface methodology for experimental modeling and optimization of CO2 adsorption onto NaOH-modified nanoclay montmorillonite

Abstract

In this work, operational conditions and adsorbent properties of modified montmorillonite nanoclay (MMT) with NaOH were investigated to improve CO2 adsorption capacity. To optimization the adsorption operational conditions, process factors e.g. reactor temperature and pressure, acid concentration for activating the surface and wt% NaOH for surface modification were evaluated through five level four factor central composite design (CCD) using RSM. According to the analysis of variance (ANOVA), wt% NaOH, pressure and temperature, respectively, were selected as the most important parameters affecting CO2 adsorption capacity in the outlet model. The optimum values are 65 °C, 1.00 bar, 5.99 M and 39.76 % for the input variables and the value of 105.55 mg/g for the response, respectively. The study of isotherm models shows the Toth isotherm model is well suited to experimental isotherm data and shows multi-layer adsorption on heterogeneous surfaces with Gaussian energy distribution. Also, the kinetic models showed that Elovich model provides the best fit to CO2 adsorption data. This suggests that the connection of CO2 in the modified montmorillonite appears to be due to the formation of chemical bonds.