Impregnation of Silica Gel with Choline Chloride-MEA as an eco-friendly adsorbent for CO2 capture

Abstract

Deep eutectic solvents (DES) are a generation of ionic liquids that benefit from low cost, good stability, and environmental-friendly features. In this research, a porous silica gel was impregnated with a eutectic Choline Chloride-Monoethanolamine solvent (ChCl-MEA) to greatly improve its CO2 capture performance. In the impregnation, the weight percentages of ChCl-MEA were used in the range of 10–60 wt% at a temperature of 25 °C. The effect of ChCl-MEA loading on the structural properties of the DES-modified silica samples was studied by BET, FTIR, and TGA analyses. Investigation of the CO2 adsorption performance at different operational conditions showed that the modified silica gel with 50 wt% ChCl-MEA (Silica-CM50) presents the highest CO2 capture capacity of 89.32 mg/g. In the kinetic modeling, the fractional order model with a correlation coefficient of 0.998 resulted in the best fit with the experimental data. In addition, the isotherm data for Silica-CM50 were well-fitted with the Dual site Langmuir isotherm model with a correlation coefficient of 0.999, representing two distinct sites for the adsorption process. Moreover, the thermodynamic parameters including Enthalpy, Entropy, and Gibbs free energy at 25 °C were obtained to be − 2.770, − 0.005 and − 1.162, respectively. The results showed the exothermic, spontaneous and feasibility of the adsorption process.