CO2 Capture over MCM-41 and SBA-15 Mesoporous Silicas Impregnated with Chitosan

Chitosan was impregnated on MCM-41 and SBA-15 mesoporous silica supports, within nominal loadings between 20 and 50 wt %. The materials were characterized by several techniques including XRD, FTIR, BET area, CHN composition, and TGA and tested as adsorbents for CO2 capture. All techniques showed the successful impregnation of chitosan on the supports, but the real loadings were lower than the nominal content, especially for the higher values. The CO2 adsorption tests were performed at 1 bar and 25 °C, and the SBA-15 adsorbent impregnated with 50 wt % of chitosan showed the best results among the functionalized materials, with CO2 uptake of 0.78 mmol g–1. The adsorption process on the chitosan-impregnated mesoporous materials was better described by the Freundlich isotherm, whereas adsorption on the pure chitosan was better fitted by the Langmuir isotherm model. The adsorption and characterization data indicate that on the MCM-41-based materials, CO2 adsorption mostly occurs on the basic sites at the outer silica surface and pore entrance, whereas on the SBA-15-based materials, the presence of interconnecting microporosity allows better diffusion of the CO2 molecule and adsorption on the chitosan chains located at the inner pore structure.