Comparative Adsorption of CO2 by Mono-, Di-, and Triamino-Organofunctionalized Magnesium Phyllosilicates

Carbon dioxide adsorbents, constituted by organofunctionalized magnesium phyllosilicates, were produced using 3-aminopropyltriethoxysilane (AMPTS), N-[3-(trimethoxysilyl)propyl]-ethylenediamine (TMSPEDA), N-[3-(trimethoxysilyl)propyl]-diethylenetriamine (TMSPETA), and tetraethoxyorthosilane (TEOS) as silicon sources with N/Si ratios of 1, 0.75, 0.5, and 0.25, by conventional and microwave heating. Adsorption studies were performed using TGA and temperature programmed desorption (TPD) methods. The results showed that the best temperatures for adsorption were 41, 45, and 90 °C, when magnesium phyllosilicate functionalized with TMSPETA, TMSPEDA, and AMPTS, respectively, were used as adsorbents. Using TPD technique, the maximum efficiency was found to be between 0.285 and 0.899 for 100% AMPTS and 33.33% TMSPETA, obtained by conventional heating. Adsorption efficiency of the materials prepared by conventional method is higher than those obtained using microwave as heating source, except for 100% AMPTS. Desorption kinetics of CO2, described using Avrami's model, show that the CO2 desorption rate constant is in the range from 0.130 to 0.178 min(-1), similar to the values for CO2 desorption from monoetamolamine-functionalized TiO2 and Li4SiO4 but in a narrower range of values.