Aminosilane-modified MCM-41 and SBA-15 mesoporous silicas were synthesized using sodium silicate extracted from gold mine tailings slurry in this study. Pure silica source was used in the synthesis of mesoporous silica in order to compare differences in textural properties and amine loading with differences in CO2 adsorption performance. CO2 adsorption analysis of the synthesized samples was carried out at 25, 75 and 100 degrees C. The results showed that the aminosilane-modified MCM-41 from slurry and aminosilane-modified SBA-15 from pure silica have the highest adsorption capacities of 1.55 and 1.37 mmol g(-1), respectively. As a result, it was found that the CO2 adsorption capacities of the aminosilane-modified samples were increased by increasing the amine contents and the specific surface area. From three kinetic models (pseudo-first-order, pseudo-second-order model and Avrami's equation), Avrami model well represented the adsorption kinetic data for all adsorbents and revealed that multiple reaction pathway occurred in the CO2 adsorption. In addition, aminosilane-modified samples presented good regenerability after four adsorption-desorption cycles.