TGA was performed to investigate the thermal characteristics of the native AC and the MEA and DEA impregnated AC. Fig. 3 shows the TGA profiles obtained under the N2 flow conditions described in Section 2.3. All adsorbents, especially the native AC, experienced
a noticeable weight loss near 100 C due to vaporization of physically adsorbed water [6]. The second weight loss of the amine impregnated AC occurred from 100 C to 250 C due to the
continuing volatilization of organic materials trapped with the MEA and DEA [6,39]. The gradual weight loss from 250 C to 500 C of the amine impregnated AC can be attributed to the thermochemical decomposition of MEA and DEA. An additional weight loss that occurred at 275 C and 285 C with a weight loss of 7.7% and 9.2% for the AC-MEA and the AC-DEA, respectively, can be attributed to the pyrolysis of the impregnated amines [40]. The pyrolysis was likely to change both the chemical compositions and the physical phases of the adsorbents. The weight loss observed in the impregnated samples between 100 C and 500 C was absent for the case of the native AC. The TGA data for the impregnated samples between 100 C and 250 C and between 250 C and 500 C suggested that the regenerating temperature for the impregnated samples should be kept below 250 C. Otherwise, decomposition of the amines would occur, and the adsorbent could not be reused.