Adsorption of Low-Concentration Carbon Dioxide on Amine-Modified Carbon Nanotubes at Ambient Temperature

A solid amine adsorbent for CO2 was developed by carbon nanotubes (CNTs) impregnated with tetraethylenepentamine (TEPA). The adsorption behavior toward CO2 (2.0 vol %) was investigated in a fixed-bed column. After modification, the adsorption capacity of CNTs–TEPA reached 2.97 mmol g–1 at 298 K. Rising temperatures from 283 to 313 K enhanced the CO2 adsorption capacity. The maximum adsorption capacity was approximately 3.56 mmol g–1 at 313 K. The adsorption capacity was also influenced by moisture and reached as high as 3.87 mmol g–1 (2.0% H2O). In comparison to many other types of modified carbon or silica adsorbents in the literature, CNTs–TEPA had a higher adsorption capacity at the same temperature. The adsorption capacity for CO2 remained almost the same after cyclic regeneration experiments. A deactivation model, capable of describing the uptake of CO2, was applied under various conditions. In all cases, the experimental data agreed with the predicted breakthrough model.