Adsorption of low-concentration carbon dioxide on amine-modified carbon nanotubes at ambient temperature

A solid amine adsorbent for CO ₂ was developed by carbon nanotubes (CNTs) impregnated with tetraethylenepentamine (TEPA). The adsorption behavior toward CO ₂ (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 CO ₂ 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% H ₂O). 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 CO ₂ remained almost the same after cyclic regeneration experiments. A deactivation model, capable of describing the uptake of CO ₂, was applied under various conditions. In all cases, the experimental data agreed with the predicted breakthrough model.