Capture of CO2 from flue gas via multiwalled carbon nanotubes

Carbon nanotubes (CNTs) were modified by 3-aminopropyl-triethoxysilane (APTS) solution and were tested for its CO2 adsorption potential at multiple temperatures (20–100 °C). The physicochemical properties of CNTs were changed after the modification, which makes CNTs adsorb more CO2 gases. The adsorption capacities of CO2 via CNTs and CNTs(APTS) decreased with temperature indicating the exothermic nature of adsorption process and increased with water content in air at 0–7%. The mechanism of CO2 adsorption on CNTs and CNTs(APTS) appears mainly attributable to physical force regardless of temperature change, which makes regeneration of spent CNTs at a relatively low temperature become feasible. The CNTs(APTS) have good adsorption performance of CO2 at 20 °C as compared to many types of modified carbon or silica adsorbents documented in the literature. This suggests that the CNTs(APTS) are promising low-temperature adsorbents for CO2 capture from flue gas.