Capture of Carbon Dioxide by Modified Multiwalled Carbon Nanotubes

This chapter investigates the physicochemical properties of raw and 3-aminopropyl-triethoxysilane (APTS)-modified carbon nanotubes (CNTs) and their CO2 adsorption properties. Effects of temperature and moisture on the CO2 adsorption in modified CNTs are also given. Carbon nanotubes are unique and one-dimensional macromolecules that have outstanding thermal and chemical stability. These nanomaterials have been proven to possess good potential as superior adsorbents for removing many kinds of organic and inorganic pollutants in air streams or in aqueous environments. The large adsorption capacity of pollutants by CNTs is mainly attributable to their pore structure and the existence of a wide spectrum of surface functional groups, which can be achieved by chemical modification or thermal treatment to make CNTs that possess optimum performance for particular purposes. The raw and APTS-modified CNTs were selected as adsorbents to study their characterizations and adsorption properties of CO2 from air streams. The physicochemical properties of CNTs were improved after modification, including the increase in defective structure and surface functional groups, which made CNTs, adsorb more CO2. With the 50% CO2 inlet, the amount of adsorbed CO2 on raw and modified CNTs was 69.2 and 96.3 mg/g, respectively. The CO2 adsorption performance of modified CNTs decreased with an increase in temperature but increased with an increase in relative humidity. The modified CNTs possess higher CO2 adsorption capacity than many types of APTS-modified silica adsorbents reported in the literature, suggesting that the APTS-modified CNTs are promising adsorbents for the capture of CO2 from air streams.