Carbon Nanotubes as a Superior Sorbent for Nitrogen Oxides

Carbon nanotubes were prepared and investigated as sorbents for NO, SO2, and CO2 in the presence of O2. The preliminary results indicate that they are a good and reversible sorbent for NO removal at room temperature. An uptake amount of 78 mg/g of NOx was obtained by TGA when the carbon nanotubes were exposed to 1000 ppm NO + 5% O2/He for 120 min. The equilibrium amount was near 90 mg/g after 12 h. TPD profiles show that NO2 and NO desorb from the NOx-saturated carbon nanotubes at well below 300 °C. FTIR spectra indicate that the adsorbed species are nitrates and trace amounts of NO2 and (NO)2 dimers. By comparison, only 29 mg/g of SO2 (at 500 ppm) and 2 mg/g of CO2 (at 10%) are adsorbed onto the carbon nanotubes in 120 min.