Functionalization of Multi-Walled Carbon Nanotubes by Diamine Precursor to Increase CO2 Adsorption

This research aims to modify multi-walled carbon nanotubes to increase the carbon dioxide adsorption capacity. To achieve this goal, pristine multi-walled carbon nanotubes were functionalized in a two-step process. In the first step, oxidized MWCNTs were prepared by pre-treatment of MWCNTs with sulfuric acid and nitric acid. In the second step, to improve the performance of multi-walled carbon nanotubes in carbon dioxide adsorption, oxidized MWCNTs were functionalized with 1,3-diaminopropane (DAP) solution. The characteristics of the functionalized MWCNTs were studied by Fourier Transform InfraRed (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), and Nitrogen adsorption-desorption analysis The CO2 adsorption capacity was measured at the temperature range of 303-323 K and pressures up to 17.3 bar using the volumetric method. Results showed that 92.71 mg/g of CO2 were captured by amine-functionalized MWCNTs at 303 K and 17.3 bar, while the adsorption capacity of the raw MWCNTs was only 48.49 mg/g under the same conditions. This result suggested that amine groups were attached to carbon surfaces in the impregnation process, making CO2 affinity sites on MWCNT surfaces which increased the adsorption capacity of MWCNTs.