Enhancement of Carbon Dioxide Capture by Amine‐Functionalized Multi‐Walled Carbon Nanotube

In this study, crude multi‐walled carbon nanotubes (MWCNT) was functionalized by a two‐step process; first using strong mixed acids (H 2 SO 4 /HNO 3 ) and then treatment with 1,3‐phenylenediamine (mPDA). The equilibrium adsorption of CO 2 on pristine MWCNT and amine functionalized MWCNT (MWCNT‐NH 2 ) were investigated. Experiments were preformed via application of volumetric method in a dual sorption vessel at temperature range of 298–318 K and pressures up to 40 bars. The results obtained indicated that the equilibrium uptake of CO 2 increased after functionalizing of MWCNT. The increase in CO 2 capture by MWCNT‐NH 2 was attributed to the existence of great affinity between CO 2 molecules and amine sites on this adsorbent at low pressures. The experimental data were analyzed by means of Freundlich and Langmuir adsorption isotherm models. The data obtained revealed a fast kinetics for the adsorption of CO 2 in which most of adsorption occurred at initial period of adsorption experiments. This renders MWCNT as a suitable adsorbent for practical applications. Values of isosteric heat of adsorption were evaluated based on Clausius–Clapeyron equation. The results demonstrated that both chemisorption and physisorption played important role in CO 2 adsorption on MWCNT‐NH 2 , whereas the physisorption process was dominant for CO 2 adsorption on MWCNT.