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

Abstract

In this study, crude multi‐walled carbon nanotubes (MWCNT) was functionalized by a two‐step process; first using strong mixed acids (H2SO4/HNO3) and then treatment with 1,3‐phenylenediamine (mPDA). The equilibrium adsorption of CO2 on pristine MWCNT and amine functionalized MWCNT (MWCNT‐NH2) 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 CO2 increased after functionalizing of MWCNT. The increase in CO2 capture by MWCNT‐NH2 was attributed to the existence of great affinity between CO2 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 CO2 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 CO2 adsorption on MWCNT‐NH2, whereas the physisorption process was dominant for CO2 adsorption on MWCNT.

Preparation and characterization of multi-walled carbon nanotubes impregnated with polyethyleneimine for carbon dioxide capture

“…As shown in the images, the prepared samples were undamaged after acid-treatment and subsequent amine functionalization. The MWCNT are strong enough to endure the acid pretreatment and impregnation of PEI [28]. The MWCNTs external surface is partially covered with a slight agglomerate of PEI, which is evenly distributed along the nanotubes.…”

Synthesis of nitrogen doped activated carbon/polyaniline material for CO2 adsorption

“…The amount of gas adsorbed by the synthesized adsorbent was determined using a volumetric apparatus that was described in our previous works …”

Carbon dioxide adsorption by modified carbon nanotubes

“…The surface area and pore volume decrease with the increasing urea loading time. The average pore diameter increases after functionalization probably due to the removal of catalysts and amorphous carbons during the heating step …”