Molecular simulation of efficient removal of HS pollutant by cyclodextrine functionalized CNTs.

DFT-D3 calculations were carried out to investigate interaction of HS and CH between numerous functionalized CNTs (f-CNTs), including hydroxyl, carboxyl, and cyclodextrin groups as potential candidates for selective adsorption and elimination of toxic pollutants. It was found that pristine CNTs as well as nanotube surface of functionalized CNTs cannot stably adsorb the HS molecule (adsorption energy of -0.17 eV). However, HS adsorption was significantly enhanced with different magnitudes upon the functionalization of CNT. For f-CNTs, HS adsorption was accompanied by releasing energies in the range between -0.34 to -0.54 eV where the upper limit of this range belongs to the cyclodextrin-functionalized CNT (CD-CNT) as the consequence of the existence of both dispersion and electrostatic interactions between the adsorbate and substrate. Findings also demonstrated a significantly weaker interaction between CH and CD-CNT in comparison to the HS molecule with adsorption energy of -0.14 eV. Electronic properties of the selected substrates revealed no significant changes in the inherent electronic properties of the CNTs after functionalizing and adsorbing the gas molecules. Moreover, DFTB-MD simulation demonstrated high adsorption capacity as well as CD-CNT ability for HS molecules against the CH one under ambient condition.