Atomic-level mechanism of the effects of NOx species on Pb adsorption over the Al2O3 sorbent surface

Abstract

Abstract NOx is widely considered to be one of the most important components in the flue gas. A systematically theoretical study based on density functional theory was conducted to provide an atomic-level understanding of the effects of NOx on Pb adsorption over the Al2O3 surface. The results suggest that the adsorption energies of Pb over Al2O3 (1\xa01\xa00) surface are larger than those of Pb over Al2O3 (0\xa00\xa01) surface. Al2O3 (1\xa01\xa00) surface is more favorable for Pb adsorption than Al2O3 (0\xa00\xa01) surface. NO and NO2 are adsorbed at the same active adsorption site (surface Al atom). NOx competes with Pb for the active sites on the Al2O3 surface. The notable charge accumulation and depletion are accountable for the intense interaction of Pb and NOx-covered Al2O3 surface. At low concentration of NOx, the adsorption of NO and NO2 over Al2O3 surface increases the Pb adsorption capacity of Al2O3 sorbent through strengthening the activity of its neighbor Al and O sites. The formation of Pb-Al and Pb-N bonds can greatly strengthen Pb adsorption over Al2O3 (1\xa01\xa00) surface in the presence of NO/NO2. However, the high-concentration NO and NO2 inhibit Pb adsorption over Al2O3 surface due to the competitive adsorption between Pb and NO/NO2.