Synthesis of N-doped TiO2 photocatalyst for low-concentration elemental mercury removal under various gas conditions
Journal
Applied Catalysis B: Environmental
Journal Volume
160-161
Journal Issue
1
Pages
558
Date Issued
2014-01-01
Author(s)
Abstract
This study proposes preparing N-doped TiO2 nanoparticles that exhibit a narrow bandgap by calcinating a mixture of Degussa P-25 TiO2 and NH4Cl at a temperature of 400°C under airtight conditions to remove gaseous elemental mercury (Hg0). Sample characterization performed using X-ray photoelectron spectroscopy and ultraviolet-visible spectra indicated that the presence of Ti3+ caused by oxygen vacancy and molecular-state N may be incorporated into a TiO2 lattice; this result was supported by an observation of the Ti-N group conducted using Fourier transform infrared spectroscopy. The formed nanoparticles exhibited a size of 32.4nm and were in a mixed form of anatase and rutile according to the X-ray diffraction spectra. The low Hg removal of TiO2 nanoparticles under the 0% O2 dark condition indicated that photocatalytic oxidation limited Hg adsorption. The reemission of adsorbed Hg caused by H2O competition for active sites can be markedly inhibited by N modification, which may be caused by strong bonding between Hg, N, and O groups. In addition, TiOxNy underwent less adsorption competition from humidity at an elevated temperature than an untreated sample did. NO exhibited substantial competition for the adsorption sites on the TiO2 surface. By contrast, under dark conditions, both SO2 and HCl slightly enhanced Hg adsorption; under ultraviolet and visible-light irradiation, both SO2 and HCl markedly reduced Hg removal. SO2 and HCl may substantially consume O2- and OH free radicals during light irradiation and subsequently reduce the transformation of Hg0 into HgO. © 2014 Elsevier B.V.
Subjects
Elemental mercury | Flue gas component | Nitrogen doping | Titanium dioxide | Visible light
Publisher
ELSEVIER SCIENCE BV
Type
journal article