TiO(2-x) nanoparticles synthesized using He/Ar thermal plasma and their effectiveness on low-concentration mercury vapor removal

Abstract

Oxygen-vacant titanium dioxide (TiO(2-x) ) nanoparticles were synthesized using thermal plasma as a heating source at various applied plasma currents and He/Ar ratios. Samples with diverse characteristics were developed and the mercury removal effectiveness was subsequently evaluated. TiO(2) nanoparticles possessing high purity and uniform particle sizes were successfully synthesized using metal titanium and O(2) as precursors and Ar as plasma gas. TiO(2-x) in anatase phase with a particle size at 5-10 nm was formed at the He/Ar volume ratio of 25/75. Further increasing the He/Ar ratio elevated the plasma temperature, causing the tungsten to melt, vaporize from the cathode, and then dope into the formed TiO(2) nanoparticles. The doped W appeared to inhibit the growth of nanoparticles and decrease the crystallinity of formed anatase. The effectiveness of oxygen-vacant sites on Hg(0) removal under the visible light circumstance was confirmed. Hg(0) removal by the TiO(2-x) nanoparticles was enhanced by increasing the O(2) concentration. However, moisture reduced Hg(0) capture, especially when light irradiation was applied. The reduction in Hg(0) capture may be resulted from the competitive adsorption of H(2)O on the active sites of TiO(2-x) with Hg(0) and transformed Hg(2+).