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High-quality Al-doped TiO2visible-light photocatalyst was prepared via a single-step direct combination of vaporized Ti, Al, and O2using a 6 kW thermal plasma system. Results showed that the formed Al-doped TiO2nanoparticles were a mixture of anatase and rutile phase and had a size between 10 and 105 nm. The absorption spectra of the nanoparticles shifted towards the visible light regions, depending on the Al2O3addition. Ti4+and Ti3+coexisted in the synthesized Al-doped TiO2; the Ti3+concentration, however, increased with increasing Al2O3addition due to Al/Ti substitution that caused the occurrence of oxygen vacancy. Hg0breakthrough tests revealed that the nanoparticles had an appreciable Hg0removal under visible-light irradiation. Nevertheless, moisture reduced Hg removal by the nanoparticles, especially when visible-light irradiation was applied, suggesting that the competitive adsorption between H2O and Hg species on the active sites of TiO2surface occurred.

A high-quality, Cu-doped TiO 2 photocatalyst was prepared via a single-step process using an atmospheric-pressure plasma torch system. Degussa P-25 was thermally doped with Cu at Cu/(Cu + TiO 2 ) ratios of 0-5 wt.%. The raw and resulting nanoparticles were characterized using TEM, XRD, UV-Vis, and XPS. TEM showed that the particle size of plasma-treated TiO 2 was generally < 50 nm. 67-75% of the resulting particles, by number were between 10 and 20 nm. The remaining particles were < 10 nm (~10%) and between 20 and 30 nm (~10%). The XRD results showed that Cu doping decreased the anatase/rutile crystalline ratio compared to untreated P-25. Nevertheless, the greater the amount of Cu added, the greater the anatase/rutile ratio was for the Cu-doped TiO 2 . The UV-Vis results showed that the absorption wavelength for plasma-treated TiO 2 extended to the visible light range, especially for TiO 2 doped with 5 wt.% Cu.

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