Abstract
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.
Highlights
Mercury (Hg) releases from nature and anthropogenic sources have been the major focus of environmental studies owing to the toxicity and bioaccumulative behaviors [1]
These observation results indicate that the injected Ti and Al2O3 powders successfully vaporized at the high flame temperature and subsequently synthesized Al-doped TiO2 nanoparticles via the recombination of vaporized Ti, O and Al atoms in the thermal plasma environment
Al-doped TiO2 nanoparticles were successfully synthesized in a single step using Ti powders, Al2O3 powders, and O2 by a nontransferred plasma torch system
Summary
Mercury (Hg) releases from nature and anthropogenic sources have been the major focus of environmental studies owing to the toxicity and bioaccumulative behaviors [1]. Several studies have indicated that an improved TiO2 photocatalyst excited by VL sources can be prepared by substitutional doping with metal atoms, such as Fe [16, 17], Er [18], and Al [19,20,21,22,23]. High-purity TiO2 nanoparticles using Ti metal as a precursor were successfully manufactured with a transferred plasma torch [24]. Our preliminary test has shown that Al-doped TiO2 nanoparticles can be successfully formed in a single step via this non-transferred DC thermal plasma system. Al-doped TiO2 photocatalyst with a broad absorption spectrum was developed under a lower plasma power (i.e., 6 kW). Few studies have examined the VL photocatalytic effects of Al-doped TiO2 on removal of Hg0 at an extreme low concentration, namely, μg Nm−3 level
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