Photocatalytic oxidation of gas-phase Hg0 by carbon spheres supported visible-light-driven CuO–TiO2

[Display omitted] •Carbon spheres supported CuO–TiO2 photocatalyst was prepared by a simple method.•Photocatalytic oxidation ability of CuO/TiO2@C on Hg0 under different light sources was studied.•The mechanism of Hg0 oxidation by CuO/TiO2@C was studied. A simplified approach for the fabrication of CuO/TiO2@C is demonstrated. In this study, low cost CuO/TiO2@C photocatalysts (CSs loading 0.25–2wt.%) were prepared, characterized and evaluated for gas-phase Hg0 oxidation. The obtained CuO/TiO2@C photocatalysts were used to remove gaseous elemental mercury under UV light and LED respectively, and the optimum doping of content of CSs was determined. The results showed that the CuO/TiO2@C photocatalysts were highly efficient in oxidizing Hg0, reaching above 64% when the CSs doping reached 0.5wt.%. We have proposed that the probable mechanism by which CuO/TiO2@C photocatalysts remove gaseous elemental mercury: with CSs doping, CSs can act as sensitizer and transfer electrons to the semiconductors, triggering the formation of very reactive radicals to improve photocatalytic efficiency.