Electrospun cerium-based TiO2 nanofibers for photocatalytic oxidation of elemental mercury in coal combustion flue gas

Photocatalytic oxidation is an attractive method for Hg-rich flue gas treatment. In the present study, a novel cerium-based TiO2 nanofibers was prepared and selected as the catalyst to remove mercury in flue gas. Accordingly, physical/chemical properties of those nanofibers were clarified. The effects of some important parameters, such as calcination temperature, cerium dopant content and different illumination conditions on the removal of Hg-0 using the photocatalysis process were investigated. In addition, the removal mechanism of Hg-0 over cerium-based TiO2 nanofibers focused on UV irradiation was proposed. The results show that catalyst which was calcined at 400 degrees C exhibited better performance. The addition of 0.3 wt% Ce into TiO2 led to the highest removal efficiency at 91% under UV irradiation. As-prepared samples showed promising stability for long-term use in the test. However, the photoluminescence intensity of nanofibers incorporating ceria was significantly lower than TiO2, which was attributed to better photoelectron-hole separation. Although UV and O-2 are essential factors, the enhancement of Hg-0 removal is more obviously related to the participation of catalyst. The coexistence of Ce3+ and Ce4+, which leads to the efficient oxidation of Hg-0, was detected on samples. Hg2+ is the final product in the reaction of Hg-0 removal. As a consequence, the emissions of Hg-0 from flue gas can be significantly suppressed. These indicate that combining photocatalysis technology with cerium-based TiO2 nanofibers is a promising strategy for reducing Hg efficiently. (C) 2017 Elsevier Ltd. All rights reserved.