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

Abstract

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 Hg0 using the photocatalysis process were investigated. In addition, the removal mechanism of Hg0 over cerium-based TiO2 nanofibers focused on UV irradiation was proposed. The results show that catalyst which was calcined at 400 °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 O2 are essential factors, the enhancement of Hg0 removal is more obviously related to the participation of catalyst. The coexistence of Ce3+ and Ce4+, which leads to the efficient oxidation of Hg0, was detected on samples. Hg2+ is the final product in the reaction of Hg0 removal. As a consequence, the emissions of Hg0 from flue gas can be significantly suppressed. These indicate that combining photocatalysis technology with cerium-based TiO2 nanofibers is a promising strategy for reducing Hg0 efficiently.