Co3O4 nanotubes embedded in the interlayer of GO nanosheets for efficient Hg0 removal from coal flue gas

Abstract

Adsorption is an efficient and practical method to remove Hg0 from coal flue gas. Surface active oxygen of the sorbents can adsorb Hg0 forming HgO which becomes the essential factor for efficient Hg0 removal. In this study, Co3O4 nanotubes were embedded into the interlayer of GO nanosheets to prepare a composite material 3D. SEM and TEM results show that GO gives a high dispersion of Co3O4 nanotubes, which is beneficial to the adsorption and activation of O2 on Co3O4 nanotubes surface. XPS results show that when the mass ratio of GO to Co3O4 was 1:2 (Go-Co3O4-1–2), the sorbent had the best Oβ/OT ratio and the best redox capacity. It means that the oxygen-containing functional groups on the GO surface can provide more active sites for the Co3O4 nanotubes to capture and activate O2 into chemisorbed oxygen. Furthermore, GO has a fast electron transfer which can improve the electron shift in the reaction of Hg0 + O2 → HgO. As a result, the Hg0 removal efficiency of GO-Co3O4-1–2 reached 94.67% under 180,000 h−1 at 250 °C, and showed a good stability. The Hg0 removal mechanism and regeneration mechanism were deduced based on the XPS results of the fresh, used and regenerated sorbent.