Using the composite material of GO and g-C3N4 nanosheets as substrate to in-situ grow Co3O4 nanosheets for efficient Hg0 removal

Abstract

Chemisorption is an effective method to remove Hg0 from coal-fired flue gas. During this process, Hg0 will convert to Hg2+ and be solidified on sorbent surface. The number of adsorption sites and the electron transfer between Hg0 and sorbents play an important role in the removal process. In the present work, GO with a rapid electron transfer was compounded with NS-g-C3N4 to improve the electron donating ability of NS-g-C3N4. After that, Co3O4 nanosheets were grown in-situ in the interlayer space of GO and NS-g-C3N4 composites. A series of sorbents were successfully synthesized by changing GO concentration. SEM and TEM results show that the corresponding Co3O4/GCN (GCN denote the GO and NS-g-C3N4 composites) sorbent has better Co3O4 nanosheet dispersibility when GO concentration is 5 mg/mL. This results in a large amount of chemisorbed oxygen, which is favor to the oxidation of Hg0 to HgO. In addition, XPS results show that the interaction between Co3O4 and GCN give a rapid electrons transfer from GCN to Co3O4, thus improving the activation of gaseous oxygen. Therefore, Co3O4/GCN-5 has excellent Hg0 removal efficiency of about 95 % at 200 °C and high stability under different flue gas conditions. A probable reaction path way was deduced by the results of XPS and Hg0 adsorption–desorption experiment.