Self-template synthesis of CuCo2O4 nanosheet-based nanotube sorbent for efficient Hg0 removal

Abstract

Adsorption method is an effective way to remove Hg0 from flue gas, and the morphology and active site of sorbents seriously affect the Hg0 removal efficiency. The hierarchical porous nanosheet-based nanotube structure can effectively reduce the mass transfer resistance and provide more active sites. Inspired by this, the organic-inorganic hybrid nanowires of Co-aspartic acid was used as the template, which can hydrolyze in water-alcohol mixed solution and coordinate with Cu2+ based on Kirkendall effect to prepare nanosheet-based nanotube of CuCo2O4 sorbents. By changing the ratio of water to alcohol, the hydrolysis rate of Co-aspartic acid nanowires will be changed resulting in different physicochemical properties for CuCo2O4 sorbents. Characterization results show that when the ratio is 1:2, the sorbent (CuCo2O4-1-2) has the best hierarchical porous nanosheet-based nanotube structure and the best redox properties. CuCo2O4-1-2, which has the widest reaction temperature window, has a high Hg0 removal efficiency of 89 % under a high GHSV of 180 000 h−1 at 250 °C and a good poisoning resistance and stability. The straight nanotube can effectively reduce the gas transfer mass resistance, and the mesoporous nanosheets structure on its surface provide more active sites for the reaction, which improves the ability of CuCo2O4-1-2 sorbent to capture and activate O2. Meanwhile, DFT calculation shows Cu-Co on the surface of CuCo2O4 is the main active site because the bond length of OO can be effectively lengthened when O2 is adsorbed on the Cu-Co site.