Highly efficient simultaneous removal of HCHO and elemental mercury over Mn-Co oxides promoted Zr-AC samples

Mn_xCo_y/Zr_z-AC prepared by impregnation method was investigated on the simultaneous removal of HCHO and Hg⁰. The samples were characterized by BET, SEM, XRD, H₂ pulse chemisorption, H₂-TPR, XPS, Hg-TPD and in-situ DRIFTS. Thereinto, the optimal Mn_2/3Co₈/Zr₁₀-AC achieved 99.87% HCHO removal efficiency and 82.41% Hg⁰ removal efficiency at 240 °C, respectively. With increased surface area and pore volume, Zr-AC support facilitated higher dispersion of MnO_x-CoO_x. Moreover, the co-doping of MnO_x-CoO_x endowed the sample with more active oxygen species and higher reducibility, which further facilitated the removal of HCHO and Hg⁰. Chemisorption was proved to predominate in Hg⁰ removal, and oxidation also worked as Hg²⁺ was detected in outlet gas. Besides, HCHO predominated in the competition of active oxygen species, especially for lattice oxygen, thus suppressed the Hg⁰ removal. According to in-situ DRIFTS, HCHO removal proceeded as HCHO_ads → DOM → formate species → CO₂ + H₂O, and was boosted by active oxygen species. Furthermore, Mn_2/3Co₈/Zr₁₀-AC was proved with excellent regeneration performance, indicating its potential in practical application.