Abstract
A series of low-cost Cu-Mn-mixed oxides supported on biochar (CuMn/HBC) synthesized by an impregnation method were applied to study the simultaneous removal of formaldehyde (HCHO) and elemental mercury (Hg
0
) at 100–300° C from simulated flue gas. The metal loading value, Cu/Mn molar ratio, flue gas components, reaction mechanism, and interrelationship between HCHO removal and Hg
0
removal were also investigated. Results suggested that 12%CuMn/HBC showed the highest removal efficiency of HCHO and Hg
0
at 175° C corresponding to 89%and 83%, respectively. The addition of NO and SO
2
exhibited inhibitive influence on HCHO removal. For the removal of Hg
0
, NO showed slightly positive influence and SO
2
had an inhibitive effect. Meanwhile, O
2
had positive impact on the removal of HCHO and Hg
0
. The samples were characterized by SEM, XRD, BET, XPS, ICP-AES, FTIR, and H
2
-TPR. The sample characterization illustrated that CuMn/HBC possessed the high pore volume and specific surface area. The chemisorbed oxygen (O
β
) and the lattice oxygen (O
α
) which took part in the removal reaction largely existed in CuMn/HBC. What is more, MnO
2
and CuO (or Cu
2
O) were highly dispersed on the CuMn/HBC surface. The strong synergistic effect between Cu-Mn mixed oxides was critical to the removal reaction of HCHO and Hg
0
via the redox equilibrium of Mn
4+
+ Cu
+
↔ Mn
3+
+ Cu
2+
.