The synthetic evaluation of CuO-MnOx-modified pinecone biochar for simultaneous removal formaldehyde and elemental mercury from simulated flue gas

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 100-300A degrees A 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 175A degrees A C corresponding to 89%and 83%, respectively. The addition of NO and SO2 exhibited inhibitive influence on HCHO removal. For the removal of Hg-0, NO showed slightly positive influence and SO2 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-beta) and the lattice oxygen (O-alpha) which took part in the removal reaction largely existed in CuMn/HBC. What is more, MnO2 and CuO (or Cu2O) 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 Mn4+ + Cu+ <-> Mn3+ + Cu2+.