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[Display omitted] Due to the accumulation of heavy metal compounds produced by the sintering process in steel industry, the catalysts used for low-temperature selective catalytic reduction of NO with NH 3 (NH 3 -SCR) might be seriously deactivated. In this work, the deactivation effect of PbCl 2 , Pb(NO 3) 2 , and PbSO 4 on Mn-Ce activated carbon supported catalyst for low-temperature NH 3 -SCR of NO was investigated and compared. Poisoned catalysts were provided by impregnating fresh catalysts with Pb(NO 3) 2 , PbSO 4 and PbCl 2 aqueous solutions, respectively. Deactivation could be observed on the poisoned samples, and the deactivation degree was following PbCl 2 > PbSO 4 > Pb(NO 3) 2. The catalytic activities of all samples were tested, and the physicochemical properties of fresh and poisoned catalysts were assessed. PbCl 2 caused the most severe deactivation of the catalyst, owing to its poor redox property and surface acidity. Cl- could also react with Mn active sites to form -O-Mn-Cl bonds, resulting in additional acid sites, although these newly generated sites were not reactive in NH 3 -SCR reaction process. PbSO 4 exhibited moderate poisoning effect due to the addition of SO 4 2-, which created new Brønsted acid sites, facilitating the NH 3 adsorption and NO reduction. Pb(NO 3) 2 had the least poisoning impact on the catalyst due to the NO 3 –, promoting the NH 3 activation. The in situ DRIFTS results revealed that NH 3 -SCR reaction over all samples was governed by Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) mechanism, and did not change due to the lead poisoning. Finally, a possible mechanistic model for different lead salts poisoning over Mn-Ce/AC catalyst was proposed. [ABSTRACT FROM AUTHOR]