The Pd supported activated carbon (Pd/AC) sorbents were pretreated by 5 vol.% O-2 or H-2, and the Hg-0 removal efficiency of the corresponding sorbents was compared in different atmospheres. X-ray photoelectron spectroscopy, X-ray diffraction and X-ray absorption spectroscopy were employed to analyze the sorbents at different stages. These results indicated that the Hg-0 removal efficiency of the untreated 1Pd/AC sorbent was higher than that of the pretreated sorbents. The efficiency of Hg removal from coal derived fuel gas is much higher in N-2-H2S-Hg-H-2 atmospheres than that in N-2-H2S-Hg atmospheres and it can be maintained at about 91.4% for 360 min. There exist three types of Pd-0 forms over Pd/AC sorbent, i.e. Pd-0, Pd2+ and Pd2H, and among which Pd is the active species for Hg removal over Pd/AC sorbent H-2 can promote the Hg removal due to the in situ reducing of palladium oxide in the process of sorbent evaluation. H-2 and O-2 in the pretreated atmosphere suppressed the Hg-0 removal due to the formation of inactive palladium hydride and easily sulfidized palladium oxide, respectively, and then the decrease of Pd-0 content. (C) 2014 Elsevier B.V. All rights reserved.