A coal-based activated carbon (AC) and an impregnated activated carbon (IAC) were used as low concentration hydrogen sulfide (H2S) oxidation catalysts at ambient temperature. The effects of O-2 and relative humidity on the performance of the samples for H2S removal were investigated. The materials before and after desulfurization tests were characterized using nitrogen adsorption, thermal analysis, XRD, TPD and SEM with EDAX. The results demonstrate that impregnation with Na2CO3 as the main agent makes the AC become an efficient catalyst for H,S oxidation, and water has a highly beneficial effect on the process. Moreover, the sulfur capacity of the IAC attains as high as ca. 420 mg S/g IAC, which mainly attributes to the high catalytic activity and it allows the pores be fully utilized. Furthermore, elemental sulfur is the dominant product, and a little amount of sulfuric acid is produced on both the AC and IAC. For the AC, the formation of sulfuric acid suppresses H2S dissociation and leads to rapid deactivation. Whereas, the impregnated Na2CO3 prevents deactivation of the IAC until the pores are almost completely saturated by products. (C) 2007 Elsevier B.V. All rights reserved.