In this article, Mn-Ce mixed oxides modified wheat straw chars were prepared by an ultrasonic-assisted impregnation method, and were employed to remove elemental mercury (Hg-0) from flue gas. Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) were employed to characterize the physicochemical properties of the catalysts. The effects of ultrasonic-assisted impregnation, Mn/Ce molar ratios, calcination temperatures, Mn-Ce loading values, reaction temperatures and main flue gas components such as SO2, O-2, NO and H2O on mercury removal using these catalysts were studied in a fixed bed reactor. The results showed that the catalyst with a Mn/Ce molar ratio of 2/1 exhibited high mercury removal activity at 150 degrees C. The optimal Mn-Ce loading value and calcination temperature were 0.12 mol/L and 250 degrees C, respectively. The presence of O-2 and NO obviously promoted Hg-0 removal. Low concentrations of water vapor and SO2 strengthened Hg-0 removal, but high concentrations of water vapor and SO2 inhibited Hg-0 removal. Finally, the mercury removal mechanism was also discussed based on experimental results and characterization analysis. (C) 2017 Elsevier B.V. All rights reserved.