Urea-based wet flue gas desulfurization (Urea-WFGD) is a promising technology because of its simple process, high desulfurization efficiency, and recyclability of the products. However, it cannot effectively remove Hg-0 from flue gas because of the low solubility of Hg-0 in water. In this study, enhancement of the removal of Hg-0 from flue gas in a urea-WFGD system using high-temperature-activated (NH4)(2)S2O8 was investigated for the first time in a spray reactor. Experiments were conducted to evaluate the effects of process parameters on Hg-0 removal. Reaction products and key radicals were detected. The reaction mechanism and pathways were also revealed. Removal of Hg-0 in urea-WFGD system was significantly enhanced by high-temperature-activated (NH4)(2)S2O8. The mechanism behind this effect is that an increase of reaction temperature significantly increases the concentration of (NH4)(2)S2O8 or liquid-gas ratio, thereby increasing Hg-0 removal efficiency. However, an increase of solution pH or urea concentration significantly decreases the removal efficiency. Changing Hg-0 or SO2 concentration has only a small effect on Hg-0 removal. NH4+, SO42-, NO3-, and Hg2+ are found in solution, and S2O82-/OH/SO4- oxidations play an important role in the removal of Hg-0. The results demonstrate that the feasibility of Hg-0 removal in urea-WFGD system was enhanced by high-temperature-activated (NH4)(2)S2O8 in a spray reactor. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.