Abstract: To further improve the mercury removal efficiency of wet flue gas desulfurization（WFGD）systems，the
characteristics of Hg0 re-emission and the mercury removal performances of different ionic liquids were studied at low SO32-
concentrations. Based on a bubble reactor，the effects of SO32- and metal ions（Fe2+，Fe3+ and Cu2+）on the characteristics of
Hg0 re-emission in WFGD systems were investigated under N2 atmosphere. The mercury removal performances of three
ionic liquid additives（HMIM［PF6］，BMIM［PF6］and BMIMCl）were also studied，and the optimal operating conditions
for the best-performing additives were obtained. The results indicate that increasing SO32- concentration at a relatively low
level can intensify the reduction of Hg2+ ，whereas Hg0 re-emission is significantly inhibited with excess concentration of
SO32- . It is also found that Fe2+ ，Fe3+and Cu2+can facilitate Hg0 re-emission. The three ionic liquid additives above show
effective inhibitions on Hg0 re-emission in the order of BMIMCl＞BMIM［PF6］＞HMIM［PF6］. Further experiments were
carried out on BMIMCl to obtain its optimal condition for inhibiting Hg0 re-emission. The optimal condition for BMIMCl is
at a mass concentration of 10 g/L，a lower pH value and a desulfurization liquid temperature at 50 ℃.

Key words: WFGD, Hg0 re-emission, SO32- concentration, metal ions, ionic liquid, mercury removal