Abstract: The objective of the study is to examine the conditions under which transition metal ion,Cu²⁺ could catalyze potassium persulfate to oxidize gaseous mercury.The effects of the concentrations of potassium persulfate and copper sulfate，and addition of sodium thiosulfate and tertiary butanol（TBA），a free radical scavenger on the efficiency of Hg removal were studied.The results showed that the efficiency of Hg removal increased with increasing concentrations of potassium persulfate，copper sulfate and the addition of sodium thiosulfate，while decreased with the addition of TBA.The oxidation reaction between Hg and K₂S₂O₈ catalyzed by Cu²⁺ followed pseudo-first-order kinetics.Direct rate constant and catalyzed rate constant were 3.52×10^-5s^-1 and 0.0927 L·mol^-1·s^-1，respectively.Furthermore，the possible reaction mechanism of gaseous mercury oxidation was also discussed.Cu²⁺ was considered as an effective complex anion activator in persulfate-thiosulfate redox system and Hg removal can be achieved by both indirect oxidation of free radicals and direct oxidation by persulfate.