Removal of gaseous elemental mercury using thermally catalytic chlorite-persulfate complex

We developed a novel oxidation method, thermally catalytic chlorite-persulfate (NaClO2-Na2S2O8, shorten as CP), to remove gaseous Hg-0. Chlorite and persulfate exhibited an outstanding performance in Hg-0 removal as compared to using chlorite or persulfate alone. The cost for using CP is 3-69 USD/lb-Hg-0 which is far lower than using Na2S2O8 (1739-2552 USD/lb-Hg-0) and NaClO2 (37-1299 USD/lb-Hg-0). Kinetics analysis indicated that the rate constant of the reaction between CP and Hg-0 is 5250 times and 11.7 times higher than that of using Na2S2O8 and NaClO2 alone. The impacts of CP concentration, thermal catalytic temperature, flue gas residence time and presence of other gases in the flue gas on the Hg-0 removal were evaluated. SO2 and NO were found to be the inhibitor and promoter, respectively, for Hg-0 removal. Mercury distribution under different atmospheric conditions was determined by using atomic fluorescence spectrometry (AFS). The active oxidizing species produced in the thermal catalysis of CP were determined to be ClO2, SO4 center dot- and HO center dot using ultraviolet-visible spectrophotometry (UV-Vis) and electron spin resonance (ESR). HgCl2 and HgSO4 were the main mercury forms in the byproduct according to the X-ray photoelectron spectroscopy (XPS) result. The mechanism of Hg-0 removal with using CP was proposed.