Influence of HCl on oxidation of gaseous elemental mercury by dielectric barrier discharge process.

Abstract The influence of HCl on the oxidation of gaseous elemental mercury (Hg 0 ) has been investigated using a dielectric barrier discharge (DBD) plasma process, where the temperature of the plasma reactor and the composition of gas mixtures of HCl, H 2 O, NO, and O 2 in N 2 balance have been varied. We observe that Cl atoms and Cl 2 molecules, created by the DBD process, play important roles in the oxidation of Hg 0 to HgCl 2 . The addition of H 2 O to the gas mixture of HCl in N 2 accelerates the oxidation of Hg 0 , although no appreciable effect of H 2 O alone on the oxidation of Hg 0 has been observed. The increase of the reaction temperature in the presence of HCl results in the reduction of Hg 0 oxidation efficiency probably due to the deterioration of the heterogeneous chemical reaction of Hg 0 with chlorinated species on the reactor wall. The presence of NO shows an inhibitory effect on the oxidation of Hg 0 under DBD of 16% O 2 in N 2 , indicating that NO acts as an O and O 3 scavenger. At the composition of Hg 0 (280 μg m −3 ), HCl (25 ppm), NO (204 ppm), O 2 (16%) and N 2 (balance) and temperature 90 °C, we obtain the nearly complete oxidation of Hg 0 at a specific energy density of 8 J l −1 . These results lead us to suggest that the DBD process can be viable for the treatment of mercury released from coal-fired power plants.