Influence of HCl on oxidation of gaseous elemental mercury by dielectric barrier discharge process Original Research Article

The influence of HCl on the oxidation of gaseous elemental mercury (Hg0) 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, H2O, NO, and O2 in N2 balance have been varied. We observe that Cl atoms and Cl2 molecules, created by the DBD process, play important roles in the oxidation of Hg0 to HgCl2. The addition of H2O to the gas mixture of HCl in N2 accelerates the oxidation of Hg0, although no appreciable effect of H2O alone on the oxidation of Hg0 has been observed. The increase of the reaction temperature in the presence of HCl results in the reduction of Hg0 oxidation efficiency probably due to the deterioration of the heterogeneous chemical reaction of Hg0 with chlorinated species on the reactor wall. The presence of NO shows an inhibitory effect on the oxidation of Hg0 under DBD of 16% O2 in N2, indicating that NO acts as an O and O3 scavenger. At the composition of Hg0 (280 μg m−3), HCl (25 ppm), NO (204 ppm), O2 (16%) and N2 (balance) and temperature 90 °C, we obtain the nearly complete oxidation of Hg0 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.