Gaseous elemental mercury removal using VUV and heat coactivation of Oxone/H2O/O2 in a VUV-spraying reactor

Abstract

A novel process on gaseous elemental mercury removal using vacuum ultraviolet light (VUV) and heat coactivation of Oxone/H2O/O2 (i.e., VUV/heat/Oxone/H2O/O2 system) in a VUV-spraying reactor was investigated for the first time. Experiments were carried out to evaluate the effects of several operating parameters (e.g, VUV wavelength, Oxone concentration, VUV radiation intensity, activation temperature, solution pH and O2 concentration) on Hg0 removal. Mechanism and kinetic law of Hg0 removal were also revealed. The results demonstrated that 185 nm wavelength showed the best performance. Hg0 removal was promoted by increasing VUV radiation intensity, Oxone concentration and O2 concentration, and was weakened by increasing solution pH and SO2 concentration. Activation temperature exhibited dual influence on Hg0 removal. Hg0 was removed by six pathways: (1) oxidized by SO4− and OH that are produced from VUV activation of Oxone; (2) oxidized by O3 and O that are produced from VUV photolysis of O2; (3) oxidized by OH that is produced from VUV photolysis of H2O; (4) removed by light-water excitation reaction; (5) oxidized by SO4− and OH that are produced from heat activation of Oxone; (6) oxidized directly by Oxone. Hg0 removal process followed a fast reaction in VUV/heat/Oxone/H2O/O2 system (i.e., presence of VUV) and a medium speed reaction in heat/Oxone/H2O/O2 system (i.e., absence of VUV).