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

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