Photocatalytic removal of NO and Hg0 using microwave induced ultraviolet irradiating H2O/O2 mixture

We developed a novel method, microwave (MW) induced ultraviolet (UV) irradiating H2O/O-2, to cooperatively remove NO and Hg-0, with the efficiencies of 89.3% and 99.5%. It also can remove 97% SO2. O-2 at a content of 2-8% was sufficient to conduct a good removal of NO and Hg-0. Ozone (O-3) and hydroxyl radical (HO center dot) were proved to be the major oxidants for the removal of Hg-0 and NO, respectively. High temperature facilitated NO removal but impaired He removal. SO2 greatly promoted the removal of NO and Hg-0 due to the formation of SO4 center dot(-) . The presence of Cl- and Br- suppressed NO removal but promoted Hg-0 removal, because Cr and Br- quenched HO center dot to produce Cl- and Br-radicals. The produced NO2 could be totally absorbed by the Na2SO3 solution that followed the main reactor. The O-3 yield and the formation of HO under different conditions were determined using iodine quantity method and electron spin resonance (ESR). The distributions of anion concentration and mercury proportion were obtained using ion chromatography (IC) and cold atom fluorescence spectrometry (AFS), and the main products were identified to be SO42-, NO3- and HgO. The mechanisms of removal of SO2, NO and Hg-0 were speculated.