Photolysis of low concentration H₂S under UV/VUV irradiation emitted from high frequency discharge electrodeless lamps

The photolysis of low concentration of H₂S malodorous gas was studied under UV irradiation emitted by self-made high frequency discharge electrodeless lamp with atomic mercury lines at 185/253.7nm. Experiments results showed that the removal efficiency (η_H2S) of H₂S was decreased with increasing initial H₂S concentration and increased slightly with gas residence time. η_H2S was increased dramatically with relative humidity from<5% to 43% while the concentration of oxygen in gas environments affected the removal of H₂S. The mechanisms for direct and indirect photolysis (generation of ozone) were illustrated by the experimental results on photolysis of H₂S under argon environments and ozonation of H₂S under air environments, respectively. The overall η_H2S by photolysis is higher than the combination of η_H2S by direct photolysis and ozonation, suggesting that hydroxyl radical-mediated indirect photolysis played an important role during photolysis processes. The main photolysis product was confirmed to be SO42- with ion chromatograph.