Photocatalytic Oxidation of Methyl Mercaptan in Foul Gas for Odor Control

Methyl mercaptan (CH3SH) is a representative odorous pollutant from various odor emission sources such as sewage and municipal solid wastes. This study confirms that CH3SH in a synthetic foul gas can be effectively decomposed by UV-C (<280 nm) photolysis using germicidal lamps, but is resistant to destruction under UV-A (365 nm) irradiation using black-light lamps. This study also demonstrates that CH3SH in foul gas can be successfully degraded by photocatalytic oxidation under UV-A irradiation using TiO2based photocatalysts. In this study, two new catalysts, NH4+-modified TiO2 (NH4+-TiO2) and SO42--modified TiO2 (SO42--TiO2), were prepared by a precipitate-refluxing method and a hydrothermal method, respectively. These two catalysts as well as the commercially available catalyst Degussa P25 (P25-TiO2) were used for the photocatalytic degradation of CH3SH. It was found that the NH4+-TiO2 catalyst achieved a better performance than P25-TiO2, whereas SO42--TiO2 demonstrated a poorer performance. The high photocatalytic activity of NH4+-TiO2 for CH3SH degradation results from its basic characteristics and the presence of an ammonium (NH4+) group on the NH4+-TiO2 catalyst surface. The photocatalytic degradation of CH3SH was further studied using the P25-TiO2 catalyst under different experimental conditions. The experimental results showed that catalyst loading, relative humidity, and initial concentration could influence the efficiency of CH3SH photocatalytic degradation significantly. It was found that a catalyst loading of 3.93 mg cm-2 and a relative humidity of 43% are two essential factors for achieving the best performance under these experimental conditions. This work provides new insights into the removal of a sulfur-containing organic substance (CH3SH) from the gas phase by both photolysis and photocatalytic oxidation processes.