Photocatalytic Oxidation of Methyl Mercaptan in Foul Gas for Odor Control

Methyl mercaptan (CH 3 SH) is a representative odorous pollutant from various odor emission sources such as sewage and municipal solid wastes. This study confirms that CH 3 SH 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 CH 3 SH in foul gas can be successfully degraded by photocatalytic oxidation under UV-A irradiation using TiO 2 -based photocatalysts. In this study, two new catalysts, NH 4 + -modified TiO 2 (NH 4 + -TiO 2 ) and SO 4 2- -modified TiO 2 (SO 4 2- -TiO 2 ), 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-TiO 2 ) were used for the photocatalytic degradation of CH 3 SH. It was found that the NH 4 + -TiO 2 catalyst achieved a better performance than P25-TiO 2, whereas SO 4 2- -TiO 2 demonstrated a poorer performance. The high photocatalytic activity of NH 4 + -TiO 2 for CH 3 SH degradation results from its basic characteristics and the presence of an ammonium (NH 4 + ) group on the NH 4 + -TiO 2 catalyst surface. The photocatalytic degradation of CH 3 SH was further studied using the P25-TiO 2 catalyst under different experimental conditions. The experimental results showed that catalyst loading, relative humidity, and initial concentration could influence the efficiency of CH 3 SH 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 (CH 3 SH) from the gas phase by both photolysis and photocatalytic oxidation processes.