Removal of volatile dimethyl sulfoxide from wastewater using hydrogen peroxide catalyzed by supported molybdenum oxide

Abstract

Due to its excellent solubility for many chemicals, DMSO is widely used as solvents in industries. The biodegradation of DMSO is pretty slow and gives out noxious and volatile compounds like dimethylsulfide, methyl mercaptan, and hydrogen sulfide. Therefore, a green and efficient DMSO removal process is needed. In this work, supported molybdenum oxide catalysts were prepared and were characterized with powder XRD, SEM, TEM, Raman, DR-UV–vis spectroscopy and XPS. These catalysts are efficiently active for the catalytic oxidation of DMSO in wastewater using green oxidant, H2O2. The degradation product of DMSO is DMSO2 which is an environmentally friendly and biodegradable compound and can be further removed by biological processes without forming hazardous sulfides. Fumed SiO2 is the best support for MoO3 and the catalytic activity increases with the increase of the MoO3 loading. DMSO (179 mmol/L) is completely removed after a 2-hour reaction at 50 °C. EPR analyses and control experiments with radical scavengers confirm that the oxidative degradation of DMSO is not a radical reaction. Thus, a non-radical oxidation mechanism is proposed for the degradation of DMSO. The kinetic study on the 30 wt% MoO3/SiO2 catalyst confirms that the catalytic oxidation reaction of DMSO is a pseudo-first-order reaction with an apparent activation energy of 68.5 kJ/mol. When the initial concentration of DMSO is further increased to 264 or 344 mmol/L, the MoO3/SiO2 catalyst can still remove it within 2 h. In conclusion, this catalyst is a promising candidate for treating industrial wastewater containing DMSO.