Photocatalytic degradation and mineralization of a malodorous compound (dimethyldisulfide) using a continuous flow reactor

Dimethyldisulfide (DMDS) degradation and mineralization were carried out in a continuous flow reactor using TiO2-P25 or ZnO as photocatalysts. The efficiency of the disappearance and of the mineralization of the DMDS showed to be very sensitive to the molar flow of the sulphur compounds. In our study, we have evaluated the limit average mineralization rate of DMDS per Watt emitted (for TiO2-P25). Catalyst deactivation has been observed after several hours of complete DMDS mineralization, which was expressed by the decrease of CO2 concentration and the appearance of residual DMDS on the outlet side of the reactor. This phenomenon is due to the inhibition of active sites on the catalyst by the formation of sulfates as final sulphur-compounds (determined by ionic chromatography). The FT-IR analysis, performed on catalyst in presence of high DMDS flow, indicated the presence of partial oxidation products such as sulfoxides, sulfones, sulfonates, sulfates and carbonyl groups. All of these disappearing after static irradiation, except for sulfate according to ionic chromatography analysis. The effect of humidity is shown; the data indicated that a detrimental effect occurs depending on the DMDS/H2O concentration ratio. Comparison of the disappearance and of the mineralization of DMDS in presence of TiO2-P25, commercial ZnO or home made nano-ZnO catalysts is presented and discussed. Nano-ZnO material, prepared at low temperature, showed an efficiency close to that of TiO2-P25 while no activity was detected in the presence of commercial ZnO.