Photolytic and Photocatalytic Degradation of Phenols in Aqueous Solution

Photolytic and photocatalytic degradation of phenols in aqueous solution were investigated under the UV irradiation of 254 nm light and VUV irradiation of 254 nm and 185 nm light. The decomposition and mineralization of 4-CP in UV/TiO2 process were both faster than in UV process. VUV irradiation led to the most efficient degradation of 4-CP. The initial concentration of 4-CP had little effect on the decomposition rate in UV and UV/TiO2 processes while in VUV and VUV/TiO2 processes the pseudo first-order rate constants decreased with the increase of the initial concentration. In UV/TiO2 process gas bubbling and liquid circulation could enhance the formation of oxidative species (HO2•) and mass transfer efficiency. The optimal air flow rate and liquid circulation flow rate were 300 mL/min and 1200 mL/min respectively in our reactor. Photocatalytic decomposition and mineralization of 4-CP were highly dependent on the nature of the organic substrate treated. Adding salt into aqueous solution could enhance photocatalytic degradation of phenols but after long operation with aqueous solution containing salt TiO2 catalyst would lose activity.