AN INSITU DIFFUSE REFLECTANCE FTIR INVESTIGATION OF PHOTOCATALYTIC DEGRADATION OF 4-CHLOROPHENOL ON A TIO2 POWDER SURFACE

An in situ FTIR technique has been employed to probe the adsorption and photocatalytic degradation of 4-chlorophenol (4-CP) on TiO2 particles in a gas/solid system. The chemisorbed 4-CP adsorbed on the TiO2 surface corresponds to a monolayer. The reaction has been followed under a number of conditions in order to investigate the roles of oxygen and water in the mechanism of 4-CP degradation. The rate of 4-CP disappearance was greatest under an oxygen atmosphere saturated with water and with UV irradiation. Under these conditions hydroquinone (HQ) was observed as a primary reaction inter-mediate and carbonates as the final product. Transformation of 4-CP to HQ was seen to occur under a variety of reaction conditions (i.e. O2/UV, N2/H2O/UV), but HQ degradation took place only in the presence of oxygen and UV irradiation. These results illustrate that the interactions of 4-CP at the semiconductor surface are complex and suggest that oxygen is intrinsically involved in the degradation reactions.