Enhanced Photocatalytic Activity of TiO2 by Doping with Ag for Degradation of 2,4,6-trichlorophenol in Aqueous Suspension

A series of Ag-TiO2 nanocatalysts were synthesized by a sol-gel method with a doping content up to 2wt%-Ag. The physico-chemical characteristics of the synthesized catalysts were characterized by X-ray diffraction, X-ray photoelectron emission spectroscopy, transmission electron microscopy, UV-visible absorption spectrometer, and optical ellipsometry to study the influence of the Ag content on the surface properties, optical absorption and other characteristics of the photocatalysts. The photocatalytic activity of the Ag-TiO2 was evaluated in the 2,4,6trichlorophenol (TCP) degradation and mineralization in aqueous solution under UV-A illumination. The experiments demonstrated that TCP was effectively degraded by more than 95% within 120 min. It was confirmed that the presence of Ag on TiO2 catalysts could enhance the photocatalytic oxidation of TCP in aqueous suspension and the experimental results showed that the kinetics of TCP degradation follows a pseudo-first-order kinetic model. It was found that an optimal dosage of 0.5wt% Ag in TiO2 achieved the fastest TCP degradation under the experimental conditions. The experimental results of TCP mineralization indicated while total organic carbon was reduced by a high portion of up to 80% within 120 min, most chlorine on TCP was more quickly converted to chloride within the first 40 min. On the basis of various characterizations of the photocatalysts, the reactions involved to explain the photocatalytic activity enhancement due to Ag doping include a better separation of photogenerated charge carriers and improved oxygen reduction inducing a higher extent of degradation of aromatics.