Silver-modified mesoporous TiO2 photocatalyst for water purification

Mesoporous anatase (TiO2) was modified with silver (Ag) nanoparticles using a photoreduction method. Performance of the resulting TiO2–Ag nanocomposites for water purification was evaluated using degradation of Rhodamine B (RhB) and disinfection of Escherichia coli (E. coli) under ultraviolet (UV) irradiation. The composites with different Ag loadings were characterized using physical adsorption of nitrogen, X-ray diffraction, X-ray photoelectron spectroscopy and UV–Visible diffuse reflectance spectroscopic techniques. The results showed that metallic Ag nanoparticles were firmly immobilized on the TiO2 surface, which improved electron-hole separation by forming the Schottky barrier at the TiO2–Ag interface. Photocatalytic degradation of RhB and inactivation of E. coli effectively occurred in an analogical trend. The deposited Ag slightly decreased adsorption of target pollutants, but greatly increased adsorption of molecular oxygen with the latter enhancing production of reactive oxygen species (ROSs) with concomitant increase in contaminant photodegradation. The optimal Ag loadings for RhB degradation and E. coli disinfection were 0.25 wt% and 2.0 wt%, respectively. The composite photocatalysts were stable and could be used repeatedly under UV irradiation.

Research highlights► Silver-modified mesoporous TiO2 was prepared and applied for the photocatalytic degradation of Rhodamine B (RhB) and disinfection of E. coli. ► The degradation of RhB and disinfection of E. coli showed high similarities. ► Ag nanoparticles created a Schottky barrier at the interface of TiO2 and Ag. ► Ag particles decreased RhB adsorption, but increased the adsorption of dissolved O2. ► The enhanced adsorption of O2 played a much more important role in enhancing the photocatalytic activities. ► The composite catalyst showed high stability.