Hydroxyapatite-supported Ag–TiO2 as Escherichia coli disinfection photocatalyst

A series of hydroxyapatite (HAP), 1 wt% Ag–TiO2 (AT1), 1 wt% Ag-HAP and 5 wt% AT1/HAP composite catalysts were prepared by incipient wetness and mechanical mixing methods. They were characterized by X-ray diffraction (XRD), FT-IR, SEM and ESCA analyses and their photocatalytic bactericidal activities were measured in suspension using Escherichia coli (E. coli), a water pollutant indicator. The surface analysis revealed that the Ag/Ti ratio is found to be ca. 0.0273 and also it indicated that the titania is present in the form of Ti4+ and Ag is present as metallic silver. Both the XRD and ESCA analyses confirmed the phase of metallic Ag particles, which played a significant role on the bactericidal activity of the Ag doped TiO2 catalysts. The FT-IR analysis of HAP revealed that the peak intensity is due to the absorbance of surface PO43− group centered at wave number 1030 cm−1 and is drastically decreased upon exposure to UV for 1 h. The HAP displayed high amount of bacteria adsorption, ca. 80% during the dark experiments compared to other catalytic systems tested. The cumulative photocatalytic properties of AT1/HAP catalytic system resulted in 100% E. coli bacteria reduction within 2 min.