Visible-Light Bactericidal Effect of Silica Gel-supported Porphyrinatoantimony(V) Catalyst on Legionella Species Occurring in the Living Environmental Fields

In order to develop a bactericidal agent which can operate under visible-light irradiation, silica gel-supported dihydroxo (tetraphenylporphyrinato) antimony (V) catalyst (SbTPP/Sio2) was prepared. Experiments to reduce concentrations of Legionella species were performed using a cylindrical SbTPP/SiO2-photocatalytic bactericidal apparatus in a cooling tower which held 8ooL of water. After 10 days, the concentrations of Legionella species were reduced to less than the detection limit, and these levels were kept until the irradiation was stopped. Also, a photocatalytic bactericidal experiment was conducted with a fountain that was filled with 13m3of water. The concentrations of Legionella species were reduced to less than the detection limit 12 days after the SbTPP/SiO2catalyst was installed in the fountain receiving sunlight irradiation. The concentrations of Legionella species were kept at less than 30CFU/100ml for 3 months until the catalyst was removed from the fountain. Thus, visible-light irradiation of the SbTPP/SiO2 catalyst induced a remarkable bactericidal activity against Legionella species in the living environment.