Efficient Photocatalytic Disinfection of Escherichia coli O157:H7 using C70-TiO2 Hybrid under Visible Light Irradiation

Efficient photocatalytic disinfection of Escherichia coli O157:H7 was achieved by using a C-70 modified TiO2 (C-70-TiO2) hybrid as a photocatalyst under visible light (lambda > 420 nm) irradiation. Disinfection experiments showed that 73% of E. coli O157: H7 died within 2 h with a disinfection rate constant of k = 0.01 min(-1), which is three times that measured for TiO2. The mechanism of cell death was investigated by using several scavengers combined with a partition system. The results revealed that diffusing hydroxyl radicals play an important role in the photocatalytically initiated bacterial death, and direct contact between C-70-TiO2 hybrid and bacteria is not indispensable in the photocatalytic disinfection process. Extracellular polymeric substances (EPS) of bacteria have little effect on the disinfection efficiency. Analyses of the inhibitory effect of C-70-TiO2 thin films on E. coli O157: H7 showed a decrease of the bacterial concentration from 3 x 10(8) to 38 cfu mL(-1) in the solution with C-70-TiO2 thin film in the first 2 h of irradiation and a complete inhibition of the growth of E. coli O157:H7 in the later 24 h irradiation.