3.3. Effect of intensity of VL
Experiments to investigate the light intensity effect on photocatalytic disinfection efficiency of the NS are performed using white LED as light source. Fig. 3a shows that the disinfection efficiency increased with the increasing of VL intensity from 3 to 223 mW cm−2. At the lower light intensity (3 and 15 mW cm−2) and in the presence of photocatalyst, there was only a little decrease in cell density, which suggests the low photon is inducing the limited photocatalytic reaction. Along with the increasing of VL intensity (87 and 200 mW cm−2), the disinfection efficiency also increased and there existed an induction period at the first 2 h, indicating that the bacterial defense system is in response to protect bacterial cell. Further increasing the VL intensity to 223 mW cm−2, the induction period was disappeared, which suggests that the self-defense system of bacterial cell does not function at high flux of photons, and the completely inactivation 7 log of bacterial cells was achieved within 6 h irradiation. However, in the light control with the intensity of 223 mW cm−2 (Fig. 3a), the bacterial population remained constant after treatment, which suggests that the photolysis of VL is not effective to inactivate E. coli K-12 even at high intensity. Thus, the intensity of VL is also one of the most important parameters in the photocatalytic disinfection.
3.3. Effect of intensity of VL
Experiments to investigate the light intensity effect on photocatalytic disinfection efficiency of the NS are performed using white LED as light source. Fig. 3a shows that the disinfection efficiency increased with the increasing of VL intensity from 3 to 223 mW cm−2. At the lower light intensity (3 and 15 mW cm−2) and in the presence of photocatalyst, there was only a little decrease in cell density, which suggests the low photon is inducing the limited photocatalytic reaction. Along with the increasing of VL intensity (87 and 200 mW cm−2), the disinfection efficiency also increased and there existed an induction period at the first 2 h, indicating that the bacterial defense system is in response to protect bacterial cell. Further increasing the VL intensity to 223 mW cm−2, the induction period was disappeared, which suggests that the self-defense system of bacterial cell does not function at high flux of photons, and the completely inactivation 7 log of bacterial cells was achieved within 6 h irradiation. However, in the light control with the intensity of 223 mW cm−2 (Fig. 3a), the bacterial population remained constant after treatment, which suggests that the photolysis of VL is not effective to inactivate E. coli K-12 even at high intensity. Thus, the intensity of VL is also one of the most important parameters in the photocatalytic disinfection.
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