3.4. Effect of pH on photocatalytic disinfection
Fig. 3b shows pH effect on the photocatalytic disinfection of E. coli K-12 by the NS under VL irradiation (white LED) with the intensity of 200 mW cm−2. The pH value was adjusted at the beginning of the photocatalytic reaction by addition of NaOH or HCl (0.5 mM) to the mixture of the NS and bacteria, and the pH value did not change within the reaction time. In dark and light controls, at studied range of pH 5–8 ( Fig. SM-5), the cell density did not change after 10 h, which suggests that no disinfection effect or photolysis to E. coli K-12 by the NS or VL irradiation at different pH. Total inactivation of 107 cfu mL−1E. coli K-12 was achieved after 8 h treatment at pH 8 ( Fig. 3b). At more acidic or neutral pH, the cell density decreased only 2.5 log within 10 h irradiation. The results showed the inactivation of bacteria was more sensitive at alkaline pH than at acidic and neutral pH, which is probably due to more oxidative species produced at more alkaline pH so that it exhibits higher disinfection efficiency at alkaline pH.
3.4. Effect of pH on photocatalytic disinfectionFig. 3b shows pH effect on the photocatalytic disinfection of E. coli K-12 by the NS under VL irradiation (white LED) with the intensity of 200 mW cm−2. The pH value was adjusted at the beginning of the photocatalytic reaction by addition of NaOH or HCl (0.5 mM) to the mixture of the NS and bacteria, and the pH value did not change within the reaction time. In dark and light controls, at studied range of pH 5–8 ( Fig. SM-5), the cell density did not change after 10 h, which suggests that no disinfection effect or photolysis to E. coli K-12 by the NS or VL irradiation at different pH. Total inactivation of 107 cfu mL−1E. coli K-12 was achieved after 8 h treatment at pH 8 ( Fig. 3b). At more acidic or neutral pH, the cell density decreased only 2.5 log within 10 h irradiation. The results showed the inactivation of bacteria was more sensitive at alkaline pH than at acidic and neutral pH, which is probably due to more oxidative species produced at more alkaline pH so that it exhibits higher disinfection efficiency at alkaline pH.
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