The Effects Of Manganese Oxide Particles On Photocatalytic Bactericidal Activity Of TiO2 And ZnO

Photocatalytic bactericidal technology has been paid so much attention for its low consumption and high efficiency, and has been used widely in water treatment. To kill disease-causing bacteria in water is extremely important to water treatment, especially to drinking water treatment. Natural water contains disease-causing bacteria and impurity particles. The latter can affect photocatalytic bactericidal activity by influencing the property of the photocatalyst or the photocatalytic process. This work selected two usual photocatalyst (TiO₂ and ZnO) to kill the drinking water indicative bacteria E. coli ATCC 8099, and three kinds of manganese oxide particles (α-MnO₂,β-MnO₂ andγ-MnOOH) as impurity particles. The following are the main contents of the study: photocatalytic bactericidal activity of TiO₂ under different UV, the influence on photocatalytic bactericidal activity of TiO₂ and ZnO with different crystalline manganese oxide, at different initial pH values (4.0, 6.0 and 8.0),with different concentration of manganese oxides and under different UV. The results are that UV with shorter wavelength and lighter intensity can increase the bactericidal activity of TiO₂; manganese oxide particles can inhibit it and the sequence isα-MnO₂>γ-MnOOH>β-MnO₂,but manganese oxide particles have little inhibition on ZnO;the different initial pH values can inhibit the photocatalytic bactericidal activity of TiO₂ with the manganese oxide particles, the sequence is pH8.0>pH4.0>pH6.0,but pH values have no influence on ZnO with the manganese oxide particles; accompanied by the increasing of manganese oxide concentrations, the inhibition on the photocatalytic bactericidal activity of TiO₂ also increases, but the photocatalytic activity of ZnO would not be inhibited,even with high manganese oxide concentration; the photocatalytic bactericidal activity of TiO₂ will be inhibited by manganese oxide particles under long-wave UV, which won't happen under short-wave UV. And manganese oxide particles can't inhibit the photocatalytic bactericidal activity of ZnO under long-wave or short-wave UV.In conclusion, the photocatalyst ZnO is stable for manganese oxidation particles in water, and the photocatalytic bactericidal activity of TiO₂ will be inhibited under long-wave UV, but the inhibition under short-wave UV will greatly reduce.