PHOTODECOLORIZATION OF METHYL-ORANGE USING SILVER ION MODIFIED TIO2 AS PHOTOCATALYST

The photodecolorization of methyl orange catalyzed by the Ag+ ion modified TiO2 suspended solution was both theoretically and experimentally studied. A semitheoretical kinetic equation was obtained, R(i) = (((6.32 X 10(-3))(0.11)[MO(b)])/(l + 0.11[MO(b)]))[TiO2]0.24[Ag+b]0.46P0.46, which correlated the experimental results well with an average deviation of 2.2%. The results revealed that Ag+ ion could trap photogenerated electrons to avoid the recombination of electrons and holes and significantly improve the photodecolorization of methyl orange. The experimental results also indicated that Ag+ ion was more favorable for promoting this reaction than Cu2+, Co2+, Fe3+, and Ce4+ ions. The counterion NO3- was better than SO42- ion for photodecolorization of methyl orange. The activity of rutile form TiO2 was comparable to the anatase form in the presence of Ag+ ion. The effect of bubbling oxygen and nitrogen in photodecolorization of methyl orange was insignificant in the presence of Ag+ ion. On the other hand, the effect of bubbling oxygen was significant in the absence of Ag+ ion. The decolorization rate increased with pH and reached a maximum value at pH 8.75, and then decreased in higher pH due to the precipitation of Ag+ cation with OH- anion. The calcination temperature of TiO2 gave an insignificant effect on the photodecolorization of methyl orange in the presence of Ag+ compared to that in the absence of Ag+ ion. Increasing loading of Ag+ ion significantly increased the apparent primary quantum yield.