Photocatalytic degradation of aniline at the interface of TiO2 suspensions containing carbonate ions

The degradation of aniline has been investigated using aqueous TiO2 suspensions containing carbonate ions as photocatalyst. The addition of carbonate to Degussa P-25 increased the number of active adsorption sites at its surface. For the TiO2 suspensions containing carbonate ions the intensity of adsorption of aniline increased to 6.9 x 10(2) from 5.5 x 10(2) mol(-1) dm(3) in case of bare TiO2 suspensions. This in turn results in the increased interfacial interaction of the photogenerated charge carriers with the adsorbed aniline and thus enhancing the rate of its photodecomposition to 6.5 x 10(-6) mol dm(-3) s(-1) compared to 2.7 x 10(-6) mol dm(-3) s(-1) in the absence of Na2CO3. The maximum efficiency of this photocatalyst has been obtained upon addition of 0.11 mol dm(-3) of Na2CO3 at pH 10.8. The photocatalytic action is understood by the simultaneous interaction of intermediates, (OH)-O-center dot and CO3 center dot-1 and their reactivity with aniline. Azobenzene, p-benzoquinone, nitrobenzene, and NH3 have been identified as the major products of the photooxidation of aniline. Both the reactant and products have been followed kinetically. The photodegradation follows Langmuir-Hinshelwood Model. The mechanism of the occurring reactions has been analyzed and discussed. In the presence of Na2CO3, 3 x 10(-3) mol dm(-3) of aniline could be photodegraded completely in about 6 h while all organic intermediates decomposed completely within about 10 h. (c) 2006 Elsevier Inc. All rights reserved.