Journal of Industrial and Engineering Chemistry, Vol.8, No.1, 22-27, January, 2002
Photocatalytic Decomposition of 4-Nitrophenol over Titanium Silicalite (TS-1) Using Hydrogen Peroxide as an Oxidant
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Titanium silicalite (TS-1) having Si/Ti ratio of 26.3 was synthesized and used as a photocatalyst for decomposition of 4-nitrophenol (4-NP) in water. The photocatalytic activity of TS-1 for decomposition of 4-NP was found to be greatly affected by H2O2. In the absence of H2O2, TS-1 exhibited only small catalytic activity irrespective of pH. In the presence of H2O2, on the other hand, TS-1 showed a marked increase in photocatalytic activity. Especially, in acidic conditions, the addition of H2O2 in reaction solution resulted in a remarkable enhancement of photocatalytic activity. It seemed that titanium-hydroperoxide species are formed by the interaction of framework titanium in TS-1 with H2O2 and .ㆍOH radicals are formed easily from titanium-hydroperoxide species under UV illumination. In this experimental condition, most of the 4-NP molecules and .ㆍOH radicals are likely present in tiny volume of the TS-1 pore. As a result, in the presence of H2O2, the photocatalytic decomposition of 4-NP over TS-1 can be enhanced due to the efficient formation of .ㆍOH radicals and the close proximity of .ㆍOH radicals to the reactant molecules.
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