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Kinetics of Simultaneous Photocatalytic Degradation of Phenolic Compounds and Reduction of Metal Ions with Nano-$TiO_2$

Vinu, R and Madras, Giridhar (2008) Kinetics of Simultaneous Photocatalytic Degradation of Phenolic Compounds and Reduction of Metal Ions with Nano-$TiO_2$. In: Environmental Science and Technology, 42 (3). pp. 913-919.

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The simultaneous photocatalytic degradation of phenol and 4-nitrophenol and reduction of metal ions like copper $(Cu^2^+)$ and chromium $(Cr^6^+)$ was studied with solution combustion synthesized nanoanatase $TiO_2$ (CS $TiO_2$) and commercial titania, Degussa P-25. The presence of metal ion reduces the rate of degradation of phenol and 4-nitrophenol. It was found that $Cu^2^+$ reduction to $Cu^+$ is accelerated in the presence of phenol. In the case of $Cr^6^+$, CS $TiO_2$ enhances the initial adsorption of $Cr^6^+$ and complete reduction is achieved within the first 10 min of UV irradiation. The presence of phenol or 4-nitrophenol also enhances the initial adsorption of $Cr^6^+$ and its reduction. The metal ion reduction in the presence of CS $TiO_2$ is compared with that of Degussa P-25. The rate of reduction of metal ions in presence of Degussa P-25 is twice as slow as that of CS $TiO_2$ in presence of both phenol and 4-nitrophenol. The presence of $Cu^2^+$ and $Cr^6^+$ also induces the formation of the intermediates which were not observed for the phenol-CS $TiO_2$ system. The formationand consumption of the intermediates are modeled with a simple series reaction mechanism. A detailed dual-cycle, multistep reaction mechanism of $TiO_2$ photocatalysis for the simultaneous degradation and reduction is proposed and the model is developed following the network reduction technique. The kinetic rate constants in the model are evaluated for the systems studied.

Item Type: Journal Article
Publication: Environmental Science and Technology
Publisher: American Chemical Society
Additional Information: Copyright of this article belongs to American Chemical Society.
Department/Centre: Division of Mechanical Sciences > Chemical Engineering
Date Deposited: 04 Mar 2008
Last Modified: 19 Sep 2010 04:43
URI: http://eprints.iisc.ac.in/id/eprint/13292

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