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Gas phase photocatalysis and liquid phase photocatalysis: Interdependence and influence of substrate concentration and photon flow on degradation reaction kinetics

Paper ID Volume ID Publish Year Pages File Format Full-Text
48310 46501 2008 10 PDF Available
Title
Gas phase photocatalysis and liquid phase photocatalysis: Interdependence and influence of substrate concentration and photon flow on degradation reaction kinetics
Abstract

The photocatalytic degradation of metolachlor in water and butyric acid in air on coated TiO2 has been investigated to study the interdependency on the degradation rate of the UV photon flux and the concentration of the organic compound. Experimental results clearly showed that the kinetic change of order with respect to light intensity depended on the value of the concentration of organic compound. The fitting of experimental results with the Langmuir–Hinshelwood (L-H) model emphasized that the corresponding “apparent adsorption constant”, KR, could not be considered as an equilibrium constant in the dark since the value of KR varied with regard to the photon flow. The assumption of a pseudo-steady-state for the concentration of hydroxyl radicals associated either with L-H model (under certain conditions) or Eley–Rideal model explains consistently the dependence of the apparent kinetic parameter, kobs, and KR with the light intensity. A rate expression taking into account the interdependency of the degradation rate on the UV photon flux and the initial concentration of the organic compound is proposed and validated for a liquid and a gas phase reaction. The constants of this correlation are independent of the initial concentration and light intensity.

Keywords
Photocatalysis; Liquid phase; Gas phase; Langmuir–Hinshelwood model; Eley–Rideal model
First Page Preview
Gas phase photocatalysis and liquid phase photocatalysis: Interdependence and influence of substrate concentration and photon flow on degradation reaction kinetics
Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 78, Issues 3–4, 7 February 2008, Pages 232–241
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis