This report discusses the effects of the initial concentration of 4-chlorophenol (4-CP) on its solar light photoinduced oxidation/mineralization kinetics on Bi2WO6 catalyst. Photocatalytic degradation followed the Langmuir-Hinshelwood (L-H) mechanism. From the kinetic data the Langmuir adsorption equilibrium constant of 4-CP on the Bi2WO6 surface and the L-H maximum reaction rate for 4-CP oxidation have been evaluated. Chromatographic and spectroscopy studies show the presence of p-benzoquinone and maleic acid as the main reaction products; these compounds first increase and then decay until they disappear. Chemical oxygen demand (COD) and produced CO2 measurement show that photocatalytic mineralization of the phenolic compound was readily possible in a wide concentration range. 1. Introduction In recent years, a large number of investigations have focused on the development of visible light induced heterogeneous photocatalyst for its applications in solar energy conversion and environmental wastewater purification [1–4]. In this sense, efforts have been directed to developing nanostructures based on Bi2WO6, the simplest member in the Aurivillius family [5–10]. This compound was first studied by Kudo and Hijii [11] and Zou and coworkers [12]; their works revealed that Bi2WO6 could perform as an excellent photocatalytic material, because it presents enhanced activities for the oxidative water splitting reaction. As a result, the solar light photocatalytic degradation of many pollutants as rhodamine B [13], green malachite [14], benzene [15], and 2,4-dichlorofenoxiacetic acid (2,4-D) [16] has been studied. The photoinduced degradation of 4-chlorophenol (a water soluble hazardous material widely used in paper, pharmaceutical, pesticide, and coal industries) [17–19] with Bi2WO6 nanocatalysts under visible light irradiation has been tested [20, 21]. This method induces an important decrease in the organic load and toxicity of wastewater; however, these authors have considered that the photodegradation reaction follows first order kinetics [22], thus obtaining the overall oxidation rate constant from linear plots of versus . Nonetheless, this constant does not describe each of the steps of the overall reaction mechanism; hence, its value will depend in general on the detailed conditions under which the experiments are carried out. However, less effort has been expended on measuring the kinetic parameters of environmental pollutant degradation and mineralization according to a heterogeneous catalysis model like Langmuir-Hinshelwood kinetics. Knowledge of these
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