TiO2 Assisted Photocatalytic Decomposition of 2-Chloronaphthalene on Iron Nanoparticles in Aqueous Systems: Synergistic Effect and Intermediate Products

2-Chloronaphthalene (2-CN), used as an intermediate for organic synthesis, is a new type of persistent organic pollutant. In this work, the decomposition efficiency and decomposition mechanism of 2-CN by zero-valent iron (ZVI) assisted TiO2 photodecomposition were studied in aqueous medium. Under UV light intensity of 38 mW cm–2, the optimal conditions for photodecomposition at an initial concentration of 5 μmol L–1 of 2-CN were pH 3 and 0.04 g L–1 TiO2 and ZVI, as catalysts. Then, the decomposition efficiency of 2-CN reached 66 and 100% in the UV/TiO2 and UV/ZVI/TiO2 systems, respectively. Based on analysis of the primary intermediate products of 2-CN, the chlorine on 2-CN was first replaced by a hydroxyl group to form 2-hydroxynaphthalene, and then the naphthalene ring was opened and gradually demethylated to produce small molecules, such as water and carbon dioxide.