Photoconversion of polychlorinated naphthalenes in organic solvents under simulated sunlight: Solvent effect and mechanism.

Affiliation

Kang Q(1), Bao S(2), Chen B(3).
Author information:
(1)Northern Region Persistent Organic Pollution Control
(NRPOP) Laboratory, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John's, NL, A1B 3X5, Canada.
(2)College of Environment and Resources, Jilin University, Changchun, 130012, China; School of Chemistry and Environmental Engineering, Changchun University of Science and Technology, Changchun, 130022, China. Electronic address: [Email]
(3)Northern Region Persistent Organic Pollution Control
(NRPOP) Laboratory, Faculty of Engineering and Applied Science, Memorial University of Newfoundland, St. John's, NL, A1B 3X5, Canada. Electronic address: [Email]

Abstract

In this work, the organic solvent effect on the photoconversion of polychlorinated naphthalenes (PCNs) under the simulated sunlight, as well as the mechanism and influence factor were studied. Eight organic solvents were selected to demonstrate the solvent effect on the photoconversion by the theoretical calculation method. It was found that the photoconversion rates of 1-chloronaphthalene (CN-1) in different organic solvents were in the order of dimethyl sulfoxide > methanol > acetonitrile > ethanol > dichloromethane > toluene > n-hexane > acetone. The result, obtained by the density functional theory (DFT) computation and the polarized continuum model (PCM) analysis in the framework of self-consistent reaction field (SCRF), indicated that the photoconversion was affected by the hydrogen-donating ability and electron-withdrawing potential of the solvents, as well as non-specific solute-solvent interactions. The photoconversion in acetonitrile for the five PCNs (1-chloronaphthalene, 2-chloronaphthalene, 2,3-dichloronaphthalene, 1,2,3,4-tetrachloronaphthalene, and 1,2,3,4,5,6,7,8- octachloronaphthalene) all fitted well with the first-order kinetic equation; and the reaction rate decreased with the increasing of number of chlorine atoms of the PCNs. Products analysis proved that the photoconversion process of PCNs went through two stages, namely the initial stage of dechlorination and the later stage of oxidative ring opening. It was found that inorganic ions (NO3-, Cl-, Fe3+, and Fe2+) promoted or inhibited the photoconversion by generating or quenching of the reactive oxygen species, and chlorophyll a promoted the photoconversion through the generation of singlet oxygen.