Photocatalytic degradation and detoxification of o-chloroaniline in the gas phase: Mechanistic consideration and mutagenicity assessment of its decomposed gaseous intermediate mixture

Abstract

The photocatalytic degradation of o-chloroaniline (o-ClA) on a TiO2 thin film was investigated using o-ClA as a model of semi-volatile organic compounds. The degradation efficiencies of o-ClA with ca. 4300μgL−1 were up to 99.0% within a 300min illumination. The degradation kinetics of o-ClA followed a pseudo first-order reaction. Two intermediates, chlorobenzene and phenol, were found in the gas phase, and trace phenol and o-dihydroxybenzene were also detected on the surface of the TiO2 film. Based on the identified intermediates and the theatrical calculation data of the frontier electron densities and point charges, a photocatalytic degradation mechanism was proposed tentatively. When tested using SOS/umu and Ames assay, neither the o-ClA nor the gaseous intermediates at different degradation times presented mutagenic activity to strain TA1535/pSK1002(−S9) as well as TA98(±S9) and TA100(−S9) at all tested doses. However, o-ClA at high doses did show weak mutagenic activity to strain TA1535/pSK1002 in SOS/umu assay and to strain TA100 in Ames assay with S9 metabolic activation. However, the mutagenic toxicity of the gaseous intermediates decreased rapidly as the degradation time increased, and when tested using both mutagenicity assays, no mutagenic activity was seen after 300min. Therefore, by combining mechanistic consideration with mutagenicity assessment, photocatalytic technology was found to be an effective detoxification method for gaseous aromatic amines.