Degradation of Benzo[a]pyrene using TiO2 and Ag-loaded BiVO4 Photocatalysts: Evaluation by the Ames Mutagenicity Assay

摘要

Photodegradations of benzo[a]pyrene (B[a]P) on Ag-loaded BiVO4 and TiO2 (P25) photocatalysts as well as on a direct photolysis under UV or visible light irradiation have been investigated using the Ames mutagenicity assay to assess the possibility of producing active mutagens in the degradation processes. The Ames test was performed for residues after evaporating acetonitrile from the treated solutions, and evaluated by counting the revertant colonies grown on minimal glucose agar plates in the presence and absence of rat liver enzymes and cofactors (S9mix). In the case of the TiO2 photocatalysis and the direct UV photolysis, the number of the revertant colonies of TA100 with S9mix decreased to the control level (100 - 150 counts) with decreasing B[a]P concentrations during the UV irradiation. No increase was observed for the revertant colonies of TA98 and TA100 in the presence and absence of S9mix. Thus, the B[a]P degradation by the above two methods does not induce mutagenic activities on both TA98 and TA100. On the other hand, for Ag-BiVO4, the number of TA98 revertant colonies gradually increased from the control level (ca. 60 counts) with visible light irradiation and reached ca. 400 counts after 10 h in the absence of S9mix. This result clearly indicates that some active mutagens inducing the frame-shift direct acting mutation were produced in the B[a]P degradation by the use of Ag-BiVO4.