Ecotoxicological characterization of photoelectrocatalytic process for degradation of pentachlorophenol on titania nanotubes electrode

摘要

Luminescence bioassay using Vibrio fischeri and in vitro ethoxyresorufin-O-deethylase (EROD) induction bioassay using H4-IIE rat hepatoma cell were employed to test toxicity changes during the photoelectrocatalysis process for the degradation of pentachlorophenol (PCP) on TiO_2 nanotubes electrode. Acute toxicity of the reaction solution reduced by 83% after 120min of irradiation. Bioassay-derived 2,3,7,8-TCDD equivalents (TEQ_(bio)) increased from 0.72 to 6.72 ng l~(-1) during the former reaction stage, decreasing rapidly to 1.25 ngT1 during the latter reaction stage. HRGC/HRMS analysis detected polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/ Fs) congeners in the reaction mixtures. TEQ_(bio) and chemical-derived 2,3,7,8-TCDD equivalents (TEQ_(cal)) were about of the same order of magnitude. Both results illustrated the formation of dioxins and their removal by photoelectrocatalysis. Moreover, photoelectrocatalysis showed a significant priority over direct photolysis and photocatalysis depending on the reaction conditions, not only for PCP removal but also for reduction in toxicity.