Session: Current Status of Environmental Research on Water Contaminants:

Propiconazole (PRO) is a widely used triazole fungicide, and has been widely detected in water. Due to its hepatocarcinogenic effect and potential risk to human, the elimination of PRO in water is necessary. This study investigated the kinetics and degradation mechanism of PRO during UV and UV/H₂O₂ processes. The degradation rate of PRO in the UV/H₂O₂ process was well fitted to pseudo-first order kinetic. The removal of PRO was enhanced by increasing H₂O₂ concentration, but the presence of dissolved organic matter (DOM) inhibited, implying that DOM acted as a radical scavenger. The removal of PRO was effective in alkaline pHs. Transformation products (TPs) of PRO during UV/H₂O₂ process were identified using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-qTOF/MS). Two TPs (TP-1 ([M+H]⁺=306) and TP-3 ([M+H]⁺=324)) were observed during the UV photolysis process, whereas a total of 7 TPs were observed including TP-1 and -3 in the UV/H₂O₂ process. The mechanism of degradation of PRO by the UV/H₂O₂ process showed three pathways: 1) Ring cleavage, 2) continuous hydroxylation, and 3) hydroxylation followed by hydrolysis or chlorination. Most of the TPs identified in this study were consistent with the results of previous studies, and TP-2 ([M+H]⁺= 340) was newly identified. The toxicity assessment of TPs produced during the UV/H₂O₂ process need to be further studied.

<b>Fig. </b><b>1</b>. Proposed degradation pathways of PRO in (a) UV and (b) UV/H<sub>2</sub>O<sub>2</sub> processes.

Fig. 1. Proposed degradation pathways of PRO in (a) UV and (b) UV/H₂O₂ processes.

Kyung-Duk Zoh

Appearances