Photodegradation of etridiazole by UV radiation during drinking water treatment

Chao Liu, Zhimin Qiang*, Fang Tian, Tao Zhang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Scopus citations


The photodegradation of etridiazole (ETZ) in water by UV radiation at 254 nm was investigated. Results indicate that the simulated first-order rate constants decreased with the increase of initial ETZ concentration (i.e., 5, 20 and 30 μM), and did not show any pH dependence within the range from 6.0 to 8.0. The quantum yield was 0.46 ± 0.02 mol E-1 at pH 7.0. H2O2 was generated at trace levels in the range from 0 to 1.0 μM during photodegradation of ETZ. Direct photodegradation was responsible for the decomposition of ETZ in distilled water by UV radiation. Three organic byproducts were identified: 5-ethoxy-3-dichloromethyl-1,2,4-thiadiazole, 5-ethoxy-1,2,4-thiadiazole-3-carboxylic acid and 5-ethoxy-3-hydroxyl-1,2,4-thiadiazole. About 90% of chloro mass in the initial ETZ was released as Cl- at the end of photodegradation. In contrast, the formation of sulfate and nitrate was insignificant. In general, ETZ decayed more quickly in groundwater than in sand-filtered or surface water. It is reasonably deduced that ETZ may not get removed effectively under a typical UV dose of 40 mJ cm-2 at most water treatment plants that employ UV radiation for disinfection.

Original languageEnglish (US)
Pages (from-to)609-615
Number of pages7
Issue number5
StatePublished - Jul 2009
Externally publishedYes


  • Byproducts
  • Etridiazole fungicide
  • Photodegradation
  • Quantum yield
  • UV radiation

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • General Chemistry
  • Pollution
  • Health, Toxicology and Mutagenesis


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