Degradation of diuron in aqueous solution by ozonation

Abstract

Degradation of diuron [3-(3,4-dichlorophenyl)-1,1-dimethylurea] in aqueous solution and the proposed degradation mechanism of diuron by ozonation were investigated. The factors that affect the degradation efficiency of diuron were examined. The generated inorganic ions and organic acids during the ozonation process were detected. Total organic carbon removal rate and the amount of the released Cl⁻ increased with increasing ozonation time, but only 80.0% of the maximum theoretical concentration of Cl⁻ at total mineralization was detected when initial diuron concentration was 13.8 mg L⁻¹. For N species, the final concentrations of NO₃ ⁻ and NH₄ ⁺ after 60 min of reaction time were 0.28 and 0.19 mg L⁻¹, respectively. The generated acetic acid, formic acid and oxalic acid were detected during the reaction process. The main degradation pathway of diuron by ozonation involved a series of dechlorination-hydroxylation, dealkylation and oxidative opening of the aromatic ring processes, leading to small organic species and inorganic species. The degradation efficiency of diuron increased with decreasing initial diuron concentration. Higher pH value, more ozone dosage, additive Na₂CO₃, additive NaHCO₃ and additive H₂O₂ were all advantageous to improve the degradation efficiency of diuron.

Keywords:

• Diuron
• ozone
• degradation byproducts
• degradation pathways
• degradation mechanism

Acknowledgments

The authors thank the Natural Science Foundation of China (No. 10475040) for financial support.