Dehalogenation, degradation and mineralization of diuron by peroxone (peroxide/ozone) treatment

Removal of diuron from aqueous solution by peroxone (hydrogen peroxide/ozone) oxidation was investigated using Box-Behnken statistical experiment design and the response surface methodology (RSM). Effects of diuron, H2O2 concentrations and initial pH on the extent of diuron, total organic carbon (TOC) and adsorbable organic halogen (AOX) removals were investigated. Ozone dose was kept constant at 45 mg min-1. Optimum reagent doses yielding the highest diuron, TOC and AOX removals were also determined. Hydrogen peroxide dose and pH were the most effective parameters for pesticide removal while hydrogen peroxide dose had the most significant effect on AOX removal (dehalogenation). All parameters affected mineralization (TOC removal) of diuron. Nearly complete removal of diuron was achieved within 5 minutes, while complete mineralization and dehalogenation were not achieved even within 60 minutes at high diuron doses indicating formation of some intermediate products. The optimal H2O2/pH/diuron ratio resulting in the maximum pesticide (100%), TOC (82%) and AOX (95%) removal was found to be 340/8/10.