Heat-Activated Persulfate Oxidation of Diuron in Water

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Heat-activated persulfate oxidation of diuron, a commonly found herbicide in groundwater, was evaluated in this study. Sulfate radicals SO4- was the principal oxidizing agent responsible for the diuron degradation. The diuron decomposition exhibited a pseudo-first-order kinetics pattern at all the conditions tested. The observed rate constants determined at 50-70°C well fit the Arrhenius equation, yielding an activation energy of 166.7±0.8kJmol-1. Temperature, persulfate dose, initial diuron concentration, pH, and three common groundwater solutes (CO32-,HCO3-, and Cl-), to different degrees, influenced the degradation. Typically, high temperature, high persulfate dose, and low initial diuron concentration increased the decomposition rate of diuron. At the tested pH range of 5.5-8.1, the highest degradation rate (kobs=0.18min-1) occurred at pH 6.3. The three groundwater anions inhibited the diuron decomposition with the following order: CO32->HCO3->Cl- The major oxidation products in this study were C15H15ON3Cl4 (P3, m/z=376.2), C16H16O4N3Cl4 (P4, m/z=420.3), and C17H17O7N3Cl4 (P5, m/z=465.4), different from those produced during hydroxyl radical-induced advanced oxidation. The in situ chemical oxidation (ISCO) technology can be achieved in practice through combination with in situ thermal remediation.



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