Heat-activated persulfate oxidation of diuron in water

Heat-activated persulfate oxidation of diuron, a commonly found herbicide in groundwater, was evaluated in this study. Sulfate radicals (SO4 center dot-) 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 degrees C well fit the Arrhenius equation, yielding an activation energy of 166.7 +/- 0.8 kJ mol(-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 (k(obs) = 0.18 min(-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 (P-3, m/z = 376.2), C16H16O4N3Cl4 (P-4, m/z = 420.3), and C17H17O7N3Cl4 (P-5, 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. (C) 2012 Elsevier B.V. All rights reserved.