Diuron abatement in contaminated soil using Fenton-like process

Abstract

The use of catalyzed H2O2 propagations (CHP) by the Fenton-like process has been evaluated for the treatment of contaminated soil by diuron ((qDiuron)o=40mgkg−1) at natural neutral pH. The interaction of H2O2 with the soil in batch system has been previously studied at four different initial H2O2 concentration (20,000–40,000–60,000–120,000mgkg−1) at room temperature in order to evaluate the oxidant decomposition by the natural reductants species (soil organic matter and iron minerals).The oxidation of diuron using only H2O2 at an initial concentration of 60,000mgkg−1 was firstly determined (XDiuron=55%). Another test was developed to study the effect of the addition of citrate (CCitrate=3000mgkg−1) as a chelating agent to increase the removal of the contaminant up to 73% suggesting that the concentration of iron mobilized by citrate from the soil (CFe≈40mgkg−1) promotes the Fenton's reaction. Finally, a third experiment was assessed using an extra amount of iron salt (CFe3+=600 mg kg−1) in addition to citrate, resulting to an increase in the diuron removal (XDiuron>80%) because citrate makes stable iron chelates with Fe3+ and increases the generation of OH in aqueous phase and a higher diuron removal is obtained.Ecotoxicity measurements in the soil and liquid phases at initial and after the Fenton's treatment by the Microtox® bioassay demonstrated that low toxicity is obtained in the treated soil and temporal toxicity values in the liquid phase is in direct correlation with the residual H2O2. The toxicity values decrease with the H2O2 concentration to not toxic values with a final total degradation of the oxidant.