Simultaneous degradation of hexazinone and diuron herbicides by H2O2/UV and toxicity assessment

Abstract

Diuron (DR) and hexazinone (HX) are potent herbicides worldwide consolidated in agricultural practices. In Brazil,their mixed formulation has been intensively applied to cultures of sugar cane crops. However,when detected in agricultural watersheds, these compounds are potentially toxic to aquatic organisms and may be potentially carcinogenic. Advanced oxidation processes (AOP) is an alternative treatment of DR/HX in aqueous environment. In this study, we evaluate the H2O2/UV simultaneous degradation and photolysis process of DR/HX using central composite design. The HX and DR initial concentrations were close to 7 and 20 mg L-1, respectively. in the system, the planning showed that the H2O2concentration has bigger influence than pH. The optimum degradation conditions (7 mmol L-1of H2O2and pH 2.8) provide a total organic carbon removing of 96.4% while the photolysis process only 17.2%. Since neither of the herbicides were detected after 2 min of reaction, it was not possible to differ kinetics degradation process of DR and HX during the process. After the treatment, the toxicity was tested using Vibrio fischeri bioluminescent bacteria and showed a decrease when H2O2/UV is applied. Degradation H2O2/UV was successfully employed,showing excellent performance due to increased mineralization.Printed in Brazil -