Effects of coupling hybrid processes on the treatment of wastewater containing a commercial mixture of diuron and hexazinone herbicides. (20th December 2019)

• Record Type: Journal Article
• Authors: Souza, F.L.; Rocha, R.S.; Ferreira, N.G.; Rodrigo, M.A.; Lanza, M.R.V.
• Is Part Of: Electrochimica acta. Volume 328(2019)
• Publication Date: 2019-12-20
• Subjects: Herbicides -- Electrochemical oxidation -- Electro-Fenton -- Photoelectro-Fenton -- Boron-doped diamond -- Oxygen-diffusion cathode; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2019.135013
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: This work evaluates the effects of coupling Conductive Diamond Electrochemical Oxidation (CDEO) with electrogenerated peroxide (CDEO-H2 O2 ), iron (II) catalyst (electro-Fenton, EF) and UV irradiation (photoelectron-Fenton, PEF) techniques for the treatment of wastewater containing a commercial mixture of Diuron and Hexazinone herbicides. Although the techniques employed in this study exhibited significant differences in terms of current charge, energy consumption and amounts of byproducts formed, they have shown to be capable of degrading and mineralizing both herbicides (Diuron and Hexazinone). The application of electrooxidation technique with and without hydrogen peroxide generation led to the oxidation of both herbicides, where removal rates ranging from 74% to 99% and 77%–92% were obtained for Hexazinone and Diuron, respectively. Hexazinone and Diuron were completely removed after 90 min in the EF process. PEF was found to be the most efficient technique for having drastically reduced the time for complete degradation of the herbicides, although 25% of organic carbon remained in solution after 120 min of electrolysis. Higher rates of herbicides degradation were obtained in this order: PEF > EF > CDEO/H2 O2 /UV > CDEO/H2 O2 > CDEO > UV. The result indicates that the production of oxidants is promoted by the hybrid processes, and this leads to an improvement in the oxidation of the pollutants. The synergistic coefficient obtained for the coupled techniques were higher than one in terms of both herbicides degradation and Total Organic Carbon (TOC) removal. Two important sub-products of reaction were identified, and their degradation route is in agreement with the reports published in the literature. Essentially, this work draws attention to the synergistic effect caused by the coupling of techniques involving the treatment of chemical agents in wastewater and sheds light on how to use this coupling technique for the development of more efficient treatment processes. Highlights: Oxidation capacity increases in the following order: UV < CDEO < CDEO-H2 O2 < EF < CDEO/H2 O2 -UV < PEF. Diuron and Hexazinone are similarly oxidized under bare CDEO techniques. Higher rates of herbicides decay were obtained in hybrid processes due to the enhancement of oxidants production. Synergistic coefficients greater than 1 were obtained for the coupling of H2 O2, Fe (II) and UV to CDEO.