Degradation and mineralization of sulcotrione and mesotrione in aqueous medium by the electro-Fenton process: a kinetic study

• Published in: Environmental science and pollution research international 2012-06, Vol.19 (5), p.1563-1573
• Main Authors: Murati, Minir, Oturan, Nihal, Aaron, Jean-Jacques, Dirany, Ahmad, Tassin, Bruno, Zdravkovski, Zoran, Oturan, Mehmet A.
• Format: Article
• Language: English
• Subjects: Acids; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Benzoic acid; Biodegradation; Carbon dioxide; Carboxylic acids; Carboxylic Acids - chemistry; Chlorine; Cyclohexane; Cyclohexanones - chemistry; Earth and Environmental Science; Ecotoxicology; Efficiency; Electrodes; Environment; Environmental Chemistry; Environmental degradation; Environmental Health; Environmental impact; Environmental Sciences; Free radicals; Herbicides; Herbicides - chemistry; Hydrogen-Ion Concentration; Hydroxyl radicals; Hydroxylation; Kinetics; Mesylates - chemistry; Mineralization; Nitrobenzoic acid; Organic carbon; Oxidation; Pesticides; Pollutants; Research Article; Solutions; Total organic carbon; Toxicity; Urbanization; Waste Water Technology; Water Management; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - isolation & purification; Water Pollution Control; Water Purification - methods
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-011-0667-1

Introduction The degradation and mineralization of two triketone (TRK) herbicides, including sulcotrione and mesotrione, by the electro-Fenton process (electro-Fenton using Pt anode (EF-Pt), electro-Fenton with BDD anode (EF-BDD) and anodic oxidation with BDD anode) were investigated in acidic aqueous medium. Methods The reactivity of both herbicides toward hydroxyl radicals was found to depend on the electron-withdrawing effect of the aromatic chlorine or nitro substituents. The degradation of sulcotrione and mesotrione obeyed apparent first-order reaction kinetics, and their absolute rate constants with hydroxyl radicals at pH 3.0 were determined by the competitive kinetics method. Results and discussion The hydroxylation absolute rate constant ( k abs ) values of both TRK herbicides ranged from 8.20 × 10 8 (sulcotrione) to 1.01 × 10 9 (mesotrione) L mol −1  s −1 , whereas those of the TRK main cyclic or aromatic by-products, namely cyclohexane 1,3-dione , (2-chloro-4-methylsulphonyl) benzoic acid and 4-(methylsulphonyl)-2-nitrobenzoic acid, comprised between 5.90 × 10 8 and 3.29 × 10 9  L mol −1  s −1 . The efficiency of mineralization of aqueous solutions of both TRK herbicides was evaluated in terms of total organic carbon removal. Mineralization yields of about 97–98% were reached in optimal conditions for a 6-h electro-Fenton treatment time. Conclusions The mineralization process steps involved the oxidative opening of the aromatic or cyclic TRK by-products, leading to the formation of short-chain carboxylic acids, and, then, of carbon dioxide and inorganic ions.