A detailed investigation on electro-Fenton treatment of propachlor: Mineralization kinetic and degradation intermediates

• Removal of propachlor from water has been investigated by electro-Fenton process.
• The rate constant of oxidation reaction of propachlor was determined.
• Various intermediates were identified during the degradation of propachlor.
• The total organic carbon removal values confirmed the complete mineralization.
• A general reaction sequence for propachlor mineralization was proposed.

In this study, electrochemical removal of propachlor from water has been investigated by electro-Fenton process which provides continuous electrochemical production of hydroxyl radical which is a highly oxidizing agent. This radical can react with propachlor unselectively and can oxidize it into carbon dioxide and water. Effects of applied current, catalyst (Fe2(SO4)3) and supporting electrolyte (Na2SO4) concentrations on the degradation rate of propachlor have been examined and determined as 200 mA, 0.20 mM and 25 mM, respectively. The oxidation reaction showed a second-order reaction kinetic with an absolute rate constant value of (3.6 ± 0.2) × 109 M−1 s−1 which was determined by competition kinetic experiments. Total organic carbon analysis was employed to follow the mineralization of propachlor. The total mineralization was completed in a seven-hour electrolysis at 300 mA indicating that the electro-Fenton process is very effective in the mineralization of propachlor in water. Oxidation of propachlor with hydroxyl radical led to the formation of intermediate species. Some of these species were detected and quantified by chromatographic and spectroscopic methods such as HPLC, GC–MS and IC. A plausible mineralization pathway for the electrochemical removal of propachlor was proposed based on the identified by-products.

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