Comparative study of electrochemical oxidation of herbicide 2,4,5-T: Kinetics, parametric optimization and mineralization pathway

Oxidative degradation of herbicide 2,4,5-T was studied by electrochemical advanced oxidation processes anodic oxidation and electro-Fenton (EF) using Pt/carbon felt and BDD/carbon felt cells. The effect of main operating parameters on oxidation of 2,4,5-T and mineralization of its aqueous solution were investigated. The rate constant for oxidation of 2,4,5-T by (OH)-O-center dot was determined as (3.7 +/- 0.2) x 109 M-1 s(-1) using competition kinetics method. The EF process with BDD anode was shown to be very efficient reaching 94% mineralization in 3 h treatment. Based on identified aromatic intermediates, short-chain carboxylic acids, released inorganic ions and total organic carbon removal measurements, a plausible oxidation pathway for mineralization of 2,4,5-T by hydroxyl radical was proposed. In addition, the evolution of solution toxicity during treatment was monitored by Microtox method showing the formation of toxic aromatic/cyclic intermediates. The results showed also that EF process was able to remove efficiently toxic intermediates and consequently solution toxicity. (c) 2016 Chinese Institute of Environmental Engineering, Taiwan. Production and hosting by Elsevier B.V.