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

Abstract

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 was determined as (3.7 ± 0.2) × 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.

Keywords

• 2,4,5-T
• Electro-Fenton
• Anodic oxidation
• Mineralization
• Hydroxyl radical
• TOC removal