Anodic Oxidation of the Insecticide Imidacloprid on Mixed Metal Oxide (RuO2-TiO2 and IrO2-RuO2-TiO2) Anodes

In this work, we evaluated the performance of the Ti/RuO2-TiO2 and Ti/RuO2-IrO2-TiO2 electrodes as electrocatalytic materials in the degradation of the insecticide imidacloprid (ICP). The temperature and current density operating parameters were investigated, and the degradation was followed by measurements of TOC and by UV-Vis spectroscopy. The complete oxidation de ICP (100% mineralization) was achieved by applying 40 mA cm(-2) when Ti/RuO2-TiO2 or Ti/RuO2-IrO2-TiO2 were used at 60 degrees C during 2 or 3 h electrolysis, consuming 33.3 kWh m(-3) and 47.5 kWh m(-3) of energy, respectively. Raising the temperature promoted a significant change in the results compared to those obtained at 25 degrees C. TOC removal, mineralization current efficiency and electric charge data indicated a system operating under mass transport control. The ICP absorption spectra showed suppression of the peak at 265 nm and increasing the peak at 214 nm, with the electrolysis time, indicating breakdown of the insecticide's molecular structure and formation of short chain compounds, before its complete mineralization. Degradation process occurred via direct anodic oxidation and Cl-2-mediated oxidation. The study showed that the electrochemical degradation process using DSA anodes is feasible and can be a good alternative for removing the insecticide in water or sewage treatment plants. (c) 2017 The Electrochemical Society. All rights reserved.