Layered platforms of Ti4O7 as flow-through anodes for intensifying the electro-oxidation of bentazon

Abstract

In this study, we prepared Ti4O7 porous electrodes with continuous layered structures characterized by different layer-to-layer distance (from 2 to 10 μm) but the same total void fraction (88–90%), to modulate the electrodes' permeability and the volumetric electrochemical surface area (from 90 to 840 cm2 cm−3). These platforms were evaluated as anodes in the electro-oxidation (EO) of bentazon in a three-electrode cell under galvanostatic conditions, operated both in traditional batch (TB) or batch recycle flow-through (BRFT) modes. The performance was significantly enhanced when the liquid was recirculated through the lamellar structure of the electrodes. In BRFT mode, the electrode interlayer gap was found to be a key factor to control the bentazon and total organic carbon (TOC) conversions. For the best conditions evaluated (BRFT, 10 μm-interlayered Ti4O7 electrodes with a volumetric surface area of 90 cm2 cm−3), the effect of the applied current (1 or 3 mA) and liquid flow rate (10, 12 or 14 mL. min−1) was investigated. Specific energy consumption (SEC) values were estimated to reveal the performance of each of the EO treatments from an energetic point of view. The use of 10 μm-interlayered Ti4O7 electrodes at 1 mA in BRFT mode at a flow rate of 14 mL min−1 showed the best results, yielding 85% bentazon removal, 57% mineralization and SEC values of 0.006 kWh.gTOC −1 after 6 h of treatment. This contribution highlights the use of layered Ti4O7 electrodes as a promising strategy for intensifying EO processes, pointing to a trade-off between the accessibility to the internal electrode structure and the volumetric electrode surface area to enhance the contact between the target molecules and the hydroxyl radicals physisorbed on the electrode surface, while minimizing simultaneously the energy requirements.