Dynamic cross-flow electro-Fenton process coupled to anodic oxidation for wastewater treatment: Application to the degradation of acetaminophen

In this work, we present an integrated dynamic cross-flow electro-Fenton (DCF-EF) system for the treatment of the pharmaceutical, acetaminophen (paracetamol), in aqueous medium. A carbonaceous electrocatalytic membrane was used as cathode, allowing the continuous production of H2O2 during EF in dynamic filtration mode. The transmembrane pressure (TMP) and current were the two driving forces of the system, whose influence strongly affected the global efficiency. It was found that H2O2 production from the electrochemical reduction of dissolved O-2 was favoured at higher TMP values as a consequence of an increase of the O-2 partial pressure, and higher H2O2 amounts entailed an increase in the efficiency of the process. Current also had a positive effect on H2O2 production and acetaminophen degradation and mineralization efficiencies up to an optimal value. Complete degradation of the drug and 44% mineralization were achieved under optimal conditions (2.0 bar and 100 mA). On the other hand, the results pointed out that the use of a Ti4O7 rod as counter electrode (anode) had an important contribution to the mineralization of the acetaminophen's solutions owing to the formation of hydroxyl radicals ((OH)-O-center dot) on its surface, which highlighted the oxidative power of this anode material. The oxidation mechanisms involved during the process were assessed by electrochemical measurements with both electrodes (carbon membrane and Ti4O7 rod), and a degradation pathway for paracetamol oxidation was proposed based on the identification of the main aromatic and aliphatic degradation by-products. This DCF-EF process is presented as a potential alternative for water treatment and reuse in which the integration of membrane and electrochemical technologies brings together separation science and advanced oxidation.