Electro‐Oxidation of the Pharmaceutical Furosemide: Kinetics, Mechanism, and By‐Products

Abstract

Furosemide is a widely prescribed diuretic whose unambiguous presence in water appointed it as an emerging pollutant. This work focuses on the electrochemical degradation of this drug in aqueous solutions by electrochemical advanced oxidation processes, electro‐Fenton and anodic oxidation, using Pt/carbon‐felt and boron doped diamond (BDD)/carbon‐felt cells with H2O2 electrogeneration. The higher oxidation power of the electro‐Fenton process using a BDD anode was demonstrated. The oxidative degradation of furosemide by electrochemically generated •OH radicals follows a pseudo‐first order kinetics. The absolute rate constant of the oxidation reaction of furosemide by •OH was determined using a competition kinetics method and found to be 3.4 × 109 M−1 s−1. The evolution of the total organic carbon removal during the treatment as a mineralization efficiency parameter was investigated. It was found that the electrochemical degradation of furosemide yields formation of aromatic by‐products which are oxidized afterwards to aliphatic carboxylic acids before their conversion to CO2 and inorganic ions (NH4+, NO3–, Cl–, and SO42–). The toxicity assessment by the Microtox® method revealed formation of oxidation reaction intermediates more toxic than the parent molecule. Nevertheless, the overall results confirm the high effectiveness of anodic oxidation and electro‐Fenton processes for the removal of furosemide and its by‐products from aqueous media.